Nucleophile functional group Subject

Sulfonate esters are subject to the same limitations as alkyl halides Competition from elimination needs to be considered when planning a functional group transforma tion that requires an anionic nucleophile because tosylates undergo elimination reactions just as alkyl halides do... 

The use of halides as nucleophilic reagents is mostly covered by the chemistry of organometallic reagents that are readily formed from halides. This subject is covered by several volumes in the Chemistry of the Functional Groups series405"408 and elsewhere409"41. Thus this area of synthesis is not covered in the present work and the reader is directed to these sources for details. 

Polyurethanes are produced by the reaction between alcohols and isocyanates. Isocyanates have a very reactive functional group that is subject to nucleophilic attack by an alcohol to give a carbamate or urethane ... 

In addition to the acidity of the phosphonium salt, other factors also determine the choice of base, e.g. the reactivity, (i.e. the electrophilicity) of the carbonyl component. The presence of sensitive functional groups in the phosphonium salt also has an influence on the suitability of certain bases. If the phosphonium salt contains a carbonyl group, for example, there is the risk that this may be subject to nucleophilic attack by alkyl metals. In addition, the base, in particular its cation, intervenes to a considerable extent in the stereochemical course of the Wittig reaction (see Section C). 

Enzymes involved in the cleavage of carbohydrates can also function by the above mechanism. Figure 2.18 shows that amylose hydrolysis by p-amylase occurs with the help of four functional groups in the active site. The enzyme-substrate complex is subjected to a nucleophilic attack... 

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