Mousavipour S Hosein, Ramazani Shapour, Shahkolahi Zahra
Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran.
J Phys Chem A. 2009 Mar 26;113(12):2838-46. doi: 10.1021/jp807122m.
The kinetics and mechanism of the reaction of OH with furan have been theoretically studied. The potential energy surface for each possible pathway has been investigated by employing DFT, G3MP2, and CCSD methods. The potential energy surface consists of one hydrogen-bonded complex and two energized intermediates. Three different pathways are suggested to be possible for the title reaction. The most probable channel is the hydroxyl radical addition to the C(2) position on the furan ring to cause the ring-opening process. The two other pathways are hydrogen abstraction from one of the C(2) or C(3) position on furan and hydroxyl radical substitution at the C(2) or C(3) position on furan. Abstraction and substitution channels are minor paths at low temperature, but they become comparable with addition channels at high temperature. Addition and substitution reactions proceed via formation of two energized intermediates, Int(1) and Int(2). Multichannel RRKM-TST calculations have been carried out to calculate the individual and overall rate constants for addition and substitution reactions. Direct-dynamics canonical variational transition-state theory calculations with small curvature approximation for tunneling were carried out to study hydrogen abstraction pathways.
已对OH与呋喃反应的动力学和机理进行了理论研究。通过采用密度泛函理论（DFT）、G3MP2和耦合簇单双激发（CCSD）方法，研究了各可能反应途径的势能面。该势能面由一个氢键复合物和两个激发态中间体组成。对于该反应，提出了三种不同的可能途径。最可能的通道是羟基自由基加成到呋喃环上的C(2)位置，引发开环过程。另外两条途径是从呋喃的C(2)或C(3)位置之一夺取氢，以及羟基自由基取代呋喃的C(2)或C(3)位置。夺取氢和取代通道在低温下是次要途径，但在高温下它们与加成通道相当。加成和取代反应通过形成两个激发态中间体Int(1)和Int(2)进行。已进行多通道RRKM-TST计算，以计算加成和取代反应的各个速率常数和总速率常数。采用小曲率隧道近似的直接动力学正则变分过渡态理论计算，研究了氢夺取途径。
