267 



that in the cases mentioned above, and especially in that of the 

 isomeric cinnamic, allo-cinnamic , and iso-cinnamic acids 1 ), an 

 isomerism should be possible, which occasionally should create 

 the possibility of resolving the compound into optically active 

 isomerides. It may be, that a special nature of the substitutes 

 X, Y, and Z can be the cause of such an exception of the rule, 

 that ethylene-derivatives have generally a plan-symmetrical con- 

 figuration. Although this problem, which is of the highest im- 

 portance with respect to our views of the stereometrical arran- 

 gement of the atoms in wnsaturated carbon-derivatives in general, 

 is yet of a dubious character, however, if Erlenmeyer's obser- 

 vations may be supposed to be exact, - - it then can hardly be 

 doubted, that he has been able to demonstrate 2 ), that the bromina- 

 tion of the mixed zinc-salt of d-phenyl-lactic acid and inactive 

 cinnamic acid gives a dibromo-cinnamic acid, which appears to be 

 towgyratory; while, if the mixed salt of cinnamic acid and 

 l-phenyl-lactic acid be employed, a ^^rogyratory dibromo-cinnamic 

 acid is formed. This fact, in combination with the other, that he 

 could regenerate the free cinnamic acid 3 ), now showing a real optical 



!) E. Erlenmeyer Jr. Ber. d. d. Chem. Ges., 36, 23401, (1903); 38, 2562, 3496, 

 (1905); 39. 788, 1570. (1906); E. Erlenmeyer Jr., C. Barkow, and O. Herz, 

 Ber. d. d. Chem. Ges., 40, 653, (1907); E. Erlenmeyer Jr. and A. Arnold, Ann. 

 der Chemie, 337, 329, (1904). Cf. also: C. Liebermann and B. Halvorsen, 

 Ber. d. d. Chem. Ges., 36, 176, (1903); W. Marckwald and R. Meth, Ber. d. d. 

 Chem. Ges., 39, 1176, 1966, 2598, (1906); E. Biilmann, Ber. d. d. Chem. Ges., 

 42, 182, 1443, (1909); 43, 568, (1910); 44, 3152, (1911); E. Erlenmeyer Jr. and 

 G. Hilgendorff, Biochem. Zeits. 74, 137, (1916); 77, 55, (1916). 



2 ) E. Erlenmeyer, Jr., Biochemische Zeitschr., 97, 198, 231, 244, 261, (1919); 

 See however: W. Marckwald and R. Meth, Ber. d.d. chem. Ges. 39, 

 1176, (1906). 



3 ) E. Erlenmeyer and G. Hilgendorff, Biochem Zeits., 35, 134, 

 (1911); 43, 445, (1912). Starting from Storax-cinnamic acid, first the dibromide 

 was prepared, which by destination with water- vapor was changed into racemic 

 phenyl-bromo-lactic acid. This was separated into its optical antipodes by 

 means of the cinchonine-salts. Each of the optically active acids was then 

 reduced by sodmw-amalgame, and the optically active phenyl-lactic acid thus 

 obtained, changed into cinnamic acid by crystallisation from strong hydrochloric 

 acid. This cinnamic acid was optically active (in alcohol, about 30'), and 

 gave by addition of bromine and boiling with water and sodium-hydroxide, 



C 6 // 3 CH CH CCONa, 

 finally the so^twm-salt of phenyl-oxy-acrylic acid'. \ / 



which was also optically active and showed a rotation opposite to that of 

 the phenyl-bromo-lactic acid originally used. The optically active cinnamic 



