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Mechanism of loss of water from substituted alcohols Chalmers, William 1927

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MECHANISM OF LOSS OF WATER FROM SUBSTITUTED ALCOHOLS.  by William  Chalmers.  U.B.C.  LIBRARY  CAT ^ 1 ^ 3 #7- I£*2!2£2l2&i  I ACC. NO. *••—«•»'!. -:  MECHAHISM OF LOSS OF WATER FROM SUBSTITUTED ALCOHOLS.  by William  Chalmers,  A Thesis submitted for the Degree of Masters of Arts in the Department of Chemistry.  The University of British Columbia April, 1927.  €3JJ±L  LOSS OF WATER FROM SUBSTITUTED ALCOHOLS.  Theoretical Part I,Although the problem of addition reactions has received extensive experimental and theoretical treatment at the hands of many workers the closely related problem of separation reactions has been strangely neglected. Data on separation reactions are not meagre but no attempt has hitherto been made, so far as the writer is aware, at a comparative study of the experimental data which is at present at hand.  The general neglect of the  study of separation reactions is difficult to understand as the phenomena are surely as important practically as addition reactions and if the theoretical side is more complex it is correspondingly more instructive.  The writer  has accordingly begun a study of separation reactions in their most general aspects.  For reasons to be mentioned  later the present study has been largely confined to those reactions in which a double bond is formed in an organic molecule by the loss of the elements of water.  The account  is also confined to the discussion of the problem of the formation of the double bond. Most modern text books on Organic Chemistry in discussing the manner in which the elements of hydrticid or water are split off in the formation of the double bond, quote Saytzeffs* Rule to the effect that hydrogen atom  •  - 2 -  splits off from the least hydrogenated carbon atom.  It  seems to be implied in many cases, that the rule is quite general and applies in many cases, that the rule is quite general and applies to any substituent.  As far as  I am  aware there has however, been no attempt to collect any data to prove this.  It will later be shown that the rule  holds only approximately in a limited field and is entirely insufficient as a general rule.  There are also a number of  cases where the rule is exactly contrary to the truth if considered in its wider sense.  Saytzeff himself, had con-  sidered only the higher Alkyl ipdides. He states in refutation of an incorrect rule that has been put forth by Marlcownikoff that "where several differently hydrogenated carbon atoms stand in the same proximity to the carbon combined with the iodine" the hydrogen comes from the least hydrogenated carbom atom."  It is also to be mentioned that  in Meyer and Jacobsons iehrbucbr there is a brief discussion of the  B  oxy  Acids and the formation of ismers on the 2 loss of water therefrom . There is also a discussion in Houbens "Methoden" of the loss of water from aromatic alcohols-'.  1. 2. 3.  These accounts will be discussed later.  liebigs Annalen - 180 - 2?6 - 1878. Erster Band Erster Teil - p. 933, 934 Zn. Houben " M e " Methoden der Grganischen Chemie," Vol. 2, p.901.  «  3-  The writer has gathered together in the lists appended a number of those cases of the loss of water from the substituted alcohols which include of course the oxyacids oxy-ketones oxy-aldehyde^halohydrins, etc., in which the structure of the unsaturated product or products produced was determined.  The collection makes no claim to  completeness but it is fairly representative.  The sub-  stituted alcohols were specifically chosen rather than halogen compounds for several reasons. When the elements of hydrogen halide are abstracted from a dihalogen compound a complexity is introduced into the relationship by the fact that either or both may come out*  In the case of  oxy-acids and halohydrins. the hydroxyl group can be abstracted without affecting the other groups present. From a practical standpoint the dehydration of substituted alcohols is much easier to carry out, with smoother and less violent reactions than is the case with halogen compounds,  there is for this reason a good deal more reliable  data on hydroxy compounds than on halogen compounds.  It is  further to be noted that the relationships deduced from this particular class of compounds can be applied almost quantitatively to the halogen compounds.  This experimental work  to be described in Part II has shown that the action of P. CI. on unsym, methyl, ethyl, ethyleneoxide and the dehydration of the corresponding chlorhydrin each gives a chloramylene containing approximately dof of the isomer  - 3& -  LOSS OF WATER FROM SUBSTITUTED ALCOHOLS. List of Examples.  