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题名: Gas-phase non-identity S(N)2 reactions at neutral nitrogen: a hybrid DFT study
作者: Yang, J ; Ren, Y ; Zhu, HJ ; Chu, SY
刊名: INTERNATIONAL JOURNAL OF MASS SPECTROMETRY
关键词: S(N)2 at neutral nitrogen ; hybrid DFT method ; reaction mechanism ; nucleophilicity ; TRANSITION-STATE GEOMETRIES ; NUCLEOPHILIC-SUBSTITUTION ; METHYL HALIDES ; SN2 REACTIONS ; ANIONS ; DISPLACEMENT ; BARRIERS
英文摘要: The gas-phase non-identity nucleophilic substitution reactions at saturated nitrogen Y-+ NH2X --> NH2Y + X- (Y, X = F, Cl, Br and I) were evaluated at the level of MPW1K/6-31+G(d, p). The enthalpies of reactions are exothermic only when the nucleophile is the lighter halide. Central barriers (DeltaH(YX)(not equal)) for reactions in the exothermic direction are slightly higher than the corresponding barriers at carbon. The lower overall barriers relative to the reactants (DeltaH(YX)(b)) than the corresponding reactions at carbon suggest that S(N)2 reactions at nitrogen may be more facile than at carbon. Both the central barriers (AH(YX)(not equal)) and the overall barriers (DeltaH(YX)(b)) correlate well with reaction exothermicity. Further interesting features of the non-identity reactions at nitrogen are the reasonable correlation between the central barriers (DeltaH(YX)(not equal)) with the composite geometrical looseness (%L-not equal), geometrical asymmetry (%AS(not equal)), and charge asymmetry of the transition structures (Deltaq (X - Y)). The data for the central barriers and the overall barriers show good agreement with the prediction of the Marcus equation and its modification, respectively. Kinetic and thermodynamic investigations predict that the nucleophilicity of X- in the S(N)2 at nitrogen decreases in the order F- < Cl- < Br- < I-, the leaving-group ability increases in the order F > Cl > Br > I. (C) 2003 Elsevier B.V. All rights reserved.
出版日期: 2003
卷号: 229, 期号:3, 页码:199-208
语种: 英语
ISSN号: 1387-3806
内容类型: 期刊论文
URI标识: http://ir.kib.ac.cn/handle/151853/15462
Appears in Collections:植物化学与西部植物资源持续利用国家重点实验室_期刊论文

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Recommended Citation:
Yang, J; Ren, Y; Zhu, HJ; Chu, SY.Gas-phase non-identity S(N)2 reactions at neutral nitrogen: a hybrid DFT study,INTERNATIONAL JOURNAL OF MASS SPECTROMETRY,2003,229(3):199-208
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