Kinetics and mechanism of interaction of dipeptide (glycyl–glycine) with ninhydrin in aqueous micellar media

✍ Scribed by Mohd. Akram; Neelam Hazoor Zaidi; Kabir-ud-Din

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 170 KB
• Volume: 38
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.20195

✦ Synopsis

Abstract

The rates of reaction between ninhydrin and dipeptide glycyl–glycine (Gly–Gly) have been determined by studying the reaction spectrophotometrically at 70°C and pH 5.0 in aqueous and in aqueous cationic micelles of cetyltrimethylammonium bromide (CTAB). The reaction follows first‐ and fractional‐order kinetics, respectively, in [Gly–Gly] and [ninhydrin]. The observed rate constant is affected by [CTAB] changes and the maximum rate enhancement is ca. three‐fold. As the k~ψ~ − [CTAB] profile shape is characteristic of bimolecular reactions catalyzed by micelles, the catalysis is explained in terms of the pseudo‐phase model of the micelles (proposed by Menger and Portnoy and developed by Bunton and Romsted). The presence of inorganic salts (NaCl, NaBr, Na~2~SO~4~) does not reveal any regular effect but the data with organic salts (NaBenz, NaSal) show an increase in the rate followed by a decrease. The kinetic data have been used to calculate the micellar binding constants K~S~ for Gly–Gly and K~N~ for ninhydrin and the respective values are 317 and 69 mol^−1^ dm^3^. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 643–650, 2006