Acta Phys. -Chim. Sin. ›› 2006, Vol. 22 ›› Issue (11): 1393-1398.doi: 10.3866/PKU.WHXB20061117

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Simulating Calculation of the Dissociation-Association Equilibrium of Dimer and Monomer of Trimethylaluminum in Gas Phase

WU Shu-Ying;YANG Li-Xin;SONG Chun-Xia;WANG Wen-Bo   

  1. College of Chemistry, Xiangtan University, Xiangtan 411105, P. R. China
  • Received:2006-05-30 Revised:2006-07-23 Published:2006-11-06
  • Contact: YANG Li-Xin

Abstract: Both the C2h and C2v configurations of trimethylaluminum dimer (d-TMA) and the C3h structure of monomer were obtained by full optimization at B3LYP/6-311++G(3df, 2pd) level. With Complete Basis Set method CBS-4M as emphasis, the thermodynamic function values of each species of TMA in gas-phase equilibrium at 1.01×105 Pa and in the range of 300~550 K were calculated by simulation. Through the consideration of the triplet-state configuration of d-TMA and the effect of heterolytic reaction on system entropy value, ΔrHm and ΔrSm of the dissociation reaction of d-TMA were accurately calculated at the same time. The plot of lnKd vs 1/T had a perfectly linear relation: lnKd=−9624.4363/T+20.2303, and the correlation coefficient R2=1.0000, which agreed quite well with the predecessors′ experimental results. Based upon these findings, a new dissociation-association reaction mechanism of d-TMA in gas phase was proposed.

Key words: Trimethylaluminum, Dimer, Dissociation-association equilibrium, Heterolytic reaction, Thermodynamic functions, Equilibrium constants