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1. Design and synthesis of new chiral units for potentially ferroelectric liquid crystals : liquid crystals… Wang, Xin 1987

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1. DESIGN  AND  FERROELECTRIC  SYNTHESIS LIQUID  OF NEW CHIRAL  CRYSTALS:  THI IRAN UNIT. 2. HETEROGENEOUS 1,1'-BINAPHTHYL  LIQUID  FOR  POTENTIALLY  CRYSTALS  CONTAINING  OF THE  RACEMIZATION  CATALYSIS  BY TITANIUM  UNITS  DIOXIDE  POWDER.  by XIN A  THESIS  SUBMITTED  WANG  IN PARTIAL  THE REQUIREMENTS MASTER  FULFILMENT  FOR THE DEGREE OF  OF  SCIENCE  in THE  FACULTY  OF G R A D U A T E  DEPARTMENT  We  accept  OF  this thesis  to the required  THE UNIVERSITY  ©  CHEMISTRY  as  conforming  standard  OF BRITISH  November,  STUDIES  1987  XIN W A N G , 1987  COLUMBIA  OF  A OF  In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives.  It is understood that copying or  publication of this thesis for financial gain shall not be allowed without my written permission.  Department of The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date  DE-6(3/81)  "Dec  Abstract Supervisors: Dr. R.E. Pincock New  liquid crystals  and Dr. G.S. Bates  have been synthesized  have been studied. It was found that a family 2R,3S-epithio-4'-alkoxybiphenyl system Of  of ( + )-2-methyl  pentanoates  2S,3R-epoxy-4'-alkoxybiphenyl  MEAOBP-S-8 and MEAOBP-S-9 show  is in agreement the  molecule  behaviour  a monotropic  with the argument  plays  an important  of this ester  smectic  smectic  in determining  dioxide  increased  relationship  dipolar  distinction  interaction of  liquid  of optically  in the presence  (anatase) powder. This  proportional  B phases;  crystalline  system.  The reaction rate of the racemization can be moderately  are not.  A and B phases;  C phase. This  that the internal  role  but a similar  pentanoates  only the smectic  chiral  phases  of (-)-2-methyl  are liquid crystals  the liquid crystals, MEAOBP-S-7 exhibits  MEAOBP-S-10 shows  and their transition  first  order  of finely  active divided  catalyzed reaction  with the concentrations  binaphthyl titanium  has a  of both the catalyst and  the binaphthyl. The catalyzed reaction can be poisoned permanently of polynuclear dependent  aromatic  compounds  and the poisoning  of the number of the aromatic  efficiency is  rings the poison posesses. By  comparison with the catalyzed racemizations nickel  of binaphthyl  and carbon and from the kinetic and mechanistic  titanium  dioxide  phenomenon  catalyzed racemization, we conclude  is common  by the addition  among heterogeneous  that  inorganic  by platinum,  studies  (1) this solids  extended to other simple reactions, and that (2) the mechanism catalysis  probably  involves  a radical anion  ii  intermediate.  on the catalytic  and can be of the  Table of  Contents  CHAPTER 1 DESIGN AND SYNTHESIS OF NEW CHIRAL UNITS POTENTIALLY FERROELECTRIC LIQUID C R Y S T A L S : LIQUID C R Y S T A L S CONTAINING A THIIRAN UNIT 1.  2.  3.  Introduction  FOR 1  „  1.1  Transition phases of  1.2  Structure of  1.3  Design and synthesis  2  liquid crystals  ferroelectric of  2  liquid crystals potentially  7  ferroelectric  liquid  crystals  10  1.4  The previous work concerning R O - P h - P h - O C O - R *  12  1.5  The present work  13  Results  and Discussion  2.1  Synthesis  of  2.2  Identification  2.3  Conclusion  17  new compounds  17  of  27  new liquid crystals  29  Experimental  30  3.1  General  ".30  3.2  4'-Alkoxy-biphenol: General  3.3  (-)2S,3S-Dihydroxy-2-methylpentanoic acetal of  procedure  3.4  3-Pentanone  3.5  acid 3-Pentanone acetal of (-)-2-methyl 4'-heptyloxybiphenylpentanoate  31 acid  33  (-)-2S,3S-dihydroxy-2-methylpentanoic 34  2S,3S-dihydroxy-  34  3.6  (-)2-Methyl  2S,3S-dihydroxy-4'-heptyloxybiphenylpentanoate  3.7  ( + )2S-Methyl  3.8  2-Methyl  3.9  (-)2-Methyl 2R,3S-epithio-4'-heptyloxybiphenylpentanoate (MEAOBP-S-7) ;  2S,3R-epoxy-4'-heptyloxybiphenylpentanoate  37  2S,3R-epithio-methylpentanoate  3.10 S(-)-(c)!v1ethoxy-(0)trifluoromethylphenyl acetates  39  40  4'-alkoxybiphenyl  CHAPTER 2 HETEROGENEOUS C A T A L Y S I S OF THE RACEMIZATION OPTICALLY ACTIVE 1,1'-BINAPHTHYL BY TITANIUM DIOXIDE POWDER  iii  35  .42 OF 46  4.  Introduction  -  4.1  Heterogeneous  4.2  Catalyst  4.3  Racemization of binaphthyl 4.3.1  catalysis  4  titanium oxide  5  of binaphthyl  of binaphthyl  60 The carbon catalyzed racemization  60 Platinum catalyzed racemization  61  The object  Results  59  by C, Ni, and Pt The Interaction of binaphthyl with Raney  5.  7  57  racemization of binaphthyl  4.3.3 Catalyzed racemization  4.4  7  50  Uncatalyzed racemization  4.3.2 Photocatalytic  4 7  of the present  nickel  study  61 62  and Discussion  63  5.1  Preliminary  kinetic  studies  and reproducibility  63  5.2  The Effect of concentrations of catalyst, binaphthyl and additives on catalytic activity  72  i.  5.3  Catalytic  activity  of modified titanium  dioxide  75  5.3.1  Preheating titanium dioxide  75  5.3.2  Acid-washing  77  5.3.3  Illuminating titanium dioxide  titanium  dioxide  77  5.3.4 Reducing titanium dioxide  78  5.3.5 Other sources  80  of titanium dioxide Titanium dioxide  from  titanium tetrachloride Rutile materials  82  5.3.6 Colloidal titanium dioxide 5.4  5.5 6.  .80  Speculation on the catalytic mechanism on the basis previous and present kinetic results Conclusion  82 of 83 85  Experimental  86  iv  6.1  General  6.2  Synthesis  6.3  Preparation of  6.4  Kinetics of Reactions  6.5  .86 of  Racemic  1,1'-Binaphthyl  Optically  Uncatalyzed  Active  .87  1,1'-Binaphthyl  and Titanium  Dioxide  .87 Catalyzed 88  Procedure for attempted Titanium reactions  6.6  Product  Analysis  and Adsorption  6.7  Preparation of  6.8  Reduction of Titanium  dioxide  photocatalytic 89  Experiments  using glc  Titanium Dioxide from Titanium Tetrachloride Dioxide  BIBLIOGRAPHY  90 90 91 92  v  Lists  Table  1: Selected  Table  2; Ferroelectric  (page  9)  Table  3; Phase transition  Table  4;  'H nmr  structures  of  (page  Table  6: A  classification (page  Table  7: Properties  Table  8: Dependence  binaphthyl  Table  racemization, part  Table  of  of  10: Catalytic  racemization, part  of  (page 4)  polarization  C,H -0-Ph-Ph-OCO-R*  (page  17  the tertiary  by alkylation of  of  heterogeneous  proton  in the thiiran  13)  ester  4,4'-biphenol  catalysts  (page  32)  according to the their  50)  different  forms  of  titanium  dioxide  (page  51)  Kobs of Aldrich anatase catalyzed racemization  on the concentration  9; Catalytic  liquid crystals  22)  5: 4'-Alkoxybiphenols  functions  ferroelectric  liquid crystals  shift  Table  principal  some  Tables  liquid crystals with large spontaneous  chemical  and its precursors  of  of  activity  of  of  binaphthyl  (page 73)  modified titanium dioxide towards  the  1 (page 76)  activity  of  modified  2 (page 79)  vi  titanium dioxide towards  the  of  Table  11; Catalytic  activity  of  modified titanium dioxide  towards  racemization, part 3 (page 82)  Table  12: Catalytic  racemization  of  activity  optically  of  four  inorganic solids towards  active binaphthyl  (page 84)  the  Lists  Figure  1: Partial  4'-heptyloxy-  J  of  H nmr spectra of  biphenyl pentanoate  Figures  (-)-2-methyl  2R,3S-epithio-  (400MHz, CDCI ): (1) normal spectrum; (2) }  spectrum with irradiation at 3.70 ppm; (3) spectrum with irradiation at ppm  1.15  (page 23)  Figure 2: Liquid crystal phases biphenyl  pentanoate: (1) smectic  Figure 3; Chiral smectic biphenyl  pentanoate  (X200) (page  order kinetic  1,1'-binaphthyl  by highly  Figure 5; Several active  binaphthyl  of  by highly  Figure 7: Dependence  of  kinetic  by highly  of  B (X100) (page  (-)-2-methyl  26)  racemization of  runs of  the concentration of  optically  (page  64)  of  dioxide  titanium dioxide  catalyzed racemization of  the concentration  of  (page  of  (page 65)  on the  optically  dispersed titanium dioxide  (page  active  67)  the additive benzene  catalyzed racemization  viii  active  catalyzed racemization  dispersed titanium dioxide  of  25)  2R,3S-epithio4'-decyloxy-  by highly dispersed titanium  observed kinetic rate constant 1,1'-binaphthyl  (2) smectic  catalyzed  observed kinetic rate constants 1,1'-binaphthyl  2R,3S-epithio4'-heptyloxy-  dispersed titanium dioxide  identical  Figure 6: Dependence  (-)-2-methyl  A;  C phase  Figure 4; First  optically  of  of  on the  optically  68)  active  Figure 8: Dependence the observed kinetic active  of the concentration of the additive rate constant  1,1'-binaphthyl  Figure 9: Dependence observed kinetic 1,1'-binaphthyl  Figure  catalyzed racemization  of  on  optically  by highly dispersed titanium dioxide  (page 69)  of the concentration of the additive  anthrance on the  rate constant  of  catalyzed racemization  by highly dispersed titanium dioxide  10: Dependence  of  the concentration  observed kinetic rate constant 1,1'-binaphthyl  of  naphthalene  by highly  of  catalyzed  dispersed titanium  ix  of  optically  (page 70)  of the additive  pyrene  racemization  optically  dioxide  active  (page  of  71)  on the active  Acknowledgements I wish to express encouragement  and guidance  Bates for his generous this  my  grateful  thanks to Dr. R.E. Pincock  during the course  opportunity  for  his  of this work, and to Dr. G.S.  and guidance during the  last year  of  thesis. I would like to thank Barbara Frisken for her time and help  assistance My Chemistry  of  identifying the  thanks are extended to the staff Department  from the Chinese gratefully  liquid crystal  for  their excellent  government  in  materials. and the technicians  sevice. The fiancial  and the University  of  British  of  the  assistance Columbia  is  acknowledged.  Finally, I would  like to thank  my wife, Chun, for  understanding.  x  her patience  and  CHAPTER  1 DESIGN AND  POTENTIALLY  SYNTHESIS  FERROELECTRIC  LIQUID  CONTAINING  A  OF NEW CHIRAL CRYSTALS:  THIIRAN  UNIT  UNITS  LIQUID  FOR  CRYSTALS  The based  advent  on  the  deal  exhibit  1.1  interest  for  with  the  it  to  two  have  OF  at  two  and  an  and  organic  crystals  LIQUID crystals  to  isotropic  organic  engineering first  crystals  has  1  aroused  of  new  smectogens  of  this  thesis  part  compounds, and  began  botanist  form  liquid  light-valve  which  hopefully  will  potentially  also  be  can  ferroelectric.  CRYSTALS  interesting  145°C  hundred  in  who  1888, w i t h  prepared  properties.  a turbid liquid  is  compounds  the  of  cholesteryl  benzoate  heated,  crystal  When  liquid. At  its  1 7 9 ° C , the  formed. Since has  research  turbid  then, about  been  found  to  only  three  states  one  exhibit  liquid  phase(s). centuries,  solids, ordered; very  materials solid  in to  liquids.  in  or  and  bound  and  order  a true  have  gases.  liquids, they  which  is  are  occupy  liquid  are  and  atoms  or  disordered;  relaxed  as  of  molecules in  disordered. Liquid  progressively  a  crystals also  solids.  ordering  Their  magnetic  In s o l i d s , bound  also  s t a t e s , they  ordinary  considered  are  gases,  bound  they  crystals  one  matter  are  are  proceeds  from  a  liquid.  crystals  Although  liquid  scientists  liquids,  weakly  Liquid  by  liquid  Austrian  every  liquids  of  electrooptic  smectic  nature. The  novel  an  For  and  of  Reinitzer,  disappears  true  this  liquid  liquid  only  of  of  collapses  and  synthesis  science  found  crystal  ferroelectric  the  PHASES  lattice  of  of  synthesis  TRANSITION  and  fast-switching,  in  properties  The  bistable,  applications  the  Friedrich  a  INTRODUCTION  properties  considerable suitable  of  1.  and/or  grey  area  exhibit  possess  between  certain  properties  properties,  electric  fields.  2  for  true  aspects that  solids of  are  example,  and  both  the  not  found  can  be  true solid in  either  controlled  3  The liquid crystals commonly referred in the literature are thermotropic liquid crystals, i.e. their properties are temperature dependent. The other major branch of liquid crystals, called lyotropic liquid crystals, are often two-component systems composed of water and amphiphilic compounds, and will not be described. (See references 2-3 for reviews on this subject) Thermotropic liquid crystals, which form naturally over a specific temperature range, are further classified as either nematic or smectic. "Nematic" comes from the Greek word for thread; nematic crystals have a thread-like pattern when viewed through a microscope equipped with crossed polarizers. "Smectic" from the Greek for soap, decribes these crystals' greasy or soapy properties. \j<  Isotropic structure (unordered, nonliquid crystalline)  A  LlUilKllJl...:  Hill llllllllll llllllllll llll nm IIIIIIIIII iin in in 11 ml Smectic A structure  ///////////  f///////////\ //////////A //////////  Ordinary nematic structure  Cholesterfc structure  Smectic C structure  (Reproduced from reference 2) A general description of many of the various types of liquid crystal phases are given below (page 4). In a typical nematic liquid crystal, the only structural restriction is that the long axes of the molecules maintain a  4  Thermotroplc liquid crystals have either nematic or smectic structures Tartan*  Qptterf erteertte*  CtoM  swwtare  NEMATICS  Crdbtary nematic  Unlaxlaity positive  Sehlleren; threaded; marbled; pseudoIsotropic; homogeneous  Parallelism of long molecular axes  p-Azoxyanisole; jMrwthoxybertzytldene; rtft4utyl)eniline  ChoWtttrtenemetlc  Unlax laity negative or Isotropic; optically active  Focal conic with Orandjean steps; homogeneous; Isotiopic  Nematic packing In planes; superimposed twist m direction perpendicular to long axes of molecules  Chotassyy! aunanoate  Isotropic; optically active  Platelet with ttandjoan steps  Cubic  Choiestenjl nonanoate  Blue phase  *  STRUCTURED  SMECTICS  Smectic B  Uniaxially positive  Mosaic; stepped drops; pseudo-isotroplc; homogeneous  Layer structure; molecular axes orthogonal to the layers; hexagonal arrangement within the layers  Ethylethoxybenzylideneamlnocinnamate; twephthaUris-butylaniNne  Smectic E  Biaxlally positive  Mosaic; pseudo-isotroplc  Layer structure; molecular axes orthogonal to the layers; ordered arrangement within the layers  CH-n-propyBerphenytdlcarboxylate  Smectic 0  Biaxially positive  Mosaic  Layer structure with ordered arrangement within the layers  2^4-r>Pentylpheny1)-M4-rt" pentyloxyphenytlpyrlmldlne  Snwdlc H  Biaxlally positive  Fan  Tilted analogue of smectic F  Smectic 1  Biaxially positive  Hexagonal correlation bv Mosaic; fan-shaped with stripes across the-plane and the tilt direction Is uniform the fans toward neighboring molecules  4-rKPentytMnzenethlo-4'-/v octyloxybenzoate  texture  UNSTRUCTURED  SMECTICS  Smectic A  Uniaxially positive  Focal conic (fan-shaped or polygon); stepped drops; homogeneous; pseudo-isotroplc  Layer structure; molecular axes orthogonal to the layers; random arrangement within the layers  Dietriylazoxybenzoate  SfllOCtlC C  Biaxlally positive  Broken focal conic; echlieren; homogeneous  Layer structure; molecular axe* mted to the layers; random arrange ment within the layers  Oodecytoxyazoxybenzene  Smectic D  Isotropic  Isotropic; mosaic  Cubic structure  4'^ctadecytexy-3'-nltrodlphenyl < carboxyllc acid  SmoctJc F  Biaxlally positive  Sehlleren; broken focal conic  Layer structure  2-(4-r>^en1ylphenyt)-5-(4r>pontyloxyphonyl>n  f lit•• •  .pyrvniora I H M "UqJt Cfy»M» a* ftototfatf M m "  (Reproduced  from  ty A i.« w k a a w w a H f k e M i  reference  2)  5 parallel  or nearly parallel arrangement  nematic  phase always changes  Cholesteric formed  by some  compounds. They have  liquid crystals, first optically  orthogonal  Smectic smectic their  the  smectics  phase, the molecules  of  smectic  are the least  phases, of  the molecules freely  are arranged  about  their  ordered of  phase, the molecules  A  to the phases  within each about their  which  layer  the  orthogonal  are arranged with  of  the  layers. The  is random, and the  long axes. In the smectic B  in layers with the molecular  in a hexagonal close-packed  rotating quite rapidly in-plane  and  molecules.  