Reactions of substituents not directly attached to the heterocyclic ring

4 Reactions of substituents not directly attached to the heterocyclic ring 

In general, substituents removed from the ring by two or more saturated carbon atoms undergo normal aliphatic reactions. A notable exception is the reverse Michael reaction which is undergone by p -substituted ethyl compounds such as 2-(p-hydroxyethyl)pyridine (see Section 3.2.3.4.4). 

Substituents directly attached to fused benzene rings or aryl groups mostly undergo the reactions of those on normal benzenoid rings. Naturally a substituent on the benzenoid ring in quinoline or isoquinoline should be compared with that on a naphthalene rather than with a benzene nucleus e.g. 

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