Note.  Reactions noted in Beilstein*s "Handbuch" and the original source of which were not referred to are  characterized "by B.H. Reactions noted in Meyer and Jacobsons» "Lehrbuch" are characterised "by M.O.J. The Journals are denoted as follows A  - Liebigs "Annalen"  B  -  Beriohte der deutschen chemischen G-esellsehaft.  Bl  *  Bulletin de la SociStg chimique  C.r.A.  Comptes Rendus.  Hydrocarbons. 1.  (CH )  CH . CH(OH)CH  3 2  (CH )  3  C:CH(CH )  3 2  3  Wischnegradshi A 190, 334. 2.  ( C H 3 ) 2 C (° H ) • C H  (CH )  C:CH(CH )  (CH )(C H ) C:CH 3  23  2  Ipatjew B. 36, 2002. 3*  CH  5  . CH(OH) CH  . CH  2  3  CH  3  . CH:CH.CH .  B.H.  3  «  - 3"b -  B. B.-oxy Acids and flitriles. 1. CH .CH(OH) CH COOH  3  CH  3  B.H.  3  2.  2. C„H CH(OH) . CH COOH 2  . CH : CH COOH  CH  2  CH : CH . CH. . COOH 2  3  CH CH . CH : CH . COOH 3 2 Pittig & Spenger A 283, 74(1894). 3.  (CH )  . CH . CH(OH) . CH  . COOH  (CH ) CjCH.CH COOH 3 2 2  B.H.  (CH,) CH.CH.-CH.COOH 3 2 4. CH  3  . CH(OH) .CH(CH )  . COOH  3 CH, . CH;C(CH ) COOH  3  3  B.H.  5.  (CH) . C(OH)CH . COOCnH 3 2 2 2 5  6.  (CH) C(OH) .CH CN 3 2 2  7.  (CH) . C(0H) . CH(CH ) COOH C:C(CH_) COOH 3 2 3 3 (CH ) . CH . CH . CH(OH) . CH COOH 3 2 2 2 (CH ) CH.CH CH:CH.COOH B.H.  8.  3 2  (CH ) C:CH(COOC„H ) 3y2 2 ^ B.H.  (CH ) 32  C:CH(CN)  3  (CH ) CH . CH : CH . CH . COOH 3 2 2  30 -  9.  (CH ) CH . CH(OH) . CH(CH ) COOH  3 2  3  (CH )  3 2  10.  . CH . CH : C(CH ) COOH  B.H.  3  (CH ) . CH . CH . CH .CH(OH) CH . COOH 3 2 2 2 2 (CH ) CH.CH . CH CH : CH(COOH) 3 2 2 2 (CH ) CH . CH  11.  •  . CH : CH.(CH COOH)  (CH,) CH . CH(OH) . CH . (CH .CH .CH )(COOC H ) 2 3 2 2 2 3 3 CH .CH; CH.CH (CH CH CH )(COOC H )  Other Ozy - Acids - Simple and Substituted. 1. CH  . CH(OH) . CHC1.C00H  CH .CHtCCl.COOH  3  B.H.  3  2. CH CI, CH(OH) . CH . COOC H 2 2 25 CH C1:CH . COOC H . 3. CH CI , CH(OH) . CH  B.H.  . (CN)  CH CI CH : CH(Clf) lespieau 4. CH . CH 3 ^  C.r. I30, 1410.  . C(CH )(0H) . COOH 3 CH . CH j C(CH' ) COOH  3  3  B.H.  3. CH_.CH(OH) . CH . (CH,) COOH  3  3  CH . CH : CH(CH ) COOH 3 3  B.H.  - 34 -  6.  (CH,)  . C(OH) . CHC1. COOH  3 z  (CH ) . C : C CI . COOH 3 2  B.H.  B - oxy Aldehydes. 1.  CH  . CH(OH) . CH  . CHO  3  CH  2  • CH:CH.CHO  3 Grignard Reif.  2.  CH  4  1, 116,  . CH . (OH) . CH . (CH ) CHO  3  3 CH  3.  Bl  CH  • CH  3  3  . CH : CH(CH ) CHO  3  B.H.  . CH(OH) . CH. (CH ) . CHO  2  3 CH . CH . CH:C(CH ) . CHO  3  2  3  M db J. Vol. II p. 892. 4.  CH,. CH(OH). CH. (CH,) CHO  3  3 CH . CH . CH:C(CH )(CHO)  3  2  3  Ozy - keto Compounds. 1.  CH . CH(OH) CH . CO. UH  3  2  3  CH . CH:CH. CO. CH  3  3 B. H.  2.  (CH ) . C(OH). CH . COCH .  3 2  2  3  (CH ) . C : CH.COCH 3 2 3  B.H.  - 3e -  3.  (CH ) CH . CH(OH) CH . COCH 3 2 2 3 (CH ) CH*CH:CH.COCH 3 2 3  A.  (CH ) . CH . CH . (OH) . CH . COCH 3 2 2 3  B.H.  (CH ) C : CH. CH . CH CO.CH 3 2 2 2 3 B.H.  F. Nitro Compounds* 1.  (CH ) . C.(OH). CH(HO ) CH  B.H.  (CH ) C:C(NO ). CH 3 2 2 3  G-. Alhoxyl Derivative. General:RA C(OH). CH OX 2 2  R C : CH(OX) 2  (R » any alhyl group, X • any alkyl or aryl group) B<§hal and Sommelet C.r. I38, 89,92, H. Phenyl Derivatives. 1.  C,H . CH . C(OH)(CH ) CH . CH . C.H 6 63 2 3 2 2 5 C , H . CH: C(CH ) . CH . CH . C H 6 3 3 2 2 6 3 Houhen "Die Methoden" V o l . 2 , 9 5 1 .  •  - 3f -  2. C H . CH . CH . C(OH)(CH . C H ) 6 3 2 2 2 6 ^ 2 C,H . CH . CH C(CH . C H ):CH.(C H ). & 5 2 2 2 6 5 05 Ibid. I, Halohydrins. 1. CH . CH.(OH). CH CI. 3 2 2,  (CH ) . C(OH). CH CI  CH CH : CHC1 B.H. 3 CH : CH . CH CI 2 2 (CH ) . CrCHCl B.H.  CH : C(CH ). CH2 CI 3#  (CH ) . C(OH). CHC1. CH y 2. 3  (CH,) . C : C CI . CH 3 2 3 B.H.  4.  (CH,) . C(OH). CH . CH Cl (CH ) . C :CH.CH Cl 3 2 , 2 2 3 2 2 Henry. C.r« 143, 1224.  3, (CH )(C H ). C(OH). CH Cl 3 25' 2 (CH )(C H ), C : CHC1. 3 23 CH CH : C (CH ). CH Cl) 3 3 2 J 40% (C.H ).(CH Cl) C:CH ) 2 3 2 2 (See Experimental Part)  •  4 -  (C.H_) (C-Hj C:CH CI. As a general rule where data are available it is fairly certain that the two prooesses lead to the same isomers, although probably not always in the same proportions. As already mentioned the determination of the proportions of isomers formed in the dehydration of the simple and substituted alcohols has not been approached from a comparative standpoint. Accordingly it far from certain that even a thorough qualitative search for the various isomers possible have been made.  Before any conclusive generalisa-  tions can be drawn it will be necessary for extensive research of a quantitative nature to be done. A beginning has been made in the experimental part of the present research as will be later described in the second part of the paper.  