Acta Phys. -Chim. Sin. ›› 2003, Vol. 19 ›› Issue (05): 389-392.doi: 10.3866/PKU.WHXB20030502

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Reaction Mechanism of the Gas-phase Elimination of 2-bromopropionic Acid

Li Yong-Hong;Chen Li-Ping;Xu Wen-Yuan;Hong San-Guo   

  1. Department of Chemistry, Jiangxi Normal University, Nanchang 330027
  • Received:2002-07-04 Revised:2002-10-11 Published:2003-05-15
  • Contact: Hong San-Guo

Abstract: The gas-phase elimination of 2-bromopropionic acid was investigated using density functional theory (DFT) method. Molecular structures were calculated at the B3LYP/6-31G** level. The results obtained show that the gas-phase elimination of 2-bromopropionic acid proceeds via a semi-polar five-membered cyclic transition state, where the acidic H of the group COOH assisted the leaving Br atom, and the carboxylic oxygen stabilized this transition state. The single-point energies of all optimized molecular structures by B3LYP/6-31G** were counted at B3LYP/6-311++G (3df,3pd) level. The activation energy(Ea1=ETS1-ERe)of the rate-controlling step obtained at B3LYP/6-311++G (3df,3pd) level was 189.5 kJ•mol-1,which is closely correlated with the available experimental data(180.3±3.4) kJ•mol-1.The relative error is 5.08%.

Key words: 2-bromopropionic acid, Gas-phase elimination, Density functional theory(DFT), Reaction mechanism