Hydrogen bonding in some adducts of oxygen bases with acids. Part 8.—Proton chemical shifts and thermodynamic data on the association of chloroacetic acids with some oxygen bases
The association between the chloroacetic acids (mono-, di-, tri-) and a series of bases (3, 5-dichloropyridine, pyridine-N-oxide, dibenzylsulphoxide, diphenylsulphoxide, triphenylphosphine oxide, trioctylphosphine oxide) in CCl4 was studied by measuring the n.m.r. hydrogen bond shift of the acidic proton. The observed chemical shifts are in the same order as the infrared vOH band shifts obtained previously. The thermodynamic parameters calculated for the association agree with those derived from infrared data, but there are anomalies in the correlation of chemical shift with enthalpy of formation for the “stronger” bases.