Concerning the distant polar interaction in free energies of transfer. An explanation and an estimation procedure

Abstract

For polyfunctional compounds, free energies of transfer from gas to aqueous solution require corrections for the interactions of polar groups (Distant Polar Interactions). These corrections can be made with very few adjustable parameters by using a model of the solvation process assuming hydrogen bonding is the major source of the effect on free energy of transfer for polar groups, and that hydrogen bonding is perturbed by polar effects, measured by Taft o*. Parameters evaluated for polyfluoro, polychloro, and polybromo compounds successfully predicted the free energies of transfer for mixed polyhalogen compounds. Preliminary parameters have been evaluated for ethers, amines, phenyl groups, nitriles, and esters.

Uncatalyzed and Amine Catalyzed Decarboxylation of Acetoacetic Acid: An Examination in Terms of No Barrier Theory

“…Free energies of transfer were estimated using group additivity (1,52). It was necessary to estimate some of the contributions since there are no free energy of transfer data for either imines or enamines.…”

The enols of acetic acid and methyl acetate

“…We estimate the free energy of transfer by making use of the sequence: isobutene: 2-methoxypropene: I, 1 -dimethoxyethene, assuming that the effects of replacing CH! by OCH, are constant except that there will be a distant polar Interaction (16,17) for the two methoxy groups in 1,l-dimethoxyethene. For lack of information allowing a better correction we will assume that this is the same as the interaction in CH2(OCH3), (17), namely 1.56 kcal mol-'.…”

“…by OCH, are constant except that there will be a distant polar Interaction (16,17) for the two methoxy groups in 1,l-dimethoxyethene. For lack of information allowing a better correction we will assume that this is the same as the interaction in CH2(OCH3), (17), namely 1.56 kcal mol-'. Thus we end up with an estimated free energy of transfer of 1.02 kcal mol-' for 1,ldimethoxyethene, to which we assign an uncertainty of 2 1 kcal mol-I.…”

The tetrahedral intermediate from the hydration of N-methylformanilide

“…This cannot be measured because of the rapid hydrolysis of the amide acetal in aqueous solution (16), and so must be estimated. We did so using a method which we reported recently (17), making use of group additivity modified by a Taft p*-Zcr* correlation to allow for "Distant Polar Interactions" (18). The free energy of transfer requires contributions for each structural feature, and p* values for each non-aliphatic group to allow for the effect of other polar substituents on the solvation of that group.…”