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Catalysis in aromatic nucleophilic substitution. Part 12.1 Kinetics of the reactions of some 2-phenoxy- and 2-( p-nitrophenoxy)-3-nitro-5-X-thiophenes with benzylamine and N-benzylmethylamine in benzene

1998; Royal Society of Chemistry; Issue: 2 Linguagem: Inglês

10.1039/a705667b

2050-8239

Giovanni Consiglio, Vincenzo Frenna, Elisabetta Mezzina, Antonio Pizzolato, Domenico Spinelli,

Synthesis and Reactions of Organic Compounds

The rate constants of the title reactions have been measured in benzene at 20 °C. The reactions with benzylamine are not base-catalysed. The second-order kinetic constant for the reactions with N-benzylmethylamine, with the exception of the unsubstituted compound (X = H), increases in a hyperbolical way with increasing nucleophile concentration. A non-linear regression treatment of kinetic data allows the calculation of k1 and k3B/k–1 for each catalysed system. k3B/k–1 is not a monotonic function of the X substituent. This result has been rationalised on the grounds of a specific base–general acid (SB–GA) mechanism for the base catalysis.