755 



.ÜHHO. 

 C„H,CH=CH— C < Q > C^CH=CHC„H3 



Also when we assume lliat on solidifying a change in stnictnre 

 of the donble molecule takes place and that the formation of the 

 truxillic acids occurs in the double molecule itself and not between 

 two double molecules it is possible to give structural forniidae for 

 a- and ;?-cinnamic acid. 



C„H, CH — CH, — CO 



/ \ 







\ / 



CO - CH, — CH C„H, 

 C,H.CH = CH — COH 







C„H, CH = CH — C OH 



In the first representation it is not evident wh^' the structure of 



should make the acid more stable than that of (i; in the second 

 representation (his is, however, better visible, although a lactide of 

 the formula a will also not possess much stability. Yet thete are 

 some facts which lead us to believe that the lactide formnla is a 

 very probable one. 



An argument in favour of this formula is furnisiied by the' follow- 

 ing experiments. 



The cinnamates, namely the acid potassium-, the normal potassium-, 

 the calcium- and the barium salt have on exposure to light, in the 

 solid condition always yielded li-truxiliic acid only and not in one 

 instance «-truxillic acid, although their preparation had been modified 

 in different ways. The result was the same whether we started from 

 «- or from /?-cinnamic acid; the temperature also made no difference. 



No salts can, therefore, be derived from the «-acid. 



If the difference between the «■ and the /J-cinnamic acid consisted 

 merely in the position of the molecules in the "Raumgitter" it would 

 be rather strange (when the o-arrangemeut is the more stable one) 

 that this grouping does not occur in the salts. If for the «-cinnamic 

 acid the lactide form is accepted, the non-existence of salts speaks 

 for itself. 



We might argue that in the salts no double molecule need occur, 

 or else that these molecules possess a somewhat different structure ; 

 for the acid potassium salt, however, this does not do because the 



