Kinetics and Thermochemistry of Hydroxyacetonitrile\n(HOCH<sub>2</sub>CN) and Its Reaction with Hydroxyl Radical

The potential energy surface for\nOH + HOCH<sub>2</sub>CN was investigated\ncomputationally with B2PLYP-D3/cc-pVTZ density functional theory for\ngeometries and frequencies, and coupled-cluster theory with double,\ntriple and perturbative quadruple excitations approximately extrapolated\nto the complete basis set limit for energies. The results were employed\nwith canonical variational transition state (TS) theory and an Eckart\ntunneling model to obtain rate coefficients, <i>k</i>, for\nthree channels, (1) H abstraction from the C–H bonds, (2) H\nabstraction from the O–H bond and (3) addition to the nitrile\nC atom. Over 220–450 K, <i>k</i><sub>1</sub>(T) =\n2.07 × 10<sup>–13</sup> (T/298 K)<sup>2.264</sup> exp(+15\nK/T) cm<sup>3</sup> molecule<sup>–1</sup> s<sup>–1</sup> and is the dominant pathway, accounting for ca. 85% of total reactivity\nat 298 K and 1 atm. <i>k</i><sub>2</sub>(T) = 5.16 ×\n10<sup>–15</sup> (T/298 K)<sup>3.470</sup> exp(+440 K/T) and\nthe high-pressure limit for channel 3, <i>k</i><sub>3,∞</sub>(T), was found to be temperature-independent with a value of 2.2\n× 10<sup>–14</sup> cm<sup>3</sup> molecule<sup>–1</sup> s<sup>–1</sup>. Consideration of the low-pressure limit and\nfalloff indicates the high-pressure limit is the relevant quantity\nfor atmospheric conditions. Intramolecular hydrogen bonding both stabilizes\nthe TSs and makes them less flexible. The tropospheric lifetime of\nHOCH<sub>2</sub>CN with respect to reaction with OH is estimated to\nbe ∼45 days. Its major degradation product is predicted to\nbe HC(O)CN, with minor contributions from HOC(O)CN and other species.\nThermochemistry for HOCH<sub>2</sub>CN and these two products was\nobtained.