Sufficient experimental data has, however, been  gathered together to draw certain general relationships and to indicate the general lines upon which research in this field must proceed to elucidate the problems occurring therein. The experimental researches in the loss of water from the unsiibstituted alcohols, as cited in the previous pages, show that Saytzeffs* rule holds only in as far as it indicates the reaction which has taken place to the greater extent.  They show that probably all possible isomers are  formed but that the yield of the compound to be expected by the rule increases, when one of the groups attached to the carbinol carbon atom becomes secondary and tertiary.  „  - 3 -  If one takes Saytzeffs* rule in its wL der sense and applief it to the de^hydration of an alcohol such as say, butylene, chlorhydrin  CH_ CH CH(OH) CH. CI an 5  obvious difficulty arises.  2  d  Will the hydrogen atom split  off from the ethyl group or the CH 2 CI group. The oarbon atomB concerned are both equally hydrogenated "so that the rule even taken as indicating only the major product of the reaction shows itself as insufficient. Hor is this the only difficulty to be met with. An examination of the reactions listed for compounds of the type CH_ CH(OH) CH 0 X. Where X o i s the oarfcnyl, aldehyde, ethoxy, cyanide or phenyl group shows t h a t the r e a c t i o n goes p r a c t i c a l l y e n t i r e l y i n the direction. CH CHg CH (OH) CH2 X (H ) C2H^ CH : CHX.  It might be thought from this that Saytzeff»s rule was perfectly applicable in simple oases such as this, where X is a negative substituent. Yet if we consider the Chlorhydrins we see that the simple alcohols are not alone in refusing to adhere to the rule. The chlorhydrin of propylene gives two insomers. CH, . CH : CHC1 CH(OH) CH, CI * CH : CH . CH . CI. This behaviour prevents the qualification of the rule in the CHyX  manner suggested. Of general observations concerning loss of water from oxy compounds that have been enanciated in the liter-  - 6-  ature that given by Meyer and Jaoobaon 1B the most important. It ia to the efieot that B oxy aoida can lead to d-B and B-y unsaturated aoida. CH -  - CH0 2  CH : CH . COOH.  CH(OH) CH . COOH. -• 2 CH ; CH CH COOH. 2 2 2  A rule mentioned by Houben  ia to the effeot that  "If phenyl groupa are present, the hydrogen la aplit off in the direction of the nearest situated phenyl group. 3 experimenta of Banal and Sommelet rule.  The  lead to another general  The workers ahowed the ethera of glycols corresponding  with the formulae. ORg. (OX) . CHgOX and CI^ Rg. (OE) . CH20I In whiah X represents a univalent alayl or aryl residue are c o decomposed by heating at 110 ~ 1^0 with dry oxalio a d d yielding aubatituted aldehydes of the type CR^ CH . CHO  and CB^ R  C HO.  the following scheme representing the probable oourse of the reaction. CR2 OH . CH2 OX CRg  CR2  : CH2 OX  CRg J CHgOX  H.C HO.  The point of intereat to ua la that the hydrogen atom aplita  1. "Sehrbruch" previously mentioned. 2 . Houben - Methoden - previously mentioned. 3 . Comptea Rendu* - 1904, 138 , 89, 92.  off without exception, from the carbon atom to which the group is attached. A study of a large number of cases of the dehydration of an alcohol of the type. (Where R^ and R are hydrogen alhyl groups, and X and X are hydrogen  any groups whatever.)  which theoretically may lead to two isomers. R Rg C : CH . CH X X or R-^ R2 CH . CH : CX . Xp has led to classification into two general classes. These classes may be described as those in which appreciable quantities of both isomers are formed and those in which appreciable quantities of only one isomer have been noted. The relationships are best shown in the following table. Only compounds which are quoted in the lists previously are given,! indicated. I. Compounds Which Form Ho Isomers. General Formula R . CH (OH) . R2 Groups which are Groups from which hydrogen is left untouched. taken exclusively.  1.  *1  R  -CH P  ( C O o CH-, -CH COOH, 3 2 d. -CH .CHO, -CH„ CO . CH , 2 2 y  2  - 8 -  COOH -CH  , CH, 3  CH, -CH * CHO  COOH -CH  CI -CH  C H 2 5 2.  CH C I 2  -CH . COOEt, 2  3.  CH • CH -  - C H COOH  3 4*  5.  2  CHO  -CH CO.CH 2 3  C 6 H r CH 2 .CH 2 -  -CH2 .  CH_ -CH >  - C H 0 OCH, d ?  C00H  C ^  Compounds Which Form Isomers.  R . 1  1.  -CH CH 2 CH* |—CHp.CO.CH? p -CH ?  2  (CH ) CH3 2  II.  COOH  R . 2 (Group from which H s p l i t s o f f greater extent.)  CH -  -CH C I 2  3 2.  CH . CH 3 2  -CH .COOH 2  3.  -CH .COOH.  ~CH(CH) , -CH .CH .CH(CH ) -CH .CH(CH ) 2 3 2  In t h e c a s e o f a l c o h o l s o f the g e n e r a l R, R^^ C (OH) R2  formula  to  - ? -  r e l a t i o n s h i p s of the same type seem to h o l d .  Thus where R,  i s t h e methyl group we g e t isomers when R i s -CH CI, -C H , -CH CO.CH , CH •CH CI 2 2 2 y 2 3 2 2 CI -CH_4 . COOEt, -CH-CH, -CH d  , -CH COOH  CH, p COOH  where the hydrogen atom splits for the greater part from the R2 group. The w r i t e r i s convinced t h a t i t i s p o s s i b l e t o s e t up a s e r i e s such t h a t t h e formation of isomers i n the process of e l i m i n a t i o n can be prophesied by t h e nearness of the groups i n the s e r i e s and t h a t when t h e s u b s t i t u e n t s are f a r a p a r t i n t h e s e r i e s i t may be expected t h a t a p p r e c i a b l e p r o p o r t i o n s of only one isomer a r e o b t a i n e d .  From the r e l a t i o n s h i p s  shown above such a s e r i e s may be s e t u p .  Thus we g e t  -CHj, CI, CH2.CH_, CH2 CI, CH(CH ) -CH COOH, C H . CH , (CH CO • CH , CH OCH CH OEt, CH .CHO) 2 ' 6 5 2 2 3 2 3 2 2 Data does n o t permit the a c c u r a t e p l a c i n g of the bracketed groups. From the series we anticipate that if to the group ^sCH(OH) the groups CH, and -CH CI are attached we will get large proportions of both possible isomers on dehydration, which we observe.  If the attached groups are CH and -CH -CH,  3 CH  3 *  - 10 -  we would expect only a small proportion of one isomer and if the groups are CH and -CH .CO, CH we would expect no 3 2 3 appreciable proportion of one isomer and this is in accordance CH with experimental facts. Similarly when both -CH 3 CH and -CH  • COOK are present large proportions of both isomers  are formed but when the groups -CH • CH  3 • CH  3  and -CH  • CO, CH a r e p r e s e n t the hydrogen s p l i t s  from t h e second groupfr.  entirely  To completely j u s t i f y t h e r u l e a  g r e a t d e a l of s e m i - q u a n t i t a t i v e work w i l l have t o be done p a r t i c u l a r l y i n t h e case of a l c o h o l s where two groups such a s CH„ COCH and CH OCH are p r e s e n t . 2 3 2 3  The s e r i e s m i g h t '  b e t t e r be made up i n t h e form of t h e a c t u a l s u b s t i t u e n t s i n t h e group from which t h e hydrogen i s s p l i t off.  We would then  get H, CH , CI, COOH, CH , CH CO, OCH. OEt, CHO. When an attempt is made to explain relationships observed in the formation of the double bond in an organic molecule through loss of water or hydrogen halide the necessity for much further research of the type carried out by Michael and Henry and other workers for addition reactions is at once felt. An application of Michael's principle of neutralization and his views on affinity serve, however, to give an inkling of the relationship observed much better than ay  - 11 -  other current theory.  So far as I am aware Michael did not  consider fully the problem of the formation of the double bond but his ideas may be directly applied.  Superficial  consideration of a compound of the type CH, CH CH(OH) CH X. 3 2 2 Where X is a strongly electro negative radieal might lead us to conjecture that since the group X would have an attraction for the hydrogen atoms attached to the same carbon atom hydrogen would split off from the -CH .CH  group.  the  This is  2 3 When we consider the simple  e x a c t l y c o n t r a r y to e x p e r i e n c e . alcohols. CH,. CH(OH) CH. CH, CH, . CH : CH . CH 3 * 3 3 3 CH 3  CH)OH) . CH  -CH,, CH * CH . CH : C(CIL)  we see t h a t t h e conjunction i s J u s t i f i e d i n t h i s c a s e , however. To c l a r i f y our i d e a s on t h e processes involved l e t us consider the energy r e l a t i o n s h i p s concerned i n t h e dehydration of an a l c o h o l of the g e n e r a l t y p e . R  Xn CH -CH(OH) -CH  R 2  H 0 2 R X, C -CH -CH x pii x \ \ la  x  X„ 2 R or  X.  CH . CH -C x n li T R 2 2 Ha i  - 12 -  1  X C » CH - CH  R  or X  2  1  2  1 CH, CH = C X  *2  lb  2  lib  According to Michael and leupold the reaction must take place in such a manner that the maximum entropy possible under the given conditions is obtained. Wow the first step in the dehydration of the compound may be considered to be the formati on of water and the intermediate compound la and 13a The energy relationships involved in the formation of a molecule of water will be the same for both compounds so that this change need not be considered. A certain amount of energy must be expended, however, in the separation of H and -OH from atoms to which they are attached and this will in general be different. We would expect that compound to be formed when there is the least resistance to the loss of these atoms. We would further expect that the main difference in the energy changes in the formation of the isomers Iaand I^to be the separation of the hydrogen. Again we would exhibit least tendency to split off from a carbon atom to which an electro negative group or groups is attached and a corresponding greater tendency to split off from a carbon atom attached to a positive group such as CH*. The formation of isomers la and Ila does not complete the changes of entropy in the process. We have yet  m  - 13 -  to oonsider the union of the two free bonds i n eaoh oase to form the isomers I and l i b .  