Carbonate And Derivatives In A Variety Of Small Molecules Under The Action Of The Reaction Mechanism

In the chemical field, carbonic acid is a basic compound. Under normal circumstances, the decomposition of carbonic acid is very rapid. Here, Loerting elucidate that water molecules influence the decomposition rate. Whether one carbonic acid has a catalytic effect on other? Besides water moleculars, what is catalytic efficiency of other moleculars on carbonic acid? As far as we know, these issues have not been reported. we have adopted DFT to study carbonic acid decomposition reaction mechanism in gas at one molecules of H₂CO₃ or two H₂CO₃ ; Acid-base bifunctional small molecules (such as H₂O, CH₃OH, NH₃, HF, etc.) having a catalytic effect on the reaction continuously attracted extensive research interest, which has stimulated our study on carbonic acid decomposition reaction in the acid-base bifunctional small molecules.A wide range of carbonic acid derivatives, carbonic acid esters are important organic chemical intermediates. There is much research on these compounds, mainly concentrated in the synthesis problem. And as reaction intermediates, its stability is very important for reactions. Carbonic acid esters with small moleculars are often in a system while in the preparation and applications as intermediates. So studying the decomposition of carbonic acid esters in the role of small molecules in organic synthesis is of great significance.Considering the above facets, we start our systemic study decomposition of carbonic acid and derivatives in the small molecule (such as H₂O, HF, CH₃OH, etc.) by using the B3LYP method in the density functional theory.The thesis consists of three parts as follows:1,Mechanism study on carbonic acid decomposition at the role of small moleculesWe used the DFT method at the B3LYP/6-311G** level of theory to optimize the configurations of isolated and complex carbonic acid and all their product of complex and the structures of corresponding transition station; Then we began to discuss the relative stability of the comlex and the possible reaction pathways; At last the catalytic effect of the small molecule was compared with respect to the reaction's active energy.The results showed that: while there is a small molecule involved in the reaction, the activation energy decreases significantly, the order of catalytic effectivenes of: 2H₂O>HF>NH₃>CH₃OH>H₂O>2H₂CO₃>H₂CO₃.2,Mechanism study on methyl carbonate decomposition at the role of small moleculesWe used the DFT method at the B3LYP/6-311G** level of theory to optimize the configurations of isolated and complex carbonic acid and all their product of complex and the structures of corresponding transition station; Then we began to discuss the relative stability of the comlex and the possible reaction pathways; At last the catalytic effect of the small molecule was compared with respect to the reaction's active energy.The results showed that: while there is a small molecule involved in the reaction, the activation energy decreases significantly, the order of catalytic effectivenes for the 2H₂O>HF>CH₃OH>H₂O3,Mechanism study on Dimethyl carbonate decomposition at the role of small moleculesWe used the DFT method at the B3LYP/6-311G** level of theory to optimize the configurations of isolated and complex carbonic acid and all their product of complex and the structures of corresponding transition station Then we began to discuss the relative stability of the comlex and the possible reaction pathways and reaction activation energy .The results showed that: activation energy barrier is higher in the reaction of small molecules participating than isolated molecules; there is little difference in varieties of reaction activation energy barrier, small molecules effecting decomposition reaction is very little.4,Mechanism study on Methyl carbamate decomposition at the role of small molecules We used the DFT method at the B3LYP/6-311G** level of theory to optimize the configurations of isolated and complex carbonic acid and all their product of complex and the structures of corresponding transition station ;Then we began to discuss the relative stability of the comlex,the possible reaction pathways and reaction activation energy .The results showed that: activation energy barrier is lower in the reaction of small molecules participating than isolated molecules; while HF participating in the reactions, activation energy barrier is the smallest, the reaction carries out most easily.All calculations here are performed on PIV PC computer by using Gaussian 03 program system.