long axes perpendicular  are able to rotate  positioned  liquid crystals  such  C, F, G, H, I, J , and K.  liquid crystals  distribution of  molecules  of  include the smectic A , B, and E phases; and tilted  phases. In the smectic  molecular  lateral  A  esters, are  active organic compounds, or mixtures  are basically two types  smectics* include  liquid.  observed with cholesteryl  are miscible with ordinary nematic  smectics  distances. The  on heating to an isotropic  local nematic packing of There  over macroscopic  array. The  long axes. The  molecules  smectic  packing which is rectangular, with long-range  centers  are  also  E phase  has  positional  correlations. The close  smectic  packed  particular  C phase  is one  in layers; in a given domain the molecules  direction with respect  the molecules  in which the molecules  in smectic  associated processional In smectics  C phase rotate about their  are tilted in A  and B,  long axes with no  rotation.  I and F -', the molecules  packed. In the  randomly  to the layer planes. Like smectics  5  are tilted  in their layers. In the  plane, at right angles to the tilt direction, the molecules close  are  I phase the molecules  are  hexagonally  are tilted towards the  apex,  6  while  in the F phase they In smectics  J and G * , the molecules 5  layers. In the plane hexagonally  one side  of  the hexagon.  again are tilted within the  1  at right angles to the tilt direction they are  close packed. Smectics  directions, J hexagonal  are tilted towards  is tilted towards  J and G are distinguished by their  the apex while G towards  the side of  molecules  H and K phases  are packed  dimerisons  are similar  in a rectangular  than the hexagonal  to J and G except  net of  have been known for  a century  ferroelectric  liquid crystals  were first  by  possessing  at least  one chiral  property, i.e. shows which ferroelectric  liquid crystal  recognized  concerning  of  a ferroelectric  constant  temperature  range where ferroelectric  to describe all of  the  required to exhibit phases  field  to  coefficient.  elements point  of  view,  is the transition temperature, i.e., the  are seven smectic  liquid crystal  and (8) the viscosity  liquid crystal. From the applicative  greatest  smectic  pitch; (4) the  polarization; (6) the critical  this thesis  interest  ferroelectric  may be characterized, are (1) the  a chemist's  There  the  10  index; (5) the spontaneous  It is beyond the scope  or a mixture  polarization. The material constants , with  liquid crystals  unwind the helix; (7) the elastic  more,  in 1975.  phase which exhibits  transition temperature; (2) the tilt angle; (3) the helical refractive  or  Meyer'  (FLC) is a compound  smectic  spontaneous  smaller  J and G.  liquid crystals  ferroelectric  the  base centered net which has  While  elements  the  net.  Smectic  A  tilt  smectic  modifications  ferroelectric  phases  are retained.  which have the  symmetry  behaviour. Of these, three are  ( Sm* C, S m * I, and S m * F, here  chiral smectic  phase  ), and another four  orientationally  disordered crystal  fluid  * denotes  a  (Sm* J , G, H, and K) are  phases. Chiral smectogens  possessing  those  7 smectic least  phases  may exhibit ferroelectic  ordered phase of  the most  the seven known chiral  important one  For the purpose a high spontaneous  properties. The smectic  in so far as the application of  applications, FLC  polarization, to have a wide  from the isotropic  is  liquid  materials eight Sm*C  eutectic  are multi-component  individual  compounds. In given  phases) different  depression  observed  compounds  commercial  in some  cases  liquid crystal  are  with monotropic  to obtain thermodynamically  exhibit  phase  A  on  purposes. It is desired phases liquid  crystal  containing  phases  by  seven  (e.g. the S m A  in general miscible, and there  in, for example, the S m A  mixing. For pure compounds possible  mixtures  and is thus  crystalline  liquid required for alignment  mixtures. Indeed, many  is the  concerned.  a smectic  c o m m o n practice to broaden the temperature range of formulating  phases  materials are required to  temperature range, and to be stable, to exhibit cooling  S m * C phase  stable  to Sm*C transition phases, it is  or and  is no  upon  generally  liquid crystal  phases  by  such  formulation.  1.2 STRUCTURE  OF FERROELECTRIC  Ferroelectric increasingly  smectic  important  the numbers of  LIQUID  liquid crystals  in electrooptic  materials  CRYSTALS show potential  display  device  for  applications. However,  available for these applications  are  particularly those which exhibit a ferroelectric, chiral smectic A They  number of  typical ferroelectric  have been classified  is connected to the core R*=chiral  liquid crystals  into two types; type A unit by means  of  becoming  are  limited, C  listed  phase. in Table  in which the chiral unit  etherification  f-Ph-O-R*.  unit), and type B in which the chiral unit is joined to the  unit by esterification  f-Ph-COO-R*  or  -Ph-OCO-R*i.  core  1.  8  Table Type  1. Selected structures  of ferroelectric  liquid crystals  A  RO-Ph-OCO-Ph-O-CHjC^H^HjJCjH, RO-Ph-COO-Ph-0-CH,C*H(CH,pCH, R O - P h - N rrCH-Ph-O-CHjC'HCCHjJCjH, RO-Ph-CH=CH-COO-Ph-0-CH C«H(CH,)C H 1  J  .  j  RO-Ph-OCO-Ph-OCO-PH-O-CHjC-HCCHj^jH, RO-Ph-Ph-OCO-Ph-CHjCTiCCHjV^Hj Type B RO-Ph-Ph-COO-CH,C»H(CH )C H J  J  J  RO-Ph-Ph-OCO-C»H(CI)C H, 3  RO-Ph-COO-Ph-COO-CHjC'HCCHjJCjH, R O - P h - C O O - P h - C H = CX-COOCH C*H(CH,)C H . X = C N , C l . H. 3  1  J  R O - P h - C H = N - P h - C H =CH-COO-C*H(CH yC,H, }  RO-Ph-CH=CH-COO-Ph-COO-CH,C»H(CH,)C H 1  J  Where R = CnH2n + 1; Ph  = 1,4-substituted  • = chiral  phenyl  group;  center;  (The same notation also  is applied in subsequent  sections)  9  Examination ferroelectric  of  the structures  of  materials which typically  smectic phases shows that the optical  referred to as the chiral unit) is normally this position, it is relatively molecule  (hereafter  simply  exhibit  center (hereafter  at one end of the molecule. In  free to rotate independently  of the rest  referred to as the core unit) which  of  the  is also  rotating, and in particular to the highly sensitive polarizable central which contains  simply  core  the delocalized T T electrons . In this situation, the 11  contribution by the core to the dipole associated with the chiral center will be reduced  because the lateral dipole of  independently greatly  of the asymmetric  to the net resultant Spontaneous  property phases dipole  of  and therefore will not  contribute  dipole . 11  polarization is the second most  a spontaneous  moment, derived from dipoles  ferroelectric dissymmetry  important  polarization can be  freedom  rotation of the chiral center  whole. M o v i r g  polarization or  physical  in the orientation of  the chiral unit  increased considerably  closer  a direct  restricted rotation thus also strengthening the spontaneous  interaction  coupling  and  polarization.  with large spontaneous  14  the  in relation to the molecule as a  to the core creats  liquid c r y s t a l s " '  the  by restricting the  between the the chiral unit and the core unit via dipolar  Table 2 Ferroelectric  smectic  macroscopic  in the liquid crystal phase. The strength of  spontaneous of  rotating  a FLC, next to the transition temperature. Tilted chiral  possess  molecular  center  the core will be  polarizations  FLC  Ps(nc/cm»)  C H„-Ph-OCO-Ph-Ph-0-C^(CH,)C,H„  60  u  C,H,,-0-Ph-OCH,-Ph-COO-C H(CH,)C,H  99  ,  T  C H -0-Ph-Ph-OCH -Ph-COO-C«H(CH,)C,H, l  It  C,^ -0-Ph-Ph-OCH,-Ph-COO-C«H(CH )C H J  n  C H -0-Ph-Ph-OCO-C«HCIC«H(CH,)C H T  IJ  99  1  1  1  <  u  145 220  10  Type  B FLC's  generally  possess  higher spontaneous  polarization  type A  s y s t e m s . For instance, C,H OPhPhOCOC*HCIC*H(CH )CjH  highest  spontaneous  15  3  polarization known to date to the best  between the chiral unit and the adjacent and the less  internal rotation  of  and the core ferroelectric often  lost  adjacent  that the dipolar  unit can have detrimental phase. This  is especially  from the phase  polarization  of  to the  the type of  center  is  in the structure of the type  smectic  C phase around room  high spontaneous  polarization.  1.3 DESIGN  SYNTHESIS  AND  not only  with the strong polar  OF POTENTIALLY  exhibiting  by  groups B FLC's,  showing a wide range  temperature but also  is  "ideal" FLC's  attached, into the  producing a FLC series  the  positioned  those  thereby  of  chiral  Sm* C phase which  placing the chiral units, especially "right" location  core  in type B FLC's.  be possible to design the  11  the core unit  on the stability  diagram as the chiral  to the core . It may  our  interaction between the  effects  the  interaction  the chiral unit with respect  unit the greater will be the spontaneous Unfortunately, it seems  carbonyl group  exhibits  5  of  knowledge. It is then concluded that the greater the dipolar  than  of  chiral  extremely  FERROELECTRIC  LIQUID  CRYSTALS The  first  ferroelectric  requirement  phases  phases. Many  are  in general  strong terminal asymmetry  of  is to produce  studies  provided guidelines  in the synthesis  of  of  materials which  materials which exhibit tilted  numerous ferroelectric  liquid crystals  considered essential: (a) an alkyl-aryl—alkyl  smectic  have  for this initial operation . Three fundemental 11  possess  already  criteria  s y s t e m ; (b)  lateral dipoles; and (d) a chiral center which produces the phase, and produces the ferroelectric  11  properties. In  the  11  simpler terms, the design of a new potentially FLC is to develop the appropriate chiral and core units and then properly connect them together. The core units found in most known ferroelectric  liquid crystals  been well established in the past decade. The greater difficulty synthesizing new ferroelectric  liquid crystals now lies  have  in  in the preparation  of  the appropriate chiral units and their fusion with central core uniis in a way that the resulting molecules possess the necessary  liquid crystalline  properties. Relatively readily  available  derivatives  little investigation of new chiral units has occurred. S o optically active commercial compounds  have been successfully  well-established  core  and their  incorporated into almost  units.  For example one of the main precusors  is commercially  S(-)-2-methylbutanol which has been modified to suitable shown  all of the  available  derivatives  as  below."  These derivatives  have been used in almost all of the known FLC  structures. However, a disadvantage of those compounds  is the fact that  far,  12  the chiral  center  is not  polar  enough to  induce  very  high  spontaneous  polarizations. There acids  are a number  and several  L-lsoleucine,  for  have  active  and optically useful  since  chiral  centers  active  ferroelectric showing  liquid crystals  interest  utilizing new  to  for  those  Table s y s t e m . The  WORK  et a l .  16  17  -C^IHCJHJ  of  only  lowers the transition  acid  extremely  them possess  two  properties . 16  acid also  prepared from  used  containing  chiral  the  in synthesizing  because  many  the  of  only  of  the potential  alkyl  polarizable.  for  of  its great  variety  of  FLC  some  units  5  relationship  and to  was  units are used reported by  in the table was  used by  -C*H(CH )3  changes the phase diagram considerably. A  exploring  of  systems.  chiral  a new chiral center  temperature  the  (R» = chiral unit) is  because  in general  chiral  over  RO-PH-PH-OCO-R*  the group -C*HCIC*(CHj)C,H of  materials  units are more  RO-Ph-Ph-OCO-R*  a wide  how  insertion not  chlorine  but also  involving  and the rest  and Lesile . The unit  us not  of  corresponding  have been reported  successfully  CONCERNING  3 illustrates use  3-methyl  2-chloropentanoic  derived from  butanoic  that these  chiral units  general problems  active  crystals.  17  Studying the system great  liquid  amino  crystals .  is the fact  1.4 THE PREVIOUS  3-methyl  ferroelectric  acid has been  into  active  be reduced to the  2-chloropentanol  unusual  liquid  optically  incorporation  active  2-chloro-2-methyl  amino  available  converted to optically  3-methyl  The advantage above  for  acid, which could further  new ferroelectric  series  been modified  a l c o h o l " . Optically  Similarly, corresponding  commerically  instance, was  2-chloropentanoic optically  of  Yoshino Goodby  into the  completely  chiral  in this  smectic  but  chiral  also  C phase  13  emerges  as three  other  less  phase  temperature  Talbe  3. Phase transition  important  smectic  is decreased to near room of  liquid cvrsatlsff  phases  are lost  and the  temperature. C.H„-Q-Ph-Ph-OCO-R»  1  £L!  Phase transition (°C)  C-HCICniCCH^jH,  lso—66—SmA—53—Sm»C—*30—Cryst.  CnHCICjH,  Iso—115—SmA—96—Sm"F—93—Sm»G--7l—Sm«H  CHJC^CHJ^JH,  Iso  CHjCHjCn^CHjyCjH,  Iso—93—SmA—92JS-*Sm*G  As chiral  for  smectic  the phase  the non-chlorine C phase  diagram  noting that  similar  to the chiral  observed. The smectic  esters Sm"C  illustrates unit  1.5 THE PRESENT The original  containing esters  as the chain of  (n = 1, 2, 3) exhibit phase. It then  »Sm*G  is  of  17  such as  shortly after  is squeezed out  of  is lengthened. It is worth  importance  of  (n=3) in addition to the the carbonyl group  SmA  in relation  in type B FLC's.  WORK idea of  an epoxide our project  The proposed epoxide  phase  are no  C.H,v-0-Ph-Ph-COO-(CH,yiC»H(CHX,H,  that the direction  the present  chiral units such as the epoxide The use of  A  the chiral unit  (n = 1, 2) and S m ' G  less  in this table, there  study was to  unit into the system  unit" in a series  of  type A  incorporate of  some  polar  RO-Ph-Ph-OR*.  FLC's was  reported  started.  chiral units are the acetal unit, the diol  unit, the thiiran unit and the Mosher  unit, the  unit derived from the  so  it* Since there is a limited information available for a complete series of the listed esters, only the octyloxy homologue of those liquid crystal esters is given in this table. 1  14  Et, Et  J_(.' >-0-0- coc  E t  H  6  CnH2n+1  v ] ? coo-^-0"°" H  VV  C X 0 0 - Q - ^ - 0 - C n H 2 n +1  V V " '°-O-O"°C0  Pn-r>-coo  OCHj  CnH2n+1  CnH2n+1  15  called  Mosher  new chiral All  a c i d # . There J  of them have a polarizable stereocenter  of  reasons  for  proposing  3  :  }  the  rotation, which occurs  group be rigidly  chiral centers  polarizable. Especially  thiiran unit, the cancellation  associated with a  in the acetal  of  the two  of the proposed  unit, the epoxide  dipole  moments  in the 2-chloro-3-methylpentyl  in the diol unit, is eliminated  by the bond  chiral unit  those  of  the 2-chloro-3-methylpentyl  of  the chiral unit has a detrimental  units. It is known that the  ferroelectricity. in the case The  some  FLC's  factor  of  a large bulky  the molecular  dipole  intramolecular  motion  like C - 0 in favour  chiral  centers  is  units  is the same  important because  on the properties  introduction of the hydroxy  enlarge the temperature  of  see  if  the hydroxy  molecular may  of  as that  the the  length FLC's.  points with regard to the acetal and the  It is then interesting to  of the introduction  existence  new chiral  group. This  Furthermore, there are some  of  internal  maximized.  In addition, the length of  rings  unit and the  linkage between the two  to the the whole  aromatic  units  group and probably  a result, the polar contribution by the two is  chiral  due to  chiral centers. A s  diol  these  a chiral unit. In comparison with the chiral unit  -C*HCIC"H(CH )C H , each of  also  of  units.  