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Photochemistry of some naphthoquinols in solid polymer matrices Gudmundsdóttir, Anna Dóra 1988

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P H O T O C H E M I S T R Y O F S O M E N A P H T H O Q U I N O L S I N S O L I D P O L Y M E R M A T R I C E S By Anna Dora Gudmundsdottir B. Sc. University of Iceland, 1985 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF T H E REQUIREMENTS FOR T H E D E G R E E OF M A S T E R OF SCIENCE in T H E FACULTY OF GRADUATE STUDIES DEPARTMENT OF CHEMISTRY We accept this thesis as conforming to the required standard T H E UNIVERSITY OF BRITISH COLUMBIA October 1988 © Anna Dora Gudmundsdottir , 1988 Iii 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 Chemistry The University of British Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: i i ABSTRACT The main objective of this work was to study how polymer media can modify the photochemical reactivity of dissolved guest molecules. Three tetrahydronaphthoquinols, whose photochemistry is known to be sensitive to the reaction medium, were synthesized for this study. The photochemistry of these compounds consisted of [2 + 2] cycloaddition in solution and hydrogen abstraction-initiated rearrangement in the solid state. Different photopro-ducts from solution and solid state photolysis were interpreted as being due to reaction from different conformers in the different media. 2,3,4aa,6,7,8aa-hexamethyl-4a,5,8,8a-tetrahydronaphthoquin- l-on-4/3-ol, studied in poly(methyl methacrylate) and poly(vinyl acetate) films, was found to exhibit behavior that is intermediate to solution and solid state reactivity and is discontinuous at the glass transition temperature. 2,3,4aa,6,7,8aa-hexamethyl-4a,5,8,8a-tetrahydronaphthoquin-l-on-4a-ol, which was essentially unreactive in the solid state, was also studied. It was found to give the expected but not observed solid state product as the major product in poly(methyl methacrylate). Finally, 2 , 3 ,4aa ,6,7, 8aa:-4a ,5,8, 8a- tetrahydronaphthoquin-1-on-4/3-acetate was studied. As a result of differences in the local enviroment, this compound displayed unique photoreactivity in each of three different media: in solution i t gave 5-exo-acetoxy-l,3,4,6,8,9-hexamethyltetracyclo [4.4.0.0^>^.0^•8]decan-2-one, in the pure crystalline phase i t gave i i i 5-exo-acetoxy-2-oxy-1,3,4,6,8,9-hexamethyltricyclo[4.4.0.0'']-dec-8-en -2-one and in poly(methyl methacrylate) films 5-exo-acetoxy-1,3,4,6,8,9-hexamethyltetracyclo[4.4.0.0^'^]dec-8-en-2-one, as a major product. It has been demonstrated that polymer matrices are useful reaction media for reducing the rates of conformational interconversions to the point that alternative chemical processes that are normally too slow to be observed in solution become competitive. This leads to chemical consequences that in some cases mimic those observed in the solid state. In others, where crystals are unreactive for some reasons or where the crystal lattice can sterically impede certain reactions, new products can be formed. Iv For Oskar V TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS v LIST OF TABLES v i LIST OF FIGURES v i i i ACKNOWLEDGEMENT x INTRODUCTION 1 RESEARCH OBJECTIVES 16 Selection of compounds for this study 24 RESULTS AND DISCUSSION 26 Preparation of star t i n g materials 26 Preparation of polymer films 29 Photochemical and photophysical studies 30 Photochemistry of compound 11 31 Photochemistry of compound 12. 32 Photochemistry of compound 7.. 34 Characterization of the new photoproduct 37 Product r a t i o studies 40 SUGGESTION FOR FUTURE WORK 55 EXPERIMENTAL 56 General 56 Synthesis 62 Photochemical and photophysical studies 69 REFERENCES 102 v i LIST OF TABLES Table T i t l e Page I Product ratios from i r r a d i a t i o n of 3 i n poly(ethylene) films and n-hexane. 14 II Photoproduct r a t i o studies of compound 11 i n different solvents. 72 III Organic polymers used as reaction media 73 IV Photoproduct r a t i o studies at different extent of reaction of compound 11 i n L-PMMA. 74 V Photoproduct r a t i o studies at different concentrations of compound 11 i n L-PMMA. 75 VI Photolysis of compound 11 i n different polymer matrices. 76 VII Photoproduct r a t i o studies of compound 11 i n PVAc at different temperatures. 78 VIII Derived equations for Arrhenius plot of compound 11 i n PVAc. 79 IX Photoproduct r a t i o studies of compound 12 i n diffe r e n t solvents. 83 X Photoproduct r a t i o studies of compound 12 i n ethyl acetate at different temperatures. 84 XI Photoproduct r a t i o studies of compound 12 i n ethylene glycol at different temperatures and v i s c o s i t y . 85 XII V i s c o s i t y studies of mixtures of methanol and ethylene g l y c o l . 86 XIII Photoproduct r a t i o studies of compound 12 i n methanol and ethylene glycol mixtures. 87 XIV Photoproduct r a t i o studies at different extent of reaction of compound 12 i n L-PMMA. 88 v i i XV Photoproduct ratio studies at different concentration of compound 12 in L-PMMA. 89 XVI Photolysis of compound 12 in different polymer matrices. 90 XVII Photoproduct ratio studies of compound 12 in L-PMMA films at different temperatures. 91 XVIII Photoproduct ratio studies of compound 12 in PVAc at different temperature. 92 XIX Photoproduct ratio studies of compound 12 in PiBMA at different temperatures. 93 XX Derived equations for Arrhenius plots of compound 12 in L-PMMA, PVAc and PiBMA. 94 XXI Photoproduct ratio studies at different extent of reaction of compound 2 in L-PMMA. 99 XXII Photoproduct ratio studies at different concentration of compound ~1_ in L-PMMA. 100 XXIII Photolysis of compound 7 in different polymer matrices. 101 v i i i LIST OF FIGURES Figure T i t l e Page 1 Isomerization of stilbene 3 2 Dimerization of anthracene 4 3 Photochromic behavior of benzospirans 5 4 An energy diagram of an exciplex 7 5 Emission spectra of anthracene i n the presence of N,N-dimethyl-p-toluidine i n toluene and i n poly-(styrene) 8 6 Temperature effect on Am a x of the exciplex anthracene/N,N-dimethyl-p-toluidine 9 7 Hypothetical p r o f i l e of an exciplex i n f l u i d and r i g i d matrix 10 8 Bichromophoric molecules 11 9 Norrish Type I and II reactions 12 10 Photoreduction of w-undecylenyl benzophenone-4-carboxylate 13 11 Compounds whose photochemistry i s medium dependent 17 12 Tetrahydronaphthoquinols 18 13 Crystal structure - Reactivity correlation 19 14 Conformation equilibrium 21 15 Unexpected r e a c t i v i t y of 7 i n s o l i d state 22 16 Starting materials 24 17 Preparation of duroquinone 26 18 Preparation of the s t a r t i n g materials 27 19 Photochemistry of compound 11 31 ix 20 Photochemistry of compound 12 33 21 Photochemistry of compound 7 36 22 Photolysis of compound 17 i n the s o l i d state 37 23 Acetylation of compound 14 38 24 Photoproduct ratios at different degrees of conversion i n L-PMMA • 39 25 Photoproduct ratio s at different concentrations i n L-PMMA 40 26 Photoproduct ratios i n different polymer matrices 42 27 Arrhenius plot for compound 12 i n ethyl acetate 44 28 Arrhenius plot for compound 12 i n L-PMMA 47 29 Arrhenius plot for compound 12 i n PVAc and PiBMA 48 30 Arrhenius plot for compound 11 i n PVAc 49 31 Arrhenius plot for compound 12 i n ethylene glycol 52 32 Photoproduct r a t i o for compound 12 as a function of vi s c o s i t y at a constant temperature (ethylene glycol - methanol mixtures) 53 X ACKNOWLEDGEMENTS I wish to express my sincere thanks to Professor John Scheffer for his excellent guidance and helpful suggestions throughout the course of my research and the preparation of this thesis. I also wish to thank a l l of the members of Dr. Scheffer's research group, who made the last two years most enjoyable. Special thanks to Pauline, Graham, Raj and Gudrun for proof reading this thesis. Finally, thanks are due to the staff of the departmental NMR, MS and elemental analysis laboratories for their assistance. -1-INTRODUCTION The study of organic chemical reactions in media other than isotropic media has become an area of intense research in the past several years. The impetus for carrying out studies of this type arises from the realization that organized media can modify the chemical reactivity of complexed or dissolved guest molecules in much the same way that enzymes control the reactions of the substrates to which they are bound. Examples of organized media that have been investigated include molecular crystals, liquid crystals, monolayers, polymers, micelles, adsorption on surfaces, and inclusion complexes.1 Studies of photochemistry in polymer matrices and polymer photochemistry have become extremely important in recent years. Large industries employing photography, lithography and photocopying depend to a large extent upon photochemistry in macromolecular media. Organic polymer films containing dissolved guest molecules are readily prepared by dissolving the polymer and the guest molecule in a solvent and applying the solution to a surface and allowing the solvent to evaporate. The guest molecules in these assemblies find themselves in unique, partially ordered, environments that can be altered systematically in an easy way by changing the polymer structure, t a c t i c i t y , molecular weight, polydispersity and degree of cross linking, as well as by varying the temperature above and below the glass transition temperature(s). But despite ease of preparation and potential significance for the fields of microlithography and photogra--2-phy, the use of polymer films as solvent media for carrying out photochemi-cal transformations has received relatively l i t t l e attention compared to the pure liquid and solid phases.-^ Some of the few examples of the reciprocal interactions between polymer and excited guest molecules cited in the literature are given below. The role of free volume, glass-transition temperature (Tg)i microscopic viscosity and/or environment can be demonstrated by the manner in which the polymer medium influences the photochemistry and photophysics of guest molecules. One of the simplest photochemical processes which can be observed in polymer matrices is the cis/trans photoisomerization of the double bond in olefins such as stilbene. Gegiou et a l . showed that the quantum yields of cis/trans isomerization of stilbene decreased with increasing viscosity of the media.4 They also found that a polymer matrix such as poly(isobutylene) did not inhibit photoisomerization above the glass transition temperature (Tg) where isomerization followed f i r s t order kinetics, but below Tg complex kinetics resulted and appeared to be the result of a multiplicity of different f i r s t order processes. Postulating that an increase in free volume was necessary for the transition from trans- to cis-stilbene and that restrictions on the rotations of the phenyl groups in the solid matrices reduced the quantum yield for the process, they then suggested that the stilbene molecules were located in a range of different guest sites having different amounts of free volume. This results in a spectrum of microscopic -3-H Ph Ph Ph H Figure 1: Isomerization of stilbene. viscosities, each determining the rate constant for the observed process. Similar effects have been reported by other workers for simple isomerization in glassy polymer matrices and i t seems to be a general phenomenon. " ^  Similar considerations affect the rate of diffusing species in polymeric matrices. For example Cowell and Pitts studied the photodimerization of anthracene dispersed in poly(methyl methacrylate) (PMMA) and demonstrated that the dimerization rate in the polymer film was much reduced from values obtained in f l u i d solution or in potassium bromide pe l l e t s .8 They showed by spectral comparison that anthracene was randomly dis-persed as a true solution in PMMA, not as small crystallites as was apparent in the potassium bromide pellets. The rate of dimerization of anthracene in the polymer matrix decreased slowly as irradiation proceeded. This led -4-Figure 2: Dimerization of anthracene. Cowell and Pitts to the conclusion that the film consisted of a series of channels and cavities in which the guest molecules were constrained between irregularly packed polymer chains. Anthracene molecules situated by chance at certain proper spatial positions adjacent to their nearest neighbors would undergo photodimerization f i r s t , while dimerization was disfavored for molecules more remotely situated from their nearest neighbor. The photochemistry of benzospiropyran compounds in polymer films has been studied extensively in connection with their potential applicability to erasable photomemory systems.