Sw. Benson, SOME OBSERVATIONS ON THE STRUCTURES OF LIQUID ALCOHOLS AND THEIR HEATS OF VAPORIZATION, Journal of the American Chemical Society, 118(43), 1996, pp. 10645-10649
From comparisons of the differences in heats of vaporization of alcoho
ls (ROH) and their analogous hydrocarbons (RCH(3)) which turned out to
be 6.1 +/- 0.1 kcal/mol at 298 K it was concluded that this differenc
e represents the contribution of the hydrogen bond to the value of Del
ta H-vap(alcohol, 298 K), It is further concluded that alcohols are se
lf associated in pure liquids in cyclic clusters each of four alcohols
. These conclusions are supported by extensive, earlier studies of PVT
relations in vapors, heat capacities, and IR spectra in solutions. Gr
oup additivity tables of Ducros et al, an shown to be in excellent agr
eement with directly measured Delta H-vap(298 K) for both alcohols and
alkanes. Similar analysis of amines shows a much weaker H-bond with a
lower limit of about 2.2 kcal/mol between amines so that amines exist
mostly as monomers. Scattered data on diols of lesser accuracy sugges
t compact sandwich structures with the hydrocarbon tying together two
cyclic tetramer rings of H-bonded oxygen atoms.