碳烟前驱体形成中C4H3自由基和乙炔成环机理OA

This study systematically investigates the cyclization reaction mechanisms between n-C4H3(1-buten-3-yn-1-yl)and i-C4H3(2-buten-3-yn-1-yl)radicals with acetylene(C2H2)using density functional theory(DFT)and transition state theory(TST).The results reveal that the reaction of n-C4H3 with acetylene proceeds via a radical chain mechanism through an addition-cyclization pathway,yielding phenyl(six-membered ring),fulvenyl(five-membered ring),and four-membered ring intermediates.The product formation rates follow the order:fulvenyl(five-membered ring)＞phenyl(six-membered ring)＞four-membered ring.For i-C4H3,the intermediate structures depend on the carbon position of i-C4H3 where acetylene addition occurs:addition at the C2 position predominantly generates fulvenyl(five-membered ring)as the primary product,whereas addition at the C4 position may lead to phenyl(six-membered ring),fulvenyl(five-membered ring),or four-membered ring intermediates,with the four-membered ring forming most rapidly and the six-membered ring the slowest.Theoretical analyses demonstrate that the selectivity of reaction pathways is primarily governed by structural differences between the isomers.This work provides atomic-scale insights into the cyclization processes between acetylene and C4H3 species,establishing a foundation for refining models of soot precursor formation.