^ These colourless benzospiropyrans (A) can be converted to coloured forms (B) by reaction at the spiro carbon atom by irradiation. They revert to the colourless form via ring closure in the dark. -5-Studies by Kryszewski et a l . of benzospiropyran in amorphous acrylate polymers showed that the fhermal bleaching followed first-order kinetics above the glass transition temperature, but below Tg required a more complex mechanism postulated to involve the average free volume and segmental d i f f u s i o n . ^ They pointed out that in polymer matrices with long flexible side groups, such as poly(vinyl butyrate), the decolourization followed f i r s t order kinetics, even below the glass transition temperature. Coloured form B Uncoloured form A Figure 3: Photochromic behavior of benzospiropyrans. I. Mita, K. Horie and M. Tsukamoto have reported similar results for benzospiropyrans in amorphous polycarbonate films.^ They also found that thermal bleaching followed f i r s t order kinetics above the glass transition temperature and below Tg a more complex mechanism was observed which they suggested to be due to the inhomogeneous distribution of free volume in the polymer matrix. -6-Arrhenius plots of the apparent rate coefficient for the decolouration showed breaks at Tg, as well as at /3 and 7-transitions temperatures (T^g, T^) of the matrix polycarbonate. The T^ corresponds to the onset of phenyl group rotation in polycarbonate and T^ is associated with the motion of a few monomeric units as a whole.H They postulated that this result suggests that the rate of decolouration is controlled by molecular motion of the matrix polymer and indicates the importance of subglass transitions such as 1p and T^ for the active control of intramolecular isomerization in polymer matrices. A number of similar results have been reported for various benzospiropyran compounds.^2-14 Exciplex emission of guest molecules in glassy polymers has been used to investigate the effect of r i g i d i t y of the medium on bimolecular interac-tions. ^  Exciplexes are complexes in the excited state which do not have binding interactions in the ground state. The energy profile of an exciplex is given in Figure 4. Exciplex emission is characterized by being broad, structureless and red-shifted relative to the corresponding monomeric fluorescence.1^ -7-Figure 4: An energy diagram of an exciplex. Farid et a l . studied the exciplex formation of several compounds in solutions and in polymer films.^-^ The exciplex emission values in polymeric media were considerably shifted to shorter wavelength as compared with the maxima measured in f l u i d media at the same temperature (see Figure 5). -8-4 0 0 5 0 0 X, nm Figure 5: Emission spectra of anthracene in the presence of N,N-dimethyl-p-toluidine in toluene and in polystyrene. Moreover, they discovered that the maxima of the exciplex emission were temperature dependent in solutions and polymers. The maxima in solution were shifted to shorter wavelengths with increasing temperature, but in the polymer media they were shifted to longer wavelengths. Above the glass transition temperature similar results were obtained for the f l u i d and polymer media. -9-550 -40 0 40 Temperoture (°C) Temperoture Effect on Xmox0* t n ' Exciplex Anthrocene/N,N-dimethyl -p-toluidine in T f l - 75 °C toluene polystyrene polystyrene (80%)+ Tg -35°C butylbenzene (20%) Figure 6: Temperature effect on Am a x of the exciplex anthra-cene/N,N-dimethyl-p-toluidine. Farid et a l . explained the shift in wavelength maximum of the exciplex with temperature in f l u i d medium or in polymers above Tg as being due to a change in the energy profile of the exciplex; the shifts to shorter wave-length in polymeric matrices at temperatures below Tg were on the other hand suggested to be due to improper orientation and larger separation of the exciplex components as compared to the situation in f l u i d media. -10-in fluid solution emission excitation Configurotional porometer Figure 7: Hypothetical profiles of an exciplex in f l u i d and ri g i d matrices. In an interesting extension of this work, Farid et a l . studied certain bichromophoric molecules such as compounds 1 and 2 (Figure 8). These compounds form exciplexes intramolecularly when dissolved in f l u i d solu-tions. However, neither of these compounds showed exciplex emission when dissolved in poly(styrene). They suggested that the reason for this behavior is presumably that the most favored conformation of the molecules is one in which the two chromophores are rather far apart and there is not sufficient mobility in the matrix to permit the two chromophores to approach each other during the lifetime of the excited state. Figure 8: Bichromophoric molecules. Hartley and G u i l l e t investigated possible ways to control photodegrada-ti o n of polymers.17-19 in order to do so they studied poly(ethylene) into which had been copolymerized a small amount of carbon monoxide. They found that Norrish Type I and II reactions (Figure 9) accounted for the polymer degradation i n poly(ethylene) and they also found that a l k y l ketones dissolved i n polymer films undergo Norrish type I and I I reactions as w e l l . The quantum y i e l d for Type I degradation was independent of temperature and v i s c o s i t y while the Type I I was strongly dependent on both. -12-Figure 9: Norrish Type I and II. In similar but more recent studies Gcoden et a l . investigated the effect of elongation on the photochemistry of poly(ethylene-co-carbon monoxide) (P ( E /C0 ) ) . u The Norrish Type II reaction was the predominant process at room temperature. But when the films were elongated, the Norrish Type I reaction increased. The relative Norrish type II quantum yield was about eight times larger in undrawn films than in films cold-drawn 400%. But on the other hand, the relative Norrish Type I quantum yield was at least three times larger in cold-drawn films than undrawn. Gocden and co-workers postulated that the Norrish Type II reaction is more sensitive to constraints on molecular motions since i t requires a cyclic transition state while the Norrish Type I reaction does not depend on chain conformation and is therefore less affected. Polyethylene contains a distribution of crystalline and amorphous regions. In the crystalline regions, chains are t i g h t l y and regularly packed, whereas i n the amorphous regions, chains are somewhat randomly packed. Mechanical stretching of films orders the.random chains and therefore stretching favours extended conforma-tions of the polymer chains. The extended conformers are incapable of undergoing intramolecular hydrogen abstractions and th i s allows more of the polymer chains to undergo the slower type I photoprocess. Weiss et a l . investigated the photochemistry of the conformationally l a b i l e w-undecylenylbenzophenone-4-carboxylate (3) i n . stretched and O 1 unstretched polyethylene films and n-hexane. x When 3 i s irr a d i a t e d i n hydrocarbons i t cyclizes to y i e l d oxetane 4 or i s photoreduced to 5 and/or & v i a hydrogen abstraction from the solvent. Figure 10: Photochemistry of w-undecylenylbenzophenone-4-carboxylate. -14-While intermolecular photoreduction can occur from many conformations of 3_ in polyethylene f i l m s , formation of the intramolecular oxetane demands a sp e c i f i c orientation between the carbonyl and the o l e f i n i c group (which can only be achieved through chain c o i l i n g ) . Weiss et a l . postulated that a useful probe of the a b i l i t y of 3 to at t a i n the appropriate geometry i s given by the competition between formation of 4 and the photoreduction product 5. They found that the product r a t i o 5_/4 was independent of percent conversion i n f l u i d media and i n polymer films as w e l l , which demonstrates that no secondary processes were involved (Table I ) . Solvent % conversion [5]/[4] n-hexane 95 24 poly(ethylene) 95 7 (unstretched) 3 (streched) Table I: Product ratios from i r r a d i a t i o n of 3 i n polyethylene films and n-hexane. The data show that the intramolecular reaction mode i s less favoured i n the low-viscosity n-hexane than i n polyethylene films; stretching of the polyethylene films increases the intramolecular reaction mode as w e l l . The authors suggested that the intramolecular mode i s more favoured i n poly(ethylene) because the many degrees of rotational freedom available to 3 makes i t extremely sensitive to changes i n i t s l o c a l environment and i t s shape can respond to the solvent cavity. They had expected stretching to -15-favour extended conformers of 3 which would be incapable of undergoing intramolecular hydrogen abstraction, similar to what was observed for stretched poly(ethylene-co-carbon monoxide). They explained this unexpected result by assuming that stretching decreases the volume of amorphous sites making coiling of 3 tighter without grossly influencing the shape. The progress made on photochemistry in polymer systems indicates that the dominant factor is the free volume available within the solid at a particular temperature and the size of the group motion relative to the free volume. The free volume available to a reactive site or dissolved probe controls the course of the photochemistry and photophysical processes. Processes which require changes in free volume or movement can occur at reasonable rates only when there is sufficient free volume available to allow such movement or orientation. -16-RESEARCH OBJECTIVES. The main objective of this work is to start a general program to study systematically how polymer media can modify the photochemical reactivity of dissolved guest molecules. The simplest way to do so is to select a group of compounds that undergo unimolecular photoreactions that are known to be sensitive to the reaction medium. Since polymer matrices have properties intermediate between liquids and solids, a good starting point would be to investigate guest molecules whose solution and crystalline phase photochemi-cal behavior is known to be very different. Scheffer, Trotter and co-workers have done a systematic investigation of unimolecular reactions in solution and crystalline media. Some of their systems do behave differently in these two media, for example tetrahydro-naphthoquinones, tetrahydronaphthoquinols and a-cycloalkyl-p-substituted acetophenones -17-Ph Solid state: OH Solution: Solid state: Figure 11: Compounds whose photochemistry i s medium dependent. -18-An ideal group of compounds for this study appeared to be the tetrahy-dronaphthoquinols. These compounds give only one photoproduct i n solution and another one i n the s o l i d state when they are i r r a d i a t e d , which makes studies of the effect of polymer media easier than i f they formed a complex mixture of several compounds.22 Scheffer and co-workers investigated the solid-state and solution photochemistry of compounds possessing the basic l-oxy-cis-4a,5,8,8a-tetrahydronaphthoquin-4-ol structure. Figure 12: Tetrahydronaphthoquinols. In solution a l l the compounds afforded high yields of the corresponding [2 + 2] cage photoproducts when ir r a d i a t e d . On the other hand, for most of the substrates, photolysis i n the s o l i d state yielded only trace amounts of the cage compound; instead, photoproducts were formed which were the resul t of intramolecular a l l y l i c hydrogen-atom abstraction by the enone ^-carbon -19-a t o m f o l l o w e d b y b i r a d i c a l c o l l a p s e . T h e n a t u r e o f t h e h y d r o g e n a b s t r a c t i o n p r o c e s s ( f i v e - m e m b e r e d o r s i x - m e m b e r e d t r a n s i t i o n s t a t e ) was f o u n d t o d e p e n d o n t h e t y p e o f s u b s t i t u e n t s a t C ( 4 ) a n d o n t h e r e l a t i v e c o n f i g u r a t i o n a t t h i s c e n t e r . W i t h t h e a i d o f X - r a y c r y s t a l l o g r a p h y , i t was shown t h a t t h e C ( 4 ) s u b s t i t u e n t s c o n t r o l t h e a d o p t i o n o f o n e o f two p o s s i b l e c o n f o r m a t i o n s (B o r C) i n t h e s o l i d s t a t e t h r o u g h a p r e f e r e n c e f o r t h e b u l k i e r s u b s t i t u e n t a t t h i s c e n t e r t o l i e i n t h e p s e u d o - e q u a t o r i a l p o s i t i o n . T h e c o n f o r m a t i o n a d o p t e d d e t e r m i n e s t h e p h o t o c h e m i s t r y , c o n f o r m e r B g i v i n g r i s e t o f i v e -m e m bered t r a n s i t i o n - s t a t e h y d r o g e n a b s t r a c t i o n a n d c o n f o r m e r C l e a d i n g t o a s i x - m e m b e r e d t r a n s i t i o n - s t a t e p r o c e s s . R R H-w4^ R B C l. [2*2] Cycloodditon Closure i. Closure 2 Hemiocetol FormoTion F i g u r e 1 3 : C r y s t a l s t r u c t u r e - r e a c t i v i t y c o r r e l a t i o n s . -20-The s o l u t i o n / s o l i d state r e a c t i v i t y differences for a l l the tetrahydro-naphthoquinols were explained by suggesting that the intramolecular [ 2 + 2 ] photocycloaddition should be topochemically forbidden i n the s o l i d state. The double bonds are not only non-parallel but are too far apart to permit cycloaddition i n the s o l i d state, according to the X-ray data. The cycload-d i t i o n must occur from a different conformational isomer which