Structures, thermochemical properties, bond energies, and internal rotation potentials of acetic acid hydrazide (CH
3CONHNH
2), acetamide (CH
3CONH
2), and
N-methyl acetamide (CH
3CONHCH
3), and their radicals corresponding to the loss of hydrogen atom,
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Structures, thermochemical properties, bond energies, and internal rotation potentials of acetic acid hydrazide (CH
3CONHNH
2), acetamide (CH
3CONH
2), and
N-methyl acetamide (CH
3CONHCH
3), and their radicals corresponding to the loss of hydrogen atom, have been studied. Gas-phase standard enthalpies of formation and bond energies were calculated using the DFT methods B3LYP/6-31G(d,p), B3LYP/6-31G(2d,2p) and the composite CBS-QB3 methods employing a series of work reactions further to improve the accuracy of the ΔH
f°(298 K). Molecular structures, vibration frequencies, and internal rotor potentials were calculated at the DFT level. The parent molecules’ standard formation enthalpies of CH
3–C=ONHNH
2, CH
3–C=ONH
2, and CH
3–C=ONHCH
3 were evaluated as −27.08, −57.40, and −56.48 kcal mol
−1, respectively, from the CBS–QB3 calculations. Structures, internal rotor potentials, and C–H and N–H bond dissociation energies are reported. The DFT and the CBS-QB3 enthalpy values show close agreement, and this accord is attributed to the use of isodesmic work reactions for the analysis. The agreement also suggests this combination of the B3LYP/work reaction approach is acceptable for larger molecules. Internal rotor potentials for the amides are high, ranging from 16 to 22 kcal mol
−1.
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