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本文以正丁醇中卤离子(I~-或Br~-)与卤代烷烃(C_(16)H_(33)Br或C_(16)H_(33)I)的交换反应为例,首次采用示踪原子法研究卤素非同位素交换反应的动力学,并与同位素交换结果做了比较。发现反应符合S_N2机构。不同交换反应的速度有显著差异,次序为碘-碘交换>碘-溴交换>溴-碘交换>溴-溴交换。利用溶剂效应解释了这一次序。测得了这几种交换的若干动力学参数等。本文介绍的方法对于用示踪原子法定量探讨S_N2机构的有机化学反应具有普遍意义。
In this paper, the exchange reaction of halide (I ~ - or Br ~ -) and haloalkane (C_ (16) H_ (33) Br or C_ (16) H_ (33) I) in n-butanol is taken as an example. The kinetics of halogen non-isotopic exchange reaction was studied by the method of stochastic atomic absorption spectrometry and compared with the isotope exchange results. The reaction was found to be in line with the S_N2 mechanism. The rate of different exchange reactions was significantly different, the order of iodine - iodine exchange> iodine - bromine exchange> bromine - iodine exchange> bromine - bromine exchange. Solvent effects explain this sequence. Measured the exchange of several of these kinetic parameters. The method described in this paper is of general significance for quantitatively exploring the organic chemistry of S_N2 mechanism by tracer atom method.