must be a minor one, since conformer B and C would be preferred i n solution as w e l l . The obvious candidate for the reactive conformer i n solution i s A. I t was suggested that the hydrogen abstraction process was much slower than the cycloaddition process and therefore no hydrogen abstraction product were observed i n solution. Lewis has pointed out that two l i m i t i n g conditions are possible when conformational isomers can react photochemically i n solution to give different p r o d u c t s . " ^2 Case I: The rate for conformational isomerization i n the excited state i s greater than the rate for formation of the photoproducts, , k2 » k3, k4. Case I I : The rate for conformational isomerization i n the excited state i s less than the rate for formation of photoproducts, kj_, k2 « k3, k^. -21-Figure 14: Conformational equilibrium. In case II the ratio of the f i n a l products w i l l depend on the excited-state conformer population (A*, B* and C*) and hence also on the ground state conformer distribution and extinction coefficients. Since i t is certain that A is a minor conformer in solution and is unlikely to have an extinction coefficient greatly different from conformers B and C, i t appears that the case I situation is followed in the present instance. Thus in the case I situation, conformational equilibrium is established during the lifetime of the excited state, and the photoproduct composition depends only upon the relative photochemical reaction rates (Curtin - Hammett principle). Further studies by Scheffer and co-workers on the tetrahydronaphthoqui-nol system showed that one of these compounds (2) behaved differently from the other ones in i t s solid state r e a c t i v i t y . ^ When i t was irradiated in -22-benzene i t afforded quantitative yields of the expected cage product 8 whereas i r r a d i a t i o n of crystals gave r i s e to 9 as the sole product. Figure 15: Unexpected r e a c t i v i t y of 2 i n the s o l i d state. A remarkable difference was noted between these results and those obtained with the tetrahydronaphthoquinols mentioned above. This concerned the r e g i o s e l e c t i v i t y of the s o l i d state hydrogen transfer step. The endo hydrogen atom at C(5) i s v i r t u a l l y equidistant from C(2) and C(3), and i n every case studied except 1_ transfer occurs to C(3), presumably so as to form the more favorable resonance s t a b i l i z e d r a d i c a l at C(2); b i r a d i c a l closure then leads to products analogous to 10. X-ray crystallography revealed the probable cause of the unique photobehavior of enone 1_ i n the s o l i d state: a p a r t i c u l a r close contact between the methyl group at C(3) and a methyl group of a neighboring molecule located below i t i n the l a t t i c e . This contact was suggested to raise the activation energy of the normally favoured hydrogen transfer to C(3) through steric hindrance of the downward motion of the methyl group which accompanies pyramidalization at this centre; there was no such contact involving the methyl group attached to C(2), which allows hydrogen transfer to C(2) and compound 9 to be formed. With this explanation for the different reactivities in solution and the solid state in mind, i t seemed reasonable to expect the polymer medium to restrict the motions required for conformational isomerization in the ground state and the excited state and therefore to affect the photochemistry of these tetrahydronaphthoquinols. Organic molecules dissolved in polymer films find themselves in environments that, while s t i l l restricting diffu-sion and major conformational changes to a considerable degree, are much more isotropic than those existing in the crystal. In other words the polymer media provides a "smooth" reaction cavity that is different from that observed in crystals and, therefore i t is possible to observe chemical behavior in this medium that is different from that observed in both the liquid and crystalline phases in some instances. -24-SELECTION OF COMPOUNDS FOR THIS WORK. It was decided to select three of the tetrahydronaphthoquinols mentioned above to begin with, and investigate how polymer media might modify the photochemistry of these compounds. These compounds would have to be selected carefully in order to get as much information as possible about the polymer media, specifically to determine in what ways polymer matrices are different from solutions and solid state media, in their effect on solute photoreacti-v i t y . These three compound were: Figure 16: Starting materials. The f i r s t compound selected i s 2 , 3 , 4aa, 6 , 7 , 8ao:-hexamethyl-4a, 5 , 8 , 8a-tetrahydronaphthoquin-l-on-4/8-ol, (11). Depending on the photochemical behavior of this compound polymer matrices could be c l a s s i f i e d as being more s o l i d - l i k e or more s o l u t i o n - l i k e . The second compound selected i s 2,3,4aa,6,7,8aa-hexamethyl-4a,5,8,Sa-te trahydronaphtoquin-1- on- 4a- o l (12) This compound was es s e n t i a l l y unreactive i n the s o l i d s t a t e .2 2 This was suggested to be due to an unusually long distance between the /3-carbon atom of the enone and the intended a l l y l i c hydrogen atom, as X-ray data indicated. Another explana-ti o n could be that the c r y s t a l l a t t i c e packing does not allow the reaction to take place. Photolysis of this compound in polymer matrices could give information on which of these p o s s i b i l i t i e s i s more l i k e l y . 2,3,4aa,6,7,8aa:7hexamethyl-4a,5,8,8a-tetrahydronaphtoquin-l-on-4/3-acetate (7) was selected because of i t s unusual r e a c t i v i t y i n the s o l i d state due to s t e r i c compression.-^ The polymer matrix should provide a "smooth" reaction cavity that i s different from that observed i n the c r y s t a l , so the effect of s t e r i c compression should have changed i n the polymer matrix. RESULTS AND DISCUSSION SYNTHESIS OF STARTING MATERIALS. The synthesis of the naphthoquinols required for this study can be divided into two parts; f i r s t oxidation of durene to duroquinone and secondly conversion of duroquinone into naphthoquinol. The synthesis of duroquinone has been accomplished by using a sequence of reactions estab-lished by L.I. Smith-^ outlined in Figure 17. Duroquinone Figure 17: Preparation of duroquinone. The f i r s t step involves n i t r a t i o n of durene using n i t r i c acid dissolved i n s u l f u r i c acid. The dinitrodurene formed i n the f i r s t step i s then reduced with SnCl2 i n acetic acid to form a stannous complex, which i s oxidized into duroquinone by FeCl3 i n hydrochloric acid solution In the second part of the preparation of the s t a r t i n g material, naphtho-quinols are synthesized using a sequence of reactions established by Scheffer and co-workers outlined i n Figure 18. Duroquinone I NaBH , I 0 Figure 18: Preparation of the sta r t i n g materials. In the f i r s t step, naphthoquinone i s prepared by Diels-Alder addition of duroquinone to 2,3-dimethyl-l,3-butadiene i n a sealed tube. Reduction of the naphthoquinone with sodium borohydride yielded 60:40 mixture of the a -28-and yS-naphthoquinols (compounds 12 and 11 respectively). These naphthoquinols were easily separated and some of the /3-alcohol was acetylated with acetic anhydride in pyridine to form naphthoquinol-acetate (compound 7). PREPARATION OF POLYMER FILMS. Before use, the polymer was freed of s t a b i l i z e r and other low molecular weight impurities by dissolution i n chloroform or acetone and reprecipita-t i o n by addition of methanol or n-hexane, suction f i l t r a t i o n , and vacuum drying. This process was repeated three times. The films were prepared by applying ca. 0.5 ml of a solution containing polymer and photoactive guest to the top of a microscope s l i d e and d i s t r i b u t i n g i t evenly over the surface using a second s l i d e as a straight-edge. Typ i c a l l y , the solutions consisted of 1.0 g of polymer and 70 mg of substrate i n 30 ml of chloroform. After coating, the films were a i r dried for 24 h and then dried under vacuum for 48 h at room temperature. The films so prepared had thicknesses of approxi-mately 5 - 1 0 microns as determined by a profilometer (Tencor) measurement. -30-PHOTOCHEMICAL AND PHOTOPHYSICAL STUDIES. Photochemistry of 2,3,4aa,6,7,8aa-hexamethyl-4a,5,8,8a-tetrahydronaphthoquin-l-on-4/3-ol (11). Irradiation of compound 11 in benzene at room temperature led essentially to quantitative yields of the cage compound 1.3, whereas photolysis of 9 9 crystals of compound 11 afforded very high yields of ketol 14." These results were interpreted as being due to reaction from different conforma-tions of 11. in different media as explained previously (page 19) . In the solid state, conformer 11B is the exclusive conformer present and has i t s double bonds improperly oriented for cycloaddition. Instead i t undergoes relatively slow excited state hydrogen abstraction to afford 14 (see Figure 19). In solution, on the other hand, the reaction is thought to occur through conformer 11A which is in rapid equilibrium with conformer 11B even though i t s equilibrium concentration is low. It gives rise to 13 as the exclusive photoproduct because of a relatively high rate of intramolecular [ 2 + 2 ] photocycloaddition. -31-14 13 Figure 19: Photochemistry of compound 11. The proposed mechanism predicts that the 13:14 r a t i o should be temperature and/or v i s c o s i t y dependent. In methanol, however, no tempera-ture dependence was observed from +20 to - 60°C. Only i n ethylene glycol at -10 °C (vi s c o s i t y 65 cp) did photoproduct 14 s t a r t to appear i n the gas chromatographic traces. I t was s t r i k i n g , therefore, to f i n d that i r r a d i a -t i o n of enone 11 i n the low molecular weight poly(methyl methacrylate) (L-PMMA) matrices at room temperature gave 14 as a major product (50%). These results indicate that the L-PMMA films can be viewed as a phase between those of the s o l i d state and solution. The effect of the polymer medium on the photochemistry of compound 1_1 can be explained q u a l i t a t i v e l y i n the following way: the isomerization between conformers 11A and 11B occurs -32-with large structural changes in the molecule which require concomitant changes of the local polymer environment associated with the generation of free volume. Therefore, the r i g i d structure of the polymer slows down the isomerization rate, both in the ground state and the excited state. If compound 11 is dispersed homogeneously throughout the polymer matrix, the non-homogenous structure of the matrix should give rise to a spectrum of isomerization rate constants. Lewis-^ has pointed out that, when the conformational isomerization rates are of the same order of magnitude as the reaction rates, the Curtin-Hammett principle no longer s t r i c t l y applies and the photoproduct ratio no longer depends only on the different photochemical reaction rates but also on the conformer populations in the ground state. This allows the slower hydrogen abstraction process to be observed, because conformer 11B is the most populated in the ground state. Photochemistry of 2,3,4aa,6,7,8aa-hexamethyl-4a,5,8,8a-tetrahydronaphthoquin-l-on-4a-ol (12). Photolysis of compound 12. in solution2 2 afforded the intramolecular [2 + 2] photocycloaddition product 15, presumably through conformer 12A. Compound 12 crystallizes in conformation 12C, the controlling factor being the preference for the hydroxyl group to l i e in the pseudo-equatorial position. Intriguingly, crystals of enone 12 proved to be photochemicaly inert. In polymer films, however, enone 12 was far from inert; irradiation in L-PMMA at 20 °C gave a mixture of compound 15 (20%) and 16 (80%). Photoproduct 16. -33-corresponds to the product expected (but not observed) from photolysis of enone 12 in the solid state; such a reaction has been observed for an analogue of 12 that lacks methyl groups at C(6) and C(7).2 2 The present results thus indicate that the lack of reactivity of enone 12 in the solid state is most lik e l y due to a crystal lattice packing effect that is not present in the polymer matrix. 