Neighboring group effect, macromolecular

Macromolecular reactions proceed more or less similarly to those of low-molar-mass compounds. Special features are seen through the neighboring group effect and the whereabouts of the by-products. ... 

The reactivity of macromolecular and low-molar-mass groups is about the same when neighboring group effects are taken into consideration. 

If there is only a small number of reactive groups per macromolecule, the environment of these groups is not changed as the reaction proceeds. The macromolecular chain simply acts as a diluent. Of course, neighboring group effects can also play a role, especially if five- and six-membered cyclic transition states can be formed. An example of this is the partial imidization of poly(methacrylamide) at temperatures above 65°C ... 

Because each reaction is a particular case, it is difficult to establish general rules. Certain reactions on polymers can be strongly accelerated by the macromolecular nature of either the reagent or the substrate. Such behavior is generally accounted for by the presence of neighboring groups, or the influence of the chain stereochemistry, or the effect of electrostatic attractions or repulsions, and so on but in most cases the apparent reactivity of polymers is definitely lower than that of simple model molecules, due to a reduced accessibility to the reaction sites. 

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