Theoretical study on the reactions of C2H5 with CnH2n+1OH (n = 1 - 4): Predicted rate constants and branching ratios

Abstract

The mechanisms of the reactions of C2H5 with CnH2n+1OH (n = 1-4) have been investigated by CCSD(T)//B3LYP/6-311++G(3df,2p) for n = 1 - 3 and CCSD(T)//B3LYP/6-311+G(d,p) for n = 4. Our chemical quantum results show that the C2H5 + CH3OH reaction can take place via H-abstraction or substitution channels. The former is the major channel with barrier energies of 13.0 and 14.4 kcal/mol while the latter has to pass over much higher barriers of 42.2 – 52.3 kcal/mol. Similarly, the C2H5 + CnH2n+1OH (n = 2 - 4) reactions can mainly occur via H-abstraction channels with barrier energies of 10.4 - 16.4 kcal/mol. The b-H abstraction channel has the lowest barrier energy (11.7 kcal/mol) for t-C4H9OH while o/a-H abstraction channels have the lowest barrier energies (10.4 - 13.0 kcal/mol) for the others. The rate constants and product branching ratios for individual channels as well as total rate constants have been calculated for the temperature range 300-2500 K by TST theory with Eckart tunneling corrections. The optimized geometries of the related species and predicted heats of reactions agree well with available data.