16 15 Figure 20: Photochemistry of compound 12. The L-PMMA matrix is more solid-like for compound 12 than for compound 11, which is consistent with the fact that the product ratio for compound 12 in solution was much more affected by temperature and viscosity than was the case with compound 11. In benzene and ethyl acetate, photoproduct 16 appeared in the gas - chromatographic traces and was only 3% and 6% (respec-tively) of the products formed at room temperature while i t constituted up -34-to 12% of the products formed in methanol. When compound 12 was irradiated in a viscous solvent like ethylene glycol, one third of the product formed at 20 °C was 16. The 15/16 ratio decreased as the photolyses were carried out at lower temperatures in a l l of these solvents (see Table IX) . The mechanism shown in Figure 13 indicates that compound 12 is more lik e l y to be sensitive to changes in viscosity and temperature than compound 11. When compound 12. undergoes isomerization from conformer 12C to conformer 12A in order to form the [ 2 + 2 ] photocycloaddition product, the OH group has to f l i p from a pseudo-equatorial position to a pseudo-axial one. This process should be affected by viscosity and temperature. For compound 11, however, the OH group remains pseudo-equatorial in both conformer 11A and 11B, which should make the isomerization faster and less subject to environmental factors than for compound JL2. This mechanism also explains why hydrogen bonding solvents such as methanol increase formation of 16; they form hydrogen bonds with the OH group which makes the OH group bulkier and therefore retards the isomerization. Photochemistry of 2,3,4aa,6,7,8aa-hexamethyl-l-oxy-4a,5,8,8a-tetrahydronaphthoquin-4/3-ol-acetate (7) . Photolysis of compound 7 in benzene led essentially to quantitative yields of cage compound 8, whereas irradiation of crystals gave compound 9. The source of the unique reactivity of compound 2 in crystalline media was suggested to be a particularly close contact between the methyl group at C(3) and a methyl group of a neighboring molecule located below i t in the l a t t i c e , as previously described (page 22). There are several examples in the literature of organic molecules whose solution phase and solid state behavior are very different owing to the anisotropic steric environment of the crystal l a t t i c e . ^ ' ^ ^ Termed the reaction cavity by Cohen^^, the environment around a given molecule in the bulk of a crystal may sterically impede certain reaction pathways of that molecule and allow others in a manner that is completely dependent on the packing arrangement. Molecules dissolved in polymer films, on the other hand, find themselves in environments that, while s t i l l restricting diffu-sion and major conformational change to a considerable degree, are much more isotropic than those existing in the crystal. If the explanation for the unique reactivity of compound 7 in crystalline media is correct, then immobilizing compound 2 1° conformer 7B in a matrix that lacks the specific close contact to the C(3) methyl group and which slows the conformational isomerization to 7A might well lead to compound 1_0 (Figure 21) . - 3 6 -10 9 8 Figure 21: Photochemistry of compound 7. Such was indeed found to be the case, when compound 7 was irradiated in L-PMMA at room temperature. The photoproduct mixture consisted of 47% 10, 9% 9 , 35% 8 and 9% of unknown. The ratio of the photoproducts was temperature-dependent and at -50 °C the photoproduct mixture consisted of same products as above but in different ratio 65:8:20:7. It can be concluded that as a result of differences in the local environment, compound 1_ displays unique and characteristic photoreactivity in each of three different media: isotropic liquid solutions, the pure crystalline phase and in L-PMMA films. CHARACTERIZATION OF THE NEW PHOTOPRODUCTS. P h o t o p r o d u c t 16 c o r r e s p o n d s t o f r o m p h o t o l y s i s o f 12 i n t h e s o l i d f o r a n a n a l o g u e o f c o m p o u n d 12 t h a t c o m p o u n d 17.22 t h e p r o d u c t e x p e c t e d b u t n o t o b s e r v e d s t a t e ; s u c h a r e a c t i o n h a s b e e n o b s e r v e d l a c k s m e t h y l g r o u p s a t C ( 6 ) a n d C ( 7 ) , F i g u r e 22: P h o t o l y s i s o f c o m p o u n d 17 i n t h e s o l i d s t a t e . P h o t o p r o d u c t 16 was a n a l y z e d b y t h e f o l l o w i n g t e c h n i q u e s : IR, NMR, MS a n d e l e m e n t a l , a n a l y s i s . T h e d a t a o b t a i n e d w e r e i n c o m p l e t e a g r e e m e n t w i t h t h e v a l u e s r e p o r t e d i n r e f e r e n c e 22 f o r t h e a n a l o g o u s p h o t o p r o d u c t o f c o m p o u n d 17, c o m p o u n d 18, whose s t r u c t u r e was p r o v e d b y X - r a y c r y s t a l l o g r a p h y . -38-Keto-acetate 10 was isolated as a colourless o i l . I t s structure was proved by comparison with an authentic sample which had been synthesized by acetylation of the corresponding keto-alchol, compound 14. The IR, NMR and mass spectra were i d e n t i c a l for these compounds, and i n addition, they had the same GC retention time. The authentic sample formed crystals which melted at 53 - 55 °C, while photoproduct 10 did not c r y s t a l l i z e at a l l which must be due to minor impurities. H Pyridine (CH3CO)20 14 10 Figure 23: Acetylation of compound 14. PRODUCT RATIO STUDIES IN POLYMER MATRICES. In order to investigate further how polymer matrices modify the photo-chemistry of compounds 7 , 11 and 1 2 , the photoproduct ratios were studied while the environment was altered systematically. Photoproduct ratios at different degrees of conversion in L-PMMA. The product ratios for compounds 7 , 1JL and 12 were studied in L-PMMA and found to be independent of percent conversion. This demonstrates that no secondary processes are involved in forming the photoproduct (see Figure 24). It also indicates that a l l the molecules in the starting materials experience similar sites of the polymer matrices.2^ 1 0 0 . 8 0 . 6 0 . 20. compound 11 compound 12 compound 7 16/(16+16) <9-H0)/(8 + 9+10) 0 . 0 0 . 0 2 0 . 4 0 . 6 0 . 8 0 . 1 0 0 . % conversion Figure 24: sion in L-PMMA. Photoproduct ratios at different degrees of conver--40-Photoproduct ratio studies at different concentrations in L-PMMA. The effect of varying the concentration of compounds 7, 11 and 12 was also studied in L-PMMA. Identical photochemical results were obtained over substrate/L-PMMA ratios ranging from 1% to 60% by weight (see Figure 25). The finding that some photoproduct 9 is formed in the polymer matrix may indicate the presence of microcrystals of compound 1_ in this medium. It is more l i k e l y , however, that this simply reflects a close competition between the two hydrogen transfer pathways leading to 10 and 9. The observation that the photoproduct ratios are independent of the concentration and degree of conversion of the starting material indicates that the guest molecules are li k e l y to be homogeneously dispersed throughout the polymer matrices. 100. 80. 60. 40. 20. 0.0 0. 20. 40. 60. 80. C o n c e n t r a t i o n (%w p o l y m e r ) Figure 25: Photoproduct ratios at different concentrations in L-PMMA. compound 11 compound 12 compound 7 14/(13+14) 16/(15+16) (9+10)/(8 + 9+10) -41-Photoproduct ratio studies in different polymer matrices. In order to see how polymers other than L-PMMA would modify the photochemistry of compounds 7, 11 and 12, the product ratios were studied in the polymers l i s t e d in Table III, page 73. The effect of the molecular weight (M^ weight-average molecular weight) of the polymer was investigated by studying the photoproduct ratios for compounds 11 and 12 in high molecular weight poly(methyl methacrylate) (H-PMMA) and in medium molecular weight poly(methyl methacrylate) (M-PMMA). The results were identical to those obtained in (L-PMMA). The density of a polymer is essentially independent of the molecular weight (Mw) of the polymer above a certain molecular weight.37 L-PMMA, M-PMMA and H-PMMA have M „ values 5.3 x 104, 16 x 104 and 61 x 104 g/mol3^ respectively which are a l l above the c r i t i c a l molecular weight for PMMA (104 g/mol).39 This indicates that the r i g i d i t y of the polymer matrix is not altered significantly by changing from L-PMMA to H-PMMA and therefore the photochemistry of the guest molecules is not affected. -43-The photoproduct ratios for compounds 7, 11 and 12 were also studied in two other amorphous polymers, poly(vinyl acetate) (PVAc) and poly(isobutyl methacrylate) (PiBMA). In PVAc the product ratio was similar to what was observed in L-PMMA, whereas PiBMA was more solution-like (see Figure 27). The difference in the product ratios in PVAc, PMMA and PiBMA can be explained as being due to differences in the length of the side group of the polymer chains, larger side groups giving more f l e x i b i l i t y . Kryzsewski et a l . have shown that the decolouration rates of benzospirans in PVAc and PMMA are similar, while PiBMA gave larger rate constants.^ They suggested that the length and f l e x i b i l i t y of the side chains played the major role in the different decolouration rate constants. Finally, a partly crystalline polymer was investigated, poly(ethylene glycol) (PEG). At room temperature this polymer exists as a mixture of crystalline and amorphous regions. The polymer gave the [2 + 2] photocy-cloaddition products !as the major photoproduct in a l l cases. This can be explained i f the guest molecules are dissolved in the amorphous part of the polymer where isomerization is not restricted any more than in a viscous solvent. -44-Temperature-dependent photochemistry of compounds 11 and 12. The temperature dependence of the photochemistry of compound 12 in solution was studied quantitatively in ethyl acetate over the range -60 to 30 °C. As the temperature was decreased, slightly more of product 16 was formed at the expense of compound 15. When the data were plotted as ln(15/16) versus 1/T (Figure 27), a straight line was obtained. This result is consistent with two competing first-order processes that have different activation energies with the assumptions discussed below. .—I 3 3.5 3.0 2.5 2.0 1.5 3.0 3.5 4.0 4.5 5.0 1/T x IO -3 Figure 27: Arrhenius plot for compound 12 in ethyl acetate. As mentioned previously (page 21), i t appears that, in the present instance, the product ratio w i l l depend only upon the relative photochemical reaction rates. Then the slope of the straight line in the Arrhenius plot -45-gives A[Ea(15) - Ea(16)] as + 1.9Kcal/mole. It has to be taken into consideration that the photochemical reactions compete with some deactiva-tion processes of the excited molecule. Therefore the composition of the photoproducts are not going to reflect the relative difference of the activation energies unless the deactivation processes can be neglected. A possible sequence of steps followed in the photorearrangement of 12 to 15 and 16 is shown below (also see Figure 20). 3(S0) ^ 3(SX) (1) 3(SX) kl t 3(TX) (2) k k-2 3(Tj_) K2 BR-C • 3(SQ) (3) BR-C 16 (4) 3(T1> k 5 t IS (5) 3(TX) 3(S0) (6) It seems likely that the hydrogen abstraction process (step 3) and the [2 + 2] cycloaddition (step 5) are important contributions to AEa. Reversion to SQ is predicted on theoretical grounds to be particularly important for hydrogen abstraction reactions.4^ Making the reasonable assumption (for purpose of linearity of the Arrhenius plot) that k^ » k_2, the reversible hydrogen abstraction can be neglected. This then predicts that AEa is equal to the activation energy for reaction 5 minus the activation energy associ-ated with step 3. If i t is assumed that the deactivation processes can be neglected, then this result indicates that the activation energy for the hydrogen abstrac-tion process is less than that for the [2+2] cycloaddition. S t i l l more of -46-th e cage product is formed at temperatures between -60 to 30 °C. This implies that the pre-exponential factor for the cycloaddition process must be considerably larger than that for the hydrogen abstraction process. According to the Arrhenius plot the intercept gives lnCA^/A^g) as 7. It can also be speculated that the Curtin-Hammett principle does not apply for the solution photochemistry of compound 12 That would imply that the isomerization rate between conformers 12C and 12A would be of the same order of magnitude as the photochemical reaction rates. The product ratio would then depend on the relative photochemical reaction rates as well as on the ground state conformer population. This suggestion is consistent with the fact that compound 12 is generally more affected than compound 11 by processes which retard the isomerization rate, such as low temperatures and viscous and/or hydrogen bonding solvents. If this suggestion is correct, the kinetics are no longer first-order and the Arrhenius plot should be curved. But because the product ratio does not change rapidly with temperature in comparison with the accuracy of the measurement of the product ratio, the temperature dependence of the photochemistry of compound 12 would have to be studied over an extended temperature range in order to see any deviation from f i r s t order-kinetics. The temperature dependence of the photochemistry of compound 12. was also studied in L-PMMA. As the temperature was lowered, more of photoproduct 16 was formed at the expense of 15 in L-PMMA as in ethyl acetate. The temperature dependence was studied over the range +1 to +110 °C. When the data were plotted as ln(15/16) versus 1/T, a straight line was obtained, which had a slope of 3 x 103 K (see Figure 28). -47--2.0' ' ' • 1 2.5 3.0 3.5 4.0 1 / T x 1 0 " 3 Figure 28: Arrhenius plot for compound 12 in L-PMMA. The temperature effect was also measured in PVAc (Tg = 28 °C) and PiBMA (Tg = 53 °C) to be able to assess the effect of passing through the glass transition temperature. The results of these measurements, plotted as ln(15/16) versus 1/T are shown in Figure 29. This indicated qualitatively that in PVAc and PiBMA the 15/16 ratio increases more rapidly above the glass transition temperature than below i t . The data for the studies in PVAc can be f i t t e d by two reasonably good straight lines of different slopes which break at the glass transition temperature. The data for PiBMA can also be f i t t e d by two straight lines, having slightly different slopes which break at T_. - 4 8 -P V A c 5 3 . 