

Electron Theory in Organic Chemistry . 675 



Thus carbons in the meta positions are in one group and 

 those in the ortho and para in another. 



The distance between the planes must depend on the con- 

 ditions of stable equilibrium, which are extremely hard to 

 work out. 



The following points are worthy of notice : — 



1. The general assumptions made in the paper on absorp- 



tion spectra are generally consistent with the above 

 model, but possibly it was not accurate to neglect the 

 values of the mutual induction coefficients between 

 the electrons of a group attached to the ring and the 

 ortho carbons. Nor can we say that the assumption 

 that m m and m p are nearly equal is correct : this, 

 however, can only be settled by direct observation of 

 the 7 band. An alteration in these values will not 

 affect the value of m greatly. 



2. Since we have found ??? = *275 (C = l) 



and for ethylene ?n = *13, 

 it follows that the ortho carbons in benzene are closer 

 than those carbons of ethylene, and so the free valency 

 electrons are more difficult to displace. 



3. It will be seen that the directions of the line joining 



a carbon atom to the 3 atoms to which it is linked 

 and the line perpendicular to the plane of the free 

 electron are directed almost to the four corners of a 

 tetrahedron. This will make for stability. 



4. A substance C 5 H 5 or C 7 H 7 could not be analogous to 



benzene. 



In conclusion it may be remarked that the system deve- 

 loped by Noyes in the Journal of the American Chemical 

 Society, where one atom is supposed to be linked to another 

 by the passage of an electron from one to the other, leaving 

 them with opposite charges, does not seem to be consistent 

 with the existence of ring systems consisting of an odd 

 number of atoms, many of which are known and some of 

 which, as cyclopentane and its derivatives, are extremely 

 stable. 



March, 1915. 



