Multi-channel Study Of The Reaction Mechanism

The free radicals play an important role in the combustion reactions. Some reactions are the main reason of the secondary pollution. Recently these reactions have attracted more attention than before. In order to control the pollution effectively, we must investigate the mechanisms of these reactions. In this paper, we have investigated the mechanisms of four reactions by using the vibrational mode analysis.The molecule complexes are very ubiquitous in the science of molecule, which play an important role in catalyzes, energy transition and biochemistry. These complexes are also very important in determining the mechanism of some reactions. In the last two chapters, we discussed the two kind of hydrogen bond complexes formed between chiral molecule and some small molecules.This paper includes 8 chapters. Chapter 1 consists of four parts. In part 1, we briefly introduce the theoretical background of the multi-channel reaction. In part 2, we introduce the background of molecule complexes and chiral. In part 3, we narrate some basic knowledge of infrared spectrum. In part four, we expound the primary work of this paper. In chapter 2, we introduce the related calculating methods used in this paper.From the chapter 4 to chapter 7, we have investigated the mechanisms of four reactions (F + CH2CO, OH + CH2CO, NO2+ CH3S and CH3S + O2) using vibrational mode analysis. All the species involved in these reactions are optimized employing B3LYP method at 6-311++G(d,p) basis set level. The main products of these reactions are CO + CH2F, CO+CH2OH, NO + CH3SO and HO2 + CH2S, respectively. We have analyzed the frequencies of all species and assigned the vibrational modes. The vibrational mode analysis shows that the reaction mechanism is reliable. When using vibrational mode analysis to elucidate the mechanism, we find that the only imaginary frequency of a transition state is always related to the breaking or forming bond. If theconfiguration of a species changes, it is certain that its frequencies should change accordingly. If a bond is weakened, its frequencies are red-shifted, namely move to the lower region; Likewise, if a bond is strengthened, its frequencies will blue shift to the relatively higher frequency region. So using the vibrational mode analysis to elucidate the reaction mechanism is reasonable.In chapter 7, we reported theoretical study on the interactions between the 1,3-butanediol and the chiral hydrogen peroxide. The complexes formed between two isolate chiral hydrogen peroxide (R and S) and 1, 3-butanediol have been investigated by using B3LYP method at different basis set levels. Four pairs of equilibrium structures have been determined, all of which are cyclic double-hydrogen bonded structures at the largest basis set level. The optimized geometric parameters, interaction energies and chirodiastatic energy for various isomers at different levels are estimated. The infrared spectrum frequencies and IR intensities for various complexes are reported.In chapter 8, the hydrogen bonding of 1:1 complexes formed between alanine and water molecule have been completely investigated using B3LYP method at varied basis set levels from 6-31G to 6-311++G(d,p) and MP2 method at the 6-31++G(d,p) level. Eight reasonable geometries have been determined. The optimized geometric parameters and interaction energies for various isomers at different levels are estimated. The infrared spectrum frequencies, IR intensities and the vibrational frequency shifts are reported. Finally the solvent effects on the geometries of the alanine-water complexes have also been investigated using self-consistent reaction-field (SCRF) calculations at the B3LYP/6-311++G(d,p) level. The results indicate that the polarity of the solvent has played an important role on the structures and relative stabilities of different isomers.