On the basis of calculated acidities of the vinylogues of formic acid
and vinyl alcohol, Dewar and Krull have concluded that the higher acid
ity of carboxylic acids relative to alcohols is due to stabilization o
f the conjugate anion by resonance delocalization. More detailed calcu
lations on some of the compounds that they have considered shows indee
d that delocalization of charge in the anion plays a role in the acidi
ty of buta-1,3-dien-1-ol 1 relative to vinyl alcohol and of 3-hydroxyp
rop-2-enal 2 relative to formic acid. However, these calculations show
that this conclusion is not applicable to the relative acidities of e
thanol, vinyl alcohol and formic acid or of 2 relative to 1.These are
due to the charge distribution in the neutral molecule, in keeping wit
h the ideas proposed by Siggel et al.