The purpose of this work is to compare the enthalpies of hydrogen-bonded
interactions involving a variety
of proton donors and acceptors. Excess molar enthalpies
, as a function of mole fraction,
are
presented for single hydrogen-bonded systems involving propan-1-ol +
dipropyl ether, + tripropylamine,
+ dipropyl sulfide, and + heptan-4-one, dipropylamine + dipropyl
ether, + tripropylamine, + dipropyl
sulfide, and + heptan-4-one, and propane-1-thiol + dipropyl ether,
+ tripropylamine, + dipropyl sulfide,
and + heptan-4-one. Partial molar enthalpies at infinite
dilution
(x
i
=0),
calculated from an analysis
of the data near x
i
= 0, were used
in an attempt to determine the relative strengths and propensities
of
the hydrogen-bonded interactions OH···O, OH···N,
OH···S, NH···O, NH···N, NH···S, SH···O,
SH···N,
and SH···S. The component molecules are all fully
propylated, thus localizing the source of the hydrogen-bonded interaction. For the systems involving a strong hydrogen
donor, i.e., alkanol, the liquid phase
hydrogen bond strength order mirrors that calculated for interactions
in the gas phase from ab
initio
molecular orbital theory. In the systems involving a relatively
weak hydrogen donor, i.e., secondary
amine and a thiol, the hydrogen bond strength appears to be related to
the available surface area of the
hydrogen acceptor atom.