tetrahedral  is more  are a number  range  such effect group  component  increase  of can be  applied  into the chiral  units.  of the acetal unit near  suppress the free  of the  group into the  of the  rotation and relative spontaneous  polarization. However, it has been known that such a bulky group  is not  desired  .  in terms  of the  introducment  of  liquid crystalline  phases.  This acid, usually served as a reagent to determine the enantiomeric excess of optically active alcohols, also was used mainly because there was no evidence that it has been used in the synthesis of any FLC's. J  Finally, those systems commercially  from two  are conveniently  simple  starting materials  2S,3S-dihydroxy-2-methylpentanoic S(-)-(a)-methyoxy-(o)-trifluoromethyl By analogy with similar expected to have chiral smectic higher spontaneous  polarization.  available  acid  11  synthetically  in optically  pure  and the Mosher  or  form acid (  acetic acid ).  molecules, those target phases  compounds  and also hoped to exhibit  are even  2. RESULTS  2.1  SYNTHESIS The  the two  OF NEW  synthesis  AND  COMPOUNDS  of the target  compounds  acid (hereafter  the diol acid) and the preparation of  reaction of  1,3-propandiol  resolving agent  and racemic  18  laboratory) gave  a solid  simple  ammonia  diol acids  (previously  from the  by  solution yielded the (-) diol  rotation  of  purity was  prepared  in our  salt which  decomposition  left  of  the optical  only the (-) diol The  acid was used  synthesis  4'-alkoxybiphenol. In practice, it was  choose  the appropriate  corresponding  base  sodium  ferroelectric of  far superior  hydride  liquid  was employed  found that the key  the desired phenolic for the conversion  of  materials  in preparation in applying  bromide  to sodium  in aqueous  hydroxide  of  this  to  the biphenol to the  methoxide  or  iodide  in methanol solution  tetrafuran solution. The isolated yields  17  of  crystals,  monoether was  In this case, sodium  in anhydrous  in  (ca. 77% ee).  the designed  alkoxide, which then reacts with an alkyl  give 4-alkoxybiphenol.  solution was  of  of  in the synthesis  conventional Williamson  method to the preparation  to  requirement  salts  (-) diol acid had a value  Because  purity  two  examined by the measurement  the two enantiomers. The  the  in the  acid and the (+) diol acid  (ca. 95% ee) and the ( + ) diol acid at [ a ] = + 11.3°  of  from  those  [a] =-14.0°  of  starting  salt which precipitated  [(-)amine-( + )acid]  filtration followed  good yields. The optical optical  referred to as  D-(-)-threo-2-amino-(4-nitrophenyl)-  [(-)amine-(-)acid]  solution and an oily  solution. A by  acid and  simply  4'-alkoxybiphenol  of  4,4'-biphenol.  The  reaction  started with the resolution  enantiomers, (+)2R,3R-dihydroxy-2-methylpentanoic  (-)2S,3S-dihydroxy-2-methylpentanoic  material  DISCUSSION  or are  in  Synthetic  Routo  m. *-pontanor>«, HOTt. benzana, raflux Jhr; b. HOH. DCC. DMAP. 18hr; C 6N HCI.dloxane-H,0. reflux Ihr;  d. TsCI. pyridine, 2 days; e. (|Et)^. 2 dayo; f. CP,COOH, 3-methylbeniothiarole-2-thione, reflux 18 nr.  19 a range of  50-60% for the preparation of 4'-heptyloxybiphenol  to  4'-dodecyloxybiphenol # . 3  The DCC  (N,N-dicyclohexyldiimide) esterification  above 4'-alkoxybiphenols melting point esters good  and the Mosher  (hereafter  simply  reactions  of  the  acid yielded a new series  referred to as the  Mosher  of  low  esters) in  yields. The two  hydroxy  groups  etherification with 3-pentanone good yield. This with acetone  protection  was  of  (—)—diol  in acidic  acid J. were protected  by  solution to afford the acetal 2 in  reaction did not succeed when acetel  formation  attempted.  The esterif ication out by a conventional  of  DCC  (4-dimethylaminopyridine)  2 and 4'-alkoxybiphenol coupling reaction  as  was  successfully  in the presence  a catalyst, to produce  of  compound  carried  DMAP  3 in high  yields. The hydrolysis  of  3 in a dioxane  dilute  compound 4 which could also be prepared diol acid J. and 4-alkoxybiphenol.  A  aqueous  via direct  nucleophilic  alcohol, the -OH  and thus more  species, the phenol  DCC  of  phenol  group of 4-alkoxybiphenol  reactive  coupling  high yield for the direct  should not be unreasonable. Because the Ka value than that for  solution  HCI  to the  intermediate  is  coupling could only  be achieved  of  the  coupling is  10  5  higher  more  acylpyridinium  should be able to compete with the alcohols  Unfortunately, the direct  yielded  in  in J..  inconsistent  yields of 20-50%.  'The lower yields for 4'-propyloxybiphenol to a less efficient work up procedure.  to 4-hexyloxybiphenol  were due  20  (Reproduced from The three  step procedure  yield 45%) was generally The  reference  19)  (protection, esterification preferred to the direct  dehydration of the diol  ester 4 was  reaction of 4 and p-toluenesulphonyl DMAP  and pyridine  solution, with subsequent  yield the desired compound be the same capable of  chloride  as that of  and deprotection, overall  esterification. accomplished  in a methylene  by the chloride,  treatment with triethylamine  5 in 50% yield. The optical purity  of  5 should  the starting material ±, since there are no  causing the racemization  in the above  to  steps  procedure.  The next task was to replace the oxygen atom of the epoxide  in 5  with the sulfur atom and to prepare the final target compound 6. The procedure" chosen involved the use of trifluoroacetic the target  2-methylbenzothiazole  2-thione  acid. The reaction should again retain the optical purity  compound 6. It is  both stereocenters  interesting to note that the configuration  attached to the former epoxide  are cleanly  and of of  inverted. The  21  double  inversion can be explained by the following  (Reproduced from In a model was  converted to  its thiiran counterpartner  condition  shift  unique fingerprint The use of depended  2-methyl  at room temperature  5 (50% yield) however  of the above  to  identify  each compound  compounds  of  largely on the relationships  between chemical  shifts  l  groups  chemical  shift of the tertiary proton  the tertiary  group, the value  increases, by up to 0.31 ppm  attributed to the long-distance  has  and structural is  ester, as seen in Table depends  attached to the carbonyl groups. By replacing the  proton  is apparently  constitution  in these esters  shift of the tertiary proton also  group with the 4-alkoxybiphenyl  a  concerned.  higher for the thiiran ester than for the epoxide  of  1 to 6 provide  the determination  of  more  found that the »H  H nmr spectra for  The magnitude  in 75%  required slightly  experiments, it was  of the single hydrogen of  environment". The chemical  type  methylpentanoate  (refluxing).  During the course nmr chemical  10  20)  study, racemic 2R,3R-epoxy  yield. The conversion of rigorous  reference  mechanism .  of the chemical in the epoxide  deshielding effect  4.  on the  methyl shift  of  esters. This by  the  22 Table  3 *H nmr  and its  chemical  shift  of  the tertiary  proton  in the thiiran ester  precursors  COMPOUND  CHEMICAL  SHIFT  SIGNAL  SHAPE  (ppm> CjH,  C,H,  o o X  I  H-C»—C*-COOPhPhOC,H„  3.92  double  3.45  dd  3.36  triplet  3.70  dd  3.53  triplet  3.05  triplet  3.56  dd  doublet  C J H J CH)  OH  OH  t i - C * — C*-COOPhPhOC,H  I  CJH,  * I  u  CH,  tl-C •— C •-COOPhPhOC,H 1 1 C,H, CH,  lJ  t l - C * — C*-COOPhPhOC H„ 7  ^I^J  •  OH  I  CH,  OH  t  HTC»—C»-COOCH,[a] CjH.CH,  t l - C * — C»-COOCH,[a] C^CH,  tl-C*—C»-COOCH, C,H, CH, [a]. Excerpted f r o m  G.S. Bates' P h D  thesis, University  of  Alberta  (1976).  23  Figure 1 Partial *H nmr spectra of (-)-2-methyl 2R.3S-epithio-4'-heptyloxybiphenyl pentanoate (400MHz, CDCI,): (1) normal spectrum; (2) spectrum with irradiation et 3.70 ppm; (3) spectrum with irradiation at 1.21 ppm  24  4-alkoxybiphenyl Another  group.  interesting aspect  that the methylene signals was  adjacent  of  !  H nmr  to the only  confirming that those  protons  tertiary proton gave two  are not chemically  verified by the decoupling experiments  irradiations  are respectively  spectrum of the thiiran ester  (see figure  1). If the  applied at the chemical shifts  peaks of  p p m , respectively) will collapse  the two into less  protons  3.70 ppm  Ha  on these two  is shielded  protons. A s  seen  by the thiiran ring resulting  being 0.32 ppm higher than for  are  and  coupled  1.65-1.74 and  multiple peaks  It is expected that the shielding effect is different  (at  multiple  equivalent, which  1.21 ppm of the two adjacent protons the methylene protons with, the two multiple  is  1.96-2.07  accordingly.  by the ethylene  in the following in the chemical  sulphide  ring  conformation. shift  for  Hb  Ha.  Me  In the case be  of  the epoxide ester, the corresponding two protons  distinguished.  could not  25  22  IDENTIFICATION  OF NEW LIQUID  CRYSTALS  By using a polarizing microscope compounds  described  to  which are the liquid crystals  identify  which are capable  in the proceeding  of  being  Unfortunately, it was  coupled with a heating stage, the section were studied in an attempt and whether they  possess  phases  ferroelectric. observed that none of  the liquid crystal, although the melting points  the Mosher  are generally  esters  around  was  room  temperature.  150-r  —.  0 I  i 6  i  2  4  i 6  ,  1  i  10  12  N u m b e r of C a r b o n s (n) It was  disappointing to  the dodecyloxy epoxide esters  homologues  of  did not exhibit  observe that the n-heptyloxy, the the acetal esters, the diol  and the  any liquid crystal phases at all. However, it  was pleasing to note that all five compounds ( M E A O B P - S - 7 , 8, 9, 10, 1 2 # \ M E A O B P 2,3-epithio  esters  n-decyloxy,  of  the thiiran esters  is the abbreviation  of  2-methyl  4'-alkoxybiphenyl£entanoate) were indeed liquid crystal  Identification of observations  the phase types was made by  of the textures  exhibited by four of  prepared  materials.  microscopic  the thiiran  esters  #*The n-dodecyloxy homologue also was prepared and preliminarily measured of the phase temperature, showing similar phase sequence to the decyloxy.  26  I  27  Figure 3 Chiral  smectic C phase of  biphenyl pentanoate  (X200)  (-)-2-methyl  2R,3S-epithio  4'-decyloxy-  28  ( M E A O B P - S - 7 , 8, 9  10). Typically  for  phase  the  liquid on cooling. The n-heptyloxy  appears  n-nonyloxy A  phase  desired  from  members  or the chiral  isotropic  inclusive  isotropic  smectic  the n-heptyloxy  exhibit  B phases  on cooling  liquid. But the decyloxy  C phase  homologue  member  on cooling directly  from  shows  the  the  isotropic  MEAOBP-S-7  |  64—*SmA  MEAOBP-S-8  |  62.6—•SmB  49—*+C  MEAOBP-S-9  I  62.0—•SmB  55—*C  MEAOBP-S-10  I  62—*»SmC»  show A not  a crystal  like  and B. Since be FLC  liquid crystal  they  do not  ("monotropic"  is  means  measurement  of  the  It is  phase  possess  a potentially  that this  the  chiral  ferroelectric  rare that the  smectic  A  recently  reported that the  or  isotropic  cholesteric  is only  polarization  property  a compound  from  Like exhibit  shows  only  smectics  phases, they  of  this  shows  ferroelectric  shown  is required to  will  prior  sequence many  a variety  A  finally  the chiral  to smectic  smectic  the FLC's  C phase exhibit  directly either  C phase. However, it was  compound"  (isotropic  liquid crystal of  crystal  compound.  liquid. Virtually, all of phase  liquid  on cooling).  C^Hjj-O-Ph-COO-Ph-COO-CCH^C'HCCHjXCHjJjC^HtCHj^H, phase  57—  and M E A O B P - S - 9  smectic  monotropic  phase  spontaneous  cooling  same  liquid.  47—e-C  and M E A O B P - S - 7  any  the  materials.  MEAOBP-S-10  determine  60—SmB  materials, M E A O B P - S - 8  liquid crystal  to  either  Transition Temperatures ( ° C )  these  A  from  L'Quid Crystals  Of  the  different  liquid to smectic families, this  phases  of  exhibits  the  C).  family  dependent  also  of the  liquid  crystals  length of  the  long  29  chain attached to the core aromatic By  comparing the liquid crystal thiiran esters to the other  non-liquid  epoxide esters, it has been seen how difficult  discover new esters  liquid crystal  polarizability  smectic presence  of  esters  in practice  materials. The only essential  and the thiiran esters  in the thiiran esters  of the more polarizable thiiran  In comparison with the FLC's  is the slight  difference  thiiran ester is not  is quite  large  3, especially  the  group, no chiral  obtained by formulating for  stable  smectic  instance  esters  smectic range  (15 degree range) and the  far above room temperature. A s  previously, thermodynamically  of  is ascribed to the  is observed by rising the temperature, but the temperature  temperature also  difference  unit.  in Table  derived from the 2-chloro-3-methylpentyl  to  epoxide  the two three membered rings. The stabilization  liquid crystal phases  n-decyloxy  three  materials. It was surprising that the  are not the liquid crystal  between the epoxide of  rings.  A  and  of  the  transition  mentioned  and chiral  MEAOBP-S-7  C phase  C phases  may  be  MEAOBP-S-10  compounds.  2.3  CONCLUSION A  new family  of  potentially  been prepared by utilizing a novel  ferroelectric  liquid crystal  materials  chiral unit containing a thiiran  has  unit.  Replacing the thiiran unit with an epoxide unit, i.e., substituting an oxygen atom for the sulfur atom of liquid crystalline  phases.  the new liquid crystals  above, eliminated  any  3. EXPERIMENTAL  3.1  GENERAL All  reactions were carried out under a nitrogen  Tetrahydrofuran was  freshly  distilled from  a nitrogen atmosphere. Dichloromethane calcium hydride hydride was  obtained  All  solvents  apparatus  from Aldrich and used without  heating system  accurate  whole  measurements  State  University. Proton  400MHz  were  magnetic  ISO  was  Pol Mircoscope  coated with a  lab-made  phase  photos were taken using  1600 or Kodak  ISO  1000 color  resonance  spectra were obtained using  reference. Chemical  shift  Specific  were  using a Perkin-Elmer  model  obtained using a Kratos  rotations were  at the sodium d-line performed  films. The  determined  mass  using a Perkin-Elmer  at room temperature. Elemental  at the Microanalytic  Laboratory, Department  30  reported  on  as a liquid film or in  1710 Fourier  MS-50  WH-400 solution with  was  spectrophotometer. Both Low resolution and high resolution measurements  Nikon  made by Barbara Frisken (Physics, UBC) at Kent  as an internal  solution  point  liquid crystals  the ppm scale. Infrared spectra were recorded either chloroform  purification.  melting  spectrometer. Spectra were run in deuterochloroform  tetramethylsilane  other  of  to 0.1 ° C . The  camera and using Fuji  A l f a . All  use.  uncorrected. Identification Optiphot  from  Sodium  further  melting points were taken on a Gallenkamp  and were  ketyl under  distilled  in mineral oil from  were distilled before  obtained using a Nikon  FA  and pyridine were  in 50% dispersions  reagents were  Initial  benzophenone  under nitrogen when used as reaction solvents.  obtained  extraction  sodium  atmosphere.  mass spectrometer.  241  analyses of  Transform  MC  polarimeter  were  Chemistry,  31  University  of  Merck analytical were  British  Pre-Coated  thin  used The  multiplicity double, t  Columbia.  layer  for  following  abbrieviations  = triplet, m  Alkylbromide solution  —  cooled  to  multiplet, dd  combined  organic  dried  mixture  used to  the  (n-Bu) NI 4  reaction  extract  solution was NaCI  gel, eluting with  60-120  c a n be  description  for mesh  =  of  the  signal, d  =  doublets.  