0 3 . 5 4 . 0 4 . 1/T x 10~3 P i B M A T 8 t 2 . 5 3 . 0 3 . 5 4 . 0 4 . 5 1/T x 10~3 Figure 29: Arrhenius plot for compound 12 in PVAc and in PiBMA. For compound 11 no temperature dependence was observed i n methanol from +20 to -60 °C. The temperature dependence of the photochemistry of compound 11 was studied i n PVAc and the result of these measurements, plotted as ln(13/14) versus 1/T, (shown i n figure 30), can be f i t t e d by two straight l i n e s with di f f e r e n t slopes which meet at T „ . -49-4.5 Figure 30: Arrhenius plot for compound 11 in PVAc. A relatively straightforward explanation of these results is that the viscous polymer matrix exerts a strongly restrictive influence on the topochemically demanding process of conformational isomerization, both in the ground state and the excited state. As pointed out before, under these conditions the Curtin-Hammett principle no longer applies and the photopro-duct ratios reflect the ground state conformer populations. This interpre-tation is consistent with the observed overall temperature dependence in that lower temperatures would tend to favor the lower energy conformer (11B -50-or 12C) and thus lead to greater amounts of the hydrogen abstract i o n product. The reduced s e n s i t i v i t y of the product r a t i o s to temperatures below Tg compared to those above can be ascribed to a matrix-derived topochemical r e s t r i c t i o n of the motions required for conformational isomer-i z a t i o n ; above Tg free volume i s increased and such r e s t r i c t i o n s are eased. The change i n the product r a t i o slope f o r compound 12 above and below Tg i s les s i n PiBMA than i n PVAc, which can be explained by suggesting that the polymer having longer, f l e x i b l e side chains should have more f l e x i b i l i t y below Tg and therefore crossing the glass t r a n s i t i o n temperature of these polymer matrices does not modify the photochemistry of the guest molecules as much. In other words, when the product r a t i o changes as the temperature i s increased, i t i s mainly due to the polymer matrix, which becomes less r i g i d . I t i s worth noting that North came to s i m i l a r conclusion when he studied the rate of decolourization for benzopyranidoline i n a v a r i e t y of amorphous poly(acrylate) matrices.4^ He analyzed the decolouring rate constants i n terms of free volume d i s t r i b u t i o n functions and found i t provided a s a t i s -factory d e s c r i p t i o n of the phenomenon. He concluded, therefore, that the bleaching of the benzopyranidoline was c o n t r o l l e d by the a v a i l a b i l i t y of l o c a l free volume i n the polymer matrix. -51-VISCOSITY EFFECTS ON PHOTOLYSIS OF COMPOUNDS 11 AND 12. A great many theories have been developed to account for the viscosities of liquids. 5 In general, viscosity is a measurement of the energy dissipated by a f l u i d in motion as i t resists an applied, shearing force. Viscous flow can be pictured as taking place by the movement of molecules in jumps from one place in a lattice to a vacant hole. The total hole concentration can be regarded as the free volume. D o o l i t t l e4 2 and later Williams, Landel and Ferry4^ have proposed that viscosity should vary with the free volume (Vf) in the following way: viscosity - rj = A x [exp(VQ/Vf)] = B x [exp(E v i s /RT) ] Where A and B are constants and VQ is the specific volume at 0 K. Ev^s is the activation energy required to create a hole big enough for a molecule to translate into during flow. R is the gas constant and T the temperature. Rearrangement processes involving large amplitude motions, such as isomerization in molecules where bulky groups must twist with respect to a molecular axis, should have rates which depend on the f r i c t i o n a l forces exerted by the solvent.4 4 When the relative time scale for a rearrangement and the time for reorganization of the solvent are comparable, i t is possible to treat the rearrangement in the solute molecules in terms of free-volume functions. The rate constant, k, for a process depends on free volume and can be described as:4^ -52-k = kQ x [ A x exp(-a x VQ/Vf)] C x [exp(-(Ea + EQ)/RT)] Where kQ is the limiting value of k at low viscosity, A, C and a are constants. Ea is the activation energy for the rearrangement of the solute molecules at low viscosity and EQ is the activation energy for the free volume-dependent rearrangement or -ax E^g. The viscosity dependence of the photochemistry of compound 12 in solution was measured in ethylene glycol over the range 15.9 cp to 56.8 cp by changing the temperature from 27° to -7°C. The Arrhenius plot was linear in this temperature range. If first-order kinetics are assumed, the slope gives [AEa + AEQ] as 4.0 kcal/mol. 0 . 7 5 i 1 , , , . 0 . 50 -CO \ 0 . 2 5 -L O .—I s o.o -- . 2 5 3 . 3 3 . 4 3 . 5 3 . 6 , - 3 3 . 7 3 . 8 1 / T x 1 0 ' Figure 31: Arrhenius plot for compound 12 in ethylene glycol. In order to measure AEQ the temperature must be kept constant. Therefore the photoproduct r a t i o was studied i n mixtures of ethylene glycol and methanol which had different v i s c o s i t i e s at a constant temperature. When the results were plotted as ln( 15/16) versus ln(rj) a straight l i n e was observed which gave a = -0.40. ^v i s ^o r ethylene glycol i s 6.2 Kcal/mol4^, - a x Ev^s gives AEQ =2.5 Kcal/mol. AEa can then be calculated to be 1.5 kcal/mole, which i s only s l i g h t l y less than the value found for 12 i n ethyl acetate over a si m i l a r temperature range. This indicates that the effect of a viscous solvent on the rearrangment reaction for compound 12 can be added as an activation b a r r i e r to the overall activation energy. Ln(77) Figure 32: Product r a t i o for compound 12 as a function of v i s c o s i t y at constant temperature (ethylene glycol - methanol mixtures). -54-Compound 11 did not show any viscosity dependence in ethylene glycol; only trace amounts of compound 14 were formed at -10 °C. As previously mentioned i t was expected that viscous solvents would slow down the isomerization rates for compounds 11. and 12. The results indicate that the isomerization rate for compound 12 must be comparable to the time of reorganization of the ethylene glycol molecules while the isomerization rate must be somewhat larger for 11. This information is consistent with what was observed in polymer films. S t i l l there is some difference between viscous solvents and polymer matrices. The polymer matrix has a flow rate of several magnitudes higher than ethylene glycol and therefore reorganization of the polymer chains occurs much slower. As a result these matrices are able to slow down the isomerization rate for compound 11. It can be speculated that at low temperatures and/or high viscosities the photoproduct ratio w i l l depend only upon the ground state conformer population. That i s , the rate determining step has been changed from being the photochemical process at high temperatures and low viscosity to being the conformational isomerization at low temperatures and high viscosity. Similar but more complex problems have been studied by Turro et a l .4 7 These authors studied the temperature and viscosity dependence of the lifetime of t r i p l e t biradiacals derived from 2-phenylcycloalkanones. Arrhenius plots for the temperature range 20 to -90 °C were strongly curved. The biradical lifetimes were strongly affected by solvent viscosity at low temperatures but were nearly independent of viscosity at room temperature. They, therefore, suggested a transition in the ratedeterming step for biradical decay from intersystem crossing control at room tempera-ture to chain dynamics control at low temperature. SUGGESTION FOR FUTURE WORK. It has been demonstrated that polymer matrices are useful reaction media for reducing the rates of conformational interconversions to the point that alternative chemical processes that are normally too slow to be observed in solution become competitive. The resultant effect in certain instances is comparable to that observed in the solid state. Additionally, in other cases where the crystals have specific reactivity due to the constraints of the crystal l a t t i c e , or are simply inert, the reaction in the polymer matrix may result in products unique to this semi-ordered state. An interesting extension of this work could be done by studying some tetrahydronaphthoquinones dissolved in polymer matrices. These compounds a l l give hydrogen abstraction-initiated rearrangement in solution. In some cases the formation of the solution products is not topochemically allowed in crystals. This results in different solution and solid state products. Some of these tetrahydronaphthoquinones crystallize with parallel ene-dione double bonds and undergo dimerization in the solid state rather than hydrogen abstraction-initiated rearrangement. When these compounds are dissolved in polymer matrices they may no longer pack with parallel ene-dione bonds and might therefore react to give hydrogen abstraction products which are different from those observed in solution. EXPERIMENTAL GENERAL Melting points Melting points (mp) were recorded on a Fisher-Johns hot stage apparatus and are uncorrected. Infrared spectra Infrared spectra (IR) were recorded on a Perkin-Elmer 1710 Fourier Transform infrared spectrometer. It was done either: a. In KBr pellets containing 0.5 to 1% by weight of sample. b. In CHCI3 containing 5% by weight of sample. KBr pellets were made using a Perkin-Elmer evacuated die 186-0002 and a Carver laboratory press model B. Spectra of chloroform samples were obtained by pressing the solution between NaCl plates. Absorption maxima are reported in cm"-'-. -57-Elemental analysis Microanalysis were performed by the departmental analyst, Mr. Peter Borda. Nuclear Magnetic Resonance Spectra A l l NMR were recorded on a Bruker WP-400 spectrometer at 400 MHz. Deuterochloroform was used as the solvent, and tetramethylsilane (TMS) was used as the internal standard unless otherwise stated. Signal positions are given in ppm ( 6 units) and their multiplicity, coupling constants (in Hz), integrated areas and assignments ( i f made) are given in parentheses following the signal position. Mass spectra Low and high resolution mass spectra were recorded on a Kratos MS 50 mass spectrometer. A Kratos MS 80 mass spectrometer coupled with a Carlo-Erba gas chromatography was used for GC-MS study. Intensities are recorded as percentages of the most intense (base) peak and are given in brackets. Molecular ions are designated M+. -58-Gas chromatography An a l y t i c a l gas chromatographic analyses were rea l i z e d on a Hewlett-Packard 5890 A gas chromatograph. The signal from a flame io n i z a t i o n detector was integrated by a Hewlett-Packard 3302 A integrator. Helium was used as the c a r r i e r gas with a column head pressure of 15 p s i . A 15 m x 0.25 mm fused s i l i c a c a p i l l a r y Carbowax column from Quadrex corporation was used for most analyses. Retention times (rt) are recorded i n minutes and the following programs were used: Program 1: 170 °C 25 °/min 210 °C 5 min 7 min Program 2: 210 °C (isothermal). Program 3: 190 °C (isothermal). Column chromatography S i l i c a 60 (230 - 400 mesh, E. Merck) was used i n column chromatography both for p u r i f i c a t i o n and separation purposes. -59-Chemicals and solvents Solvents used for photolysis and viscosity studies were obtained from BDH Chemical or Fisher Scientific Company. Ethyl acetate and methanol (BDH spectral grade )-were used as received, without any purification. Benzene was freed of thiophene-by washing It with concentrated sulfuric acid, water, dilute sodium hydroxide and the again with water followed by drying with P2O5 and d i s t i l l a t i o n . Ethylene glycol was purified by drying i t with CaO and d i s t i l l i n g i t twice under vacuum.4^ Polymers used to make polymer films were freed of stabilizers and other low molecular weight impurities. Poly(alkyl methacrylates) (source: Aldrich Chemical Co., Inc.) were purified by dissolution in chloroform followed by reprecipitation by addition of methanol and suction f i l t r a t i o n . This was •repeated three times. Afterwards the polymers were dried under vacuum (10'-mm Hg, 48 