Effect of cationic and anionic surfactants on the addition-elimination-type interaction between o-toluidine and D-glucose

The kinetics of the o-toluidine-D-glucose reaction has been studied as a function of [o-toluidine], [D-glucose], [acetic acid], and temperature by UV-visible spectrophotometry at 630 nm in the absence and presence of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS). The reaction follows second-order kinetics, being unity in each of the reactants in both media. The effect of added surfactants has also been investigated. The model of micellar catalysis, such as the Menger-Portony model modified by Bunton, is applied to explain the catalytic role of CTAB and SDS micelles. The association/incorporation constants (K-s and K-n), the rate constant in micellar media (k(m)), and the activation parameters of this system have been calculated and discussed. The value of the rate constant is found to be higher in SDS than in CTAB. Hydrophobic and electrostatic interactions are responsible for higher reaction rates in SDS. From all observed facts, a reaction mechanism involving a nucleophilic addition-elimination path has been suggested.