98 MOLECULAR STRUCTURE 



(1.3) gives three isomeric triderivatives, viz. I . 3 . 2, i . 3 . 4, 

 and 1.3.5. Finally, C 6 H 4 C1 2 (1.4) allows of only a 

 single possibility, since 1.4.2 1 .4.3 = 1.4.5 = 1.4.6. 

 The application of these principles to a very complete 

 collection of experimental material resulted in an un- 

 exceptionable solution of the problem, and one that accords 

 satisfactorily with the indication of constitution given by 

 the formation of benzene compounds out of, and their 

 conversion into, fatty bodies. 



B. Determination of Relative Distances in the Molecule. 



The different atoms and groups in the same molecule 

 may act on one another in a way that gives information as 

 to their relative distances. This action may appear in two 

 ways. First, it may lead to a reaction, caused by combina- 

 tion and partial separation of the two groups ; but on the 

 other hand the character of a group may suffer a change, 

 which can often be followed out quantitatively. 



i. Mutual Action of Different Groups. 



An action that often occurs in the domain of organic 

 chemistry is the combination of two hydroxyl groups with 

 separation of water : 



X(OH) 2 = XO + H 2 0. 



Of this an example may be quoted. 



Many facts point to the part played by mutual distance 

 in such actions, and especially, first, that in organic 

 compounds, when two hydroxyl groups are attached to the 

 same carbon atom, they at once suffer the change, or rather 

 the existence of bodies containing the group C(OH) 2 is 

 exceptional. Chloral hydrate, which appears to have the 

 formula CC1 3 CH(OH) 2 , seems to be one of the few such 

 compounds, whilst e. g. the attempt to form the correspond- 

 ing compound, CH 3 CH (OH) 2 , leads to formation of aldehyde, 



