Theoretical Study On The Reaction Mechanism Of Butene Anions With N₂O In Gas Phase

Gas-phase anion molecule reaction plays an important role in discovering the reaction mechanisms of the new synthetic and measuring some important thermochemical values because they are in general rapid, intense and selective. Especially, gas-phase anion molecule reaction was developed greatly during the past several decades for the improvement of experimental technique and test method. And numerous papers about the experiment were published. In contrast to these experimental studies, there were only a few theoretical studies on the reactions of gas phase anion chemistry with many channels and steps. Two typical reactions (n-butene anion and isobutylene anion with N₂O, respectively) which were carried out by Charles were selected as the object of study.In the paper, on the basis of the molecular orbital theory, the tradition transition state theory as well as quantum chemistry theory, the selected systems have been investigated using Moller-Plesset perturbation theory (MP2) and comparison DFT- B3LYP, the Quadratic configuration interaction method (QCISD) calculations and the Natural Bond Orbital analysis. The structures of the intermediates and the transition states along the reaction paths were fully optimized. The thermodynamic datum were all used to obtain the potential surface. The information of orbitals was also used to explain the reaction mechanism.The whole paper consists of five chapters. Chapter 1 is mainly about the development and application of quantum chemistry and the characteristics of organic gas-phase anion molecule reaction are also concerned.In Chapter 2, we will introduce the theory and computation methods that we based on.In Chapter 3, the mechanism for the ion-molecule reaction of n-butene anion with nitrous oxide has been characterized in detail. Based on 6-31++G(d,p) basis set, usingthe second-order M?ller–Plesset perturbation theory (MP2) and comparison DFT-B3LYP, the single-point energies have also been refined at the QCISD/6-31++G(d,p) level to get more accurate energies using the MP2/6-31++G(d,p) optimized geometries. The computational results indicate that As a result, there are cis and trans isomers in n-butene anion,and both the primary carbon and secondary carbon in n-butene anion can react with N2O, the former containsα-H abstraction pathway,β-H abstraction pathway, IM11 based pathway and O-atom abstraction pathway. Theα-H abstraction pathway is the main pathway, whose primary products are cis-propenyl-diazomethyl anion, trans-propenyl-diazomethyl anion. The latter comprises methyl-H abstraction pathway, vinyl-H abstraction pathway, IM12'based pathways and O-atom abstraction pathway. The methyl-H abstraction pathway is the main pathway, whose primary product is butadienyl anion. In comparison, the latter reaction is more favorable. The O-atom direct abstraction reaction can also compete with the major reaction pathway. And its products can be detected. Furthermore,all the reactive pathways, regardless of the main or minor ones, are strongly exothermic processes.In Chapter 4, the mechanism for the gas-reactions of the isobutylene anion with nitrous oxide has been characterized in detailed at the MP2/6-31++G(d, p) level of the MP2. our theoretical investigations strongly suggest that the main pathways, whose energies of all stationary points lie below that of the original reactants (isobutylene anion + N₂O), can be expressed as pathways 1 and 2 of the Channel 1, which are two reciprocally competitive pathways. The primary products were cis-CH₂(CH₃)CCN₂-+H₂O, trans-CH₂(CH₃)CCN₂- + H2O, and a trace amount of C4H7O- + N2 should also be monitored in the experiment.