Enols as intermediates in nitrosation and halogenation of malonamide and malonic acid

TL;DRAbstract

Catalysed nitrosation of malonamide(MA) was carried out in aqueous acidic solution at 25ºC. In the presence of bromide ion as a catalyst, the reaction was always first order in [HNO(_2)] despite the changes in acidity. However, the kinetic behaviour of SCN(^-) catalysed reaction varied from first order to zero order with [SCN(^-)], suggesting that the reaction occurs via an enol intermediate and the rate limiting step can move from enolisation to nitrosation under certain conditions. lodination and bromination of malonamide were investigated in aqueous acidic solution at 25ºC. At low acidity, the iodination of malonamide was zero order in [I2], which is in good agreement with the proposed mechanism where the reaction occurs via an enol intermediate and enolisation is the rate limiting step. The deuterium isotope effect on iodination of malonamide was also examined and the result strongly confirmed the existence of enol form in the reaction. The acid catalysed enolisation can be expre

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