595 



displacement of a COOH-groiip alone, because then it would have 

 to be converted into n truxillic acid bv heating with hydrochloric 

 acid, whereas it is not changed by this operation. There must, 



^CCC 



Co OH 



Vll 



therefore, two groups viz. a C^Hj- and a COOH-group have been 

 displaced from one side of the ring to the other in the formation 

 of ^ cocaic acid from « truxillic acid. This can take place in two 

 ways, in which in one case formula II arises and in the other case 

 all CgHj- and COOH-groups will lie on one side of the ring. 



Formula II is built up of 2 molecules of noi-mal cinnamic acid, 

 and the other formula is formed from 2 molecules of alio cinnamic 

 acid. The [i cocaic acid was found on illumination of the stable 

 barium salt of normal cinnamic acid together with i» truxillic acid. 



0,593 gr. of cinnamic acid, as barium salt, yielded 0,168 gr. of 

 iS truxillic acid and 0,092 gr. of ^ cocaic acid after 27 hours' 

 illumination. 



It appears therefore from this, that foru)ula II must be assigned 

 to ^ cocaic acid. Besides it is very improbable that a substance for 

 which the heavy groups are all found on one side of the ring would 

 arise by melting with KOH. 



After what has been said about the conversions of the 6 truxillic 

 acids, the following rules may be given ; 



