In these latter cases the reaction may proceed in different directions; thus, with the aromatic hydrocarbons, chlorine in the cold or in the presence of a carrier substitutes in the benzene nucleus, but in the presence of sunlight or on warming, substitution takes place in the side chain.
Blom found that on brominating orthoacetamido-acetophenone in presence of water or acetic acid, the bromine goes into the benzene nucleus, whilst in chloroform or sulphuric acid or by use of bromine vapour it goes into the side chain as well.
alkyl side chain.
amide nitrogen of an asparagine amino-acid side-chain might be glycosylated.
If methyl benzene is reacted with chlorine in the presence of uv light, substitution takes place in the alkyl side chain.