Cyclohexylamine, proton transfer

The equilibrium shown m the equation lies to the right =10 for proton transfer from the conjugate acid of aniline to cyclohexylamine making cyclohexylamine 1 000 000 times more basic than aniline... 

Streitwieser and Boerth studied the kinetic acidities of cycloalkenes with lithium cyclo-hexylamide (LiCHA) in cyclohexylamine for comparison with those of benzene and toluene66. The relative rates of deprotonation and the corresponding equilibrium pK values are tabulated in Table 12. These proton transfer transition states are stabilized by conjugation of the reacting C—H bond with the double bond. 

The simplest reaction characteristic of compounds that are regarded as salts of carbanions is that of proton transfer (see Proton Transfers Involving Anions and Dianions) and a number of these have been studied. A typical example is the reaction of methane with lithium amide. This reaction is a model for many known hydrogen isotope exchange reactions of hydrocarbons with lithium and cesium cyclohexylamide whose kinetics have been measured in cyclohexylamine. The model reaction does involve a preliminary weakly bound complex that isomerizes via a transition structure to methyllithium coordinated to ammonia (Figure 3). 

In a recent study [175] of the methoxide ion catalysed tritium exchange in methanol of weakly acidic fluorinated bicycloalkanes (pIT ca. 20), comparison of the rates of exchange for six compounds, with ion-pair pK values determined in cyclohexylamine containing caesium ions, gave a Bronsted plot with slope (a) within experimental error of unity. The isotope effects for proton compared with deuteron transfer (feH/feD = 1.2) are similar to those observed with chloroform. The charge on these polyfluorocarbanions may also be localized on carbon [175]. 

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