Catalysis of trinitrobenzene–anilide σ-complex formation and decomposition in dimethyl sulphoxide in the presence of tetraethylammonium chloride and perchlorate
- 1 January 1978
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 7,p. 673-677
- https://doi.org/10.1039/p29780000673
Abstract
The effect of tetraethylammonium chloride and perchlorate on the reaction TNB + PhNH2+ DABCO ⇆ TNB,NHPh–+ DABCO,H+, in dimethyl sulphoxide at 25°, has been investigated. The equilibrium constant for σ-complex formation increases by 340-fold on increasing [Et4NCl] from 0 to 1.2M. This increase in K results from a 2.5-fold increase in the forward rate constant and a 140-fold decrease in the reverse rate constant. The corresponding changes in these parameters obtained with Et4NClO4 are modest though in the same direction. The effect observed with Et4NCl is larger than in past studies of electrolyte effects on σ-complex formation and decomposition, or in SNAr processes. The catalytic effect of Et4NCl in the present system is ascribed to association of Cl– with the conjugate acid of DABCO to yield the DABCO,H+⋯ Cl– heteroconjugate complex with consequent decrease in the rate of the reverse reaction.Keywords
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