305 



if he had used a quantity of alcohol insufficient for total etherifi- 

 cation, the result might perhaps have been better. 



Frankland and Price x ) made analogous experiments in 1897 

 with inactive glycerinic acid and tewgyratory amyl-alcohol, but 

 they also obtained a negative result. The laevogyratory 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 Marckwald 

 and MacKenzie 2 ), who heated racemic mandelic acid with l- 

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

 acid appeared to be /a^ogyratory, while a dextrogyratory acid was 

 obtained from the ether-mixture after incomplete saponification. 

 This experiment clearly shows that the velocity of etherification 

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

 the etherification of the dextrogyratory acid, and that, in accordance 

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

 acid is also more rapidly decomposed by saponification than the 

 ether of the laevogyratory 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 3 ) drew attention to the fact that his famous experi- 

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

 enantiomorphous fi-methyl-glycosides, or those of the action of the 

 yeast-ferments on both the corresponding ot-methyl-glycosides, demon- 

 strate the same principle as was brought to the fore by Marck- 

 wald and MacKenzie. 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. 



*) P. F. Frankland and A. S. Price, Proceed. Chem. Soc., 133, 9, (1897); 

 Journ. Chem. Soc., 71, 353, (1897). 



2 ) W. Marckwald and A. MacKenzie, Ber. d. d. Chem. Ges., 32, 2130, 

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

 p. 113. 



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

 A. MacKenzie, ibid., 33, 208, (1900). 



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