Role of gemini surfactants (m‐s‐m type; m = 16, s = 4–6) on the reaction of [Zn(II)‐Gly‐Phe]⁺ with ninhydrin

Abstract

aIn the present paper, reaction of zinc-glycylphenylalanine ([Zn(II)-Gly-Phe] + ) with ninhydrin has been investigated in gemini (m-s-m type; m = 16, s = 4-6) surfactants at temperature (70°C) and pH (5.0). Monitoring the appearance of product at 400 nm was used to follow the kinetics, spectrophotometrically. The order of the reaction with respect to [Zn(II)-Gly-Phe] + was unity while with respect to [ninhydrin] was fractional. The reaction constants involved in the mechanism were obtained. In addition to the rate constant (k Ψ ) increase and leveling-off regions are observed with the geminis, just like as seen with conventional surfactant hexadecyltrimethylammonium bromide (CTAB), the former produced a third region of increasing k Ψ at higher concentrations. A close agreement between observed and calculated rate constants was found under varying experimental conditions. A suitable mechanism consistent with the experimental findings has been proposed.

Kinetic and mechanistic investigations of [Zn (II)‐Trp]+ and ninhydrin in aqueous and cationic CTAB surfactant

“…The reaction mechanism for the title reaction was proposed as Scheme . This has established that electrons of a lone pair of amino group are required for nucleophilic attack on the carbonyl group of ninhydrin . But, attack by amino nitrogen electrons of lone pair is impossible because electrons are attached to zinc (II).…”

Diaryl Prolinols in Stereoselective Catalysis and Synthesis: An Update

“…[18a] In 2014 Shah and co-workers investigated the aldol reaction, catalyzed by α,α-L-diaryl prolinols, between aromatic aldehydes and acetaldehyde, which was in situ generated from hydrolysis of vinyl acetate operated by a lipase. [19] Lipase Novozym 435 in combination with (R)-bis(3,5-bistrifluoromethylphenyl)-prolinol ent-1 b afforded the best results when used in iPrOH at room temperature. More stable in situ reduced products 6 were isolated in high yields and enantioselectivity (Scheme 6).…”

Mixed micellization study of dodecyltrimethylammonium chloride and cetyltrimethylammonium bromide mixture in aqueous/urea medium at different temperatures: Theoretical and experimental view

“…Surfactants are organic compounds that contain both hydrophilic and hydrophobic parts in its structure, and they can form aggregation in aqueous solution because of hydrophilic‐lipophilic balance (HLB) . This aggregation behavior of the surfactants is observed after a certain concentration of the surfactants which is known as critical micelle concentration ( cmc ), and below this concentration monomeric form of the surfactant is predominated . The physico‐chemical properties of the surfactants aggregation, eg, cmc , degree of counterion dissociation, and thermodynamic parameters depend on HLB .…”