That change which takes place  with the g r e a t e s t i n c r e a s e i n entropy wil be determined by the r e l a t i o n s h i p of a l l the atoms i n t h e molecule.  In both  Of the s t e p s , formation of l a and l b and H a and l i b we might apply M i c h a e l ' s d i s t r i b u t i o n p r i n c i p l e . In the f i r s t step we must oonsider t h e r e l a t i v e a f f i n i t i e s o f the H and of -OH for the atoms t o which they are a t t a c h e d .  The p r o p o r t i o n s of l a and H a foxmed w i l l  depend p r i n c i p a l l y upon the a f f i n i t y of hydrogen for the two groups R  S9 C - S,  and  r,  c  L  C  \  wliere S. and § 2 represent the remainder of the molecule in the respective oases and the proportions of the two isomers formed will be dependent upon the intensities of the affinities concerned. In the second step also we must oonsider the relative affinities of the groups together with the effect produced by the crowding *  S_  1 C\  and ^  S„  of the bonds.  2 -C H . CHX^ I  s3 B CH . CH- -  s4 -C  ^  Xg  The r e l a t i v e p r o p o r t i o n s of isomers due t o these changes w i l l be dependent upon t h e r e l a t i v e a f f i n i t i e s of the group*.  - 14 -  The combined effect will be seen therefore to be the resultant of the interplay of many affinities in the molecules. In further disucssion of these ideas it will be in the interests of clearness to choose a specific example. The simplest possible is proplene chlorhydrin.  Here we may  represent the theoretical steps to be CH  3  . i CH(QH)  . CH CI 2  H 0 2 •¥  CH 3  • CH- CH- CI 1 1  or  CH P - CH- CHP CI c 1 C 1  Ha  la CH 2  CE^ : CH : CHCJ  : CH . CH C I . 2  lib  lb  We may assume that so far as the first step is concerned, the isomer Ila will be formed to the greater extent. However, the second step would tend towards the foimation of lb since one of the carbon atoms holding the (Momentarily) free bond is attached to the positive CH group and the other to the 3 negative CI atom.  There are thus two opposing tendencies and  we must assume that they nearly balance in the case of propylene chlorhydrin since both isomers are present are produced in considerable proportion.  In the case of B-hydroxy  butyric acid CH , CH(OH) CH , COOH  CH , CH : CH . COOH  -15 -  we must ass-ume that the second effect greatly exceeds the first.  I t i s to be further noted that i f the change la  lb takes place much more readily than I l a  l i b the double  bond in lb will be l e s s reactive than in l i b .  This i s  certainly true i n these chloropropylenes and teaSr related compounds. In view of the lack of data i t i s f u t i l e to develop these conceptions.  This much can be said, however,  that the formation of isomers would be expected to be the role rather than the exception.  Here the theory i s i n  accord with experiment and i n contradiction to Saytzeff*s rule.  Further, the foxmation or non-fonnation of isomers  i s not due to the mere presence of an electronegative or positive group but i s due to a p a r t i c u l a r degree of electro positive o r negative nature of the group.  This i s verified  by the presence of chlorine among the H and CH substituents in the series previously given. Conclusion and Summary. The chief aim of the present discussion has been to point out the importance and i n t e r e s t i n the neglected field of separation r e a c t i o n s .  I t has been shown that  Saytzeff's rule i s incorrect and a rule has been suggested which f i t s the facts b e t t e r .  Michael's views on a f f i n i t y  have been applied to the problem and have been shown to indicate the relationships observed.  l^a -  Theoretical  Part II.  Following the plan of the writer to make quantitative determinations of the proportions of isomers form in the loss of water from substituted alcohols, the chlorhydrins were chosen as a suitable family with which to "begin the study.  