Enthalpies of formation of lactams

Combustion calorimetry is used to measure the enthalpies of combustion and formation of azacyclooctan-2-one (I), azacyclononan-2-one (II), and azacyclotridecan-2-one (III) in the crystalline, liquid, and gaseous states. Conformational analysis is conducted, and quantum chemical calculations of the compounds’ enthalpies of formation in the gas phase for conformers corresponding to the global minima are performed. The experimental findings and published data are used to determine mutually congruent combinations of enthalpy parameters for a number of nonsubstituted lactams. The strain energies are estimated. Trends in their changes are considered for the series of cycloalkanes and lactams.