Kinetic studies of bold σ -adduct formation and nucleophilic substitution in the reactions of ethyl 2,4,6-trinitrophenyl ether, some phenyl 2,4,6-trinitrophenyl ethers, and phenyl 2,4-dinitronaphthyl ether with aniline in dimethyl sulfoxide

The reaction of ethyl 2,4,6-trinitrophenyl ether with aniline in dimethyl sulfoxide containing Dabco occurs in two stages. The first gives 5, the σ -adduct intermediate on the substitution pathway, which has been identified spectroscopically. The second yields 2,4,6-trinitrodiphenylamine, the substitution product. Kinetic studies show that proton transfer is rate limiting both in the formation of the intermediate and in its subsequent acid-catalysed decomposition. Phenoxide is a considerably better leaving group than ethoxide and the substitution reactions of phenyl 2,4,6-trinitrophenyl ethers and phenyl 2,4-dinitronaphthyl ether with aniline in DMSO occur without the accumulation of intermediates. The kinetics indicate both uncatalysed and base-catalysed pathways. The kinetic and equilibrium data for reaction of the ethyl and phenyl ethers are compared with data for σ -adduct formation from 1,3,5-trinitrobenzene and aniline.Key words: nucleophilic substitution, proton transfer, base catalysis, σ -adducts