THE SPACE RELATIONS OF ATOMS. 453 



For such a case static formulae, whether structural or 

 tetrahedral, have no ready explanation. Bischoff's explana- 

 tion is that in formula II. the methyl groups can oscillate 

 much more freely than in I. It is II. therefore which 

 must be formed according to the "dynamic hypothesis" 

 which states that "those configurations are the most 

 favoured in which the components of the system can 

 oscillate most freely V 



In the cases mentioned above, where the methyl groups 

 cause closure of the ring, it is again their effort to gain room 

 for their oscillations which causes them to crowd together 

 the hydroxyl groups, so that expulsion of water with ring- 

 formation follows. The dispersion of the methyl groups is 

 observed also in open chain compounds. Thus /3-tri-methyl 

 ethylidene lactic acid CH 3 



CH3.C.CH3 



H C.OH 



COOH yields 

 CH 3 



not CH 3 . C. CH 3 ,but H 



I CrT.C.CH 



H C :CO 



3* 



CO 



CH, 



Bromine atoms also tend to separate as widely as possible. 

 Thus a-di-brompropionic acid becomes a-/3-brompropionic 

 acid 



Br H 



CH 3 . C— COOH = Br . CH — C— COOH. 

 Br Br 



1 It may be added that as like atoms have like oscillations, they will be 

 the most prone to collide, and in a favoured configuration they must be far 

 removed from one another. Moreover, atoms which though unlike are of 

 like nature (degree of positivity) must to a less degree be far removed from 

 one another. 



