Theoretical kinetic studies are performed on the multichannel thermal decomposition of acetaldehyde. The geometries of the stationary points on the potential energy surface of the reaction are optimized at the MP2(full)/6-311++G(2d,2p) level of theory. More accurate energies are obtained by single point energy calculations at the CCSD(T,full)/augh-cc-pVTZ+2df, CBS-Q and G4 levels of theory. Here, by application of steady-state approximation to the thermally activated species CHCHO* and CHCHOH* and performance of statistical mechanical manipulations, expressions for the rate constants for different product channels are derived. Special attempts are made to compute accurate energy-specific rate coefficients for different channels by using semiclassical transition state theory. It is found that the isomerization of CHCHO to the enol-form CHCHOH plays a significant role in the unimolecular reaction of CHCHO. The possible products of the reaction are formed via unimolecular decomposition of CHCHO and CHCHOH. The computed rate coefficients reveal that the dominant channel at low temperatures and high pressures is the formation of CHCHOH due to the low barrier height for CHCHO → CHCHOH isomerization process. However, at high temperatures, the product channel CH + CHO becomes dominant.

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Spontaneous dipole orientation is studied for a set of simulated porous ASW ice films on a substrate held at temperatures ranging from 10 K to 140 K. It is found...

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