Studies on Kinetics of Hydroxylation of p-Rosaniline Hydrochloride by Sodium Hydroxide in Micellar Environment

Abstract

Basic hydrolysis of p-rosaniline hydrochloride in presence of solution
of anionic surfactant, e.g., sodium dodecyl sulphate (SDS), cationic surfactant,
e.g., hexadecyl trimethyl ammonium bromide (C₁₆TABr) and nonionic
surfactant, e.g.,  triton X-100 has been studied. C₁₆TABr is known to
increase the rate of reaction of triphenyl metIiyl carbonium ions with the
hydroxide ion, where as the anionic micelles of SDS and non-ionic of
TX-100 inhibit this rate. At lower concentration of NaOH, reaction rate
increase rapidly with cationic surfactant concentration and with increasing
hydroxide ion concentration, an inhibition effect is observed for all surfactant
concentrations studied. The addtion of monohydric alcohol, viz.,
ethanol, n-propanol, n-butanol and solvent like acetone and ethylene glycol
decreases the cationic micellar catalysed rate of carbinol formation and on
the other hand increase the anionic micellar inhibited rate. The effectiveness
of these solvents in reducing the extent of overall inhibition by sodium
dodecyl sulphate has been found to follow the order: ethylene glycol <
n-propanol < n-butanol. These trends are discussed with reference to the
probable factors that are responsible for the change in the reaction rate in
the presence of organic solvents. The effect of polyethylene glycol has also
been investigated in the presence of C₁₆TABr. Effect of various salts, viz.,
KCI, KBr, KNO₃, K₂SO₄ and NaCI has also been studied on this reaction.