dissolved  in a s o l u t i o n  solution was  refluxed  added  into  of  for  10min,  the  refluxing  solution  was  then r e f l u x e d  poured  into  aqueous  the o r g a n i c with  compounds  saturated  (1x50ml) and water  dialkoxy, monoalkoxy  compounds  Gel  of  (0.90g) w e r e  washed  solution  i n the  doublet  M g S O , and then evaporated  containing  The three silica  over  BDH silica  used  PROCEDURE  t e m p e r a t u r e , a n d next  was  60F-254 were  spectrum: s  =  (9.3g, 5 0 m m o l ) w a s  p o r t i o n . The  (3x30ml), saturated was  GENERAL  ( 5 0 m m o l ) and  room  1 0 0 m l ) . Ether  »H n m r  (0.50M, 100ml). A f t e r  in one  Gel  are u s e d  in the  3.2 4 ' - A L K O X Y - B I P H E N O L :  MeONa/MeOH  silica  chromatography.  each signal  4,4-Biphenol  sheets  chromatorgraphy, while  column  of  TLC  separated  to  by  dichloromethane. (See Table  solution  to  afford  and unreacted  5)  (1N,  solution  (1x50ml). This  using column  3 hr,  (3x100ml). The  NaHCO,  dryness  derivatives  HCI  for  solution the  crude  biphenol.  chromatography  on  32  Table 5; 4'-Alkoxybiphenols  by alkylation of  4.4'-biphenol  R  YieldfSA  mx>/°C^  HHnmr fpprrA  C,H,  21  176-177  7.44(t,  4H). 6.96(d. 2H). 6.88(d, 2H),  3.96(t,  2H), 1£3(m=6. 2H), 1.06(t, 3H) C H, 4  24  171-172  744(d, 2H). 7.38(d, 2H), 6.93(d. 2H), 6.90(d, 2H),  3.99(t,  2H),  1.78(m=5,  2H),  1.5l(m=6,  2H), 1.00(t. 3H) CH,,  38  157-158  7.44(t.  4H),  6.95(d. 2H), 6.88(d, 2H),  3.97(t,  2H), 1.79(m=5, 2H). 1.34-1.53(m. 4H). 0.93(t, 3H) C H„ 4  43  169-170  7.44(d, 2H), 7.38(d, 2H), 6.93(d, 2H). 6.90(d, 2H), 3.98(t, 2H), 1.80(m=5. 2H),  1.44-1.53(m,  2H). 1.32-1.40(m, 4H), 0.92(t, 3H) C H 7  1 4  55  148-149  7.43(t.  4H). 6.94(d,  2H),  1.80(m=5,  2H),  6.88(d.  2H),  2H),  3.98(t,  1.41-1.5l(m,  2H).  1.26-140(m, 6H). 0.89(t, 3H) C,H„  51  160-161  7.45(d, 2H).  2H). 7.40(d. 1.80(m=5.  2H),  6.93(t,  2H),  4H),  3.99(t,  1.43-1.52(m,  2H),  1.25-142(m, 8H), 0.90(t, 3H) C,H  l t  49  143-144  745(d, 2H), 7.40(d, 2H). 6.96(d, 2H), 6.93(d, 2H), 3.98(t, 2H). 1.80(m=5, 2H),  1.40-1.50(m,  2H), 1.24-140(m, 10H), 0.89(t. 3H) C H„ I t  56  139-140  7.45(d. 2H), 7.40(d. 2H). 6.95(d. 2H). 6.93(d, 2H). 3.99(t, 2H). 1.80(m=5, 2H).  1.41-1.51(m.  2H), U 4 - 1 . 4 0 ( m , 12), 0.88(t. 3H) C„H„  60  160-161  7.44(d.  2H),  6.93(d,2H), 1.40-1.5l(m, 3H)  7.40(d,  3.98(t, 2H),  2H),  2H),  6.96(d.  2H),  1.80(m=5,  2H),  1.24-1.40(m,  16H).  0.88(t,  33 3.3 (•-Y2S.3S-DIHYDROXY-2-METHYLPENTANOIC  ACID  The procedure used was analogous to that of B e r g l ' s o n " . Finely ground racemic acid (3.24g, 21.2mmol) and 1-(4-nitrophenyl)-  1,3-propanediol  D-(-)-threo-2-amino  (4.5g, 21.2mmol) were mixtured in ethanol  (15ml). The s o l i d dissolved on heating. The solution was then left to stand at room temperature for  18 hr, and the precipitated salt was collected and  recrystallizad from ethanol to give 3.4g of the [(-)base-(-)acid] salt. The salt was then decomposited by using aqueous (40ml). The mixture was filtered to recover  10% ammonium  1.4g of optically  hydroxide active  (-)amine. The filtrate was acidified to pH 1 with aqueous 2N HCI and continuously extracted with ether for 24 hr to give  1.2 g (70.5%) of  (— )dioI acid. Recrystallization from ethyl acetate gave  crude  1.15 g of the pure  product. m.p.(°C): 150-151. [c] =-14.0° 23  (c 3.53, H 0 , 95% ee). 2  «H nmr (CDCI ) in p p m 3  :  0.97 (t, 3H); 1.39 (s, 3H); 1.50 (m=5, 2H); 3.25 (dd,  1H). In addition, the ( + ) - d i o l acid ([o]  = +11.3°, c 4.43, H 0 , 77% ee) 2  was also obtained from the mother solution via the same procedure in 68% y i e l d and  1.5 g of optically active (-)amine was recovered.  34  3.4 3-PENTANONE  ACETAL  OF  (-V2S.3S-DIHYDROXY-2-METHYLPENTANOIC  ACID  (-)-2R,3R-Dihydroxy-2-methylpentanoic p-tolunesulphonic  acid (0.l47g) were dissolved  pentanone-benzene water-extraction solution was yellow  oily  (1:1, 60ml). The  apparatus  cooled  1.61g  mixture was then heated  of  in a  until the solution turned yellow. The  mixture, which was  oil  into a mixed solvent  reaction  to room temperature, and next evaporated to give a  gel, eluting with a solvent yellowish  acid (1.47g, 10mmol) and  of  purified by column chromotography ethyl acetate-petrolum  ether  on  silica  (1:4) to afford  (yield 75%). The structure was confirmed  by  'H nmr  spectrum. »H nmr  (CDCI ) in ppm: 9.65 (s, IH); 3.88 (dd, 1H); 1.69-1.87 (m, 6H); 3  (s, 3H); 1.06  (t, 3H); 0.99 (t, 3H); 0.92 (t, 3H).  ir (CHCI ): 1747 cm" . 1  3  3.5 3 - P E N T A N O N E  ACETAL  OF  (-V-2-METHYL  2S.3S-DIHYDROXY-  4'-HEPTYLOXYBIPHENYLPENTANOATE  Eu Et  ..C00-Q-O-6-CnH2n 1 +  1.56  a  35 3-Pentanone  acetal  of  (-)-2S,3S-dihydroxy-2-methylpentanoic  (2.l6g, 10mmol), 4-heptyloxybiphenol N.N'-dicyclohexylcarbodiimide (I.Ommol) were  room temperature  for  (3.13g, ll.Ommol),  (225g, 11.0mmol) and  mixed in CHjCI  (20ml). The  2  18 hr. The  the solvent  >H nmr  solution was  (1x50ml), 5% acetic anhydrous  stirred at  urea was acid MgS0  solution 4  evaporated to produce the crude ester. The crude product  dichloromethane  m.p.(°C):  mixture  (2x50ml), dried over  further purified by column chromatography  ether gave  4-dimethylaminopyridine  precipitated N.N'-dicyclohexyl  filtered and the filtrate washed with water (2x50ml), and again with water  acid  to give a yellowish  pure solid  and was  on silica gel, eluting with  solid. Recrystallization  from  petroleum  3.60g (yield 80%).  71-72. (CDC!,) in ppm: 7.53  (d, 2H), 7.47 (d, 2H), 7.14  3.99 (t, 2H), 3.92 (dd, 1H), 1.92 (m=5, 2H), 1.80  (d, 2H), 6.96 (d, 2H),  (m=5, 2H), 1.68-1.80 (m, 4H),  1.67 (s, 3H). 1.28-1.50'(m, 8H), 1.13 (t, 3H), 0.92-1.13  (m, 6H), 0.90 (t, 3H).  ir (CHCI,): 1748 cm- . 1  exact  mass  for  3.6 (-V2-METHYL  This ester  CJOH^OJ:  A ; 3-Pentanone  4'-heptyloxybiphenyl of  482.3023  2S.3S-DIHYDROXY-4'-HEPTYLOXYBIPHENYLPENTANOATE  can be prepared by two  Method  solvent  cacld 482.3021, found  pentanoate  H,0-dioxane  acetal  methods. of  (-)2-methyl  (1.2g, 2.5mmol) was  (1:5) (60ml) and a solution  2S,3S-dihydroxy dissolved fo  in a mixed  2N HCI (2ml) was  36  added in one portion. After solution was  (3x50ml). The combined organic  and evaporated to dryness  4  purified by column chromatography  layer was dried over  extract  anhydrous  on silica gel eluting with from ethyl acetate to  give  0.73g (yield 70%).  Method B; (-)2S,3S-dihydroxy-2-methylpentanoic 0.5mmol), n-heptyloxybiphenol  (156mg, 0.6mmol),  (112mg, 0.6mmol), and 4-dimethylaminopyridine dichloromethane for  1 hr, the  to produce the crude ester, which was  dichloromethane, followed by recrystallization pure ester  refluxed for  cooled to room temperature and diethyl ether used to  the solution MgjS0  the mixture solution was  (5ml). The  18 hr. The precipitated  filtrate washed with water again with water  mixture  N,N-dicyclohexylidimide (O.lmmol) were mixed  solution was stirred at room  N,N-dicyclohexyl  urea was  (2x5ml), 5% acetic  (2x5ml), dried over  give the crude product. The  acid (73.5mg,  MgS0  4  in  temperature  removed and the  acid solution  (1x5ml), and  and evaporated to dryness  purification was the same  as Method A .  to  (yield  20-50%). >H nmr (CDCI ) in ppm; 7.56 (d, 2H), 7.47 (d, 2H), 7.14 (d, 2H), 6.96 (d, 2H), 3  3.99 (t, 2H), 3.68  (dd, 1H), 1.80 (m=5, 2H), 1.84 (s, 3H), 1.50-1.65 (m, 2H),  1.40-1.50 (m, 2H), 1.28-1.40 (m, 6H), 0.89 (t, 3H). mp.(°C):  113-114.  ir (CHCI,): 1747 [a]  =  exact  -0.5° mass  mp.(°C):  1  (c 2.10, CHCI,).. for C H 0 s : cacld 414.2397, found 414.2394. 25  microanalysis  (-)2-Methyl  cm .  for  34  C H 0 j : calcd C: 72.42, H; 8.27; found C: 72.50, H: 8.33. 35  34  2S,3S-dihydroxy-4'-decyloxybiphenyl  121-122.  pentanoate  37 »H n m r : 7.56  (d, 2H), 7.47  (d, 2H), 7.14  3.68  (dd, 1H), 1.80  2H),  1.28-1.40 ( m , 12H), 0.89  ir  (CHCI ):  1747  3  [o] = exact  -0.5° mass  microanalysis  m.p.(°C):  (m,  (t, 3H).  Cj.H^Oj: cacld  456.2865, f o u n d  Ci,H Oj: calcd  456.2866.  C : 73.65, H: 8.83; f o u n d  4 0  2S,3S-dihydroxy-4'-dodecyloxybiphenyl  C : 73.68, H: 8.91.  pentanoate  118-119. (d, 2H), 7.47  (dd, IH), 1.80  2H),  128-1.40  (CHCI ): 3  (d, 2H), 7.14  ( m = 5 , 2H), 1.84  ( m , 14H), 0.89  1747  (d, 2H), 6.96  (s, 3H), 1.50-165  (d, 2H), 3.99  (t, 2H),  ( m , 2H), 1.40-1.50  (m,  (t, 3H).  cm- . 1  = - 0 . 5 ° (c, 3.01, CHCI,).  [a] exact  mass  for  microanalysis  C, H O : cacld  for  0  4 4  5  C H O : J 0  (+ Y2S-METHYL  4 4  }  4-dimethylaminopyridine (414mg, O.lmmol) reaction  484.3177, f o u n d  calcd  484.3175.  C: 74.33, H; 9.16; f o u n d  C : 74.26, H:  9.27  2S.3R-EPOXY-4'-HEPTYLOXYBIPHENYLPENTANOATE  4-Toluenesulphonyl  The  (s, 3H), 1.50-1.65 ( m , 2H), 1.40-1.50  1  3.68  3.7  (t, 2H),  cm" .  for  »H n m r : 7.56  ir  (d, 2H), 3.99  (c 2.88, C H C I , ) . for  (-)2-Methyl  ( m = 5 , 2H), 1.84  (d, 2H), 6.96  chloride  (50mg) were  in a n h y d r o u s  mixture  was  (3l8mg, 0.15mmol) added  into  and  a solution  pyridine-dichloromethane  stirred  at  room  temperature  of  (1:1 for  48  (-)diol  4 m l ) at hr.  ester 0°C.  38  Distilled triethylamine solution, which  immediately  room temperature  for  (2ml) was then added into the  turned a red color. The reaction was stirred at  an additional 48 hr. The reaction was  adding cold 6N HCI solution extremely seven. The  solvent  (3x10ml), dried over  by  became  and the  was washed with brine (1x20ml), and water  M g S 0 . The solvent 4  was  removed to afford  I58mg pure product  [o]  (c 2.46, CHCI,).  a mixture,  on silica gel with  as eluent, followed by recrystallization  ether to give +1.3°  quenched  until the pH value  then purified by column chromatography  dichloromethane  =  slowly  solution was then extracted with dichloromethane  combined organic  which was  reaction  from  petroleum  (yield 50%).  m.p.(°C): 89-90. >H nmr  (CDCI,) in ppm: 7.46 (d, 2H), 7.48 (d, 2H), 7.14 (d, 2H), 6.96 (d, 2H),  3.99 (t. 2H), 3.36 (t, IH), 1.80  (m=5, 2H), 1.70 (m=5. 2H), 1.67 (s, 3H),  1.40-1.50 (m, 2H), 1.24-1.38 (m, 6H), 1.15 (t, 3H), 0.89 (t, 3H). ir (CHCI,): 1753 c m - . 1  exact  mass  for  microanalysis  C j H j 0 : cacld 396.2292, found  for  2  3  4  396.2293.  C H , , 0 : cacld C: cacld C: 75.73, H: 8.13, found C: 75.60, J}  4  H: 8.28.  (+)2-Methyl [a]  =  +1.3°  2S,3R-epoxy-4'-decyloxybiphenyl-pentanoate (c 3.39, CHCI,).  mp.(°C): 85-86. »H nmr in ppm; 7.45 (d, 2H), 7.48 (d, 2H), 7.14. (d, 2H), 6.96 (d, 2H), 3.99 (t, 2H), 3.36 (t, 1H), 1.80 (m=5, 2H), 1.70 (m=5, 2H), 1,67 (s, 3H), 1.40-1.50 (m, 2H), 1.24-1.38 (m, 12H), 1.15 (t, 3H), 0.89 (t, 3H). ir (CHCI,): 1753 cm- . 1  39  exact  mass  for C , H , 0 : cacld 438.2760, found 438.2765. 2  3  4  microanalysis  for C , H , 0 : cacld C: 76.68, H: 8.73; found C: 76.55, H: 8.80.  ( + )2-lvlethyl  2S,3R-epoxy-4'-dodecyloxybiphenyl-pentanoate  [o]  =  +1.3°  2  3  4  (c 1.98, CHCI,).  mp.(°C): 88-89. >H nmr  in ppm; 7.45  (d, 2H), 7.48 (d, 2H), 7.14  2H), 3.36 (t. IH), 1.80  (m=5, 2H), 1.70 (m=5, 2H), 1.67 (s, 3H), 1.40-1.50 (m,  2H), 1.24-1.38 (m, 16H), 1.15 ir (CHCI ): 1753  cm .  exact  C H 0 :  for  microanalysis  3.8 2-METHYL  (t, 3H), 0.89 (t, 3H).  1  3  mass  (d, 2H), 6.96 (d, 2H), 3.99 (t,  3 C  for  4 2  cacld 466.3072, found 466.3071.  4  C H , O : calcd 30  4  C: 77.21, H; 9.07, found C: 77.10, H; 9.11.  4  2S.3R-EPITHIO-METHYLPENTANOATE  OOCH,  To  a solution  of  racemic  2-methyl  2R,3S-epoxy  methylpentanoate  (144mg, 1mmol) and N-methylbenzothiazole-2-thione  (220mg, 1.2mmol)  ml dichloromethane  of  was  dropwise  (140mg, 1.2mol) in dichloromethane stirred at room temperature dryness. The silica  product  was  for  added a solution  (3 ml) at 0 ° C . The  18 hr. The  purified twice  gel, eluting with dichloromethane  dichloromethane-petroleum  ether  by  in 2  trifluoroacetic  acid  mixture was  further  solution was then evaporated column  chromatography,  and a mixed solvent  (3:7), respectively, to afford  on  of neat  liquid  to  40  171mg  (yield  70%).  >H nmr  (CHCI,) in  (s, 3H);  1.58-1.72  ir  (CHCI,):  exact  3.9  1724  mass  for  ppm; (m,  3.77  IH);  (s, 3H); 3.56  1.18  (dd,  1H);  1.87-2.02  (m,  1H);  1.76  (t, 3H).  cm->. C,H  (-Y2-METHYL  1 2  0 S:  cacld  2  160.0555, f o u n d  160.0554.  2R.3S-EPITHlQ-4'-HEPTYLOXYBIPHENYLPENTANOATE  fTvlEAOBP-S-7^  CnH2n + 1  To  a solution  of  ( + )2-methyl  2S,3R-epoxy-4'-heptyloxybiphenyl-pentanoate N-methylbenzothiazole-2-thione(55mg, dropwise  added  a solution  dichloromethane refluxed which with  for  was  purified  mjD.(°C): =  >H n m r  temperature.  twice  53mg  by  and  (3:7), r e s p e c t i v e l y . pure  0.3mmol)  trifluoroacetic  18 hr. E v a p o r a t i o n  (20:1) g a v e  3.99  room  dichloromethane  ether  [o]  at  of  a  (100mg, 0.25mmol)  of  the  column mixed  The  2ml  solution  gave  the  chromatography, of  from  dichloromethane  (35mg, 0.3mmol)  reaction  solvent  (yield  acid  solvent  Recrystallization product  in  and  was  crude  on  silica  in  was 3ml  next product, gel,  eluting  dichloromethane-petroleum petroleum  ether-ethyl  acetate  51%)  67-68.  -1.2°  (c  (CHCI,)  1.80, in  (t, 2H), 3.70  1.65-1.74  (m,  1H),  CHCI,).  ppm: (dd,  7.25  1H),  1.41-1.51  (d, 2H), 7.47  1.96-2.07 (m, 2H),  (m,  (d, 2H), 7.12 IH),  1.28-1.32  1.89  (d, 2H), 6.95  (s, 3H),  (m, 6H),  1.80  1.21  (d, 2H),  (m=5,  2H),  (t, 3H), 0.90  (t,  41  3H). ir (CHCI,): 1725 c m - . 1  exact  mass  for  microanalysis  C H JOJS: } J  for  3  calcd 412.2064, found  CJJHJJOJS:  calcd  412.2066.  C: 72.96, H : 7.59, S: 7.79; found C: 72.91,  H: 7.43, S:  7.88.  (-)2-Methyl  2R,3S-epithio-4'-octyloxybiphenylpentanoate  m.p.(°C): [a]  (MEAOBP-S-8).  63-64.  = -1.2°  (c 2.32, CHCI,).  ir (CHCI,): 1725 c m - . 1  exact J  mass  H nmr  for  C H„0,S: J 6  calcd 426.2220, found  in ppm: 7.53 (d, 2H), 7.47  2H), 3.70  (d, 2H), 7.12  (dd, IH), 1.96-2.07 (m, IH), 1.89  426.2215. (d, 2H), 6.95  (s, 3H), 1.80 (m=5. 2H), 1.65-1.74  (m, 1H), 1.41-1.51  (m, 2H), 1.28-1.32 (m, 8H), 1.21  microanalysis  C H, 0,S:  for  J6  4  calcd  (d, 2H), 3.99 (t,  (t, 3H), 0.90 (t, 3H).  C: 73.22, H: 8.04, S: 7.50; found  C: 73.11,  H: 7.90, S: 7.30.  (-)2-Methyl m.p.(°C): [a]  2R,3S-epithio-4'-nonyloxybiphenylpentanoate  (MEAOBP-S-9)  62.5-63.5.  = -1.2°  (c 3.07, CHCI,).  ir (CHCI,): 1725 c m - . 1  exact  mass  for  microanalysis H;  8.13, S:  >H nmr  C , H , O , S : calcd 440.2376, found 440.2377.  for  t  7  C H j 0 , S : calcd J 7  C: 73.59, H : 8.24, S: 7.28; found C: 73.43,  7.12.  in ppm: 7.52  2H), 3.70  6  (d, 2H), 7.47  (d, 2H), 7.12 (d, 2H), 6.95  (dd, 1H), 1.96-2.07 (m, 1H), 1.89  (d, 2H), 3.99 (t,  (s, 3H), 1.80 (m=5, 2H), 1.65-1.74  (m, IH), 1.41-1.51 (m, 2H), 1.28-1.32 (m, 10H), 1.21  (t, 3H), 0.90  (t, 3H).  42  (-)2-Methyl  2R,3S-epithio-4'-decyloxybiphenyl-pentanoate  (MEAOBP-S-10).  mp.(°C): 75-76. [a]  = -1.2°  »H nmr  (c 2.11, CHCI ). 3  in p p m : 7.52  (d, 2H), 7.47 (d, 2H), 7.12  (d, 2H), 6.95 (d, 2H), 3.99 (t,  2H), 3.70 (dd, 1H), 1.96-2.07 (m, IH). 1.89 (s, 3H), 1.80 (m=5, 2H), 1.65-1.74 (m, 1H), 1.41-1.51 ir  1725  (CHCI3):  exact  mass  for  microanalysis H  :  8.59, S:  (m, 2H), 1.28-1.32 (m, 12H), 121  (t, 3H), 0.90 (t, 3H).  cm- . 1  C„H„0jS:  for  cacld 454.2532, found 454.2530.  C „ H 3 , 0 S : calcd 3  C: 73.98, H: 8.43, S: 7.03; found C: 73.87,  7.16.  (-)2-Methyl  2R,3S-epithio-4'-dodecyloxybiphenylpentanoate  (MEAOBP-S-12).  mp.(°C): 64-65. [o]  = -1.2°  »H nmr  (c 2.38  3  in ppm: 7.52  2H), 3.70  (d, 2H), 7.47  (d, 2H), 7.12  (d, 2H), 6.95 (d, 2H), 3.99 (t,  (dd, 1H), 1.96-2,07 (m, IH), 1.89 (s, 3H), 1.80  (m, 1H), 1.41-1.51 ir (CHCIj): exact  CHCI ).  mass  1725 for  microanalysis H: 8.86, S:  (m, 2H), 1.28-1.32 (m, 16H), 1.21  (m=5, 2H), 1.65-1.74  (t, 3H), 0.90 (t, 3H).  cm . 1  C H ,OjS:  for  30  4  cacld 482.2844, found 482.2843.  C H jO S: 30  4  3  calcd  C; 74.66, H: 8.77, S: 6.62; found C: 74.61,  6.79.  