Calculations methyl chloride identity

Wolfe and Kim s view of the origin of secondary a-deuterium KIEs has been challenged by two different groups. Barnes and Williams (1993) calculated the transition state structures and the secondary a-deuterium KIEs for the identity SN2 reactions between chloride ion and several substituted methyl chlorides (reaction (11)). 

Table 8 The AMI calculated semiclassical secondary a-deuterium KIEs, the stretching and other contribution to the KIEs and the C—Cl transition state bond lengths for the identity SN2 reactions between chloride ion and substituted methyl chlorides.0...

Tertiary alkyl halides are easier to reduce than secondary alkyl halides, which are, in turn, easier to reduce than primary alkyl halides. Ease of reduction of a carbon-halogen bond is governed by the identity of the halogen atom (a) iodides are easier to reduce than bromides, (b) chlorides are so difficult to reduce that they often appear to undergo no direct reduction, and (c) no report of the direct reduction of an alkyl monofluoride has been published. Finally, the existence of the radical anion [RX ], formed by addition of one electron to an alkyl monohalide, has never been demonstrated Andrieux and coworkers [8] have discussed why such a species is not expected for simple alkyl monohalides, but why radical anions of aromatic halides are distinct intermediates in the electrochemical reduction of aromatic halides. Canadell and coworkers [9] have described the implications of theoretical calculations pertaining to the lifetime of the water-solvated radical anion of methyl chloride. 

DPT calculations indicated that the mechanism most Hkely involves three steps electrophilic substitution, oxidation and reductive ehmination. The inactivity of the iodine complexes prompted us to investigate the counterion dependence. For the methyl-substituted complexes (Scheme 23, R = CH3) we synthesized the acetate (X = OCOCH3) 22 and the chloride complex (X = Cl) 23. The catalytic conversions are within experimental error identical to the results of the bromide complex 20. This indicates that the dissociation of a counterion is a necessary condition for the activity of the complex [59]. 

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