Uhsymmetrical methyl, ethyl, ethylene  ehlorhydrin is of special interest as it is the simplest compound containing a C(0H) group attached to a -CH -CH  group and two differently substituted  groups. The isopropyl compound would also be of interest  in comparing the effect of a mono and dimethyl substituted group.  As a number of derivatives that would be prepared  in the dehydration of the compounds are not described in the literature, it was felt that a study of these would be of value.  - 1^6-  Exp erimental. The chlorhydrin employed during thi s research were prepared by the Barbier-Grignard reaction, chloractone being allowed to react with an ethereal solution of magnesium alkyl bromide.  The chloractone employed was pre-  pared by the ehlorination of acetone according to the 1 2 methods of Cloes and Frith . A large quantity of this compound having a boiling point of 120°C. was obtained. As this had been fractionated many times and came over entirely within a range of less than 1 degree it is considered that the product was very pure. The density was 20 found to be D^ * 1.161. It was further found that even after a constant boiling product was obtained the last portions of the distillate became dark colored on standing for several days.  It was found that if the last fifth  portion of the distillate was set aside the remainder did not become colored even on several months standing.  The  •t  method of Hyriahide^ was followed in carrying out the reaction of chloracetbne with the magnesium ethyl bromide. This worker pointed out that shaking and strong cooling during the addition gave better yield with a purer product  1. Cloez - Annales de Chemie (6) 9 Page 164. 2. Paul Frith - liebigs Annalen 279, Page 310. J. Kyriahides.  - 16 -  than if only the ordinary precautions are observed. reaction was first carried out by Tiffeneau  This  who claimed a  yield of 72f., but gave no details of his method. Forneau 5 and Tiffeneau later noted the firmation in this reaction of a secondary product of boiling point so close as to be inseparable by fractionation.  Kyriahides stated that his  method gave only traces of this product.  This worker was  concerned, however, only with the preparation of moderately pure oxide and did not re isolate the pure chlorhydrin.  The  constants determined in this research are 20 B.P. 148 -150 J>A 1.0^0 4  Tiffeneau gave t h e i n s t a n t s . B.P, 152 - 153  0  DQ  - 1.068.  They a p p a r e n t l y prepared what they considered t h e p u r e c h l o r h y d r i n by t h e a c t i o n of hydrogenpchloride on the oxideH.  In view of t h e f a c t t h a t t h e isomeric chlorhy-  di^n would be expected to be formed i n considerable p r o p o r t i o n i n t h i s a d d i t i o n , and t h a t t h i s compound would by analogy with t h e lower homologues have a b o i l i n g p o i n t a t l e a s t 5° h i g h e r than the o t h e r , i t i s j u s t i f i a b l e to assume t h a t these a u t h o r s have not prepared t h e pure compound.  4. 5.  Tiffeneau - Comptes Rendres 134-774 (1902). Forneau and Tiffeneau - Comptes Tendres 145-437 (l907i»  - 17  It was ascertained that the low yield obtained in this reaction was due to inefficient stirring of the addition product, as this covers the unattached reagent and prevents reaction.  To remedy this a stirring device was arranged by  which a glass-rubber bearing was employed.  This was per-  fectly air-tight and did away with the arduous labour required by Kyriahide»s shaking method. the preparation of unsym. methyl  It was employed in  isopropyl  chlorhydrin.  Here, unfortunately, the full value of the stirring was not apparent as the addition product was found in this case to be liquid.  It is of value, however, to learn that such a  stirring device can be employed in a reaction of this type. A device of this type has not hitherto been employed in conducting Grignard's reaction. Timeihas not yet permitted the complete purification of the unsymn. methyl isopropyl Chlorhydrin.  The  yield of product distilling between the limit 72° and 8.5 at 38 mm. was 40^. It is not described in the literature. A large quantity of oxide was prepared by the method given by Kyriahides. product of B.P. 80 - 81  Repeated fractionations gave a  Kyriahides gave the broad limits  78-830 and Forneau and Tiffeneau gave 81 -82 . The action of P.CI on the oxide was carried out .5 by the addition of P.CI to the oxide, strongly cooled in a freezing mixture and the reaction completed by warming in a water bath.  