290 



also obtained a negative result. The laevogyrate amyl- alcohol was 

 then combined with inactive dibenzoyl-glycerinic acid ; although the 

 ether could be obtained in beautiful crystals, no fission of the 

 acid was found after saponification. 



The first positive results were obtained in 1899 by Marck- 

 w a 1 d and Mac Kenzie 1 ), who heated racemic mandelic acid with 

 l-menthol at 155 C. for one hour; the remaining, not attacked 

 acid appeared to be ^yogyratory, while a dextrogyrate acid was 

 obtained from the ether-mixture after incomplete saponification. 

 This experiment clearly shows that the velocity of etherification 

 of laevogyrate mandelic acid with l-menthol is smaller than that of 

 the etherification of the ^^rogyrate acid, and that in accordance 

 with this fact, the ether of the more rapidly formed dextrogyrate 

 acid is also more rapidly decomposed by saponification than the 

 ether of the laevogyrate acid. This of course agrees with the 

 character of the saponification-process, as that of an "equilibrium"- 

 reaction: the ether which is more rapidly formed, must also be 

 saponified more quickly, should the equilibrium-constant remain 

 unchanged. 



Fischer 2 ) drew attention to the fact that his famous experi- 

 ments of the action of emulsine on the mixture of both the 

 enantiomorphous (3-methyl-glycosides, or those of the action of the 

 yeast-ferments on both the corresponding a-methyl-glyco sides, demon- 

 strate the same principle as was brought to the fore byMarck- 

 w a 1 d and Mac Kenzie. The remark is undoubtedly true (Chapter 

 VIII); the so-called "specificity" of enzyme-action is indeed only 

 based upon a great difference in the rate of attack of either 

 antipode by the same ferment or enzyme, which are always them- 

 selves dissymmetrical substances. 



Marckwald and Mac Kenzie 3 ) determined the ratio of 

 etherification- and saponification-velocities of the laevo-, and dextro- 

 gyrate mandelic acids with respect to l-menthol, at a value of o,po. 

 If the saponification be completed, the free acid obtained is inactive, 

 which is a fresh proof that both antipodes have the same affinity 



1) W. Marckwald and. A. Mac Kenzie, Ber. d. d. Chem. Ges. 32. 2130. 

 (1899); Cf. also: F. S. Kipping and W. J. Pope, Proceed. Chem. Soc. (1898), 

 p. 113. 



2) E. Fischer, Ber. .d. d. Chem. Ges. 32. 3617. (1899); W. Marckwald and 

 A. Mac Kenzie, ibid. 33. 208. (1900). 



8 ) W. Marckwald and A. Mac Kenzie, Ber. d. d. Chem. Ges. 34.469. (1901). 



