Computational Investigation on the Formation and Decomposition Reactions of the CHO Compound.

Gas-phase mechanism and kinetics of the formation and decomposition reactions of the CHO compound, a crucial intermediate of the atmospheric and combustion chemistry, were investigated using ab initio molecular orbital theory and the very expensive coupled-cluster CCSD(T)/CBS(T,Q,5)//B3LYP/6-311++G(3df,2p) method together with transition state theory and Rice-Ramsperger-Kassel-Macus kinetic predictions. The potential energy surface established shows that the CH + CO addition reaction has four main entrances in which CH + CO → (CHCCHCO) is the most energetically favorable channel. The calculated results revealed that the bimolecular rate constants are positively dependent on both temperatures ( = 300-2000 K) and pressures ( = 1-76,000 Torr).

Theoretical Investigation of the Mechanisms and Kinetics of the Bimolecular and Unimolecular Reactions Involving in the CH Species.

A theoretical study of the mechanisms and kinetics for the CH system was carried out using molecular orbital theory based on the CCSD(T)/CBS//B3LYP/6-311++G(3df,2p) method in conjunction with statistical theoretical variable reaction coordinate transition-state theory and RRKM/ME calculations. The calculated results indicate that buta-1,3-diene, but-1-yne, and CH + H can be the major products of the C + C reaction, while CCH + CH and CH + H play an important role in the C + C reaction. In contrast, the CH fragmentation giving rise to C + C and CH + H becomes the key reaction paths under any temperature and pressure.

Combination Reactions of Propargyl Radical with Hydroxyl Radical and the Isomerization and Dissociation of -Propenal.

Ab initio investigation for the ground-electronic potential energy surface (PES) of the CHCCH + OH combination and the -CHCHCHO isomerization and decomposition has been performed at the UCCSD(T)/CBS(TQ5)//M06-2X/aug-cc-pVTZ level of theory. Thermal and microcanonical rate constants, as well as branching ratios in the 300-2000 K temperature range have been predicted based on optimized structures and vibrational frequencies of species involved using statistical theoretical VRC-TST and RRKM master equation computations. The calculated results are in good agreement with the prior reported data, particularly as an accurate scaling of the energy barriers was carried out.