286 



inactive, non-resolvable substance in such a way, that one of the 

 atoms or radicals placed round the asymmetric carbon-atom is 

 substituted by another group or atom, then a product will generally 

 be obtained, which itself is also endowed with rotatory power. 

 Whether this will be greater or smaller than that of the original 

 substance, cannot be predicted, because general rules concerning 

 the influence of the chemical nature of substitutes on the magnitude 

 of the specific or molecular rotation of the molecule in solution, 

 have up till now not been established with great success. l ) As 

 already mentioned, a number of experimental investigations of 

 this kind have been made by Guye, Walden, Patterson, 

 Frankland, Rupe and many others; but definite laws which 

 might hold in al cases, have not yet been found. 



If no racemisation occurs during the reaction, we can suppose 

 that the new configuration in space will in general correspond 

 to that of the original antipode; however, this is certainly not 

 always the case, as a change of place of the radicals round the 

 asymmetrical atom during the reaction must indeed be considered 

 a strong possibility 2 ). Racemisation under such circumstances is 

 not seldom observed, especially if a phenyl-group be directly 

 linked to the asymmetrical carbon-atom; - - so that the final 

 reaction-product appears to be inactive. This sustains the view 

 that a certain "mobility" of the substitutes round the asymmetric 

 atom must be supposed to exist, which under favourable circum- 

 stances may lead to a complete interchange of place between 

 the four radicals round the asymmetrical central-atom, and to a 

 final rearrangement in such a way, as to reproduce the enantio- 

 morphous configuration of the original molecule. 



But even if no such change of configuration as is pictured 

 here, takes place during the process, we are by no means certain, 

 that the optical rotation of the obtained product will not have 

 the opposite algebraic sign to that of the original molecule. 



x ) The theoretical development of the phenomenon of optical rotation is yet 

 far from being accomplished; see about this: G. H. Livens, Phil. Mag., (6), 25, 

 817, (1913); 26, 362, 535, (1913); 27, 468, 994, (1914); 28, 756, (1914) ; M. Born, 

 Dynamik dev Krystallgitter, (1915); H. Rupe, Ann. der Chem., 409, 327, (1915); 

 414, 99, 111, (1917). 



2 ) Cf. also: Ch. van Loon, Proefschrift Delft, (1919), p. 74. The reduction 

 of indene-oxide gives mixtures of cis- and trans-hydrtndene-l-2-diol, in which the 

 5-isomeride is predominant if the solutions be acid, but in which the ^raws- 

 compound preponderates in alkaline solutions. 



