237 



S warts l ), who first tried to solve this question, prepared 

 fli>ro-chloro-bromo-acetic acid: CFClBr.COOH, which by means of 

 strvchnine was resolved into its antipodes, the optical activity of which 

 was measured, but appeared to diminish rather rapidly because 

 I i' i>mi; iv^ing racemisation. On carefully heating both antipodes, 

 carbon-dioxide was split off, and fluoro-chloro-bromo-methane: 

 CFClBrH resulted. The product obtained appeared however to be 

 quite inactive, its constitution evidently involving a great tendency 

 to auto-racemisation. 



It was only recently that convincing proof was given of the truth 

 of the theory in cases like this also. Pope and Read 2 ) succeeded 

 in resolving chloro-iodo-methane-sulphonic acid: CHClf(S0 3 H) into 

 its antipodes, and in measuring the optical activity of its ammoniurn- 

 salt: (A/)/? appeared to be about 44 in aqueous solution. In this 

 way full evidence was given that the question put above must be 

 considered as completely proved. 



19. Up till now no general rules have been found as to the 

 magnitude of the rotatory power of those compounds which have 

 only one single asymmetric carbon-atom. At first the opinion was, 

 that the greater the chemical difference between the four groups or 

 atoms linked to the asymmetric carbon-atom was, the greater also the 

 rotatory power would appear to be. However all kinds of irregularities 

 and exceptions became gradually known; for instance it proved 

 that the salts of active acids had often just the opposite rotatory 

 power, or a feebler one, than the acids themselves, although the 

 introduction of the metal-atom in place of the hydrogen-atom of 

 the carboxyl-group augmented in many cases the chemical contrast 

 between the four substitutes. 



Guye 3 ) especially tried to give a rational explanation of this 

 and similar phenomena, by the compelling idea of the asymmetry- 

 product. His theory starts with the hypothesis that the degree of 

 molecular dissymmetry depends on the difference in mass of the 

 four substitutes linked to the asymmetric carbon-atom. If the masses' 

 of the four substitutes be supposed to be concentrated at the corners 



J) F. Swarts, Bull, de la Soc. Chim. (3). 15. 1134. (1896); Mem. de 1'Acad. 

 roy. de Belgique, 54. (1895); Bull, de 1'Acad. Belg. (3). 81. 38. (1895). 



2) W. J. Pope and J. Read, Journ. Chem. Soc. 105. 811. (1914); Proc. Cam- 

 bridge Phil. Soc. 17. 475. (1914). 



3) Ph. A. Guye, Compt. rend, de 1'Ac. d. Sc. Paris 110. 744. (1890); These, 

 Paris, (1891); Confer, dev. la Soc. Chim. Paris, (1891). 



