Electron Theory in Organic Chemistry. 667 



Thus, for example, in a substance of the type abcC . Cdef, 

 there will not be free rotation about the bond joining the two 

 carbon atoms, and the experimental evidence shows that there 

 can be at the most two positions of stable equilibrium about 

 such an atom, and these are mirror images of each other. 



In connexion with this it is important to observe that the 

 original position of a valency electron need not affect its 

 position when saturated. For example, nitrogen appears to 

 have three primary valencies and two secondary ones. On 

 reducing the primary valencies we obtain ammonia, NH 3 . 

 On treating this with HC1 we obtain ammonium chloride, 

 NH 4 C1. It would be wrong to suppose that one of the 

 hydrogens in this substance is united to the nitrogen in a 

 different manner to the other three; nor can we say that on 

 splitting off the HOI again the H last added on is the one 

 split off. 



Similarly, if a quaternary salt like RjI^RsI^NOl is formed, 

 the arrangement of the 11 groups round the N is independent 

 of the order in which they are linked to it. 



Lastly, in the previous paper the absorption of light in the 

 visible and nearer ultraviolet regions was attributed to 

 the vibrations of the electrons of the type marked 7 in fig. 1. 

 It is now suggested that the vibrations of the a and /3 type 

 cause absorption in the infra-red region; for it is known that 

 these bands are characteristic of certain pairs of atoms, 

 e. g. all substances containing a C — H linkage seem to show 

 a very similar set of bands in this region. 



2. The first point which appears to need investigation is 

 the existence of ethylene, as contrasted with the non-existence 

 of free methyl or methylene. 



Now Bohr has shown that an atom consisting of a nucleus 

 with one electron round it is incapable of free existence in 

 the presence of similar atoms, but that such atoms combine 

 in pairs; in other words, the stability of the equilibrium of 

 such a system is small *. It would appear that the fact that 

 attempts to produce free methyl always lead to the production 

 of ethane may be due to a similar cause. 



Now in the previous paper (loc. cit.) it has been shown 

 that electrons moving in separate orbits have an effect 

 analogous to mutual induction of currents on one another. 

 It is therefore to be expected that forces will arise tending to 



* The stability of a system in stable equilibrium may be measured by 

 the finite impulse which is required to carry it so far from its post that 

 it will not return to it, or, in other words, the impulse which will just 

 -carry it to the nearest position of unstable equilibrium. 



2X2 



