We have determined the heat of formation of 1,1 -dimethoxyethene, Delt
a H-f(l) = -75.56 +/- 0.87 kcal mol(-1), by measuring the heat of hydr
olysis. The heat of vaporization, 8.47 +/- 0.10 kcal mol(-1), was esti
mated from the boiling points at various pressures. The standard entro
py of gaseous 1,1-dimethoxyethene, 82.02 +/- 2. cal deg(-1) mol(-1), w
as calculated using frequencies obtained by MO calculations at the 6-3
1G* level. The free energy of transfer, 1.02 +/- 1, was estimated by
additivity with allowance for a distant polar interaction. Thus the fr
ee energy of formation in aqueous solution, Delta G(f)(aq) = -37.07 +/
- 1.48 kcal mol(-1), could be calculated. The free energies of hydroly
sis for enol ethers appear to be insensitive to structure; we used an
average value and so calculated the values of the free energies of for
mation of the enols of acetic acid and methyl acetate, -67.90 +/- 1.67
and -52.48 +/- 1.53 kcal mol(-1), respectively. These values are in g
ood agreement with other recent evaluations. This method should be app
licable to related enols.