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).
View Article and Find Full Text PDFA 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.
View Article and Find Full Text PDFAb 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.
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