Theoretical Investigation on Mechanism, Thermochemistry, and Kinetics of the Gas-phase Reaction of 2-Propargyl Radical with Formaldehyde

• 来源期刊: 高等学校化学研究（英文版）
• 年，卷（期）: 2019,（5）
• 页码范围: 884-891
• 页数: 8页
• 语种: 英文
• DOI: 10.1007/s40242-019-9054-0

摘要

Gas-phase mechanism and kinetics of the reactions of the 2-propargyl radical(H2CCCH),an important intermediate in combustion processes,with formaldehyde were investigated using ab initio molecular orbital theory at the coupled-cluster CCSD(T)//B3LYP/6-31 l++G(3df,2p) method in conjunction with transition state theory(TST),variational transition state theory(VTST) and Rice-Ramsperger-Kassel-Marcus(RRKM) calculations for rate constants.The potential energy surface(PES) constructed shows that the H2CCCH+HCHO reaction has six main entrances,including two H-abstraction and four additional channels,in which the former is energetically more favorable.The H-abstraction channels slide down to two quite weak pre-complexes COM-01(-9.3 kJ/mol) and COM-02(-8.1 kJ/mol) before going via energy barriers of 71.3(T0/P1) and 63.9 kJ/mol(T0/P2),respectively.Two post-complexes,COM-1(-17.8 kJ/mol) and COM-2(-23.4 kJ/mol) created just after coming out from T0/P1 and T0/P2,respectively,can easily be decomposed via barrier-less processes yielding H2CCCH2+CHO(P1,-12.4 kJ/mol)and HCCCH3+CHO(P2,-16.5 kJ/mol),respectively.The additional channels occur initially by formation of four intermediate states,H2CCCHCH2O(I1,1.1 kJ/mol),HCCCH2CH2O(I3,4.5 kJ/mol),H2CCCHOCH2(I4,10.2 kJ/mol),and HCCCH2OCH2(I6,19.1 kJ/mol) via energy barriers of 66.3,59.2,112.2,and 98.6 kJ/mol at T0/1,T0/3,T0/4,and T0/6,respectively.Of which two channels producing I4 and I6 can be ignored due to coming over the high barriers T0/4 and T0/6,respectively.The rate constants and product branching ratios for the low-energy channels calculated show that the H2CCCH+HCHO reaction is almost pressure-independent.Although the H2CCCH+HCHO →I1 and H2CCCH+HCHO →I3 channels become dominant at low temperature,however,they are less competitive channels at high temperature.