• S Sundaram

      Articles written in Journal of Chemical Sciences

    • Kinetics of chlorination of ketones by 1-chlorobenzotriazole

      P S Jayaraman S Sundaram N Venkatasubramanian

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      The kinetics of chlorination of aliphatic, aralkyl and alicyclic ketones by 1-chlorobenzotriazole (cbt) have been studied in aqueous acetic acid media. In the presence of a mineral acid (HClO4), the order of the reaction with respect to [ketone] is one and that with respect to [cbt] is zero, suggesting the enolisation of ketone as the slow step, followed by a fast attack of the halogenating species. A primary kinetic isotope effect (kH/kD=6·6) is also noticed, when acetone and acetone-d6 are used as the substrates. Initial addition of chloride ion leads to a first order dependence on [cbt] and a fractional order (0·6) on [acetone]. Thermodynamic parameters for the reaction have also been reported. A negative Hammett reaction constant (ρ=−0·57) has been obtained for the halogenation of substituted acetophenones bycbt.

    • Alkaline hydrolysis of arylesters of diphenylphosphorodiamidates—evidence consistent with an elimination—addition mechanism

      P Krishnan S Sundaram N Venkatasubramanian

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      The alkaline hydrolysis of a series of aryl phosphorodiamidates has been studied in aqueous ethanol and aqueous DMSO mixtures. Although the reactions do not show any saturation kinetics with respect to the hydroxide ion, the low solvent isotope effect, the highly negative Bronsted β value, the large Hammett ρ for the leaving aryloxy group and the decrease in rate with increase in the proportion of DMSO in the solvent mixtures indicate that the hydrolysis proceeds by an elimination-addition pathway. Comparison of rate data with other hydrolytic E1CB reactions show that the title reaction belongs to the (E1CB)R category.

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