ARCHITECTURE OF MOLECULES 



219 



CO.OH 



CO. OH 



H 



II 



If this is so it follows that when it is heated and is resolved 

 into water and the anhydride, of which the following is the 

 formula, rotation must occur : 



Many similar cases are known. It may be supposed that the 

 atoms attached to the central framework of carbon have the 

 power of attracting or repelling one another, as in the case of 

 ethylene dichloride (Dutch liquid) mentioned above, and it has 

 been thought that the relative masses, that is the atomic weights 

 of such atoms or groups, may have something to do with this. 

 The law connecting mass with optical activity or with rotation 

 of two semi-molecules round one valency has, however, not been 

 discovered. 



Within the last few years many cases have become known in 

 which apparently the existence of an asymmetric atom of carbon 

 within the molecule is not essential to the development of optical 

 activity. It appears, therefore, that a modification of the 

 original theory is necessary so as to include those compounds 

 which are optically active, and whose activity can only be 

 attributed to a want of symmetry in the molecule considered as 

 a whole. 