3.10 S(-WcW1ETHOXY-foVrRIFLUOROMETHYLPHENYL ACETATES  4 - A L K O X Y B I PHENYL  43  A  solution of  S(-)-(o)-methoxy-(o)trifluoromethylphenylacetic  (0.855mmol, 200mg), N,N-dicyclohexylcarbodiimide 4-alkoxybiphenol dichloromethane N,N-dicyclohexyl with water  (1.03mmol),  (1.03mmol), and 4-dimethylaminopyridine (5ml) was stirred at room temperature  (1x5ml), dried over  acid solution  MgSO« and the solvent  with dichloromethane. The ester was  typically  80% or  from  petroleum  further  ether or by  3  1  (on all  evaporated  0  3  7  in this order :  to give the crude  on silica gel, eluting  purified either  by  sublimation. The yield  was  samples).  The m.p.( C), 'H nmr (ppm) data, exact  C H -  washed  higher,  ir (CHCI ): 1766 e n v  listed  18 hr. The  (3x5ml) and again with water  ester, which was purified by column chromatography  recrystallization  for  (0.09mmol) in  urea was removed by filtration and the filtrate  (3x5ml), 5% acetic  acid  as  80-81; 7.64-7.71  mass, and element  analysis  data are  follows. (m, 2H), 7.57 (d, 2H), 7.45-7.53  6.96 (d, 2H), 4.00 (t, 2H), 3.71  (s, 3H), 1.84  (m, 5H), 7.18 (d, 2H),  (m=6, 2H), 1.06 (t, 3H); cacld  444.1508, found 444.1520; calcd C: 67.71, H: 5.23, found C: 67.67, H: 5.14.  C H , - ; 55-56; 7.64-7.71 4  (m, 2H), 7.57 (d, 2H), 4.00 (t, 2H), 3.71  (s, 3H), 1.80  (m=5, IH), 1.45-1.55 (m, 2H), 1.00 (t, 3H); calcd 458.1664, found 458.1667; calcd C: 68.26. H; 5.51, found C: 68.21, H; 5.42.  C H -: s  n  20-21; 7.64-7.71  (m, 2H), 7.57 (d, 2H), 7.45-7.53  6.96 (d, 2H), 4.00 (t, 2H), 3.71  (s, 3H), 1.80  (m, 5H), 7.18 (d, 2H),  (m=5, 2H), 1.40-1.52 (m, 2H),  1.25-1.40 (m, 2H), 0.90 (m, 3H); calcd 472.1820, found 472.1817; calcd 68.78, H: 5.77; found C: 68.79, H; 5.66.  C:  44  C H - : 31-32; 7.64-7.71 4  1 3  (m, 2H), 7.57 (d. 2H), 7.45-7.53  (m, 5H), 7.18 (d, 2H),  6.96 (d, 2H), 4.00 (t, 2H), 3.71 (s, 3H), 1.80 (m=5, 2H), 1.40-1.52 (m, 2H), 1^5-1.40 (m, 4H), 0.89 (m, 3H); calcd 486.1976, found 486.1977; calcd  C:  6927, H ; 6.02; found C: 6921, H ; 5.94.  C H 7  l 5  16-17; 7.64-7.71  :  (m, 2H), 7.57 (d. 2H), 7.45-7.53  6.96 (d, 2H), 4.00 ( t, 2H), 3.71 125-1.40  (m, 5H), 7.18 (d, 2H),  (s, 3H), 1.80 (m=5. 2H), 1.40-1.52 (m, 2H),  (m, 6H), 0.88 (m, 3H); calcd 500.2132, found  5002132; calcd  C:  69.73, H: 6.26, found; C; 69.66, H; 623.  C , H - : 41-42; 7.64-7.71 1 7  (m, 2H), 7.57 (d, 2H), 7.45-7.53  (m, 5H), 7.18 (d, 2H),  6.96 (d, 2H), 4.00 (t, 2H), 3.71 (s, 3H), 1.80 (m=5, 2H), 1.40-1.52 (m, 2H), 125-1.40  (m, 8H), 0.89 (m, 3H); calcd 514.2288, found  514.2286; calcd  C;  70.16, H; 6.48, found C: 70.10, H; 6.41.  C H 9  1 9  43-44; 7.64-7.71  :  (m, 2H), 7.57 (d, 2H), 7.45-7.53  6.96 (d, 2H), 4.00 (t, 2H), 3.71  (m, 5H), 7.18  (d, 2H),  (s, 3H), 1.80 (m=5, 2H), 1.40-1.52 (m, 2H),  1.25-1.40 (m, 8H), 0.89 (t, 3H); calcd 528.2444, found 528.2443; calcd  C:  70.57. H: 6.69, found C: 70.55, H; 6.63.  34-35; 746-7.71  CJOHJJ-:  (m, 2H), 7.57 (d, 2H) 7.45-7.53  (m, 5H). 7.18 (d. 2H),  6.96 (d, 2H), 4.00 (t, 2H), 3.71 (s, 3H), 1.80 (m=5, 2H). 1.40-1.52 (m. 2H), 125-1.40  (m. 12H), 0.89 (t, 3H); calcd 5422600, found  70.96, H  :  6.89, found C: 70.93, H ; 6.77.  C  47-48; 7.64-1.71  1 3  H J 5  :  (m, 2H). 7.57  2H), 6.96 (d, 2H), 4.00 (t, 2H), 3.71  542.2603; calcd  (d, 2H), 7.45-7.53  C:  (m, 5H), 7.18 (d,  (s, 3H), 1.80 (m =5, 2H), 1.40-1.52 (m, 2H),  1.25-1.40 (m,  14H), 0.88 (t, 3H); calcd 570.2912, found 570.2910; calcd  71.68, H: 7 2 5 , found C: 71.60, H: 7.34.  CHAPTER  2 HETEROGENEOUS  OPTICALLY  ACTIVE  CATALYSIS  OF THE RACEMIZATION  1.1'-BINAPHTHYL BY TITANIUM DIOXIDE  J  46  OF  POWDER  4. Heterogeneous industrial  chemicals  both industry surface  and therefore  Heterogeneous  without  reactions  substrate takes  has become  increase  catalysts  the specific  chemical  catalytic  intense efforts  active  in  deals with the  1,1'-binaphthyl.  properties  in two  in so  far as  phases. The  important  compared with homogeneous  problems, such as the structure areas, the modification  of  systems  is a process  different  their  surfaces,  attain  equilibrium  surface  in which catalyst  phases. The reaction  it is catalytic, only  and  naturally  at the phase  bounding the two three  distinction of  catalysis  of  of  change.  system  boundary, at the two dimensional  active  of  are solids which increase the rates  undergoing  are to be found  place, at least  optically  the rates at which chemical  heterogeneous  dimensional  a focus  many  CATALYSIS  by virtue of  themselves  A  in the production of  of the racemization of  4.1 HETEROGENEOUS  and which  is crucial  and academia. The second part of this thesis  catalysis  chemical  catalysis  INTRODUCTION  lies  in the fact  the surface  and change  heterogeneous that  catalysis  topchemical  and the distribution  of the surface  as  by the  of  its  reaction  occurring, must be considered. Reactions proceeding reactants  proceeding at the surfaces  homogeneously  are  the rates  of  less accessible  reactants  in the reactive  the former  differ  from  those  case, the  are confined to a thin layer over the  of which is relatively  reactions  solids  in several ways. First, in the former  and intermediates  the volume  of  small. Second, the kinetics  than those of  homogeneous  47  of  surface  reactions  are determined by the concentrations layer. Third, the kinetics  of  surface,  surface  of  in that  the  reactions  are  48  less reproducible the surface  than those of homogeneous  and its method of  The progress  of  reactions  since  prepartion have profound  a heterogeneous  catalytic  the nature  effects.  reaction consists  s t e p s " : (1) the diffusion of the reactants to the catalyst, (2) the of the adsorption-compound, catalyst-reactant, (3) the chemical the surface, (4) the decomposition and finally  (5) the diffusion of  catalyst. Unless slowest they  of  they all accidentally  each other  Completely reaction would several steps  away  and products  information  to a large extent  change at  from the  the overall velocity  carries  since  out a particular of each  during the course of  of  the  the  task has yet to be achieved. has been collected for  catalyzed reactions. Exactly what type  is determined  formation  catalyst-product,  and importance  to say, this formidable of  five  reactions).  knowing the extent  Nevertheless, a great deal  of  the same velocity, it is the  which determines  (consecutive  for all reactants  reaction. Needless  obtained  possess  understanding how a catalyst  involve  of heterogeneous  the compound, the  the reaction products  these five processes  all follow  of  of  of  a variety  information  is  by the method used to study  the  reaction. Kinetic  methods  given reaction and also process  are useful  in determining the number  in determing which step  may be rate-determing. T o determine  heterogeneous  many mechanistic  approaches  character of towards  steps  in the  how the reaction  product(s) change with the structure and electric should be one of  or steps  of  could also provide  valuable  Furthermore, well-developed  product(s) with reactant  the  catalyst  studying of  the  stereochemistry  information for analyzing catalyzed isotopic tracer  catalytical  rate or  catalyzed reactions. In addition, the stereochemistry  product(s) and the variation of  in  method has been  reactions.  applied  49  successfully  to  studying  rate-determing of  a  steps,  the  and  nature  studying  of  adsorbed  species,  stereochemical  identifying  changes  during  the  course  reaction. A  great  catalysis  has  molecules  deal  of  been  gained  adsorbed  adsorption  which  compounds  on  on  10 k c a l / m o l e  of  adsorption  by  the  might  the  of  insight  occur. The  higher,  involves  forces  condensation  less  those  in  catalyzed  is  a  and  during  adsorption  is of  of  nature are  first  type  heat  of  and  heats  two  of  heterogeneous the  roughly involves  molecule  two  types  which  are  adsorption  less  However,  than  in  adsorptions  a  may  of of  usually  the  in  similar are  chemical order  second to  type  those  correspondingly  10 k c a l / m o l e .  specific not  or  formation  chemisorption. The  of  usually  of  adsorption  attraction  physisorption.  r e a c t i o n , either  the  termed  chemisorption,  called  mechanism  studying  surface, with  or  the  surface. There  occurring than  into  This  heterogeneous  be  precisely  classified. Despite for as  studying applied  the  the  to  lack  of  Kinetic reproducibilty, impossible.  specific  which,  of  heterogeneous many  catalyzed  have in  when  may  a  good be  catalysis  points  of  still  variety  approach  of has  Mechanisms  remain  methods certain of  mysterious  cases,  been  could  kinetic  hampered  view  as  limitations  many and  cause  analysis  is  by  disputed  only  when  possible.  the  problems  a thorough possible,  s t r a i g h t f o r w a r d . T h e r e f o r e , the comes  available  due  methods.  traditionally  many  not  each  reactions.  mechanistic  studies  a wide  catalysis,  precise  the  as  are  reactions  Even  results  there  catalyzed  of  from  that  heterogeneous  heterogeneous to  fact  problem  kinetic  the  best are  of study  interpretation understanding approached  50 Heterogeneous  catalysts  they perform, and of  great  may be classified according to the  significance  and their electrical and thermal Table  A  6.  their Principal  Classification  is the correlation  functions  between these  conductivity . 34  of  Heterogeneous  Catalysts  According  to  Functions  Class  Metal oxides  Metals  and  Salts  and acids  sulphides Conductivity  type  semi-conductors  conductors  or Functions  A sites  key aspect  oxidation-reduction  polymerization  dehydrogenation  dehydrogenation  isomerization  Hydogenolysis  isomerization  cracking  of  heterogeneous  is the presence  of  in the  a support, thus a finely  of  exploration and utilization of trial and error of  CATALYST  active  reference  divided solid  is  new catalysts  efforts, intuitive  is fundamantally  assessments, and above  TITANIUM  and technology  of  most extensively  all, a  oxide studied  OXIDE literature and sulfide  references  dealing with the  chemistry  semiconductors, of which T i 0  over years. Its applications  cover  areas such as catalysis, adsorption, supports, and TiOj also common  a  luck.  There are numerous  most  of  optimal".  great deal  4.2  catalysis  in the solid for which there are no equivalents  The matter  insulators  hydrogenation  reaction run in the absence often  <  is the  2  a variety  of  is one of  pigments. The use of titanium dioxide as a catalyst  has  the  51  received  more  oxidation of  and more  water  attention  since  on illuminated T i 0  the first  report  on the  in a photoelectric  2  sustained  chemical  cell  in  1972". Titanium anatase, rutile  dioxide  can be formed  and brookite, all of  can occur naturally. Small are normally  present  chemical  A titanium  amounts  is  less  activity . Rutile 27  with cassiterite, S n 0  of  impurities  2  while  linear  of  dioxide  are summarized of  Property  Anatase  mp.(°C)[a]  change  Density(g/I)[b] Dielectric  of  in Table  of  synthetically  Ti0  a  2  of  co-ordination  selected properties  7. Properties  because  molecules  modifications,  n-type  the nature of  and  is  forms  in anatase.  of  the  2. Forms  of  Titanium  Dioxide  Rutile  Brookite  1855  change  3.90  4.27  4.13  48 (powder)  110-117(powder)  78(natural  5.5-6.0  7.0-7.5  5.5-6.0  rutile  its  isomorphous  are present  2  the different  the Different  to  and  Fe, Nb, T a , Sn, Cr, and V  to render T i 0  important  has 6:3  number  Table  which can be prepared  in the three forms  semiconductor". Brookite inert  in the three crystalline  to rutile  crystal)  Constant[a] Hardnessfa] (mohs' scale)  [a]. J A N A F  Thermochemical  Tables, Air  Force  Contract  AFO  4(611)- 7554,  midland, Michigan, A u g . 1965. [b]. P. Pascal, Nouveau Traite de  Chemie  Minerale, M a s s o n , Paris(1963). Stoichiometric about  10  35  ohm  cm  cm by controlled  titanium  dioxide  is  an insulator  at room temperature; this  introduction  of  oxygen  with a resistivity  of  lowered to 0.1  ohm  can be  vancancies".  52 There has been limited reports  in studying thermal catalytic  of titanium dioxide. However, it is known that titanium dioxide facilitate  a number of  Thermal isomers  isomerization of  isomerization of  selectively  of  o-pinene over T i O , catalyst  and their surface activity of propylene  in chemical structure properties  isomerizations oxide  its  are of  in  and the nature of  secondary  31  are due to  in so far  as the of  suggested that an in order  isomers. examples  is the isomerization  studies, that the isomerization of butenes  prepared from TiCI ) proceeds through three different 4  respectively, protonic the pretreatment  of  butenes  extensive  on T i O , (anatase mechanisms,  involving  sites, Lewis acid sites, and basic sites, depending  temperature  of the T i O  }  on  catalyst.  In other words, as has been observed on alumina, those  catalytic  can take place on Bronsted acid sites of the catalyst. Double  bond migration takes place on the basic s i t e s " of T i O , , through carbanions as on M g O , " while cis-trans o-bonded carbocations L is a Lewis A  electrons,  the isomerization  over titanium dioxide. It is concluded by Guisnet", after  reactions  TiO,  bound to the Ti atom through the O atom  One of the well-established  mechanistic  of  bonding  importance  is concerned. In the case of  different  catalytical  o camphene  over T i O , to Me,CO or EtCHO, Fukui  adsorbed substrate was to covert  gave  depending on heat treatment on the activity  S i O , , AI,Oj and T i O , in converting  their differences  could  alkenes.  catalyst". It was explained by L i u " that, the difference activities  activity  as in the case  acid site.  c-<j:-c-c L  isomerization occurs  of Webb's carbonium  allylic  through ion ( A ) " , where  53 Such an intermediate  (A), which allows  can be formed without any C - H  to  charge  unless  the catalyst  activity  of  A  of  organic  is being  reactions  on the surface  of  T i O , that comprises  catalyzed by T i 0  can not  2  photocatalytical  pioneering approach concerning the production  of  hydrogen gas  photoredox sensitized  organic  only because  of  new, alternate  but also  involving heterogeneous  for  be  semiconductors  of  its relationship  and radical  semicoductor/liquid  light  ion  to  and the  interface, either the semiconductor  whereas  in the  transfer  initiates  latter  production of  functional  general  problems  or the  contacting  reactions  electron transfer  itself  function as the chromophore. In the former  change results through direct  for  not  intermediates.  interface. Specifically, for reactions  chemical  important  sensitized redox  induction of  for  Studying  is  systems, either the solid  initially excited. Semiconductor  the semiconductor/liquid  may  by  photocatalysis  the absorption of  routes  uncovering new techniques  because  In irradiated heterogeneous liquid may  catalyzed  on illuminated semiconductors.  phototransformations  modiification  occurring  across at the  or the case, net  an excited state,  case, sensitization through either electron or  energy  reactions.  The energetics  for  by  26  occurring  its potential  catalyst.  Fujishma and Honda , has stimulated a  at discovering  reactions  due  occur  this  effort  the special  catalyst  conditions.  irradiated by photons. It is the  splitting of water, by  adsorbent  charge) and  of  worldwide  involve  dioxide  importance  catalytic  group  electron (negative  structure, even under thermal  However, most  isomerization,  32  (hole) to adsorbed molecules  its semiconductor  geometrical  bond-breaking . Indeed, titanium  has been proven to be able to provide positive  only  the critcal  derived from the working model  interfacial  electron transfer  proposed originally  by  can be  Gerisher . 