| The organolithium compounds (R1R2CLiX, X=F, Cl, Br, etc.) are important active-organic intermediate. They have ambiphilia (electrophilic reactivity and nucleophilic reactivity). In organic synthesis, they not just have the reacting character of the unsaturated-carbenoid H2C=C:, but more stable than it. The experiment of the synthesis of the unsaturated-carbenoid H2C=CLiCl by using the alkyl-lithium and the chloroethylene has been reported. Recently, the studying result of the using of the organolithium compounds in organic synthesis showed that they have the merits such as singular product, selective advantage, moderate reacting, etc. So they have the widely using prospect in the organic synthesis. But the studies about the cyclo-organolithium compounds have not been reported. In order to perfect the system of the organolithium compounds, we studied some cyclo-organolithium compounds about their structures and characters.1. The Theoretical studies of Geometries, Isomerizations, Hydrogen Transfers of 1-halo-1- lithiocyclopropane and 1-halo-1- lithiocyclopropeneStructures of cyclo-organolithium compounds of 1-halo-l-lithiocyclopropane and 1-halo-l- lithiocyclopropene have been studied in detail by ab initio at B3LYP/6-311+G** level, obtained two equilibrium geometries and one respectively. Because aromatic structures are existed in 1-halo-l-lithiocyclopropene when o orbital in the plane of triatomic ring, so there is only one stable equilibrium geometries of it.Geometries (1) of 1-halo-l-lithiocyclopropane are more stable than geometries (2), and geometries (2) can transform to (1) under some conditions. We worked out transition states of every structure, and studied their thermodynamic and kinetic properties. Because only geometries (1) of 1-halo-l- lithiocyclopropane can be stablely existed, so the speeds of hydrogen transfer decide their life. In case of this, we studied the intramolecular reaction of H-migration of 1-halo-l-lithiocyclopropane. The results of computation indicated that there were two kinds of TS (1 and 2 in figure 4). In terms of the result of computaion of TS, we studied thermodynamic and kinetic properties of these reactions, and we got the average life of geometries (1).2. Mechanism of Formation of organolithium compounds of C2HnCLiX (X=F, Cl, Br; n=2,4)Mechanisms of formation of organolithium compounds of C2HnCLiX (X=F, Cl, Br;n=2, 4)by the reaction of C2HnCXY+CH3Li-C2HnCLiX (X=F, Cl, Br; Y=H, F, Cl, Br; n=2, 4) have been studied in detail by DFT method at B3LYP/6-311+G** level. We use two main methods (exchange H by Li; exchange halogen by Li) to synthesize compuounds of C2HnCLiX. The result indicated that a five-membered cyclic structure was formed in every transition state. The potential profile for every reaction was obtained by the calculation of IRC. At the same time, we studied thermodynamic and kinetic properties of these reactions.3. Theoretical studies of geometries of cyclo-organolithium compounds of1-halo-l- lithiocyclobutane and 1-halo-l- lithiocyclobuteneThe density functional theory (DFT) at B3LYP/6-311+G** level was employed to study the equilibrium structures of C4HnLiX (X=F, Cl, Br;n=4, 6).The result of computation indicated that there were two equilibrium structures of C4H6LiX (X=F, Cl, Br), but one of C4H4LiX (X=F, Cl, Br).The possible reaction of isomerization of C4H6LiX (X=F, Cl, Br)has been discussed.4. Theoretical studies of geometries and intramolecular reaction of hydrogen transfer of cyclo-organolithium compounds of C4HnCLiX (X=F, Cl, Br; n=4, 6, 8)Structures of cyclo-organolithium compounds of C4HnCLiX (X=F, Cl, Br;n=4, 6, 8)have been studied in detail by ab initio at B3LYP/6-311+G** level, obtained two equilibrium geometries respectively. Geometries 3a and 3b nearly have identical structure. Geometries 4a has aromatic structure, so it is most stable. We have studied the intermolecular reaction of H-migration, which will affect the stable of substance. Every transition states have been worked out, and the potential... |
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