CAJ | 학술논문

过氧烷基自由基分子内氢迁移是低温燃烧反应中的一类重要基元反应。本文用等键反应方法计算了该类反应的动力学参数。所有反应物、过渡态、产物的几何结构均在B3LYP/6-311+G(d,p)水平下优化得到。本文提出了用过渡态反应中心几何结构守恒作为反应类判据,并将该分子内氢迁移反应分为四类,包括(1,3)、(1,4)、(1,5)、(1,n)(n=6,7,8)氢迁移类。分别将这4类反应类中最小反应体系作为类反应的主反应,并分别在B3LYP/6-311+G(d,p)低水平和CBS-QB3高水平下得到其近似能垒和精确能垒。其余氢迁移反应作为目标反应,在B3LYP/6-311+G(d,p)低水下计算得到其近似能垒,再采用等键反应方法校正得到目标反应的精确反应势垒和精确速率常数。研究表明,采用等键反应方法只需在低水平用从头算计算就可以得到大分子反应体系的高精度能垒和速率常数值,且本文按等键反应本质的分类方法更能揭示反应类的本质,并对反应类的定义给出了客观标准。本文的研究为碳氢化合物低温燃烧模拟中重要的过氧烷基分子内氢迁移反应提供了准确的动力学参数。
과양완기자유기분자내경천이시저온연소반응중적일류중요기원반응。본문용등건반응방법계산료해류반응적동역학삼수。소유반응물、과도태、산물적궤하결구균재B3LYP/6-311+G(d,p)수평하우화득도。본문제출료용과도태반응중심궤하결구수항작위반응류판거,병장해분자내경천이반응분위사류,포괄(1,3)、(1,4)、(1,5)、(1,n)(n=6,7,8)경천이류。분별장저4류반응류중최소반응체계작위류반응적주반응,병분별재B3LYP/6-311+G(d,p)저수평화CBS-QB3고수평하득도기근사능루화정학능루。기여경천이반응작위목표반응,재B3LYP/6-311+G(d,p)저수하계산득도기근사능루,재채용등건반응방법교정득도목표반응적정학반응세루화정학속솔상수。연구표명,채용등건반응방법지수재저수평용종두산계산취가이득도대분자반응체계적고정도능루화속솔상수치,차본문안등건반응본질적분류방법경능게시반응류적본질,병대반응류적정의급출료객관표준。본문적연구위탄경화합물저온연소모의중중요적과양완기분자내경천이반응제공료준학적동역학삼수。
Intramolecular hydrogen migration in alkylperoxy reactions is one of the most important reaction classes in hydrocarbon combustion at low temperatures. In this study, the kinetic parameters for reactions in this class were calculated using the isodesmic reaction method. The geometries for al the reactants, transition states, and products were optimized at the B3LYP/6-311+G(d,p) level. A criterion based on conservation of the reaction-center geometry of the transition state was proposed for the reaction class, and the intramolecular hydrogen migration reactions studied were divided into four classes, i.e., (1,3), (1,4), (1,5), and (1,n) (n=6, 7, 8) hydrogen migration. The simplest reaction system for each reaction class was defined as the principal reaction;the approximate single-point energies were obtained at the low level of B3LYP/6-311+G(d,p) and accurate single-point energies were obtained at the high level of CBS-QB3. The other reactions in this class were chosen as the target reactions and the approximate single-point energies were obtained at the B3LYP/6-311+G(d,p) level. The energy barriers and rate constants of these target reactions were corrected using the isodesmic reaction method. The results showed that accurate energy barriers and rate constants for the reactions of large molecules can be obtained by a relatively low level method using the isodesmic reaction method. In this study, classification of the basic isodesmic reaction showed the essential features of the reaction classes. The present work provides accurate kinetic parameters for modeling intramolecular hydrogen migration reactions of hydrocarbons at low temperatures.