Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (12): 2831-2838.doi: 10.3866/PKU.WHXB201208134

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

1,2- and 1,4-Addition Reactions between Silabenzenes and HX (X=F, OH, NH2)

WANG Yan, ZENG Xiao-Lan   

  1. College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, Henan Province, P. R. China
  • Received:2012-06-20 Revised:2012-08-13 Published:2012-11-14
  • Supported by:

    This work was supported by Henan Provincial Fundamental and Frontier Technological Research Program, China (092300410207).

Abstract:

Density functional theory calculations at the B3LYP/6-311 ++ G(d,p) level were performed to study the reaction mechanism and potential energy surface of the 1,2- and 1,4-addition reactions between silabenzenes and HX (X=F, OH, NH2). The influences of substituents at the Si atom and tetrahydrofuran as a solvent on the potential energy surfaces of the reactions were also explored. The results indicated that the title reactions occur by the following two mechanisms: (1) silabenzene and one HX molecule form an intermediate complex, and then isomerize to give final product via a four-membered transition state; and (2) silabenzene and two HX molecules form an intermediate complex, and then isomerize via a sixmembered transition state to give another intermediate complex from which one HX molecule is left to afford the final product. Mechanism 2 is much more favorable than mechanism 1 kinetically. The preference for the 1,2- or 1,4-addition product is determined by kinetics and is related to the X group. The reactivity order of HX toward the addition reaction with silabenzene in gas phase is HF>H2O>NH3. Strong electron-donating and -withdrawing substituents at the Si atom have a favorable influence on the potential energy surfaces of the 1,2- and 1,4-addition reactions, while the large mesityl group has the opposite effect. Tetrahydrofuran has an unfavorable thermodynamic influence on the reactions, and kinetically on those reactions with HF or H2O. However, it favors the reactions between silabenzenes and NH3 kinetically.

Key words: Density functional theory, Silabenzene, Addition reaction, Reaction mechanism

MSC2000: 

  • O641