Cs, The Sio, Sis Generate Other Interstellar Molecular Theory Research

In recent years, the research of interstellar moleculars has become one of the most popularfileds and attracts much attention of many chemists. Generally, the interstellar space is invacuum and low temperature, which determines the particularity of the interstellar moleculars inexisting forms and structures. Reportedly, the reactivity of some interstellar moleculars is veryhigh, so they are difficult to be synthesized in laboratory, even poorly existing on the earth.Thuswe need to analyze the reactions between interstellar moleculars from the point of view ofenergy and do some investigation in theory.Researches about interstellar molecules containing C, H, O, N are offen reported, while theinterstellar moleculars bearing Si and S are seldom studied. So it is significant to investigate theformation of interstellar organic and Silicate/carbonate in studying the formation of otherinterstellar molecules from these molecules. Experimental and theoretical studies showed thatsome molecules which can transfer proton can advantage the reaction. So we researched theeffection of proton irradiation on the reaction mechanism of small interstellar molecules.In this paper, the method of quantum chemistry was used to study the microscopicmechanism of the reactions. We studied the reaction mechanism of the reactions between H2Oand CO, CS, SiO, SiS respectively. Using the Gaussian03Program and the density functionaltheory （DFT） in the level of B3LYP/6-311+G（d, p）, and the influence on the reactions were alsodiscussed with H2O, CH₃OH, HF, NH₃as catalysts. The structure of the transition state, reactants,products and intermediates in each reaction were optimized at the same level. Intrinsic reactioncoordinate （IRC） performed on the transition states was calculated. The energies of the specieswere corrected. According to the energy of each stationary point, we obtained the relative energy,and also the activation energy. The main research work of the thesis is as follows:1. The mechanisms of reactions between H₂Oand insterstellar moleculars such as CO, CS,SiO, SiS were studied. We obtained the transition states of TSa, TSb, TSc and TSd with theactivation energy of265.4,324.5,364.0and149.0kJ/mol respectively, which indicated the highenergy barriers and that the reactions were difficult to proceed under normal temperature. Theorder of energy barriers of each reaction is: SiO>CS>CO>SiS.2. The reaction mechanism of CO and H₂Ocatalyzed by H2O, CH₃OH, HF, NH₃was researched. The activation energies of each reaction were obtained. Varying the the number ofcatalyst molecules, the influence of bimolecular catalyst on the activation energy of CO and H2Owas further studied.（1） Over one-molecular catalyst above, the transition states of five-membered ring with twohydrogen bonds were obtained between the reaction of CO and H2O, the activation energy was190.3,142.4,118.7and139.3kJ/mol respectively, and the catalytic performance of catalystsshares a trend of HF>NH₃>CH₃OH>H2O.（2） Over bimolecular catalyst, the states of seven-membered ring with three hydrogen bondswere obtained in the same reaction process, which meaned stronger hydrogen bonds strength anddid good to the protolysis reaction. The activation energy was91.8,77.2,39.3and98.4kJ/molrespectively, and the catalytic performance of catalysts shares a trend of2HF>2CH₃OH>2H2O>2NH₃, showing much better catalytic performance compared toone-molecular catalyst.3. The reaction mechanism of CS and H₂Ocatalyzed by H2O、CH₃OH、HF、NH₃wasresearched. And the activation energy was obtained., The influence of the number of catalystmolecules on the activation energy of CS and H₂Owas further studied.（1） Over one-molecular catalyst, four transition states of five-membered ring with twohydrogen bonds were obtained between the reaction of CS and H2O, the activation energy was91.9,80.6,44.3and69.6kJ/mol respectively, and the catalytic performance of catalysts shares atrend of HF>NH₃>CH₃OH>H2O.（2） Over bimolecular catalyst, the states of seven-membered ring with three hydrogen bondswere obtained in the same reaction process, the activation energy was17.7,6.7,-31.3and21.5kJ/mol respectively, and the catalytic performance of catalysts shares a trend of2HF>2CH₃OH>2H2O>2NH₃.4. The reaction mechanism of SiO and H₂Ocatalyzed by H2O、CH₃OH、HF、NH₃wasresearched. And the activation energy was obtained. The effect of the number of catalystmolecules on the activation energy was further studied.（1） Over one-molecular catalyst, four transition states of five-membered ring were obtainedbetween the reaction of SiO and H2O, the activation energy was53.8,35.6,57.4and1.8kJ/mol respectively, and the catalytic performance of catalysts shares a trend of NH₃>H2O>CH₃OH>HF.（2） Over bimolecular catalyst, the states of seven-membered ring with three hydrogen bondswere obtained in the same reaction process, the activation energy was-23.3,-43.2and-26.1kJ/mol respectively, and the activation energy relative to reactant-complex was48.5kJ/mol、37.0kJ/mol、23.9kJ/mol.5. The reaction mechanism of SiS and H₂Ocatalyzed by H2O, CH₃OH, HF were studied.The activation energy was obtained. The influence of the number of catalyst molecules on theactivation energy was further studied.（1） Over one-molecular catalyst, four transition states of five-membered ring were obtainedbetween the reaction of SiS and H2O, the activation energy was39.9kJ/mol,22.3kJ/mol,39.3kJ/mol respectively. And the catalytic performance of catalysts shares a trend ofCH₃OH>HF>H2O。（2） Over bimolecular catalyst, the states of seven-membered ring with three hydrogen bondswere obtained in the same reaction process, the activation energy was-36.6,-61.2,7.0kJ/molrespectively, and the activation energy relative to reactant-complex was36.4kJ/mol,20.8kJ/mol,70.5kJ/mol. SiS, H₂Oand the catalyst are easy to form reactant-complexes, and the energies ofthe reaction systems were reduced greatly. Bimolecular catalyst Showed much better catalyticperformance compared to one-molecular catalyst.