h). Poly(etbylene glycol) (source: J.T. Baker Chemical Co.) was used as received. Poly(vinyl acetate) (source: BDH Chemical) was dissolved in acetone, reprecipitated by addition of n-hexane and suction f i l t e r e d , three times. Then i t was dried under vacuum (1CT^ mm Hg, 48 h) . Polymer films preparation. Polymer films wer-e prepared by weighing out the polymer and the guest molecules and dissolving them in chloroform (3 ml of chloroform for every 100 mg of polymer). Ca." 0.5 ml of this solution was applied to the top of a microscope slide and distributed evenly over the surface using a second -60-s l i d e as a straight edge. After coating, the films were allowed to evapor-ate slowly for 24 h at room temperature. In order to remove residual solvent the films were dried under vacuum (10"2 mm Hg) for 48 h. The films were t y p i c a l l y 5 - 10 /wn i n thickness as measured with a profilometer (Tencor). Vis c o s i t y studies. Vi s c o s i t y of methanol and ethylene glycol mixtures was determined using an Oswald viscometer from Fisher S c i e n t i f i c company (size 200; F1838). Pure ethylene glycol was used as a standard reference sample. Photolysis procedures Almost a l l photolyses were preformed using a Hanovia 450 W medium pressure mercury lamp with a uranium glass f i l t e r (thickness 2 mm, trans-mits A > 340 nm). But where i t i s stated a Molectron UV 22 pulsed N£ laser (A = 337 nm, pulse rate = 20-30 per min) was used. Photolyses done below room temperature, were carried out by storing the sample container i n a methanol bath i n a transparent Dewar f l a s k . The methanol bath was cooled with a Cryocool Immersion Cooler CC-100II from Neslab Instruments, Inc. Photolyse done above room temperature were carried out by storing the samples i n pyrex tubes which f i t t e d into a three necked round bottom f l a s k . -61-The flask was half f i l l e d with a solvent and joined to a refluxer. The solvent was then refluxed in order to maintain a constant temperature. SYNTHESIS 1. Synthesis of Duroquinone. H A. Dinitrodurene A solution of durene (13.4 g; 0.10 mol) i n chloroform (100 ml) was added to cone. H2SO4 (75 ml; 138 g). The mixture was cooled to 0 CC and fuming HNO3 (10 ml; d = 1.50 g/ml) was added drop wise, with s t i r r i n g , so that the temperature did not r i s e above 50 °C. As soon as a l l the acid had been added, the mixture was poured into a separatory funnel, the s u l f u r i c acid layer removed and the chloroform layer immediately treated with 10% sodium carbonate solution (100 ml), dried over calcium chloride and f i l t e r e d . The solvent was rotatory evaporated and the colorless s o l i d obtained was r e c r y s t a l l i z e d from ethanol, affording colorless crystals (20.1 g; 86% yield) m- 206-207 °C ( l i t .4 9 207-208 °C) . B. Reduction of Dinitrodurene A solution of stannous chloride (140.0 g; 0.74 mol) i n cone. HCl (150 ml; 180 g ) was added to a b o i l i n g solution of dinitrodurene (18.0 g; 0.08 mol) i n g l a c i a l acetic acid (200 ml; 216 g). The mixture was cooled to 10 °C, yielding crystals. After f i l t r a t i o n , the crystals were washed twice with ethanol and twice with diethyl ether to give the t i n complex [C6(CH3)4(NH2-HCl)2]2-SnCl4, (55.8 g; Yield 95%). C. Duroquinone To a solution of FeCl3 (75.0 g; 0.46 mol), water (150 ml; 150 g) and cone. HCl (20 ml; 24 g) was added [C6(CH3)4(NH2•HCl)2]2'SnCl4 (25.0 g; 0.46 mol). This mixture was allowed to stand overnight and then f i l t e r e d . The product was recrystallized from ethanol, affording yellow crystals of duroquinone (10.0 g; yield 90%). mp_: 109-110 °C ( l i t .3 4 109-110 °C) . IR: (KBr) 1636 cm-1 (C=0). NMR: 1.75 ppm (s, 12 H, 4xCH3). MS: m/e (relative intensity) 164 (M+, 100); 136 (55.2); 121 (89.4); 93 (39.5). GLC: (program #1) rt = 1.70 min 2. Preparation of 2 . 3 . 4a . 6.7.8a-hexamethyl-4a.5.8.8a- tetrahydro-1.4-naphthoquinone.4 A mixture of duroquinone (5 g; 0.030 mol), 2,3-dimethyl-l,3-butadiene (6.0 g; 0.072 mol) and a few crystals of hydroquinone was heated in a sealed - 6 4 -tube at 150 ° C for 20 hours. The resulting pale yellow s o l i d was re c r y s t a l -l i z e d twice from petroleum ether to give large pale yellow crystals of the naphthoquinone (5.5 g; y i e l d 75%) E2.- H4-115 ° C ( l i t .5 0 115-117 °C). IR: (KBr) 1674 cm"1 (C=0); 1626 cm-1 (conj. C=C) NMR: 1.13 ppm (s, 6H, C(4a) and C(8a) methyls), 1.60 ppm (s, 6H, C(6) and C(7) methyls), 1.70 ppm (d, 16 Hz, 2H, C(5)QH and C(8)QH or C(5)£H and C(8)/8H), 1.98 ppm (s, 6H, C(2) and C(3) methyls), 2.53 ppm (d, 16 Hz, 2H, C(8)QH and C(5)aH or C(8)£H and C(5)/3H) . MS: m/e ( r e l a t i v e intensity) 246 (M+, 26.8); 218 (42.5); 203 (100); 136 (31.1). GLC: (Program #1) r t = 4.75 min 3. Preparation of 2 . 3 . 4aor. 6 .7 . 8aa-Hexamethvl-4a. 5 .8 . 8a- tetrahydronaphthoquin-l-on-4fl and 4a - o l . (11 and 12 r e s p e c t i v e l y ) .2 2 Sodium borohydride (200 mg; 5.3 mol) was added to a solution of 2,3,4a,6,7,8a-tetrahydro-1,4-naphthoquinone (1.52 g; 6.2 mmol) i n 80 ml of ethanol. This mixture was s t i r r e d overnight at room temperature. After a c i d i f i c a t i o n with g l a c i a l acid and addition of cyclohexane, the solvent was removed i n vacuo. The residue was taken up i n chloroform, f i l t e r e d , washed with saturated sodium bicarbonate, and with saturated sodium chloride. Removal of solvent produced a white s o l i d which GLC (program #2) showed to be mixture of two products. Separation was achieved by careful r e c r y s t a l l i --65-zation of the mixture from 5% ethanol and 95% petroleum ether (affording compound 12) and by column chromatography ( s i l i c a g e l , 95% petroleum ether and 5% ethyl acetate) of the mother l i q u o r , y i e l d i n g compound 11 and mixed fra c t i o n s . The combined yields of compounds 12 and 11 were 780 mg (51%) and 530 mg (35%) , respectively. R e c r y s t a l l i z a t i o n of 11 from petroleum ether -ethanol gave colourless c r y s t a l s : mp_: 136 - 137 °C ( l i t .2 2 136.5 - 137.5 °C) IR: (KBr) 3472 cm"1 (OH), 1678 cm'1 (C-0), 1626 cm'1 (conj. C-C). NMR: 0.89 ppm (s, 3H, C(4a) methyl), 1.05 ppm (s, 3H, C(8a) methyl), 1.49 ppm (s, C(6) methyl), 1.60 ppm (s, 1H, exchangeable, OH), 1.67 ppm (s, 3H, C(7) methyl), 1.73 ppm (d, 16 Hz, partly submerged under methyl, 2H, C(5)QH and C(8)aH or C(5)0H and C(8)/9H) , 1.76 ppm (br s , 3H, C(2) methyl), 1.83 ppm (br s, 3H, C(3) methyl), 2.17 ppm (d, 16 Hz, 1H), 2.87 ppm (d, 16 Hz, 1H), 3.97 ppm (br s, 8 Hz, 1H, C(4)H). MS: m/e ( r e l a t i v e intensity) 248 (M+, 4.2), 187 (100), 108 (40.0), 55 (45.2), 41 (40.9). GLC: (Program #2) r t = 4.95 min R e c r y s t a l l i z a t i o n of compound 12 from petroleum ether - ethanol gave colourless c r y s t a l s : mp_: 170 - 171 °C ( l i t .2 2 170.5 -171.0 °C) IR: 3486 cm'1 (OH), 1641 cm"1 (C=0). NMR: (C6D6) 0.87 ppm (s, 3H, C(4a) methyl), 1.08 ppm (s, 3H, C(8a) methyl), 1.59 ppm (s, 6H, C(6) and C(7) methyls), 1.55 ppm (d, 16 Hz, 2H, C(5)aH and C(8)QH or C(5)£H and C(8)£H, partly submerged under methyls), -66-1.76 ppm ( s , 3H, C ( 2 ) m e t h y l ) , 1.95 ppm ( s , 3H, C ( 3 ) m e t h y l s ) , 1.68 ppm ( d , 16 Hz, 2H, C(5)QH o r C ( 8 ) a H o r C ( 5 ) £ H a n d C ( 8 ) £ H ) , 4.29 ppm ( b r s, C ( 4 ) H ) . MS: m/e ( r e l a t i v e i n t e n s i t y ) 248 ( M + , 1 5 ) , 166 ( 1 0 0 . 0 ) , 55 ( 3 2 . 0 ) GLC: ( p r o g r a m #1) r t *= 12.70 m i n 4. P r e p a r a t i o n o f 2 . 3 . 4 a a . 6 . 7 . 8 a a - H e x a m e t h y l - 4 a . 5 . 8 . 8 a - t e t r a h y d r o n a p h t h o q u i n - l - o n - 4 f f - o l . a c e t a t e ( 7 ) 5 1 A s o l u t i o n o f d r y p y r i d i n e (2 m l ; 0.026 m o l ) , f r e s h l y d i s t i l l e d a c e t i c a n h y d r i d e (1 m l ; 0.97 m m o l ) , a n d c o m p o u n d 11 ( 2 9 0 mg; 1.01 mmol) was s t i r r e d a t r o o m t e m p e r a t u r e u n d e r n i t r o g e n f o r 3 h o u r s . GLC ( p r o g r a m #3 ) i n d i c a t e d n o r e m a i n i n g c o m p o u n d 11 w i t h f o r m a t i o n o f o n e p r o d u c t , s u b s e q u e n t l y shown t o . b e c o m p o u n d 7_- T b e r e a c t i o n m i x t u r e was d i l u t e d w i t h w a t e r a n d e x t r a c t e d w i t h c h l o r o f o r m . T h e o r g a n i c e x t r a c t was w a s h e d t w i c e w i t h d i l u t e h y d r o c h -l o r i c a c i d , s a t u r a t e d s o d i u m b i c a r b o n a t e s o l u t i o n a n d w a t e r . A f t e r d r y i n g t h e s o l u t i o n w i t h MgSO^, t h e s o l v e n t was r e m o v e d i n v a c u o . T h e r e s u l t i n g o i l was s u b j e c t e d t o c o l u m n c h r o m a t o g r a p h y ( s i l i c a g e l , 10% e t h y l a c e t a t e , 90% p e t r o l e u m e t h e r ) . R e c r y s t a l l i z a t i o n o f c o m p o u n d T_ f r o m h e x a n e g a v e l a r g e c o l o u r l e s s c r y s t a l s ( 2 6 6 mg; y i e l d 9 1 % ) . m- 68 - 69 ° C ( l i t . 5 1 67.5 -68.5 °C) IR: ( K B r ) 1737 a n d 1673 c m - 1 (C=0) NMR: 0.98 ppm ( s , 3H, C ( 4 a ) m e t h y l ) , 1.08 ppm ( s , 3H, C ( 8 a ) m e t h y l ) , -67-1.53 ppm (br s, C(6) or C(7)'methyl) , 1.62 ppm (br. s, 3H, C(6) or C(7) methyl), 1.63 (d, 16 Hz, 1H, C(5)aH and C(8)aH or C(5)£H and C(8)/9H), 1.78 ppm (s, 3H, C(2) or C(3) methyl), 1.90 ppm (s, 3H, C(2) or C(3) methyl), 2.18 ppm (s, 3H, ester methyl), 2.60 ppm (d, 16 Hz, 1H, C(5)QH and C(8)aH or C(5)£H and C(8))SH) , 5.85 ppm (br s, 1H, C(4)H). MS: m/e (r e l a t i v e intensity) 290 (M+, 6.4), 187 (52), 43 (100). GLC: (program #3) r t - 5.35 min 5. Preparation of 5-exo-acetoxv-l.3.4.6.8.9-hexamethvl-tetracvclo  f4.4.0.03-71-dec-8-en-2-one (10). A solution of compound 14 (0.701 g; 0.28 mmol), dry pyridine (4 ml; 56 mmol) and freshly d i s t i l l e d acetic anhydride (2 ml; 32 mmol) was s t i r r e d at room temperature under N2 for 2 hours. A GLC (program #3) showed the formation of one product, compound 10, and the disappearance of compound 11. The reaction was worked up as for compound 7. Column chromatography of the crude reaction mixture ( s i l i c a g e l , 10% ethyl acetate, 90% petroleum ether) afforded compound 10 as a colourless o i l after solvent removal. The o i l was dissolved i n hexane and set aside at -10 0 C, whereupon small crystals were formed (70 mg; y i e l d 86%). mp.: 53 - 55 °C. IR: (KBr) 1726 and 1718 cm"1 (C=0) (CHCI3) 1745 and 1725 cm"1 (C=0) NMR: 0.89 ppm (s, 3H), 0.91 ppm (d, 7Hz, 3H, C(3) methyl), 0.95 ppm (s, 3H), 1.05 ppm (s, 3H), 1.55 ppm (s, 3H, C(6) or C(7) methyl), 1.68 ppm (s, -68-3H, C(6) or C(7) methyl), 1.75 ppm (dq, 4 and 7 Hz, IH, C(3)H), 1.85 ppm (d, 17 Hz, IH, C(8)QH or C(8)/9H) , 2.03 ppm (d, 17 Hz, IH, C(8)aH or C(8)/9H) , 2.10 ppm (s, 3H, ester methyl), 2.21 ppm (s, IH, C(5)H), 4.76 ppm (d, 4Hz, IH, C(4)H). MS: m/e (relative intensity) 290 (M+, 11.6), 230 (100), 215 (91.5), 187 (86.8) . calculated mass for 0 ^ 8 ^ 5 0 3 : 290.4061 . found: 290.4031 GLC: (program #3) rt = 3.60 min -69-PHOTOCHEMICAL STUDIES. 1. Photolysis of 2.3 .4aa.6.7.8aa-hexamethvl-4a.5.8.8a- tetrahvdronaphthoquin-l-on-4fi-ol. compound 11. ^  Preparative photolysis of compound 11 i n ethyl acetate. A solution of compound 11 (100 mg; 0.40 mmol) i n ethyl acetate (10 ml) was purged with N2 for 20 min before i r r a d i a t i o n at room temperature for 4 h. The reaction mixture was analyzed by GLC (program #2), showing formation of one new product, compound 13 (rt = 3.90; 95% area), and some unreacted st a r t i n g material ( r t = 4.95; 1%). The solvent was removed by rotatory evaporation to y i e l d a colourless o i l . The o i l was passed through a chromatography column ( s i l i c a g e l , 10% ethyl acetate, 90% petroleum ether) and r e c r y s t a l l i z e d from petroleum ether to y i e l d small c r y s t a l s , which were characterized as 5-hydroxyl-1,3,4,6,8,9-hexamethyl-tetracyclo-[4.4.0.03>9.04-8] decan-2-one. 5-hydroxy-1.3.4.6.8.9-hexamethyl-tetracyclo\4.4.0.03- 9 J 34•81 decan-2-one. compound 13. ^  mp_: 150 - 152 °C ( l i t .2 2 152 - 153 °C) IR: (KBr) 3469 cm-1 (OH), 1730 cm"1 (C-0). -70-NMR: 0.73 ppm (d, 13 Hz, 1H), 0.87 ppm (s, 3H), 0.91 ppm (s, 3H), 0.95 ppm (s, 3H), 1.00 ppm (s, 3H), 1.01 ppm (s, 3H), 1.05 ppm (s, 3H), 1.46 ppm (d, 13 Hz, 1H), 1.54 ppm (s, exchangeable, 1H, OH), 1.90 ppm (d, 13 Hz, 1H), 2.15 ppm (d, 13 Hz, 1H), 3.20 ppm (s, 1H, CH-OH). MS: m/e r e l a t i v e intensity 248 (M+, 4.8), 187 (100), 124 (75.4) GLC: (program #2) r t = 3.90 min Preparative s o l i d state photolysis of compound 11. ^  A single c r y s t a l of compound 11 (387.1 mg; 1.56 mmol) was ir r a d i a t e d under N2 for 18 h at -30 °C. After the i r r a d i a t i o n the c r y s t a l was dissolved i n ethyl acetate and analyzed by GLC (program #2). I t indicated formation of two photoprOducts, compounds 14 ( r t — 3.40; 11% area) and 1_3 ( r t = 3.90; 2% area, i d e n t i f i e d by melting point and IR), and unreacted s t a r t i n g material ( r t = 3.90; 85% area). The products were separated using column chromatography ( s i l i c a g e