This procedure is somewhat different from that  - 18 -  employed in the writer's undergraduate research when the oxide was added to the pentachloride. In one experiment 65 g. of oxide and 130 g. of P. CI  (l molecular proportion)  gave 40 g of product of B.P. 90°-145°. On several distillations this gave 14 g of product of B.P. range 130-140° o o the rest being mostly of range 90 -110 • The former portion on repeated fractional distillation gave a liquid of B.P. 20 o 133 -133 , \ » 1.0785. Although lack of time did not permit of an analysis, a study of the constants of the isomeric vicinal dihalides made it appear fairly certain that this product must be the vicinal dichloride CH . CH . C . CH .CI 3 2 . 2 CH, 5 CI It is a colorless liquid of pleasant order, decomposing slightly on distillation.  It is not mentioned in the  literature. 0  The product of range 90 -110  0  was refluxed f o r two  hours w i t h a d i l u t e s o l u t i o n of K CO s e p a r a t e d , d r i e d and 2 3 the f r a c t i o n 90°-110° a g a i n i s o l a t e d by d i s t i l l a t i o n .  From  c o n s i d e r a t i o n s given i n t h e w r i t e r ' s undergraduate r e s e a r c h i t had been considered t h a t t h i s product must be l a r g e l y the ohloramylene. CH , CH 3 2 CH  C : CHC1.  3 1  - 19 -  In this compound the chlorine atom being adjacent to the double bond is very unreactive, unlike the chlorine atoms in possible isomers.  It was found, however, that the product  gave a precipitate of sodium chloride when treated with sodium iodide in acetone solution . The amount of replaceable chlorine was thus found to be approximately 30%. ninety minutes heating of a weighed quantity with anhydrous potasBium acetate and glacial acetic acid and determination of the amount of potassium chloride present gave 30.3% replaceable chlorine.  One hours heating of a weighed quantity with an  excess of alcoholic potash gave 35.8% replaceable chlorine. This was ample proof that the original supposition was incorrect.  Re-examination of the higher fractions ob-  tained on the heating with K CO 2 3  solution gave a small  q u a n t i t y of l i q u i d of B.P. range 140-145°.  A further  q u a n t i t y of t h i s l i q u i d was obtained by s a t u r a t i n g the K CO s o l u t i o n w i t h more c a r b o n a t e .  The amount of t h i s p r o - .  d u c t , which w i l l be shown to be very probably composed of tiglyl  a l c o h o l f o r the g r e a t e r p a r t , i n d i c a t e d about 10f.  replacement i n t h e o r i g i n a l h e a t i n g with aqueous c a r b o n a t e . This i n d i c a t e s 40-45% of r e p l a c e a b l e c h l o r i n e o r 53-60% of t h e compound, (CH . CE )(CH ) . C : CHC1 3 2 3 t h e remainder b e i n g probably t h e isomers CH  1.  3 , CH : C(CE3) CE2C1 and CH2 : C(C2H^)CE2C1. For theory see Eouben*s'Kethoden" Vol. 3. P . 202.  20 -  These f a c t s i n d i c a t e t h a t the formation of 3 chloramylene by the a c t i o n of P.CI on the oxide cannot be a s c r i b e d to the formation and decomposition of the a l d e hyde d i c h l o r i d e CH-, CH2 . * CH.CHC1 CH . 2 3  CH .CH 3 2  which w i l l give only one isomer.  C : CHC1  The formation of the un-  s a t u r a t e d compound must be due t o the decomposition of the 3 v i c i n a l d i h a l i d e under t h e i n f l u e n c e of P.CI o r through t h e i n t e r m e d i a t e formation and decomposition of a complex of the type CH . CH 3 2 CH 3  C. CH2 CI 0 P CI 3  which may give a l l of t h r e e p o s s i b l e isomers.  The f a c t  t h a t a c e r t a i n amount of v i c i n a l d i h a l i d e i s formed show t h a t t h e r e a c t i o n i s probably one o r both of the l a t t e r , two. A small qtiantity of t h e pure chloramylene (C H r )(CH,)C:CHCl was prepared by h e a t i n g t h e mixture with 2 3 3 K o C0, s o l u t i o n f o r 3 0 hours and f r a c t i o n a t i n g the product. 2 3 Complete examination of the produet of B.P. 140-143  ob-  t a i n e d as a by-product was not made, but t h e l i q u i d must be a mixtureof t h e isomers CH_, CH:C(CH,), CH OH and CH p :C(C 2 H 5 ) CH OH.  The c o n s t a n t s of the former compound,  21 -  tiglyl alcohol are not given in the literature, hut the latter compound CH :C(C_H5)CH OH has been prepared by Konkadow  who gives B.P. 133-134»5°. From the analogy of  the corresponding hydrocarbons, aldehydes and acids we would expect the former to boil at a 5 -lj?° higher temperature than the latter so that the resultant product is probably largely tiglyl alcohol.  The constants of the  chloramylene (CH5)(CpH )C:CHC1 were determined to be B.P. 97-99°  D 2 0 = .9150  The constants of this compound have not been given in the li terature. The dehydration of the unsym. methyl ethyl chlorhydrin was carried out utilizing anhydrous oxalic acid. experiment was carried out as follows:  One  75 g of pure chlor-  hydrin were added to 100 g of anhydrous oxalic acid in a flask provided with a receiver, the latter being cooled. 