Carbon as a nucleophile nitriles, Grignard reagents, acetylides

4 Carbon as a nucleophile nitriles, Grignard reagents, acetylides 

Nucleophilic substitution reactions employing carbon as a nucleophile are important in synthetic chemistry in that they create a new C-C bond. A carbon nucleophile, of course, must be in the form of anionic carbon, or its equivalent. One of the simplest sources of anionic carbon is the cyanide anion. HCN is a weak acid (pATa 9.1) and forms a series of stable 

As we shall see later, other reactions of nitriles extend the usefulness of this reaction. Thus, reduction of nitriles gives amines (see Section 7.6.1), whereas hydrolysis generates a carboxylic acid (see Box 7.9). 

Organometallic reagents also provide carbon nucleophiles that can be considered to behave as carbanions. Although there are a variety of organometallic reagents available, we include here 

The formation of this product need not concern us, but its nature is important. We can deduce from the ions Mg + and Br that it contains the equivalent of R or Ar, i.e. the alkyl or aryl group has 

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