Of Ch <sub> 3 </ Sub> X (x = Oh, Cl, Br, I) Solution From The Dft Study Of Reaction Mechanism

CH₃X (X=OH, Cl, Br, I), whose chemical processes in atomosphere and circulation influence the balance of troposphere ozone, are important substances of atmosphere and combustion chemistry. At the same time, the dissociations of CH₃X (X = OH, Cl, Br, I) are basic processes of elementary chemical reactions. Thoroughly study of their dynamics and mechanisms are performed to help unconver the essence of chemical reaction process. At present, their oxygenation and photodissaciation have been given much attention all over the world. In this paper., the mechanisms of the dissociation of CH₃X (X=OH, Cl, Br, I) have been investigated by density functional theory (DFT) and the detailed potential energy surfaces have been obtained, which provide more information for further investigations.Main results of this paper are as follows:1. The possible reaction mechanism of the dissociation of CH₃OH is investigated theoretically by a detailed potential energy surface calculation at the B3LYP/6-311++G(d, p) and CCSD(T)/6-311++G(d, p)(single point) levels. The study reveals three different atomic H loss processes: two direct dissociations through O-H and C-H bond cleavage channel, respectively; And one type of the subsequent secondary methyl H loss from methoxy radical product. And the study also indicate that two molecular hydrogen elimination channels are present: 4-center elimination involving hydrogen atoms on both the C and O sites, and 3-center elimination from the methyl group which displays two different micro-pathways. Intrinsic reaction coordinate (IRC) calculations are performed at 6—311++G(d, p) level to convince the transition states.2. The possible reaction mechanisms of the dissociation of CH₃X (X=Cl, Br) are investigated theoretically by a detailed potential energy surface calculation at the B3LYP/6-311++G(3df, 2p) levels. Results show that the dissociation mechanisms of CH₃X (X=Cl, Br) consist of OX bond, OH bond cleavage channel and molecular hydrogen elimination channel, interestingly, the three processes being subsequent secondary dissociations from radical product. Two transition states have been discussed respectively and also been convinced by IRC calculations in this paper.3. The possible reaction mechanism of the dissociation of methyl iodide (CH₃I) is investigated theoretically by a detailed potential energy surface calculation at the B3LYP/LANL2DZ levels. We find that the dissociation mechanism of CH₃I consists of OX bond, OH bond cleavage channel and molecular hydrogen elimination channel, interestingly, the three processes being subsequent secondary dissociations from radical product. Two transition states and one intermediate have been found in this paper.