Enthalpies of interaction of some amides and N-acetyl amino-acid amides dissolved in N,N-dimethylformamide at 298.15 K. The influence of branching of alkyl groups

Abstract

Enthalpies of dilution of N-isopropylformamide, N-isobutylformamide, N-sec-butylformamide, N,N-diisopropylformamide, N-isopropylacetamide, N-isobutylacetamide, N-sec-butylacetamide, N,N-diisopropylacetamide, and isobutyramide, as well as the N-acetyl- N′-methyl amides of ( d,l)-2-aminobutyric acid, ( d,l)-norvaline, and ( d,l)-norleucine, dissolved in N,N-dimethylformamide have been measured calorimetrically at 298.15 K. The results have been used to calculate enthalpic pair-interaction coefficients B 2 h which are a measure of the enthalpy of interaction between two solute molecules. The B 2 h coefficients of amides and peptides with branched alkyl groups will be compared with those with non-branched alkyl groups and will be discussed in terms of solute-solute-solvent interactions.