Chlorine leave group KIEs

Two methods were used to measure the chlorine leaving-group KIE for the 5n2 reduction of benzyl chloride to toluene by sodium borohydride in DMSO at 30 °C. One procedure involved the classical IRMS technique. The second method was a new technique in which the ratio of the chlorine isotopes was obtained by fast atom bombardment mass spectrometry on silver chloride recovered from the reaction. The KIE values found by the two methods were 1.007 and 1.008, respectively,... 

Table 1 The transition structures and chlorine leaving group KIEs for the nucleophiles at 298°C... 

Two reasons seemed possible for the different transition structures found by interpreting the experimental KIEs and theory. One was that the experimental KIEs were measured in solution whereas the theoretical calculations were done for a gas-phase reaction. A second possibility was that the chlorine leaving group KIE was interpreted incorrectly. If one could not conclude the Ca-Cl transition state bond is... 

Table 25 The secondary a-deuterium, the secondary P-deuterium, the a-carbon UC/14C, the incoming group carbon 12C/13C, the nucleophile nitrogen and the chlorine leaving group KIEs found for the Sn2 reaction between ethyl chloride and tetrabutylammonium cyanide in anhydrous DMSO and THF at 30°C...

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