PNNL

Abstract

The acidities of HNOx (where x = 1-3) have been calculated in the gas phase and in solution by using high level ab initio molecular orbital theory. Coupled cluster (CCSD(T)) energies, extrapolated to the complete basis set (CBS) limit, were used to determine thermodynamic properties of the species in the gas phase, and the fully polarizable continuum model (FPCM) was used to calculate the effect of solvent on the energy changes. The calculated gas phase heats of formation in kcal/mol at 0 K of the neutral compounds, based on extrapolations through the aug-cc-pVQZ basis set, are: ?Hf(NO) = 22.07 (calc.) vs. 21.46 + 0.04(expt.); ?Hf(HNO) = 26.39 (calc.) vs. 26.3 + 1 (expt.); ?Hf(NO2) = 10.12 (calc.) vs. 8.59 + 0.2(expt.); ?Hf(HONO2) = -29.87 (calc.) vs. -29.75 + 0.1(expt.); ?Hf(HONO) = -15.79 (calc.) vs. -7.37 + 0.32 (expt.); ?Hf(HOONO) = -0.89 (calc.); ?Hf(NO2-) = -41.95 (calc.) vs. -43.8 + 0.2(expt.); ?Hf(NO3-) = -70.76 (calc.) vs. -71.7 + 0.30(expt.); and ?Hf(ONOO-) = -16.74 (calc.). The electron affinity of NO is calculated to be 0.62 kcal/mol, based on extrapolations up through the aug-cc-pV5Z basis set, and falls within 0.02 kcal/mol of the experimental value.