l , 5% ethyl acetate and 95% petroleum ether) and only the purest fractions (>95%) were, collected. Compound 14 was r e c r y s t a l l i z e d from petroleum ether - ethanol and characterized as 2 , 3 , 3a, 4, 5 , 7a-hexahydro-3-hydroxy-1, 2 , 3a, 6 , 7-hexamethyl- ( l a , 20, 3/3, 3a/3,4a, 7aa) --1,4-methano-lH-inden-8-one. -71-2.3.3a.4.5.7a-hexahvdro-3-hydroxy-1.2.3a.4.6.7-hexamethvl- (la,2a.30.3aB,4a.7a3)-1.4-methano-lH-inden-8-one. compound 14.2 2 BE: 120 - 122 °C ( l i t .2 2 121.5 - 122.5 °C). IR: (KBr) 3467 cm"1 (OH), 1720 cm"1 (C=0). NMR: 0.88 ppm (s, 3H), 0.89 ppm (d, 7 Hz, 3H, C(3)CH3), 0.97 ppm (s, 3H), 1.03 ppm (s, 3H), 1.03 ppm (s, 3H), 1.55 ppm (br s, 3H, C(7) or C(8) methyl), 1.57 ppm (s, exchangeable, OH), 1.67 ppm (br s, 3H, C(7) or C(8) methyl), 1.68 ppm (qd, 4 Hz and 7 Hz, 1H, C(3)H), 1.84 ppm (d, 16 Hz, 1H, C(9)aH or C(9)/3H) , 2.03 ppm (d, 16 Hz, 1H, C(9)aH or C(9)/3H) , 2.20 ppm (s, 1H, C(5)H), 3.78 ppm (d, 4 Hz, 1H, C(4)H). MS: m/e ( r e l a t i v e intensity) 248 (M+, 53), 187 (56), 151 (80), 134 (100). GLC: (program #2) r t = 3.90 min Product r a t i o study of compound 11 i n different solvents. Solution samples of compound 11 i n different solvents were prepared and de-oxygenated by freeze-pump-thaw cycles under N2 atmosphere. S o l i d state samples of single crystals were also prepared and placed under N2. After the samples had been irradiated they were analyzed by GLC (program # 2). Every experiment was repeated at least twice. The average of the r a t i o of the photoproducts 13:14 for each solvent and the i r r a d i a t i o n temperature are l i s t e d i n Table II along with the solution concentration. Solvent Concentration (M) Temp. CC) 1 3 : 1 4 Benzene Ethylene glycol it Methanol ti Ethyl acetate Crystals 0.0028 0.0040 0.0036 0.0177 0.0024 20 ± 3 25 ± 3 -10 ± 1 +20 + 3 -60 ± 1 20 ± 3 20 ± 3 100:0 100:0 97:3 100:0 100:0 100:0 15:85 Table I I : Photoproduct r a t i o studies of compound 11 i n different solvents. Photolysis of compound 11 i n polymer films as reaction media. In Table I I I are l i s t e d organic high molecular weight polymers used to study.the photochemistry of compound 11 dissolved i n polymer f i l m s . Their physical properties (molecular weight, density and glass t r a n s i t i o n tempera-ture (T„)) are also l i s t e d .5 1 Polymer Molecular weight Density Tg (average) (g/ml) (°C) Poly(methyl methacrylate) L-PMMA Poly(methyl methacrylate) M-PMMA Poly(methyl methacrylate) H-PMMA Poly(isobutyl methacrylate) PiBMA Poly(ethylene glycol) PEG Poly(vinyl acetate) PVAc Low 53,000 Medium 160,000 High • 610,000 High 1.188 1300-1600 1.09 1.12 114 114 114 53 28* * Measured with a differential scanning calorimeter (Mettler). Table III: Organic polymers used as reaction media. - 7 4 -A. Photoproduct ratio at different degrees of conversion of compound 11 in L-PMMA films. Polymer films which contained compound 11 (12.1% w polymer) were prepared and photolyzed under a steady stream of N2. After irradiation they were dissolved in chloroform, and ethanol added to precipitate the polymer. The ratio of the photoproducts 1_3:14 was analyzed by GLC (program #2) and the results are li s t e d in Table IV. Concentration (%w polymer) 34 ± 2 56:44 ± 2 20 ± 3 1 2 . 1 53 ". 51 :49 " 58 " 53:47 " 60 " 52:48 " 63 " 52:48 " 87 " 52:48 " 99 " - 54:46 " Table IV: Photoproduct ratio studies at different extent of reaction of compound 11 in L-PMMA. Conversion of 11 !_3:14 Temp. CC) B. Photoproduct r a t i o studies at d i f f e r e n t concentrat ions of compound 11 i n L-PMMA. In order to inves t igate what e f f ec t concentrat ion of compound 11 d i s s o l v e d L-PMMA f i l m would have on the r a t i o of the products , polymer f i lms were prepared which contained d i f f e r e n t amount of compound 11. These f i lms were i r r a d i a t e d under a steady flow of N2 at room temperature. Afterwards they were d i s s o l v e d and analyzed by Glc (program #2). For each concentra-t i o n of compound 11 at l ea s t 6 f i lms were s tudied and the average of the photoproducts r a t i o i s shown i n Table V. Concentrat ion 13:14 Temperature (%w polymer) (°C) 1.2% 56:44 ± 2 20 ± 3 12.1% 53:47 " ft 31.8% 58:42 " ll 49.3% 57:43 " ll Table V: Photoproduct r a t i o at d i f f e r e n t concentrat ions of compound 11 i n L-PMMA. -76-C. Photoproduct ratio studies of compound 11 in different polymer matrices. Compound 11 was dissolved in different organic polymers and irradiated under a steady stream of N2. Afterwards the polymers were dissolved in chloroform and the ratio of the photoproducts 13.: 14 was analyzed with GLC (program #2). At least 6 experiments were done on the average for each polymer matrix. The result are shown in Table VI. Polymer 13:14 Temperature Concentration (°C) (%w polymer) L-PMMA 53:47 ±2 20 ± 3 12.1 M-PMMA 54:46 " " 11.7 H-PMMA 53:47 " " 20.7 PiBMA 82:18 " 17 ± 1 12.1 PVAc 57:43 " 20 ± 3 29.9 PEG 85:15 " " 14.9 Table VI: Photolysis of compound 11 in different polymer matrices. D. Product ratio studies for photolysis of compound 11 dissolved in PVAc at temperatures above and below Tg. PVAc films which contained compound 11 (4.6% w polymer) were prepared. The films were irradiated under N2 at different temperatures. Afterwards they were dissolved in chloroform and analyzed with GLC (program #2). Each experiment was repeated at least two times. The average of the ratio of the photoproducts and the temperatures for each experiment are li s t e d in Table VI. The natural logarithm of the ratio of the photoproducts and the inverse of the temperature in K were calculated and are also l i s t e d in Table VII. -78-Temperature 1/T x 103 13:14 Ln(13/14) (°C) (K" 1 ) Above PVAc T 64.7 ± 1 61.2 " 56.3 " 39.5 " 34.6 " Below PVAc T 20 ± 3 15 ± 1 -2 -8 -23 -27 -35 g' 2.96 ± 0.01 2.99 3.04 3.19 3.25 3.41 ± 0.04 3.47 ± 0.01 3.69 3.77 4.00 ± 0.02 4.06 4.20 90:10 ± 2 88:12 " 83:17 " 76:24 " 71:30 " 2.20 ± 0.2 1.99 1.58 ± 0.1 1.15 0.86 57:43 ± 2 56:44 50:50 49:51 45:55 42:58 38:62 0.28 ± 0.08 0.24 0.00 •0.024 -0.20 •0.3.2 •0.49 Table VII: Photoproduct ratio studies of compound 11 in PVAc at different temperatures. The Arrhenius plot for the data points (1/T; ln(13/14)) was graphed and was found to be linear, but the line was discontinuous at 1/Tg. The least squares method was used to f i t a line to the data points. The derived equations for these lines and their coefficients are listed in Table VIII. -79-Temperature range Calculated equations Coefficients 64.7 - 34.6 °C ln(13/14) - 14.4 - (4.16 x 103)/T 0.974 20 - -35 " ln(13/14) = 3.48 - (0.934 x 103)/T 0.987 Table VIII: Derived equations for Arrhenius plot of compound in PVAc -80-2. Photolysis of 2.3.4aa.6.7.8aa-hexamethvl-4a.5.8.8a- tetrahvdronaphthoquin -l-on-4a-ol. compound 12. Preparative photolysis of compound 12 i n methanol. Compound 12 (248 mg, 0.67 mmol) was dissolved i n methanol (10 ml) and the solution purged with N2 p r i o r to i r r a d i a t i o n with a nitrogen laser for 20 h at -52 °C. The reaction mixture was analyzed by Glc (program #1). I t showed formation of two products, compound 15 ( r t = 4.50, 72% area) and compound 16 (7.30, 18% area), and some unreacted s t a r t i n g material ( r t = 12.40; 3% area). The solvent was removed by rotatory evaporation to y i e l d a white s o l i d . The products were separated using column chromatography ( s i l i c a g e l , 5% methanol and 95% chloroform) and only the purest fractions (>95%) were is o l a t e d . The products were r e c r y s t a l l i z e d from petroleum ether and characterized. Hexahydro-1.la.4.5a.5b.6-hexamethyl-1.2.4-ethanylylidene- 3-oxacyclobutarcdlpentalen-2(lH)-ol. compound 15.2 2 Compound 1_5 was isolated as a white s o l i d . mE: 198 - 199 °C ( l i t .2 2 198 - 199 °C) . IR: (KBr) 3344 cm"1 (OH) NMR: 0.80 ppm (s, 3H), 0.89 ppm (s, 3H), 0.90 ppm (s, 3H), 0.91 ppm (s, 3H), 0.93 ppm (s, 3H), 0.96 ppm (d, 13 Hz, 1H), 0.98 ppm (d, 13 Hz, 1H), -81-1.03 ppm (s, 3H), 1.50 (d, 13 Hz, IH), 1.55 ppm (d, 13 Hz, IH), 3.45 ppm (s, IH, CHOH), 1.60 ppm (s, IH, exchangeable, OH). MS: m/e (relative intensity) 248 (M+, 11.8), 139 (37.8), 135 (100). GLC: (program #1) 4.50 min 2a.5a.6.6b-tetrahvdro-2a.4.5.6.6b.7-hexamethyl- (2a. 2ag. 5a/3. 6a. 6afl. 6b/9. 7s*) -2 . 6-methano-2H-cvclobuta \cdl isobenzofuran-6a(3H) - o l . compound 16 . Compound 16 was isolated as white flaky crystals. The spectra of this compound correlated well with the spectra of the analogous product lacking the methyl groups on the double bond, and whose structure was ultimately provided by x-ray crystallography.2 2 mp_: 163 - 165 °C IR: (KBr) 3448 cm"1 (OH) NMR: 0.87 ppm (s, 3H), 0.88 ppm (d, 8 Hz, 3H, C(7)CH3), 0.97 ppm (s, 3H), 1.01 ppm (s, 3H), 1.76 ppm (d, 20 Hz, IH, C(3)aH or C(3)£H), 1.85 ppm (s, IH, C(5a)H), 1.87 ppm (q, 8 Hz, IH, C(7)H), 1.94 ppm (d, 20 Hz, IH, C(3)aH or C(3)/3H), 2.59 ppm (s, 3H, C(4) or C(5) methyl), 2.66 ppm (s, 3H, C(4) or C(5) methyl), 2.78 ppm (s, IH, exchangeable, OH), 3.32 ppm (s, IH, C(2)H). Proton decoupling of the signal at 0.88 ppm resulted in a simplifi-cation of the signal at 1.87 ppm into a singlet. MS: m/e (relative intensity) 248 (M+, 1.3), 187 (66.3), 134 (67.2), 119 (100.0). Anal: calculated for C16H2402: C = 77 . 38; H = 9.74 -82-found: C = 77.63; H = 9.73 GLC: (program #1) 4.50 min Photoproduct r a t i o studies of compound 12. A . Product r a t i o studies of compound 12. i n different solvents. Solution samples of compound 12. i n different solvents were prepared and de-oxygenated by freeze-thaw-pump cycles under a N2 atmosphere. After the samples had been irradiated they were analyzed by GLC (program #1). Every experiment was repeated at least twice and the average of the r a t i o of the photoproducts for each solvent are shown i n Table IX along with the concen-t r a t i o n of the sample and the i r r a d i a t i o n temperature. -83-Solvent Concentration Temperature 15:16 (M) (*C) Benzene 0. .0056 20 + 3 97: :3 Methanol 0, .0085 26 + 1 88: :12 II 0. .067 -52 + 1 80: :20 Ethyl acetate 0, .0063 17 + 1 94: :6 it 0 .0063 -60 + 1 85: :15 Ethylene glycol 0. .0032 26 + 1 66: :34 it 0 .0012 -7 + 1 55 :45 Crystals 20 + 3 no rxn Table IX: Photoproduct r a t i o studies of compound 12. i n dif f e r e n t solvents. B. Product r a t i o studies of compound 12. i n ethyl acetate at different temperatures. Compound 12 (15.7 mg, 0.0633 mmol) was dissolved i n ethyl acetate (10 ml). Small samples of this solution were de-oxygenated by freeze-thaw-pump cycles under a N2 atmosphere and irradiated at different temperatures. The r a t i o of the products was analyzed by GLC (program #1) and each experiment was repeated at least twice. The average of the product r a t i o for each temperature i s l i s t e d i n Table X along with the inverse of the temperature i n K and the logarithm of the product r a t i o . The Arrhenius plot for the -84-data points (1/K, ln(15/16)) was graphed and the least squares method was used to f i t a line to the data. Temp. ( ° c ) 1/T 103 (K"1) 15:16 Ln(15/16) 30 ± 1 17 ± 1 3 ± 1 •24 ± 1 •30 ± 1 •53 ± 1 •60 ± 1 3.30 ± 0.01 3.45 3.62 4.01 4.11 ± 0.02 5.44 " 4.70 " 95:5 ± 2 94:6 95:5 92:8 92:8 90:10 85:15 2.94 ± 0.4 2.75 " 2.94 " 2.44 ± 0.2 2.31 " 2.19 " 1.73 " ln(15/16) = 6.34 - (0.96 x 103)/T (R2 = 0.906) Table X: Photoproduct ratio studies of compound 12 in ethyl acetate at different temperatures. C. Product ratio studies of compound 12. in ethylene glycol at different temperatures. The product ratio studies of compound 12 in ethylene glycol at different temperatures were conducted in the same fashion as the product study for -85-compound 12 i n ethyl acetate. The concentration of the solutions was 0.0062 M. The results are shown Table XI: Temp 1/T 15:16 In(15/16) (°C) (K"1) . 27 ± 1 3. .33 ± 0.01 66: :34 ± 1 0. ,66 ± 0..04 13 tt 3, .49 59: :41 " 0. .35 3 l l 3, .62 52: :48 " 0. ,08 -7 It 3, .76 45 :55 " -0, .20 In(15/16) = 7.34 • - (2.01 x 103)/T (R2 - 0.9998) Table XI: Product r a t i o studies of compound 12 i n ethylene glycol at different temperatures and v i s c o s i t y . D. Product r a t i o studies of compound 12. i n viscous solvents. In order to measure what effect v i s c o s i t y of a solvent would have on the r a t i o of the photoproducts of compound 12, mixtures of ethylene glycol and methanol were prepared and the i r flow time through an Oswald viscometer were measured at constant temperature (27.0 ± 0.5 °C). The v i s c o s i t y of ethylene g l y c o l4 6 and the density of the s o l u t i o n s5 2 were used to calculate t h e i r v i s c o s i t y and the results are l i s t e d i n Table X I I . -86-Compound 12 was d i s so lved i n these ethylene g l y c o l - methanol mixtures and a l l the samples were i r r a d i a t e d at the same time at a constant tempera-ture . The r a t i o of the products was analyzed by GLC (program #1) and each experiment d u p l i c a t e d . The r e s u l t are l i s t e d i n Table V along with c a l c u -l a t e d logari thm of the v i s c o s i t y of the solvent and the logari thm of the r a t i o of the product percentages. L n ( r j ) v . s . ln(15/16) was p l o t t e d and the l e a s t squares method was used to f i t a l i n e to the p o i n t s . The der ived equation i s l i s t e d i n Table X I I I . Mixture Flow time Dens i ty 3 ^ V i s c o s i t y % Methanol i n (min) (g/ml) (cp) ethylene g l y c o l at 27°C at 27 °C Pure ethylene g l y c o l 238. ,3 ± 0.5 1.110 15. 