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Kabir-ud-Din ¹, Manzoora Bano ¹, Iqrar A. Khan ¹

Affiliations
1 Department of Chemistry, Aligarh Muslim University, Aligarh-202 002, IN

Abstract

The cationic micelles of cetyltrimethylammonium bromide (CTAB) have been found to catalyse the reaction between L-glutamic acid and ninhydrin. The product spectra show peaks at 400 and 570 nm in each medium indicating formation of the same species. A kinetic study of the reaction has been made in aqueous, aqueous-organic and micellar media. Under the pseudo-first-order conditions of excess ninhydrin, the reaction rate was first-order in [glutamic] acid and fractional order in [ninhydrin] both in aqueous and micellar media. The kinetic data in micellar medium have been analysed using the pseudo-phase model. Furthermore, the reaction is catalysed by organic solvents.

Keywords

L-Gltamic Acid, Ninhydrin, Organic Solvents, Kinetics, CTAB, Catalysis.

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Kabir-ud-Din ¹, Waseefa Fatma ¹

Affiliations
1 Department of Chemistry, Aligarh Muslim University, Aligarh - 202 002, IN

Abstract

The kinetics of the reaction of ninhydrin and DL-tryptophan has been carried out in TX-100 micellar media at 40°C and pH 5.0 (sodium acetate-acetic acid buffer). The reaction rate increased with increase in [TX-100] and the rate constant - [surfactatant] data are analysed using the modified Menger and Portnoy pseudo-phase model. The rate constant in the micellar medium (K_m) and micelle binding constants of ninhydrin (K_N) aid DL-tryptophan (K_S) are evaluated.

Keywords

Ninhydrin, DL-Tryptophan, Kinetics, Micellar Catalysis, TX-100.

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Sanjeev Kumar ¹, Daksha Sharma ¹, Kabir-ud-Din ¹

Affiliations
1 Department of Chemistry, Aligarh Muslim University, Aligarh-202002, IN

Abstract

The effect of addition of symmetrical quaternary bromides (tetramethylammonium bromide, Me₄NBr; tetraethylammonium bromide, Et₄NBr; tetra-n-propylammonium bromide, Pr₄NBr; tetra-n-butylammonium bromide, Bu₄NBr; tetra-n-butylphosphonium bromide, Bu₄PBr, and tetraphenylphosphonium bromide, Φ₄PBr) on the micellization of sodium dodecylbenzenesulphonate (SDBS) has been studied at 25 °C using conductivity measurements. The critical micelle concentration (CMC) and dissociation degree (β) are determined from the conductivity vs. [surfactant] plots at various fixed [salt]. As usual, the presence of salts bring about a reduction in CMC but salts containing bulky counterions show progressively increased effect both on CMC and β. A bulky counterion seems to weaken hydration forces with concomitant decrease in the CMC. The behaviour is further explained in the light of hydrophobic interactions (among alkyl/phenyl chains of the concerned salt and surfactant) in addition to the neutralization of surface charge due to salt addition. Connecting atom (N or P) of the counterion seems to play an important role in such interactions as salts with P were more effective in reducing the CMC and thus seem to be the ideal candidate to vary hydration forces in the anionic surfactant systems.

Keywords

SDBS, CMC, Quaternary Bromide, Conductivity, Counterion Dissociation.

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