594 



It is clear that one of the 2 structural formulae I or II must be 

 assigned to the « truxillic acid. 



Coo H 



This acid does not give an internal anhydride, ') and is converted 

 bj heating with acetic acid anhydride into y truxillic acid,*) which 

 acid is again converted into a truxillic acid bj heating with hydro- 

 chloric acid.') These two acids possess therefore a similar isomerism 

 as the cis- and trans-acids, in which the a truxillic acid possesses 

 the trans-form. In the y trnxillic acid the COOH-groups are on one 

 side of the ring, this not being the case for the a truxillic acid. 

 Accordingly this latter acid must possess formula I, and the y 

 truxillic acid is formed from the « truxillic acid by displacement 

 of one COOH-group, which causes its structural formula to assume 

 the following form. (See formula VII). 



The /? cocaic acid arises from a truxillic acid by heating with 

 KOH. ') Through heating with acetic acid anhydride it is not changed 

 into another truxillic acid. In this acid the COOH-groups must 

 therefore be situated on one side of the ring, just as in y truxillic 

 acid. It can however, not have arisen from a truxillic acid by 



J) Ber. 26, 834. 



») Ber. 22, 124. 



») Ber. 22, 2245. 

 ') 1. c. 