9 46 10.0% methanol 154. .5 " 1.093 10. .15 ± 0. .05 20.0% 102. .3 " 1.068 6. .58 " 40.0% 60. ,3 1.015 3. .69 ± 0. ,04 60.0% 26. .3 " 0.954 1. ,51 ± 0. ,03 pure " - 0.7882 0. , 5 8 7 4 6 Table X I I : V i s c o s i t y studies of mixtures of methanol and ethylene g l y c o l . -87-Mixture % volume MeOH in ethylene glycol 15:16 In(15/16) A l l measured at 27.0 ± 0.5 °C ln(r,) Pure ethylene glycol 66:34 ± 1 10% methanol 69:31 20% " 71:29 " 40% " 75:24 60% " 82:18 pure methanol 88:12 0.64 i 0.04 0.79 ± 0.05 0.88 1.13 1.53 ± 0.07 1.99 ± 0.09 2.77 2.32 ± 0.01 1.88 1.31 0.41 ± 0.02 -0.53 ln(15/16) = 1.72 - (0.41 x ln(r?)) (R2 - 0.989). Table XIII: Photoproduct ratio studies of compound 12 in methanol and ethylene glycol mixtures. Photochemistry of compound 12 in polymer films as reaction media. Organic high molecular weight polymers used to study the photochemistry of compound 12 in polymer films are li s t e d in Table III. -88-A. Product r a t i o studies at different degrees of conversion of compound 12 i n L-PMMA Compound 12 was dissolved i n L-PMMA and photolyzed under N2. The polymer was dissolved i n chloroform and the r a t i o of the photoproducts analyzed GLC (program #1). The results are l i s t e d i n Table XIV. Conversion 15:16 Temp. Concentration (°C) (%w polymer) 93 ± 2 20:80 ± 2 20 ± 3 60.0 83 " 23:77 " 83 " 21:79 " 75 " 21:79 " 24 " 23:77 " 15 " 20:80 " 14 " 23:77 " Table XIV: Photoproduct r a t i o studies at different extent of reaction of compound 12 i n L-PMMA. - 8 9 -B. Product ratio studies at different concentration of compound 12 in L-PMMA films. The effect of concentration of compound 12. in L-PMMA films on the ratio of the photoproducts was studied in similar way as for compound 12 in L-PMMA films. The results are shown in Table XV. Concentration 15:16 Temperature. (%w polymer) ( ° C ) 6 0 .1 2 5 : 7 5 ± 2 20 ± 3 6 0 . 0 2 2 : 7 8 " it 2 0 . 0 2 2 : 7 8 " II 8 . 3 2 3 : 7 7 " II 0 . 5 2 5 : 7 5 " II Table XV: Photoproduct ratio studies at different concentration of compound 12 in L-PMMA. C. Product ratio studies of compound JL2 in different polymer matrices. Studies of products ratio of compound 12 in organic polymer matrices were conducted in the same fashion as for compound 11. The results are listed in Table XVI. -90-Polymer 15:U> Temperature Concentration (°C) (%w polymer) L-PMMA 23:77 ± 2 20 ± 3 8.3 M-PMMA 22:78 " " 53.1 H-PMMA 22:78 " " 11.6 PiBMA 57:43 " 17 ± 1 18.2 PVAc 28:72 " 20 ± 3 30.5 PEG 43:57 " " 25.3 Table XVI: Photolysis of compound 12 i n different polymer matrices. D. Product r a t i o studies of compound 12 i n L-PMMA films at different temperatures Compound 12 was dissolved i n L-PMMA (60% w polymer) and the r a t i o of the photoproducts was studied at different temperatures i n the same fashion as for compound 11 i n PVAc. The results are l i s t e d i n Table XVII. -91-Temperature ( ° c ) l/K (K"1) 15:16 In(15:16) 1.0 ± 1 20.0 ± 1 34.6 ± 1 65.0 ± 1 78.5 ± 1 110.0 ± 1 3.65 ± 0.01 3.41 3.25 2.96 2.84 2.61 17:83 ± 2 28:72 " 31:69 " 47:53 68:32 85:15 -1.59 + 0.1 -0.94 -0.80 ± 0.09 -0.12 ± 0.08 0.75 ± 0.09 1.73 ± 0.1 Table XVII: Photoproduct r a t i o studies of compound 12. i n L-PMMA at different temperatures. E. Product r a t i o studies of compound 12. i n PVAc at different tempera-tures . Polymer films were made from PVAc which contained compound 12 (4.6 w% polymer). Studies of the r a t i o of the photoproducts at different tempera-tures were conducted i n same fashion as for compound 11 i n PVAc. The results are l i s t e d i n Table XVIII. Temperature 1/T 15:16 In(15:16) CC) (K"1) Above PVAc T g-78.3 ± 1 2 84 + 0.01 73 27 ± 2 0 99 + 0.1 64.7 " 2 96 11 69 31 " 0 80 tt 61.2 " 2 99 tt 66 34 " 0 66 + 0.09 56.3 » 3 04 it 66 34 " 0 66 II 39.8 " 3 19 1 l i 60 40 " 0 41 + 0.08 34.6 " 3 25 tl 53 47 " 0 12 11 Below PVAc T g-20 ± 3 3 41 + 0.03 28 72 ± 2 -0 94 + 0.1 2 ± 1 3 63 + 0.01 . 26 74 " -1 05 IT -22 " . 3 98 + 0.02 18 82 " -1 52 II -35 " 4 20 tl 16 84 " -1 66 tl Table XVIII: Photoproduct ratio studies of compound 12 in PVAc at different temperatures. F. Product ratio studies of compound 12 in PiBMA at different tempera-tures . Compound 12 was dissolved in PiBMA (7.5 w% polymer). Studies of the ratio of the products at different temperatures were done in a similar fashion as for compound 11 in PVAc. The results are shown in Table XIX. Temperature 1/T 15:1_6 In (15:16) CC) (K"1) Above PiBMA T g ' 100.0 ± 1 2. ,68 + 0. ,01 77: 23 ± 2 1. ,21 ± 0. 1 78.3 " 2. ,84 It 73: :27 l l 0. ,99 It 64.7 " 2. ,96 tt 69: :31 tl 0. ,80 II 61.2 " 2. .99 tt 70: :30 It 0, .85 tt 56.3 " 3. ,04 it 70: :30 it 0, .85 l l Below PiBMA T • g-34.6 ± 1 3. .25 + 0. ,01 60: :40 ± 2 0, .41 ± 0, .08 20.0 ± 3 3, .41 + 0. .03 57: :43 II 0 .28 II 2.0 ± 1 3, .63 It 53 :47 11 0 .12 -11.0 ± 1 3. ,81 tl 48: :51 It -0 .08 -19.0 ± 1 3, .93 + 0, ,02 45: :55 11 -0, .20 tt Table XIX: Photoproduct ratio studies of compound 12 in PiBMA at different temperatures. Arrhenius plots were graphed for the data in Table IX, X and XI. They were a l l linear, but in the case of PVAc and PiBMA the lines were discontinuous at the Tg. The least squares method was used to f i t a line to the data points in each case. The derived equations are l i s t e d in Table XX along with the coefficients. -94-Polymer Temperature Equation Coefficients range (°C) PMMA 1 - 110 ln(15/16) = 9. .5 - (3. 1 X 103)/T 0.941 PVAc 34. ,6 - 78.3 ln(15/16) = 6. .6 - (2. .0 X 103)/T 0.978 t l 20 - (-35) In(15/16) = 2, .4 - (0. .98 X 103)/T 0.904 PiBMA 56. ,3 - 100 In(15/16) • 4. 1 - (1. .1 X 103)/T 0.960 tt 34. ,6 - (-19) In(15/16) - 3, .3 - (0. .89 X 103)/T 0.993 Table XX: Derived equations for Arrhenius plots of compound 12. i n L-PMMA, PVAc and PiBMA. -95-3. Photolysis of 2 . 3.4aa.6.7.8aa-hexamethyl-4.5.8.8a- tetrahydronaphthoquin-l-on-4g-ol-acetate. compound 7.3 1 Preparative photolysis of compound 7 i n ethvl acetate. A solution of compound 2 (13.1 mg; 0.0528 mmol) i n ethyl acetate (1 ml) was purged with N2 for 30 min before i r r a d i a t i o n for 4 h at room temperature. The reaction mixture was analyzed by GLC (program #1) and i t indicated that no compound 2 remained, with formation of one new product subsequently shown to be compound 8 ( r t = 4.70, 98% area). The solvent was removed i n vacuo to y i e l d a white s o l i d which was r e c r y s t a l l i z e d from chloroform. These crystals were characterized as 5-exo-acetoxy-1,2,3,4,5,8,9-hexamethyl-tetracyclo[4.4.0.03'9.04'8]decan-2-one. 5-exo-acetoxv-l.3.4.6.8.9-hexamethvl-tetracyclo f4.4.0.0J•".0^•°] decan-2-one, compound 8.5 1 m' 1*7 - 149 °C ( l i t .5 1 148.5 - 150 °C) . IR: 1743 cm'1 (C-0). NMR: 0.73 ppm (d, 14 Hz, IH), 0.83 ppm (s, 3H), 0.89 ppm (s, 3H), 0.91 ppm (s, 3H), 0.94 ppm (s, 3H), 1.01 (s, 3H), 1.39 ppm (d, 14 Hz, IH), 1.99 ppm (d, 14 Hz, IH), 2.02 ppm (s, 3H, ester methyl), 2.12 ppm (d, 14 Hz, IH), 4.50 ppm (s, IH, CH-OH). MS: m/e r e l a t i v e intensity 290 (M+, 6.4), 187 (52.1), 43 (100). GLC: (program #3) 4.70 min Preparative s o l i d state photolysis of compound 7. A single c r y s t a l of compound 7 (68.9 mg, 0.23 mmol) was irradiated under N2 at -30 ° C for 24 h. Afterwards the c r y s t a l was dissolved i n ethyl acetate and analyzed by GLC (program #1), which showed unreacted s t a r t i n g material ( r t = 5.35%, 80% area), formation of one major product, compound 9 ( r t = 4.24, 16% area), and a minor product with the same retention time as compound 8 ( r t =4.70; 2% area). The reaction mixture was passed through a chromatographic column ( s i l i c a g e l , 10% ethyl acetate and 90% petroleum ether) to y i e l d a colourless o i l of compound 9 which was characterized as 5 -exo-acetoxy-1-exo-3,4,6,8,9-hexamethyltricyclo[4.4.0.0 4•7]dec-8-en-2-one. 5-exo-acetoxy-2-exo-1.3.4.6.8.9-hexamethyltricyclo[4.4.0.0 4• 71 - dec - 8 - en-2 - one. compound 9.31 IR: (CHCI3) 1736 cm-1 (C=0). NMR: 0.89 ppm (s, 3H), 1.01 ppm (s, 3H), 1.04 ppm (s, 3H), 1.09 ppm (d, 7 Hz, 3H, C(3) methyl), 1.55 ppm (s, 6H, C(8) and C(9) methyls), 1.87 ppm (s, 16 Hz, 1H, C(10)QH or C(10)/3H), 2.07 - 2.21 ppm (m, 2H) , 2.16 ppm (s, 3H, ester methyl), 2.43 ppm (br s, 1H, C ( 7 ) H ) , 4.59 ppm (s, 1H, C ( 5 ) H ) . MS: m/e r e l a t i v e intensity 290 (M+, 3.3), 135 (100). GLC: (program #3) 4.24 min -97-Photolvsis of compound 7 in polymer films. Organic high molecular weight polymers used to study photochemistry of compound 7 in polymer films are listed in Table III. Preparative photolysis of compound 7 in L-PMMA films. L-PMMA films which contained compound 7 (33.8 mg, 0.117 mmol, 75.1% w polymer) were prepared and irradiated for 12 h at -48 °C. Afterwards the films were dissolved in chloroform and analyzed by GLC (program #3) which indicated formation of four photoproducts, and unreacted starting material (rt = 5.35, 9% area). Two of the products were major ones, compound 8 (rt = 4.70, 19% area, identified by IR and NMR) and a product subsequently showed to be compound 10 (rt = 3.60, 59% area). The two other product were minor ones; a product with the same retention time as compound 9 (rt =4.24, 7% area), and an unidentified product (rt = 3.93,7% area). Column chromatogra-phy ( s i l i c a gel, 2% ethyl acetate, 98% petroleum ether) of the crude reaction mixture afforded compound 10 as a colourless o i l after solvent removal. The o i l was characterized as 5-exo-acetoxy-1,3,4,6,8,9-hexamethyltetracyclo[4.4.0.0J• ]dec-8-en-2-one. - 98 -5 - e x o - a c e t o x y - l . 3 . 4 . 6 . 8 . 9 - h e x a m e t h y l - t e t r a c y c l o  f 4 . 4 . 0 . 0 3 ' 7 1 d e c - 8 - e n - 2 - o n e . compound 10. IR : (CHC1 3 ) 1742 and 1728 c m " 1 (C=0) NMR: 0 .89 ppm ( s , 3H) , 0 . 91 ppm ( d , 7 Hz , 3H, C (3 ) m e t h y l ) , 0 . 95 ppm ( s , 3H ) , 1 .00 ppm ( s , 3H) , 1.54 ppm ( b r s , 3H, C (6 ) o r C ( 7 ) m e t h y l ) , 1.68 ( b r s , 3H, C (6 ) o r C (7 ) m e t h y l ) , 1.75 ppm (dq , 4 and 7Hz, I H , C ( 2 ) H ) , 1.86 ppm ( d , 17 Hz , I H , C ( 5 ) aH o r C(5)/9H), 2 .03 ppm ( d , 17 Hz , I H , C ( 5 ) aH o r C(5)/3H), 2 .12 ppm ( s , 3H, e s t e r m e t h y l ) , 2 . 21 ppm ( s , I H , C ( 7 a ) H ) , 4 . 7 6 ppm ( d , 4 Hz , I H , C ( 3 ) H ) . MS: m/e r e l a t i v e i n t e n s i t y 290 ( M + , 1 0 . 5 ) , 230 ( 1 0 0 ) , 215 ( 9 0 . 5 ) , 187 ( 8 4 . 2 ) P h o t o p r o d u c t r a t i o s t u d i e s A . P r o d u c t r a t i o s t u d i e s a t d i f f e r e n t d eg r e e s o f c o n v e r s i o n o f compound 7 i n L-PMMA. L-PMMA f i l m s w h i c h c o n t a i n e d compound 2 (1.4% w p o l y m e r ) were p r e p a r e d and p h o t o l y z e d unde r N 2 . The f i l m s were d i s s o l v e d i n c h l o r o f o r m and t h e r a t i o o f t h e p h o t o p r o d u c t s a n a l y z e d by GLC (p rog ram #3) and l i s t e d i n T a b l e X X I . -99-Conversion of 2 8:9_:10:X Temp. Concentration (°C) (w% polymer) 23 ± 2 37:09:44:10 ± 2 20 ± 3 1.4% 40 " 32:08:47:12 » 43 " 33:10:45:11 " 54 " 29:12:46:13 " 86 " 37:09:43:10 " 96 " 35:10:45:10 " Table XXI: Photoproduct r a t i o studies at different extent of reaction of compound 1_ i n L-PMMA. B. Photoproduct r a t i o studies at different concentrations of compound 1_ i n L-PMMA. The effect of different concentration of compound 1_ i n L-PMMA films on the r a t i o of the products was studied i n the same fashion as for compound 11. The results are l i s t e d i n Table XXII. -100-Concentration 8:£:10:X Temperature (%w polymer) (°C) 59.4 35:9:47:9 ±2 20 ± 3 13.1 33:10:47:10 " 1.4 32:10:47:11 " Table XXII: Photoproduct r a t i o studies at different concentrations of compound 7 i n L-PMMA. C. Photoproduct r a t i o studies of compound 7 i n different polymer matrices. Studies of product r a t i o of compound 7 i n different polymer matrices were conducted i n the same manner as for compound 11. The average of the r a t i o of the products for each polymer reaction media are l i s t e d i n Table XXIII. -101-Polymer 8:9:10:X Temperature Concentration (°C) (w% polymer) L-PMMA 37: :10 :47:10 + 2 20 ± 3 13, ,1% PiBMA 71: :4: 17:8: + 2 ll 11. .6% PVAc 37: :8: 37:9 + 2 tt 12. .3% PEG 94: :1: 0:4 + 2 tt 9, .8% Table XXIII: Photoproduct ratio of compound 7 in different polymer matrices. -102-References 1. J.R. Scheffer, M. Garcia-Garibay and 0. Nalamasu, Organic Photochemistry. A. Padwa, Ed., 8, 249, (1987). 2. J.L.R. Williams and R.C. Daly, Prog. Polym. S c i . . 5, 61, (1977). 3. J . G u i l l e t , Polymer photophvsics and photochemistry. Chapter 5, Cambridge University press, (1985). 4. D. Gegiou, K.A. Muszkat and E. Fischer, J . Am. Chem. Soc.. 90, 12, (1968). 5. J.N. 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