Large Anharmonic Effects on Tunneling and Kinetics: Reaction of Propane with Muonium.

Calculations of kinetic isotope effects (KIEs) provide challenging tests of quantal mass effects on reaction rates, and muonium KIEs are the most challenging. Here, we show that it can be very important to include reaction-coordinate-dependent vibrational anharmonicity along the whole reaction path to calculate tunneling probabilities and KIEs. For the reaction of propane with Mu, this decreases both the height and width of the vibrationally adiabatic potential barrier, with both effects increasing the rate constants.

Water Catalysis of the Reaction of Methanol with OH Radical in the Atmosphere is Negligible.

Faced with the contradictory results of two recent experimental studies [Jara-Toro et al., Angew. Chem.

Anharmonic kinetics of the cyclopentane reaction with hydroxyl radical.

Cyclopentane is one of the major constituents of transportation fuels, especially jet fuel and diesel, and also is a volatile organic compound with a significant presence in the atmosphere. Hydrogen abstraction from cyclopentane by hydroxyl radical plays a significant role in combustion and atmospheric chemistry. In this work we study the kinetics of this reaction at 200-2000 K using direct dynamics calculations in which the potential energy surface is obtained by quantum mechanical electronic structure calculations.

Computational kinetics of the hydrogen abstraction reactions of n-propanol and iso-propanol by OH radical.

Propanol (n-propanol or iso-propanol (i-propanol)) is a promising clean-burning oxygenated fuel component and fuel additive. Understanding its reactions with OH radical is of great significance in both combustion and atmospheric chemistry. In this work, we calculate the rate constants and branching ratios of the hydrogen abstraction reactions of n-propanol and i-propanol by OH radical in a broad temperature range of 63-2000 K using the competitive canonical unified statistical (CCUS) model.

Quantum Effects on H Diffusion in Zeolite RHO: Inverse Kinetic Isotope Effect for Sieving.

We use canonical variational theory (CVT) with small-curvature tunneling (SCT) contributions to investigate quantum effects on the H diffusion process in the pure-silica zeolite RHO. At low temperature we find an inverse kinetic isotopic sieving effect in that the heavier isotopic species diffuses faster than the lighter one. Three quantum effects contribute to this kinetic isotope effect (KIE).

Kinetics of the Methanol Reaction with OH at Interstellar, Atmospheric, and Combustion Temperatures.

The OH radical is the most important radical in combustion and in the atmosphere, and methanol is a fuel and antifreeze additive, model biofuel, and trace atmospheric constituent. These reagents are also present in interstellar space. Here we calculate the rate constants, branching ratios, and kinetic isotope effects (KIEs) of the hydrogen abstraction reaction of methanol by OH radical in a broad temperature range of 30-2000 K, covering interstellar space, the atmosphere, and combustion by using the competitive canonical unified statistical (CCUS) model in both the low-pressure and high-pressure limits and, for comparison, the pre-equilibrium model.