CALORIMETRIC INVESTIGATION OF THE INTERACTIONS OF SOME HYDROGEN-BONDED SYSTEMS AT 298.15 K

The purpose of this work is to compare the enthalpies of hydrogen-bond ed interactions involving a variety of proton donors and accepters. Ex cess molar enthalpies H-m(E), as a function of mole fraction, are pres ented for single hydrogen-bonded systems involving propan-1-ol + dipro pyl ether, + tripropylamine, + dipropyl sulfide, and + heptan-4-one, d ipropylamine + dipropyl ether, + tripropylamine, + dipropyl sulfide, a nd + heptan-4-one, and propane-l-thiol + dipropyl ether, + tripropylam ine, + dipropyl sulfide, and + heptan-4-one. Partial molar enthalpies at infinite dilution H-i,m(E)(x(i)=0), calculated from an analysis of the data near x(i)=0, were used in an attempt to determine the relativ e 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, th us localizing the source of the hydrogen-bonded interaction. For the s ystems involving a strong hydrogen donor, i.e., alkanol, the liquid ph ase hydrogen bond strength order mirrors that calculated for interacti ons in the gas phase from ab initio molecular orbital theory. In the s ystems involving a relatively weak hydrogen donor, i.e., secondary ami ne and a thiol, the hydrogen bond strength appears to be related to th e available surface area of the hydrogen acceptor atom.