HENDERSON. 



CONCERNINQ POSITION ISOMERISM. 



641 



said, and I postpone the discussion of this aspect of the question till the 

 necessary experimental data are at hand, investigations to this end 

 heing now in progress in this laboratory. 



On the other hand, the influence of the relative positions of its 

 atoms upon the heat of reaction of a molecule, and consequently 

 upon the valence energies of the reacting atom, is an interesting 

 subject which in some of its aspects may be discussed with the aid of 

 existing data. 



The following tables contain the available data which show that the 

 introduction of a foreign group into a molecule influences the heat of 

 a reaction of an atom group of that molecule in a varying degree 

 according to the relative positions of the two groups. 



I. 



CH -> C-CHs 



y8 



COOH present.6 

 CHs • COOH - H • COOH 207 - 59 



C2H5 • COOH - CH3 • COOH 364.0 - 206.7 



higher C2H5 • C„H2,. • COOH - CHs • C„H2„ • COOH 



Cal. 



148 



157..3 



156.5 



a 



B 



CONH2 present.7 

 CH3 • CONH2 - H • CONH2 



/3 C2H5 • CONH2 - CH3 • CONH2 



283 - 135 

 439.8 — 282.7 



higher C2H6 • C„H2„ • CONH2- CH3 • C„H2„ • CONH2 



148 



157.1 



156.1 



C 



CONHCsHs present.7 

 a CH3 • CONH CeHs - H • CONH CeHs 

 P C2H5 • CONH CeHs - CHs • CONH Q,YL, 

 higher C2H6 • C„H2„ ' CONH CeH^ - 



CH3-C„H2„-C0NHC6H6 



1011 - 

 1168- 



861 : 

 1011 



150 

 157 



= 156.2 



XLII. — 41 



6 Stohmann, .Jour. f. prakt. Chem., 49, 107 (1894). 



7 Id., 52, 59 (1895). 



