756 



acid molecule must, as in the case of tlie acids, be combined to 

 the potassium salt molecule, as the acid is vei-y strongly combined 

 and cannot be extracted by ether from the solid powdered salt, as 

 has already been stated by Erlenmeykr '). 



The «-cinnamic acid would then be tlie lactide of jï-piienylhydra- 

 crylic acid. 



It is known that the «-oxyacids on being heated in a vacuum 

 are converted into lactides; ,J-oxyacids on heating give unsaturated 

 acids with elimination of water, whereas y- and rï-oxyacids very 

 readily form lactones. 



From this it appears that, as a rule, the substances possessing a 

 carboxyl- and a hydroxyl-group, always have a greater tendency to 

 split off water between these two groups, whether this takes place 

 between the groups of one molecule, or whether the reaction proceeds 

 between two molecules. 



Only the ^-oxyacids apparently make an exception. 



The ,?-phenylhydracrylic acid, for instance, on being slowly heated 

 breaks up at 180° into cinnamic acid and water according to the 

 equation : 



C,H,CHCH,COOH -^ C,H,CH=CHCOOH + H,0. 



I 



OH 

 With substances possessing no carboxylgroup this elimination of 

 water does not take place readily, as will appear from the following 

 examples : 



(CH,), C,H3CH (OH) CH,CH,CH, boils at 270° '). 

 CH3CH(0H)C,H, (CH3), boils at 248° »). 



C,H5CH.,CH (OH) C,H, melts at 62^ and distils unchanged '). 

 Non-aromatic secondaiy alcohols also generally boil unchanged '). 

 H", however, we assume that from the /J-phenylhydracrylic acid a 

 lactide is first formed, this ready elimination of water becomes 

 comprehensible. 



C,H,CHCH,CO 



/ \ 



2 C,H,CHCH,COOH -^ 0-^2C„H,CH=CHC00H 



I \ / 



OH COCH,CHC,,H, 



The transformation of other ;':?-oxyacids, on heating, may be supposed 

 to take place in a corresponding manner. 

 ^1) Berr427515 (1909). 



~) Beilstein II, p. 1067. 



5) Her. 31, 1008 (1898). 

 +) Ann. 155, 63 (1870). 



6) C. 1901 1, p. 623. 



