Chouit Hanifa, Sobhi Chafia, Bouasla Souad, Messikh Samia, Kheribeche Azeddine, Khorief Nacereddine Abdelmalek
Laboratory of Materials and Energetic Engineering, Faculty of Technology, University 20 August 1955 Skikda, BP 26, 21000, Skikda, Algeria.
Department of Physics and Chemistry, Higher Normal School for Technological Education of Skikda, Azzaba, Skikda, Algeria.
J Mol Model. 2022 Mar 26;28(4):104. doi: 10.1007/s00894-022-05086-y.
The mechanism and the regioselectivity of the non-polar [3 + 2] cycloaddition reactions between nitrile oxide and two cyclopentenes were theoretically investigated within the molecular electron density theory (MEDT) using DFT methods, namely the B3LYP, MPWB1K and ωB97XD functionals together with the standard 6-31G(d) basis set. The activation energies of these 32CA reactions are relatively high, due to the low nucleophilic power of both cycloalkenes and the relatively moderate electrophilic nature of the nitrile oxide. The B3LYP and MPWB1K functionals reproduced high relative energies values, while the ωB97XD one yields better values in the kinetic and thermodynamic energies. The completely 4-regioselectivity that observed experimentally has been explained by the analysis of the relative energies, in which the formation of 4-regioismeric cycloadducts is always the more kinetically favored one. The electron localization function (ELF) topological analysis showed that the studied 32CA reactions proceed through two-stage one-step nonconcerted mechanism. The effects of the hydrogen bonds on the regioselectivity determination have been investigated by mean both noncovalent interactions (NCI) and quantum theory of atoms in molecule (QTAIM) analyses, which confirm the presence of high strength N - H···O hydrogen bond and a supplementary weak stabilized H…F hydrogen bonds.
利用密度泛函理论（DFT）方法，即B3LYP、MPWB1K和ωB97XD泛函以及标准的6-31G(d)基组，在分子电子密度理论（MEDT）范围内对腈氧化物与两种环戊烯之间的非极性[3+2]环加成反应的机理和区域选择性进行了理论研究。由于环烯烃的亲核能力较低以及腈氧化物的亲电性质相对适中，这些[3+2]环加成反应的活化能相对较高。B3LYP和MPWB1K泛函再现了较高的相对能量值，而ωB97XD泛函在动力学和热力学能量方面给出了更好的值。通过对相对能量的分析解释了实验中观察到的完全4-区域选择性，其中4-区域异构体环加成产物的形成在动力学上总是更有利的。电子定域函数（ELF）拓扑分析表明，所研究的[3+2]环加成反应通过两阶段一步非协同机理进行。通过非共价相互作用（NCI）和分子中原子的量子理论（QTAIM）分析研究了氢键对区域选择性测定的影响，证实了存在高强度的N-H···O氢键和一个额外的弱稳定化H…F氢键。