36  As  54 shown filled  below,  a  valence  conduction  semiconductor  band  band  (VB)  is  characterized  separated  by  an  by  energy  a  band  gap  structure,  from  a  i.e.,  a  vacant  (CB).  <«;  Ecb Ef  Evb semiconductor Band  structure  electolyte;  (b) after  in  a  solution  semiconductor  semiconductor:  contact  with  an  (a) b e f o r e  electrolyte  solution contact  with  (Reproduced  from  an reference  37) After  a  semiconductor  •containing  a  equilibrate  the  potentials  formed  at  the  surface  bulk  the  of  filled  exciting  valence  band  example,  electron-hole  doping  will  pair  the  the  away  positive  the hole  charge  and  the  i.e.,  when  this  virture  of  interface  migrates  the  interface  field  bands  b a n d . In a donors  is  to  thus  bend  forms  absorption the  towards  electron  from  bulk the  renders  of in of of  the the  a  from  an  n-type  provides  inhibition pair  an  band, leaving  bending  to  electric  promotes  electron  for  the  solution  the  interface.  valence  band  electrolyte  across  and  conduction  effective  by  hole  the  in the  rich  occurs  semiconductor,  vacant  liquid  p h a s e s , an  semiconductor  hole. Thus  from  two  towards  the  in a  transfer  the  separation,  semiconductor  move  of  with  electron  photogenerated the  to  positive  semiconductor  of  of  semiconductor  or  immersed  c o u p l e , charge  Photon  deficiency for  redox  is  electron semiconductor,  the  method  collapse space  interface  for  of  the  charge  a p h o t o n , the the  the  electron  semiconductor where  region  as  oxidation  can  55 occur. A s  the oxidation of  up in the bulk of  the adsorbate  semiconductor  occurs, sufficient  to render the particle  mobile. ' Ultimately, such a charged aggregate solution-phase  reduction-oxidation  reductions. In the same  reactions  could be also  build  electrophoretically  can act as a reducing  3  and effect  charge can  center  principle,  carried out over  p-type  semiconductors. Numerous  photocatalytic  been studied, some 3  in a reversible  photocatalytic monoanions  reactions  could be similarly  driven by  by  and in addition, closed-shell  photogenerated.  I 3  dianion, a  organic redox couple, could be generated 40  have  follows.  instance, that the cyclooctatetraene  T i O , in ammonia solution,  Fox * also  on semiconductors  of which are summarized as  F o x ' demonstrated, for participant  organic  I  showed that  a net  light absorption either  adsorbed on a single  crystalline  endothermic  oxidative  coupling could be  by the tetraphenylcyclopentdienide T i O , electrode  or by the  anion  semiconductor  itself. One of the first induced by  reported oxidative  long-wavelength  ultraviolet  involves the photodecarboxylation CHjCOOH  of  cleavages  of  irradiation of a  acetic  acid.  hv, T i O , — • CH,CH, or C H  Ethane and methane are the different  4  an organic  semiconductor  41  +  CO,  main products  crystalline T i O , and powdered T i O , respectively. It was that a methyl radical CH,. is the intermediate  molecule  formed by  confirmed by  of the reaction . 41  using Bard  56  The  most  so  far  as  the  of  arylated  conversion  successful  synthetic  olefins,  4 1  3  of  acids  with  oxidation  titanium  of  obtain  the  by  dioxide  the  Ti0 ,  irradiated oxidative  virtually  in  3  cleavage  quantitative  organic most  5  examples  at  serine,  is  the  aspartic  irradiation  of  although  in  methane,  of synthesis acid,  and  platinized  Ti0  poor  of  3  conversion  .  mentioned  valence  to  by  irradiation  molecules  alanine,  generated  4 3  the  organic  glycine,  all  in  band  holes  Recently, lactate  above,  and/or  Gratzal  under  however,  hydrogen  reported  4 4  mainly  illumination  of  that  deal  with  production pyruvate  by  could  aqueous  suspensions  systems  such  powder.  to  and  of  examples  reduced  TiO,  of  experiences  is  by  (Ph) C=0  ammoniacal  electrons.  addition  variety  type  the  band  of  the  aqueous  of  efficiently  plantized  catalyzed  concerned,  containing  simply  selectivity  be  In  be  reactions  conduction  exciting  products  can  in  no  Most  most  The  suspensions and  is  sometimes  hv, T i O , — •  suspensions  acids.  glutamic  application  which  3  the  semiconductor amino  reaction  .  (Ph) C=CH One  organic  pure  Ti0 , 3  titanium-silicon reactions.  efficient  reaction  The  reaction  concerned.  Ti0  modified oxides, choice is  not  2  are  of  a  catalyst also  effective  specific  predictable,  catalysts  catalyst but  as  totally  in  in  order depends  a to on  57  4.3  RACEMIZATION Because  exists  OF BINAPHTHYL  of hindered  in t w o enantiomeric  conversion equimolar  of  rotation  of both  an e x c e s s  is d e f i n i t e l y  Furthermore, this studying  the c a t a l y t i c  and u s e d review  of  all kinds  4.3.1  of  consists  of one enantiomer  into  in t h e  an  (SM+M.l'-binaphthyl one o f the s i m p l e s t system  activity  successfully  homogeneously be  simple  reaction  enantiomers.  (R)-(-)-l.r-b1naphthyl This  the 1 . 1 * b o n d , 1,1 - b i n a p h t h y l  f o r m s . The r a c e m i z a t i o n  a solution with  mixture  about  has been  of  proven  a variety  f o r the s t u d y racemizations  of of  catalytic, heterogeneously  reactions  in o r g a n i c  chemistry.  t o be a p p r o p r i a t e  of heterogeneous  catalysts -" 4 5  photoracemization"- . A 5 6  binaphthyl,  for  brief  spontaneous,  catalytic, and photocatalytic,  will  presented.  UNCATALYZED The  Cooke  RACEMIZATION  conversion  of enantiomers  OF BINAPHTHYL of  1,1-binaphthyl  a n d H a r r i s " , a n d later o n b y C a r t e r  by those  researchers, hindered  naphthalene  units  interference  of  prevents  from  groups  coplanarity  and Liljefors '. A s 5  rotation about  achieving  s y s t e m s . Each naphthalene  being unit  studied  the t w o  c o p l a n a r i t y . It has b e e n c o n s i d e r e d  achieved  consequently  that  in e a c h n a p h t h a l e n e  in e i t h e r exists  by  pointed out  the 1 , 1 ' - b o n d prevents  in t h e 1 a n d 8 p o s i t i o n s  from  has been  one o f the t w o in o n e o f t w o  moiety ring  forms,  58 called  d or  I.  (1)  (d) d  and  I forms  Either  of  enantiomer  substituted of  naphthalenes  binaphthyl  can then exist  in o n e  (a) a r a c e m o i d , I - l , (b) a r a c e m o i d , d - d , (c) a m e s o i d , l - d ,  of  three  forms  form.  Mesoid  Racemoid  Racemoid and mesoid conformations of S-t-rj-ia'-binaphthyl M a t h e m a t i c a l l y , t h e r e are t o t a l l y for  d  ground  of  different  conformational  configurations  b i n a p h t h y l : R ( d - d ) , R ( d - I ) , R ( l - I ) , S ( d - d ) , S ( d - I ) and S ( l - I ) . B e c a u s e  rapid  it  six  =  I conversion  state  molecule  is b e l i e v e d R to  S  or  at a m b i e n t  would  be  that  in the  vice  v e r s a , there  simply  latter  there  b e t w e e n the ring s y s t e m s is n o  point  simultanously  a l o n g the with  hydrogen-hydrogen  two  =  interactions  as  R or  difference =  s t a t e . In the  path where t w o  of  the  Nevertheless, conversion  between  a  S ( l - I ) . " - ' . In the 4  contact former  hydrogens  h y d r o g e n s . Rather, there as the e n a n t i o m e r s  S.  l e a d i n g t o the  hydrogen-hydrogen  in t h e t r a n s i t i o n  conversion  conformation  S ( d - I ) and R(l-I)  simultaneous  other  state  is a considerable  involving, say, R(d-I) are t w o  referred to  crowded transition  conversion case  t e m p e r a t u r e s , the  of  points  case  there  interact  are t w o  convert. The  successive pathway  59  involving successive  interactions  is energetically  much more favorable  the simultanous route '. It is thus concluded that it is through the  mesoid  5  forms the R and S reaction was  4.3.2  1,1'-binaphthyl  measured 22.5  PHOTOCATALYTIC  convert. The activation energy  sensitizers  RACEMIZATION  OF  BINAPHTHYL  or quenchers) as well  only  1,V-binaphthyl  its enantiomer  at the angle of  0°  occurs  1,1-binaphthyl  due to steric  in the coplanar  in the ground state (22  of  additives  in the triplet  than the thermal  hindrance  of  a smaller  bond distance  stablization energy  kcal/mol) , the barrier 51  triplet  and gives  in the triplet  at the  2  occurs  state  much  is  faster  in the excited  rise to a large steric  state suggests  that the  state  hindrance,  electronic  gained as a result of the interaction of the two  1,1'-binaphthyl  hindrance.  occurs mainly  radiation  excited state in toluene. The 1.1 kcal/mol  induced  in a radical anion state  in tetrahydrofuran, while the reaction occurs  in both solvents,  the  in the triplet  The same researchers" further observed that \-ray  1,1'-binaphthyl  state.  conformation. Compared to the higher  is superior to steric  racemization of  of  racemization.  the low barrier observed  groups  excited  hydrogens  It is also noted that since the higher bond order  naphthyt  nicely  (photo  has to overcome  1.9 kcal/mol. In other words, the photoracemization  causes  was  as by a laser photolysis. The effect  revealed that photoracemization  and 8 positions barrier  of  has been studied from the effect  The conversion to barrier  the  Irie and his c o - w o r k e r s " " . The mechanism for this  photoracemization  additives  of  kcal/mole".  The work dealing with photoracemization done by  than  mainly  of  in the  low activation energies of the reaction  in THF and  1.9 kcal/mol  in toluene, as  60 compared to thermal racemization, indicates that the introduction electron to the lowest vacant molecular orbital causes an  The  RACEMIZATION  OF BINAPHTHYL BY  catalyzed conversion of enantiomers  carbons, Raney nickel and platinum was 4 5  of  contributed  a variety of  the general  heterogeneous  different  PT over Pincock  catalysis  if and how this  of  type  obtained  in these  towards  the understanding  ideas and evidences catalysis, especially  in areas  of  studies  those  this  have of  three  solids.  Since  our work  the previous  is closely  related to and, in some  work, it is therefore  heterogeneous applies  N l . AND  of the surface  actually occurs. The conculsions  bond.  investigated by  reaction", there have been much work about  catalysis  C-C  1,1'-binaphthyl  extensively  et a l - " . Since they reported the first case simple  of  C  an  electronic  structural change favorable to rotation along the fntraannular  4.3.3 C A T A L Y Z E D  of  catalysis  appropriate to review  by carbons '-", nickel *"and 4  45  aspects, similar some  features  of  platinum *" as it 47  to this simple reaction. The carbon catalyzed The racemization probably  proceeds  racemization  of binaphthyl  by a mechanism  on various  in which electron  donated to the binaphthyl by the carbon The catalytical sites the basal  carbon  for binaphthyl  racemization  is unaffected  binaphthyl  are  is  or the  located  in the presence  of of  the  on  edge  by oxidations  reductions which occur at the disorganized areas Racemization of  density  surface.  planes and not on the disorganized areas  atoms, because the catalytic rate  surfaces  and  surface.  the carbon  involve the "formation of a binaphthyl radical anion on the  may  surface.  to  61  The  idea was supported by the fact  that intercalating potassium  into  graphite enhances the catalytic  activity  of the graphite. Since  intercalating potassium-graphite  is well known to catalyze reactions  one electron transfer, it could appear that a radical anion for this particular  4.3.32 Platinum  catalytic  catalyzed  The platinum kinetics. There  reaction is  by  mechanism  reasonable.  racemization  catalyzed reaction follows  is no detectable adsorption  simple first  or interferring  order reduction  during the reaction. The aspect the catalysis  of  shows  is independent  of  the reaction that a peculiar  the concentration of  Oxygen present apparently because Cyclohexane  kinetic  of  in the reaction  is difficult effect  to explain  in that the reaction rate  platinum. solution poisoned the reaction,  competing adsorption and its reduction to water.  and cyclohexene which is reduced to  however, show a permanent concentration  of  is that  inhibitory  effect  which  the compound. It is therefore  reduction and racemization  cyclohexane, increases with the  concluded that the  sites were the same  in platinum  catalyzed  racemization. Variations probably  in activity  and the complete  due to uncontrollable The  Interaction of  Raney nickel reduction of  of the  poisoning were pointed  binaphthyl with Raney  catalyzes  binaphthyl  loss  activity  out.  nickel  both the racemization process  and the  to 4,5,6,7-octahydro-binaphthyl. There was  a greater adsorption process  of  binaphthyl than with platinum.  also  62 The non-first  racemization follows order  period, which  adsorption. The relative 1-decylmercaptan,  first  order kinetics  is probably  effects  of  after  caused by the  an initial concurrent  added poisons, e.g. sulphur  suggested that there were three different  sites, each responsible  for a separate type  of  or  catalytic  interaction with  binaphthyl.  4.4 THE  OBJECT  The effect  aim of  the present  (activity) of  optically of  OF THE PRESENT  active  highly  binaphthyl  STUDY  study  is to discover  dispersed titanium  and, if so, to experimently  The titanium  with experimental following  dioxide  catalytic  oxide on the racemization  the catalysis, and thus, hopefully, to formulate  consistent  the possible  examine the  of  kinetics  a reaction scheme  that  is  findings.  sections  (anatase from  describe  various  kinetic results  Aldrich) catalyzed racemization  for the of  binaphthyl.  5. RESULTS  5.1 PRELIMINARY It was  KINETIC  found that small  Aldrich) in acetone optically  STUDIES  active  AND  DISCUSSION  AND  REPRODUCIBILITY  amounts  of  highly divided T i 0  (anatase,  2  (ca. 10.0mg/ml) would catalyze the racemization  1,1'-binaphthyl  without  concurrent  side reaction or  of detectable  adsorption. As  in the case the other catalyzed racemizations  and his c o w o r k e r s kinetics, as seen It was  simply  , the T i 0  catalyzed  2  in Figure 4 for  available  solvent  Ti0  2  of  intensively  divided  for  and this reproducibility  particles  were  kinetic  run was never  only  particles  when in  can be  2  a period of  divided T i 0  of T i 0  2  2  would  24 hr  in not  the stirring. A  several  identical  runs),  quantitative kinetic studies to be  is that the titanium dioxide  independent  speeds  order  section.  interesting fact  racemization was  of  changed by  affected by diffusion  is, of  catalyzed  the stirring rate. Although the  varied with a variable  speed during a run. This  liquid-gas  over  2  (see Figure 5 for  allowed some  in the subsequent The  observed  activity  divided T i 0  a period of 4 hr after the completion of  good reproducibility was  good first  into colloidal  batch of finely  it was observed that the colloidal  precipitate  not  show catalytic  stirring. Finely  active  Pincock  runs.  stirring powder T i 0  in a flask. With a catalytically  done  reaction shows  would  2  is further  by the means  obtained by  acetone  several  also found that T i 0  commercially acetone  45-52  studied by  speed magnetic increasing  stirring  stirrer, the rate of a  or decreasing the  stirring  course, consistent with a reaction which  control  factors. .Because  (or liquid-solid) interface will  63  increasing the area of  increase the rate of  reactions  is  [Binaphthyl] =6jB2x10« (mol«/l) Temperature s 10JD*C Solvent sacetone  1.6 | 0  |  |  I  I  I  100  200  300  400  500  _  time (min)  Figure 4 First order kinetic catalyzed racemization of optically active 1,1'-binaphthyl by highly dispersed titanium dioxide  600  to  (Binaphthyl) «6A2x10-« (mol/l) (TiOjsioj) (mg/ml)  2-1  Temperature=10jD*C Sol vent =ecet one  X  1.95 H  B  CM  + 1.90-, B X  O  1.85-\ B  1.80-  x  1.75-1 1.70  "  i  0  y  100  i  200  i  300  i  400  I  500  i  1  . 