0  Tk temperature was then raised to and kept at 110 hour to allow formation of oxalate.  for an  The temperature was  then raised to 135 C when decomposition of the oxalate began to take place. proceeded until 170 to sublime.  The heating was increased as decomposition was reached, when oxalic acid began  The chloramylene was separated from the water  in the distillate, treated with tta HCO* to remove oxalic acid present, dried and distilled.  1.  Konkadow - B. 21 Referate 440.  The fraction 90°-120°C  - 22 -  amounted to 35 g. and the f r a c t i o n above 20° c o n s i s t i n g l a r g e l y of u n a l t e r e d c h l o r h y d r i n amounted to 20 g.  The  y i e l d was thus 55% c a l c u l a t e d to 20 g. t h e e n t i r e q u a n t i t y employed and 74.5^ c a l c u l a t e d on t h e a c t u a l amount decomposed. A small amount of t a r r y m a t e r i a l was found i n t h e r e a c t i o n flask. A p o r t i o n of t h e product obtained was then t r e a t e d w i t h sodium i o d i d e i n aoebone s o l u t i o n i n the c o l d to determine t h e r e p l a c e a b l e c h l o r i n e . pound gave 5.3270 g. of sodium c h l o r i d e .  Thus 2 4 . 1 g . of comThis corresponds  to 39*5$> r e p l a c e a b l e c h l o r i n e o r 60.5$ of t h e isomer. (C_H)(CH,)C:CHC1. d 5 5 It was found that the iodine compounds formed, viz., CH, CH:C(CH )CH J. or CH  : C(C2He)CH2 J decomposed  to a considerable extent even on standing overnight. The acetone was distilled off through a fractionating column until the temperature of the vapor reached 60°. The residue was treated with water, separated and dried over Ca Cl p . When the acetone distillate was treated with water, about 15 oc of a colorless liquid separated out, which was separated and dried.  This gave on distillation not only  chloramylene expected but also a quantity of a liquid below 80 C.  Its nature is uncertain, although it is an  olefinic compound.  The other portion was subjected to dis-  tillation and a quantity of distillate, colored with iodine came over below 110°. However, when this temperature was reached the compound suddenly decomposed with explosive  m  - 23 -  violence, setting free clouds of iodine and a tarry product. This decomposition, due to one or both of the two iodides probably present was entirely unexpected as the related allyliodide is quite stable. A small quantity of the chloramylene remaining was heated for 30 hours with a 10?. solution of K 2 C0, and the alcohol produced, of boiling point 140-143° was examined.  The compound was then heated for two hours with a  small quantity of 1% sulphuric acid solution.  The entire  solution then neutralized and saturated with K„C0 • The c  3  produet this reisolated appeared to be largely the original compound but a small portion came over at a much lower temperature, this fraction reacting to the aldehyde tests. Konkadow1 has pointed out that the alcohol CH2:C(C2H5)CH OH differs considerably in the rate with which it is converted into aldehyde on boiling with dilute sulphuric acid, from tiglyl alcohol, CH,, CH:C(CH^CHgOH.  The latter compound  is only slowly converted into aldehyde.  It will be necessary  to carry out comparison experiments with these compounds before any estimate can be made of the proportions of both isomers present, but it is fairly certain that the alcohol is largely tiglyl alcohol. Conclusion and Summary.  1. Konkadow.  B. 21, Eeferate 440.  - 24 -  It has been shown that the dehydration of unsymmetrical methyl ethyl ethylene chlorhydrin with anhydrous oxalic acid leads to the formation to the extent of 60% of the isomer in which the chlorine atom is adjacent to the double bond, the remainder being the chloride  of  tiglyl alcohol with an undetermined proportion of the chloride of Bethyl allyl alcohol.  The chlorhydrin of unsym. iaopropyl  ethylene has been prepared for the first time as has the dichloride of unsym. methyl ethyl ethylene.  The chlorine  substituted olefine (CH3) (C2H^) C : CHC1 has been prepared pure for the first time also.  It has  further been shown that the interaction of phosphorus pentachloride with the oxide of unsym. methyl ethyl ethylene leads to essentially the same product as is produced by the dehydration of the chlorhydrin together with a small proportion of the dichloride. In conclusion I wish to thank T3r. W. F. Seyer for help and advice during the progress of the research.  1  


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