Acidity of hydrocarbons. XXX. Kinetic isotope effects of the cesium cyclohexylamide catalyzed proton exchange of cyclohexane with cyclohexylamine

Computational study of carbon–hydrogen bond deprotonation by alkali metal superbases

“…A substantial body of work has been published by Streitwieser and coworkers concerning the kinetic acidities of alkanes, cycloalkanes and other very weak carbon acids using cesium cyclohexylamide (CsCyNH) as a ''superbase'' [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Proton exchange kinetics have been reported for reactions of alkanes with CsCyNH in cyclohexylamine solvent [9,12].…”

“…The influence of varying the acidity of the substrate was also studied with smaller model complexes. Although studied experimentally [7][8][9][10][11][12], the extreme reactivity of superbasic compounds has hindered the elucidation of some aspects of their chemistry requiring special experimental techniques. A computational study on the thermodynamics and barriers of hydrocarbon C-H bond cleavage by these and related alkali metal compounds may provide important insight into harnessing superbasic properties of related transition metal complexes without the complications that may arise from the redox non-innocence of d-block metals.…”

Kinetic acidity of methane

“…2 We have published related results with cyclohexane and other cycloalkanes. [3][4][5] The latter exchange reactions are slow but could be followed straightforwardly using tritium as a tracer. Methane, however, exchanges much more rapidly and being a gas introduced additional complexities that could not be handled satisfactorily at that time.…”

Concertedness and E2 elimination reactions: prediction of transition state position and reaction rates using two-dimensional reaction surfaces based on quadratic and quartic approximations

“…The anchor is the equilibrium ion pair acidity for benzene determined as 43.0 (37). Cyclohexane was shown to exchange at a rate 1.1 X lop8 times that of benzene, and isotope effects showed that internal return is not important (38 cyclohexane, which in turn means that methane is 2.4 x low5 times as reactive as benzene (39). If it is assumed that the Bronsted slope is unity, then the pKa for methane is 48.…”

“…For reasons given in the text, we believe that the estimate based on Streitwieser's approach (37)(38)(39)(40) is the most likely to be correct, and have used this value. Prudence dictates that our error estimates should include all current plausible estimates within the 95% confidence bounds.…”