600  time (min) Figure S Several identical kinetic runs of catalyzed racemization of optically ectlva binaphthyl by highly dispersed titanium dioxide *  66  whose  rate determining step is diffusion There  are two characteristic  across this  features  interface.  in these plots  with platinum, nickel and carbon catalyzed racemization  in comparison  of  optically  active  1,1'-binaphthyl. Like decrease  platinum catalyzed racemization of  or  increase  in optical rotation of  titanium dioxide was used as a catalyst Another  important  straightforward dioxide  aspect  catalyzed racemization  discovery  in the previous  nonexistence titanium  of  and the carbon, for  at the very At  beginning of  might  activity  binaphthyl  and T i 0  of T i 0 2  an  titanium important  reaction. The  indicate that the  catalyst  deactivation, which  often experience during the catalysis. The  instance, exhibit the maximum catalytic the catalyzing racemization  this point, it was  catalytical  reaction.  simply  binaphthyl, which also was  dioxide was not undergoing any progressive catalysts  organic  runs (up to halftime) in the  in the plots  2  rapid  observed when  order plots were  metal or carbon catalyzed  curvature  many heterogeneous nickel  of  binaphthyl was  in this simple  is that the first  throughout the kinetic  binaphthyl, no initial  initially might  be  of  activity  binaphthyl .  decided to determine  49  how the  influenced by the concentrations  of  in order to draw a further comparison with the other  catalyzed racemizations  by  C, Ni, and Pt.  52  THE  EFFECT  ADDITIVES  a finely  were  CONCENTRATIONS  ON  Kinetics Into  OF  CATALYTIC  were  studied  divided  c a r r i e d out  at a  concentration was rotations the  of  more  usual  less. The against the  the  rate  low  observed  concentration  constants  of  catalyst  TiOj  is  of  the t i t a n i u m like  more  carbon  increased  catalytical  The a s that  concentration catalyst  of  binaphthyl  the  mode kinetic  concentration  or  the  to  the  due t o  plotted  showed  that  catalyzed  concentration is  of  kept  the  availability  solution. o n the  concentration catalyzed  binaphthyl  reaction. A s concentration  the s a m e , a large  number  of  a limited number racemization  data  much  the  a n d the  of  is  a n d are  binaphthyl  (Kobs) increases  the  the  plantium  r a c e m i z a t i o n , as  of  ( 4 5 6 n m ) rather  clearly  the  of  of  rotation  proportional  reactions  binaphthyl  line  slope  results  concentration  platinum is  absolute  used. Unlike  catalyzed  Kobs  the  (0.00435g)  the r a t e  measurement  at the m e r c u r y  directly  dioxide  that  increased  for  of  out  5. T h e  in the  of  AND  (25.0ml). A l l  minimized. The  in F i g u r e  a n d the  carbon  compete  predominant  the  sites  TiO, remains  molecules  shows  for  was  from  rate c o n s t a n t  dependence  found  solvent  determined  ( K o b s ) is  binaphthyl  ( 1 0 ° C ) in o r d e r  (589nm) where  catalyst  c o n s t a n t , the r e a c t i o n of  acetone  carried  were  constant  r a c e m i z a t i o n , but  dioxide  was  line  BINAPHTHYL  active  (6.82x10-*mole/l) a n d the  sodium  rate  optically  racemization  samples  the w e i g h t  adding  l o w temperature  uncatalyzed, spontaneous  CATALYST.  ACTIVITY  by  titanium  OF  is  of  binaphthyl w a s  racemization  rate  gradually  of  the  sites  binaphthyl  and  reaction. Table  constant  increased.  same  the  b o t h R and S  the u n c a t a l y z e d  in w h i c h the k i n e t i c  is the  was  the 8  decreased  as  Kobs X 0.0001(1/min) Figure 6 Dependence of the concentretion of titanium dioxide on the observed kinetic rate constants of catalyzed racemization of optically active 1,1'-binaphthyl by highly dispersed titanium dioxide  69  of binaDhthvl on the concentration of binaDhthvl Concentration  of binaphthvl (mole/1)  Kobe x10 (min») 4  6.82 x 10-  6.8  5.70 x 10-«  6.8  6.11 x 10-*  7.4  7.64 x 10*  6.6  13.3 x 10*  6.0  14.7 x 10-  4  5.3  20.5 x 10*  3.1  20.5 x 10-  4.0  fTiOO =  10.0 mg/ml.  Following the kinetic work above, it was then decided to pursue an investigation to determine whether the catalysis was sensitive to organic molecules which are planar simple aromatic compounds. Figure 6 to figure 10 illustrate how the course of the catalyzed reaction was effected by the addition of aromatic compounds, benzene, naphthalene, anthracene, end pyrene. As shown in these figures, the presence of very small amounts of additives permanently poisoned the catalyzed racemization. The more aromatic rings the added compound possesses, the more effective does it stop the reaction ( benzene < naphthalene < anthrance < pyrene ). The result was probably due to chemisorption which involves edsorption of the poison on the surface. The decrease of catalyst activity was caused by coverting the active sites into inactive surface compound or  pfinsjknthylJsejUxlO- (mol/l) 4  (TiOJslOjrj (mg/ml)  0  1000  2000  3000  4000  5000  6000  [Benzene] X 1000(ml) Figure 7 Dependence of the concentration of the additive benzene on the observed kinetic rete constant of catalyzed racemization of optically active 1,!'-binaphthyl by highly dispersed titanium dioxide  [Binaphthyl] «SJS2K10-« (mol/I) fTrOJ=10jO  (mgAnl)  Temperature m 10 J>°C Solvent macetone  [Naphthalene] X 10000(mol/l) F i  *  j r t  300  • De^andence of the concentration of the additive naphthalene on  tha observed kinetic rate constant of catalyzed racemization of optically  aetive 1,r-oinephthyl  by highly dispersed titanium dioxide  fB.o*phthyl] =6*2x10* (mol/l) [TiOJslOjD (mg/ml) Temperature «10JD *C Solvent sacetone  o o o o X  A.  I/I  "T"  20  30  40  50  60  70  [Anthracene X 10000(mol/l) Figure 9 Dependence of the concentration of the additive anthrance on the observed kinetic rete constant of catalyzed racemization of optically active 1,1 '-binaphthyl by highly dispersed titanium dioxide  IN  7-1  2-f———I 0 1  1 2  1 3  1  4  — 1 5  [Pyrene] X 10000(mol/l) Figure 10 Dependence of the concentration of the additive pyrene on the observed kinetic rata constant of catalyzed racemization of optically active 1,1'-binaphthyl by highly dispersed titanium dioxide  74 by  adversely  "holes"  on  The  affecting  the  converted responsible our  a  of  similar  reaction . 5 2  of  the  solid  catalysts.  fits  the  other  assumption  and  inactive  for  c a s e , the  adsorption that  uniform  to  number  surface  mechanism  substantially  the  the  surface  activity  poisoning those case  that  is  electrons,  decline  compound  or  on  best  the  the  certain  to  sites. lab  for  electrons  or  surface  is  active  proportional  attributed  in this  unpaired  covered  catalytical  observed  that  is  that  preferentially  perhaps  been  free  activity  are  additives has  of  to  favored  the spots  by  the  the  competition  It  is  the  fraction  poisons '.  worth carbon  5  In  for  noting catalyzed  75  5.3 C A T A L Y T I C In this studies  ACTIVITY  MODIFIED  section are described  on a variety  grew out of  OF  of  titanium  some  dioxide  attempts to obtain highly  dioxide towards the racemization identical to the previous  kinetic  TITANIUM  of  DIOXIDE  experiments  involving the kinetic  modifications. These  efficient, reproducible  experiments titanium  binaphthyl. The kinetic procedure  studies  except for that  was  otherwise  mentioned.  5.3.1  PREHEATING It has  catalytical  TITANIUM  been reported that the heat treatment  activity -". Since  of this  temperature treatment  preheat-treatment  32  methods to modify stage  DIOXIDE  the catalytic  project, anatase  ranging from  was  of  TiO  is one  of  can change the  :  the  500-700°C  titanium dioxide, at the  catalytic property. It clearly  for  one to eighteen hours. The  a small  stream of  nitrogen gas  Ti0  2  neither  titanium dioxide  modified the catalysis  indicated that the racemization  of  is  independent  isomerization  of  catalysts. A l s o more  catalytic  isomerization  of  alkenes  catalytic  butenes by anatase  sites  catalytical  powders  is different  on the same  it meant that this calcination treatment sites  vapors.  of the heat treatment, which has  Apparently, the nature of this catalyzed racemization for the catalyzed  passed  improved nor destroyed the  remained the same under heat-treatment. In other words, the of  early  to maintain a low partial pressure of the evolved  However, preheating of  activity  simplest  (Aldrich) was heated in a furnace at the  carried out while  over the catalyst  effect  of  in addition to those that existed.  3 3 3 4  from that  semiconductor could not  .  activate  76  Jable 9 Catalytic activity of modified titanium dioxide towards the racemization part 1 rr\OA  Kobs  (mo/mU  xlOVmin-'l  Aldrich anatase, 2 hr heat treatment (500°C)  10.0  7.1  Aldrich anatase, 8 hr heat treatment (700°C)  10.0  6.8  Aldrich anatase, 18 hr heat treatment (700°C)  10.0  6.9  Aldrich anatase, acid washed  10.0  no catalytic  Entry  effect  1. Solvent distilled actone. 2. Concentration of binaphthyl is kept precisely et 6,82 x 10*  4  (mole/ml).  77 5.3.2 A C I D - W A S H I N G TITANIUM The  object  of the washing step  from the c a t a l y s t s " , that titanium dioxide simple  DIOXIDE  is to  is chemically  is primarily  "polish" the surface  of  inert to strong acids  impurities  the catalysts. That  led us to apply  this  technique. Accordingly, Aldrich anatase powder was  concentrated HCI or H S 0 2  used after drying at possible  solution for  4  about  immersed  previously  active  represents  the  simplest  method. kinetic  procedure  anatase powder  lost their  deactiviation was is one of  was  2  and with acetone, and  120°C overnight. The procedure probably washing  in the  20 mintues. The T i 0  filtering, rinsing with a lot of water  Under the identical  This  to remove  obviously  the cases  acid-treated,  catalytic  completely. The  in which a straightforward  of  ability  caused by the destruction  impossible. We only can say acids and the surface  used above, the  that somehow  the catalysts  the  resulted  of  the catalytic  interpretation  interaction  sites.  is  between the  in the deactivation  of  the  catalysts.  5.3.3  ILLUMINATING TITANIUM As  mentioned previously, the exploration of new titanium  photocatalytic preliminary binaphthyl  reactions  studies  is of  on possible  great  interest  Ti0  2  considerably  irradiated catalytic  to chemists. We  photocatalytic  (procedure see experimental  In s o m e  titanum  DIOXIDE  did  racemization  catalyst  reactions", catalytic  2  prepared by  of  effectiveness  systems, such as, platnized titanium  Accordingly, platnized T i 0  some  section)  enhanced by substituting pure titanium dioxide with  dioxide  dioxide  Bard's  m e t h o d " was  can be  modified  dioxides. also tried in  78 this type of  experiment.  Because the photoracemization and because of  oxygen  is the best  attempted heterogeneous  presence  of  occurs via a triplet  state  intermediate  quencher to the p h o t o r a c e m i z a t i o n " ,  photocatalytic  reactions were  carried out  oxygen gas, which was bubbled through the reaction  for 30min before  the beginning of the kinetic run. This operation  based on the fact  that the triplet  intermediate  2  of  Ti0  some  54  state of  binaphthyl  is not  in the  solution was  likely the  photocatalysis.  Nevertheless, there was  no apparent  catalytic  activity  drawn from  the  kinetic plots. Namely, the kinetic rate constants  of T i O , added  solutions  were  free solutions  without  lower than that of  exception. The T i 0  the corresponding  photocatalytic  2  much more powerful  effect  was  decreased. It was  found that the halftime  binaphthyl  increased  30 min before  an oxide  semiconductor  thus  is analogous to the removal  in the kinetic  as  of studies), in  use.  is one  of the methods  of  oxygen from the T i 0 of  on the  to  catalysis.  2  lattice  by  oxygen is associated with the  surface Ti(lll) s i t e s " . We, at this point, simply  test the doping effect  was  increasing the catalytic activity". This  evacuation at high temperatures". Loss of  binaphthyl  the  DIOXIDE  further dope the semiconductor  generation  of  oxygen was carried out by bubbling a small  nitrogen or argon for  The reduction of  of  oxygen at the concentration  4  of  rate constant  by  of the photoracemization was  (6.82x10- mole/l, the usual concentration  5.3.4 REDUCING TITANIUM  process  (if any) could be outbalanced  as the concentration  in the absence of  the experiment, the removal stream of  2  photoracemization. The kinetic  photoracemization  low as 5 seconds  Ti0  wanted to  79  Table 10 Catalytic activity of modified titanium dioxide towards the racemization part 2  Entry  mO/l  Kobs  (mq/mh  xlOVminn  Irradiating Aldrich  anatase  10.0  300  Irradiating Aldrich  anatase  1.0  730  0.0  833  0.1  217  Irradiating Irradiating Aldrich anatase, in the Irradiating presence  platinized of  0  Aldrich  presnece anatase,  Of  Oj  53  the 0.5  in  :  0.0  263  0.1  58,000  0.0  114,000  10.0  6.5  ibid (4hr)  10.0  10.3  ibid (4hr)  10.0  7.2  ibid (4hr)  10.0  7.5  10.0  6.9  10.0  7.6  ibid (8hr)  10.0  7.8  ibid (I8hr)  10.0  3.9  Irradiating, in the presence  of  0  2  Irradiating Aldrich anatase, in the Irradiating, in the absence Reduced Aldrich anatase  ibid (4hr), new  by H  batch  ibid (4hr), another  of  batch  absence of  Oj 2  (1hr)  0  2  1. Solvent distilled ectone. 2. Concentretion of binaphthyl is kept precisely et 6,82 x 10  4  (mole/ml).  80 It has catalytic  long been known that there exists  activity and electrical  a correlation between the  conductivity . Many  experimental  64  works  which such correlation has been observed were reported. These properties from  of  the semiconductor  vary  in the same or  one sample to another depending on the type  procedure of  this reduction  is described  in the experimental  section.  was slightly  anatase. This  could be  higher than that for  reported that  of  the platinum catalyzed  platinum oxide, at least  pure P t 0  it therefore  2  is not  catalytically  indicated that the above  catalyzed racemization. That racemization, the catalytic the electric  conductivity  is later used subsection  created  conductivity which helped the  active theory  of  to clarify  and  of  Hutchins ' 4  hydrogen  120 minutes  was of  required. binaphthyl,  is applied to the Pt  platinum  catalyzed  are generated as the Pt  the surface  in an arguement  also  Ti(lll)  racemization.  in the racemization  is, in the case  sites  more  platinum by the  a period of  kinetic  Aldrich  reaction, Pincock  in order to obtain highly active  reduction of  the unreduced  interpreted that the reduction  increasing the electric In the case  Since  racemization  10) seemed to be in agreement with the above theory. The  rate constant  thus  directions  the reaction. The  The results obtained from the reduced anatase catalyzed (Table  in  two  in opposite of  65  is increased. This the catalytic  is produced and as important  mechanism  finding  (see  5.4).  5.3.5 OTHER  SOURCES  Titanium dioxide In many  dioxide  OF TITANIUM  cases  used was  not  DIOXIDE  from titanium  of  catalytic  tetrachloride  studies, the modification  obtained directly  from  materials, but prepared by the h y d r o l y s i s 66  67  commercially of  titanium  of  titanium  available  tetrachloride.  