Carbanions and their reactions

In theory any organic compound such as (1) that contains a C—H bond, i.e. nearly all of them, can function as an acid in the classical sense by donating a proton to a suitable base, the resultant conjugate acid (2) being a carbanion (cf p. 21)  

In considering relative acidity, classically it is only the thermodynamics of the situation that are of interest in that the pKa value for the acid (cf. p. 54) can be derived from the equilibrium above. The kinetics of the situation are normally of little significance, as proton transfer from atoms such as O, N, etc., is extremely rapid in solution. With carbon acids such as (1), however, the rate at which proton is transferred to the base may well be sufficiently slow as to constitute the limiting factor the acidity of (1) is then controlled kinetically rather than thermodynamically (cf. p. 280). 

There are, however, other methods of generating carbanions than by proton removal as we shall see below. Carbanion formation is important—apart from the inherent interest of the species—because of 

The most general method of forming carbanions is by removal of an atom or group X from carbon, X leaving its bonding electron pair behind  

By far the most common leaving group is X = H where, as above, it is a proton that is removed, (1)— (2), though other leaving groups are also known, e.g. C02 from the decarboxylation (p. 285) of RC02e 

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