Thermochemical properties for n‐propyl, iso‐propyl, and tert‐butyl nitroalkanes, alkyl nitrites, and their carbon‐centered radicals

Abstract

AbstractDensity functional theory (DFT) based calculations are performed on a series of alkyl nitrites and nitroalkanes representing large‐scale primary, secondary, and tertiary nitro compounds and their radicals resulting from the loss of their skeletal hydrogen atoms. Geometries, vibration frequencies, and thermochemical properties [S°(T) and C°p(T) (10 K ⩽ T ⩽ 5000 K)] are calculated at the B3LYP/6‐31G(d,p) DFT level. ΔfH°298 values are from B3LYP/6‐31G(d,p), B3LYP/6‐31+G(2d,2p), and the composite CBS‐QB3 levels. Potential energy barriers for the internal rotations have been computed at the B3LYP/6‐31G(d,p) level of theory, and the lower barrier contributions are incorporated into entropy and heat capacity data. The standard enthalpies of formation at 298 K are evaluated using isodesmic reaction schemes with several work reactions for each species. Recommended values derived from the most stable conformers of respective nitro‐ and nitrite isomers include −30.57 and −28.44 kcal mol−1 for n‐propane‐, −33.89 and −32.32 kcal mol−1 for iso‐propane‐, −42.78 and −41.36 kcal mol−1 for tert‐butane‐nitro compounds and nitrites, respectively. Entropy and heat capacity values are also reported for the lower homologues: nitromethane, nitroethane, and corresponding nitrites. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 181–199, 2010