184 



FIXATION OF CARBON DIOXIDE 



CHAP. 8 



pyruvic and oxalic acid) the energy is not markedly different; but conju- 

 gation with a C=C double bond apparently has a stabilizing effect, 

 since the decarboxylation energy of benzoic and fumaric acid is as high 

 as 16-17 kcal. 



Table 8.VIII 



Heat and Free Energy of Decarboxylation" 



" Cf. bibliography to chapter 3, page 56. 



The free energies of decarboxylations of pure (solid or liquid) organic 

 acids are more negative (by as much as 10 or 15 kcal) than the total 

 energies of these reactions, and thus do not favor back reactions. The 

 AF values are negative even for benzoic and salicyhc acid, despite their 

 stabilization by conjugation. This explains why attempts of Widmer 



