• V Raj

      Articles written in Journal of Chemical Sciences

    • Guest-host interactions in the cleavage of phenylphenyl acetates by 𝛽-cyclodextrin in alkaline medium

      V Raj T Chandrakala K Rajasekaran

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      Kinetics of cleavage of phenylphenyl acetates (PPA) and several para-substituted PPAs in basic aqueous sodium carbonate-bicarbonate buffer containing 𝛽-cyclodextrin (CD) have been studied. The reaction exhibits saturation type kinetics and CD accelerates the rate of cleavage by the formation of 1G : 1H inclusion complex. The kinetic results indicate that aryloxy moiety of PPA is included in the hydrophobic cavity of CD. The overall rate constants for the cleavage of the [CD-ester] complex correlate with the Hammett 𝜎-constants and Hansch hydrophobicity parameters 𝜋. At higher concentrations of CD, there is an additional catalysis due to the formation of weak 1G : 2H complex.

    • Guest-host interactions in the alkaline bleaching of triphenylmethane dyes catalysed by 𝛽-cyclodextrin

      V Raj A Sarathi T Chandrakala S Dhanalakshmi R Sudha K Rajasekaran

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      The rates of alkaline bleaching of triphenylmethane dyes crystal violet (CV), malachite green (MG) and rosaniline (RA) have been measured spectrophotometrically in an aqueous medium at 30°C in the presence of 𝛽-cyclodextrin (CD). At lower concentrations of CD, CV forms productive 1 : 1 (G : H) complex. At higher concentrations of CD, it forms unproductive 1 : 2 (G : H) complex. For the bleaching of MG, CD accelerates or decelerates the rate depending on pH of the medium by forming 1 : 1 (G : H) inclusion complex. Analysis of rate data shows that MG undergoes fading by mixed order process. CD decelerates the water reaction and accelerates hydroxide ion reaction. In the case of RA, both water reaction as well as hydroxide ion reaction are retarded by CD by the formation of inclusion complex.

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