81  Table 11 Catalytic activity of modified titanium dioxide towards the racemization  Dart  3  Entry  n m  Kobs  tfmq/mn  xlOVmin-^  TiO, freshly prepared from TiCI  10.0  7.1  ibid  10.0  6.7  ibid  10.0  6.6  5.0  5.0  ibid  4.8  5.4  ibid  5.3  4.9  4  Colloidal Aldrich anatase after one  filtration  1. Solvent distilled actone. 2. Concentration of binaphthyl is kept precisely at 6.82 x 10* (mole/ml).  82  Titanium  dioxide  produce  freshly  catalytic  power  5.3.52 Rutile We  5.3.6  this  terms  of  binaphthyl  TITANIUM  unless  catalytic  thus  presumably  batches  obtaining  would  be  stripped the solvent  a difference  than that  of  of  of a  colloidal  of  4  11).  rutile  from  Alfa  catalyze for  the the  at  uneffective  in the  used. Therefore, one individual  separate  finer  and then filter  catalyst  particles  particles  one point, it was  solutions  decided the  in  from to  larger  solution, which  filtered the stirred suspensions  of  titanium  the filtrate, weighed the catalyst, added  was  [TiOj  for  1 hr before  correct. The value  (see Table  of  dioxide  is  similar  11, compared  powder.  25.00ml  Kobs/fTiOJ  to the  = 5.0mg/ml). Indeed, the catalytic  titanium  dioxide,  use. In any event, it  reaction solution at the  dioxide  with the smaller  could  catalysts.  non-filtered  1  was  could  "true" colloidal  better  titanium  = 4.1x10- min-  enhanced  comparable  employed  between two  filtration? At  shown that the assumption  concentration Kobs  of  conditions  solution was  acetone, and then stirred the solution  higher  effect  dioxide  activity, provided we  Experimentally, we  has  (see Table  material did not  under any  the colloidal  stirred solution by  several  particles  showed  DIOXIDE  question; is there  previously  anatase  examined the catalytical  stated previously, titanium  of  prepare  Aldrich  used to  case.  racemization ask  for  Co., but found out that this  COLLOIDAL As  material  2  to that  section was  materials  racemization anatase  in experimental  precipitated T i 0 . This  also  Chemical  described  usual activity  is  83 5.4 SPECULATION PREVIOUS So dioxide  ON THE C A T A L Y T I C  AND  PRESENT  KINETIC  MECHANISM  catalysis  increase  better, seems  interesting points  the kinetic activity  into understanding of  this heterogeneous  activity Table the  activity  is compiled Catalytic  12  rai t e m i z a t i o n  of  sections, an additional  in Table  ODticallv  other  dioxide catalysts  comparison  of  catalytic  12.  of four  activity  a few  catalysis.  of titanium  this reaction has been compared to that for the proceeding  titanium  and then to understand this  to be unsatisfactory, but does provide  Despite the fact that the catalytic  throughtout  OF  RESULTS  far, it has been shown that, our attempt on modifying  in order to  towards  ON THE BASIS  heteroqeneous inorqanic  active  solids  towards  (• K=Kcat/Kuncat >  binaohthvl  ,  rcat.i  [Bina.1  fmq/mh  f10«xM^  TiO,  10.0  6.82  10.0  3.5  0.35  acetone  Ni  37.7  25.0  25.0  5.0  0.13  n-heptane  Pt  1.0  5.0  25.0  8.0  8.0  ethanol  C  1.0  250  25.0  14.0  14.0  chloroform  Cat.  The catalyst obviously al"  most  important  t(°C)  feature  are all electron-donating  drawn from Table type  catalysts  related to the electron-donating of  isomerization  of  of  ability  of  relevant  arguement that an anion radical  is that the  and the catalytic  of  nitrobenzene  T i O , solution and probably  plays  activity  result  (confirmed by of  finding definitely  binaphthyl  four is  of the catalyst. Hattori et  identifying the intermediate  butenes. This  12  T i O , surfaces to nitrobenzene  the formation of the anion radical spectrum) in a course  Solvent  K/rCat.l  fmq->)  reported that the exposure  colloidal  K^  the T i O , favours  in  ESR catalyzed the  is likely formed  in the  an intermediate role  in the  84  catalysis.  It  pathways  does  which  the  of  is  then  involve  catalyst  depends  on  binaphthyl, catalytic catalyst  the  catalysts  Moreover, good  reasonable  as  the  one  can  other  guess  that  radical  anion  intermediate  see  ones.  activity. the  But  is  titanium  Since  least  the  dioxide  rate  of  temperature  improper  it  most  that  the  5 1  be  at  one  of  catalytic  mechanism  regardless  concerned.  solvent *",  it w o u l d  and  is  to  to  certain  successful  list  that  the  catalyst  the  and  those  in  some  sense  racemization  the  is  applied  in  the to  the  of  order  most the  as  also  concentration  catalysts  carbon as  is  of  the  active  racemization  of  binaphthyl. Also,  it  semiconductor Ti0  2  lab).  (the  is  worth  such  as  investigation  noting MoS was  2  that  preliminary  showed  similar  carried  out  by  a  studies  on  other  catalytic  results  to  that  summer  undergraduate  in  for this  85 5.5  CONCLUSION Until the completion of  catalysts  have been discovered  racemization of  binaphthyl  believed that this  to or different  phenomeon  heterogeneous  from those four  in faciliating simple  organic  far as the mechanistic  intermediate  of  process  might also  one. All  similar  be catalytically of  and previous  active  binaphthyl.  anion  kinetic  studies  do  possiblity.  the catalyst  order rate constants  2  (poison  in the order of  pyrene). A l s o , it appears  increase with the  T i 0 , decrease with binaphthyl  to small amounts  of  polynuclear  aromatic  that the finer  anatase  particles  more efficiently. Meanwhile, it is unfortunate  experimental  method has not been found to determine dioxide  concentration, compouds  benzene, naphthalene, anthrance, and  racemization  potential titanium  therefore  properties  like the racemization  present  the  at all, and it  is concerned, the radical  and are sensitive increases  is not unusual  catalysts  In particular, observed first concentration  active towards  catalysts possessing  reactions  is the favorite  not exclude this  to be catalytically  heterogeneous  in virtually the same ways. It was  catalytic  suggested that many  As  this thesis, four common  photocatalytic  racemization.  catalyze  the  that more  the nature  of  precise the  6. EXPERIMENTAL  6.1  GENERAL Melting points were determined with a Thomas  Melting Point  Apparatus  using open tube capillary  Gas-liquid Chromotagraph 5830A  Gas  (glc) was  Chromotagraphy  Unimelt  and are corrected.  performed using a Hewlett  equipped with a flame  Optical  on Chromosorb  rotation was  polarimeter with a 1dc or ([a]) was  (concentration  Solvents the exception  for of  methods were  first  one was  reproducibility acetone was 3A  Linde  1cm quartz-faced jacketed  MC rotation  rotation/[(path  "100%" was used as  length  with received.  purifying the technical grade acetone. The  anhydrous  phosphorous  in the kinetic  sieve, and succesive  small  at reflux, until the violet  studies  calcium  pyrene and naphthalene were recrystallized before experiment.  86  at one time,  of  KMn0  4  were  persisted, followed  again and distilling. Gases  grade and dried through a column of  sulfate,  first dried with type  portions  colour  magnesium  pentoxide. Due to a  then treated as following: acetone was  drying with Linda 3A sieve  241  and adsorption studies were spectrograde  problem that occured  molecular  mesh.  in g per ml)].  adopted for  distilling from  and  column  cell. Specific  that, acetone was treated with anhydrous  added to acetone  reagent  using a Perkin Elmer  ethanol and acetone. Ethanol  Two  by  kinetic  steel  W A W - D M S C , 80/100  calculated using the equation; [o]=observed  in dm) times  followed  determined  Packard  ionization detector  using nitrogen as carrier gas with a 6' by 0.125" stainless packed with 3% OV-17  Capillary  (N , 0 , 2  2  by  H,, Ar) were  sulphate. Anthrance,  being used in the  additive  87 6.2 S Y N T H E S I S The  OF  RACEMIC  procedure  Kryrinis' . To condenser  used was  a dry  0  was  1 .T-BINAPHTHYL  3-necked  added  analogous flask  9.6g m a g n e s i u m  c-bromonaphthalene  and a s i n g l e  heated to  start  heating  reflux  for  hours, with  to  20  m i n . The  the  addition  w h e n n e c e s s a r y . The added  slowly  to  chloride(prepared anhydrous was  then s t i r r e d by  hydochloric solvents  were to  washed  with  was  removed  0 ° C . The  once  the  6.3 P R E P A R A T I O N  of  of  0.l33g  distilled  from  to  of  used w a s  then h e a t e d t o benzene to  salt  for  room  reaction  anhydrous  acetone  similar  to  1,V-binaphthyl  permagnate) was  acid  magnesium  to  ether  6  slurry  the  and  200ml  mixture  mixture  was  ice. The  portions  of  10%  sulfate. The  crystallized a Bunchner  on funnel,  ( 3 0 - 6 0 ° C ) , and  crude  three  for  ° C ) in  and  several  times  in l i t e r a t u r e :  ACTIVE  100  an o i l , w h i c h  petroleum  was  cupic  reaction  transferred  ml  temperature  occurred  with  reflux  t o t h i n the  4 h at  ( 6 5 - 1 1 0 ° C ) . The  from  OPTICALLY  potassium  further  54g anhydrous  was  cold  petroleum  active  without  cooled  afford  ether, 56  proceeded  successively over  and  mixture  10% h y d r o c h l o r i c  143.5-144.5°C. mp  procedure  solution  of  stirrer  anhydrous  temperature. The  material of  overheaded  and  stirred  dry  was  100ml  extracted  amount  OF  ml  vigorous  at r o o m  Sakellerios  iodine. The  was  dihydrate  insuing  then recrystallized  crystals, mp:  The  200  mixture  in v a c u o  from  of  mixture  up t o  brown  a small  recrystallized (20.9g) w a s  the  addition  layer  crystal  a c i d , w a t e r , and d r i e d  cooling  white  drying  with  of  turnings, 72ml  suspension  overnight  slow  ether-benzene  of  that  reaction, which  reaction  a stirred  ether. A f t e r  quenched  the  reaction  by  fitted  to  1,1'-binaphthyl to  yield  lO.Og  of  and W i l s o n .  A  144-145°C.  1.1-BINAPHTHYL that  of  Pincock  in 4 0 0 m l filtered  into  7 1  acetone a  (freshly  1000ml  round  88  bottom  flask. The solution was then cooled  (-78°C) for Without  completing the crystallization, the flask placed on a rotary evaporator  rotated in air while the full  established  (5 min), it was then  between 20°C crystals  ice acetone  bath  10 min with swirling, during which time crystallization  immediately was  in a dry  and 25°C. A s  vacuum lowered  was removed  (Buchi Rotovapor of  began.  and R). The  a water aspirator  was  the flask warmed, some  (but not  of  all) of  acetone was  on the high vacuum pump. The material, which was  100% recovered,  temperature  135°C.  6.4 KINETICS  (at 589nm, c 3.7mg/ml  OF U N C A T A L Y Z E D  AND  the  solvent. The  evaporation was taken to dryness, and any residual  [a] =-174°  being  into the water bath, maintained  dissolved, then reprecipiated with the loss  resolved to  flask  removed  acetone) on heating at  TITANIUM  DIOXIDE  CATALYZED  REACTIONS Oxide semiconductor with a magnetic intensive  (0.25g) was placed  stirrer and 25.0ml of  stirring, a highly  immersed  binaphthyl  min (for completely temperature of A various  measured  next added  sample  acetone  solution  magnetic of  was  stirrer  optically  and equilibrating  extracted from  and  active  the  the solution at  by using a Pasteur pipette. This was into a one dc long polarimeter  at the Mercury  24 hr  run was started.  (app. 2ml each time) was  530A  added. After  fitted  into the solution, and after about 5  dissolving the substrate  reaction times  about 0.7g Celite was  bath. A  the solution), the kinetic  sample  was  fitted with a underwater  into a 10.0°C water  (0.00435g) was  dry acetone  divided titanium dioxide  formed. Then the flask was was  in a 100ml R. B. flask  filtered through  cell. The  line at 456nm. The cell was  reading  next placed  into  89  the polarimeter and the reading was taken with integration sec set at 5 sec. The cell was then rinsed with acetone and shaken three times f o l l o w e d by drying with a stream of dry air.  6.5 PROCEDURE FOR ATTEMPTED TITANIUM DIOXIDE  PHOTOCATALYTIC  REACTIONS Oxide semiconductor  (0.025g) was placed in a 100ml R.B. flask  fitted  with a magnetic stirrer and 25.0ml of dry acteone was added. After 24 hr intensive stirring, a highly divided titanium dioxide acetone solution was formed. Then the flask fitted with a under-water  magnetic stirrer  immersed into a 10.0°C water bath. A sample of optically active  was binaphthyl  (0.00435g) was next added into the solution, and after about 5 minutes  (for  equilibrating the temperature of the solution), the kinetic run was started. A solution (app. 5ml) was extracted from the above solution by using a Pasteur pipette. Two samples (app. 2.5ml each) were obtained this solution. One was immediately  from  measured of the optical rotation, and  the other one was placed into a quartz tube, which was fitted with a magnetic stirrer and immersed in a 10°C bath beside a high-pressure mercury lamp (450 watts). After t_ time, the optical rotation of this  sample  was measured and then compared to the initial optical rotation of the identical solution. Repeating the above procedure by only changing the reaction time (t) made "P the kinetic data. If a solution was needed to be saturated with one of three (0 , 2  N  2  gasses  or He), a very small stream of gas, previously passed through a  dehumidified apparatus, was bubbled through the solution for 30 minutes before the solution was divided into t w o parts.  90  6.6 PRODUCT  ANALYSIS  The conditions  ADSORPTION  used were  started at a temperature rising rate of  AND  of  EXPERIMENTS  increased up to 250°C  the binaphthyl  were  present. This  of  signal and solvent  signal  (retention time  concentration  in the kinetic  solutions  of  concentration  binaphthyl  studies) was  made  up by  even a was  0.33 x 10'  6.7 PREPARATION  4  Hydrochloric  concentration  DIOXIDE  charged  fitted with a condenser, a hotplate-magnetic pressure  equalizing funnel. After  tetrachloride period of followed  stirrer  the stirring was  was added dropwise  to the flask  could tell the could  TETRACHLORIDE  into a two-necked combination  started, 50 ml  and a titanium  2 h. Centrifuging,  by washing the precipitate with deionized water, was  repeated  three times, in which the liquid was then removed with a Pasteur was  ground in a mortor  before heating again at 700°C  and pestle  in a furance  for  flask  through the funnel over a  25 minutes, and was then heated to reflux for  The precipitate  (10.00  difference.  FROM TITANIUM  acid (1.0M, 50 ml) was  of  + a ml)]. It was  tested. In other words, the glc  mole/1 binaphthyl  OF TITANIUM  binaphthyl  diluting the initial solution  down to 0.50 ml, the glc still  above two samples  of  compared to a series  4  identify  min)  (6.82x10-*mole/l, the  ml) with a ml acetone. (6.82x10- mole/lx[l0.00ml/(10.00ml then found that  = 0.30  racemization.  minimal  able to detect, a solution  dilute binaphthyl  done,  indicated that there was no side reaction such as a  In order to know exactly what  of  at a  12.29 minutes. In all experiments  reduction reaction occured during the catalytic  difference  runs  20°C/min and completed within 20 minutes. Binaphthyl  only  usual  GLC  as f o l l o w s : the gas chromatography  170°C and this  appeared at the retention time  the glc was  USING  into a fine  pipette.  powder  12 h. The final product  was  a white  powder.  6.8 REDUCTION  OF TITANIUM  Aldrich titanium dioxide apparatus. A  slow  stream  of  DIOXIDE 0.80g was placed hydrogen after  concentrated HjSO« solution and calcium titanium dioxide  powder  operated at 380°C  of  1 hr to  hydrogenation  bubbled through the  chloride was passed over  during the reduction  for times  in the  the  process. The procedure  18 hr. Reduced titanium  appeared greyer as the duration of the treatment  increased.  was  dioxide  BIBLIOGRAPHY  1.  N.A.  Clark  and S T . Lagerwall, ADDI. Phvs. Lett. 36 899 (1980).  2.  G.H. Brown and P.P. Crooker, Chemical  3.  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