Effect of Cationic Micelles on the Kinetics of Interaction of Ninhydrin withl-Leucine andl-Phenylalanine

J of Physical Organic Chem

Rub

Akram

et al. 2014

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.

“…

M_{nin}^{S}

Section: Resultsmentioning

confidence: 99%

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

J of Physical Organic Chem

Rub

Akram

et al. 2014

“…Other required information related to kinetic experiments could be found in articles. [31][32][33][34][35][36] 3 | RESULTS AND DISCUSSION…”

Section: Kinetic Measurementsmentioning

confidence: 99%

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

J of Physical Organic Chem

Rub

2019

Kinetic and mechanistic investigations of [Zn (II)‐Trp]+ and ninhydrin in aqueous and cationic cetyltrimethylammonium bromide (CTAB) surfactant have been executed in CH3COOH‐CH3COONa buffers of pH 5.0. Spectrophotometric as well as conductometric techniques were employed to carry out the study at experimental temperature. The values of rate constant (kobs in aqueous and kψ in CTAB surfactant) and binding parameters (KB for [Zn (II)‐Trp]+ and KN for ninhydrin) have been determined by the means of a computer program referred to as linear least squares technique. Fractional‐ and first‐order kinetics were found in ninhydrin and [Zn (II)‐Trp]+, respectively, in aqueous and cationic CTAB. Study was catalyzed and accelerated by CTAB surfactant. An increase in CTAB surfactant concentration from 0 to 45 mmol kg−1 resulted to an increase in kψ from 2.5 × 10−5 s−1 to 22.7 × 10−5 s−1. Surfactant concentration beyond 45 mmol kg−1 had a slow decreasing effect in kψ. In order to elucidate CTAB effect on kψ, a pseudo‐phase model of micelles was applied.

“…To improve their performance, surfactants are generally used in the presence of additives. Studies on surfactants and their mixtures with a variety of additives in aqueous solutions are therefore of interest regarding their technical applications (24)(25)(26). The presence of grown micelles imparts high viscosity to solutions, which might be of importance in industrial formulations as it enhances performance and customer appeal of the products.…”

mentioning

confidence: 99%

Micellar association in simultaneous presence of organic salts/additives

Khan

Kabir-ud-Din

2002

J Surfact & Detergents

Self Cite

Viscosity measurements under Newtonian flow conditions had been performed on cetyltrimethylammonium bromide (CTAB) aqueous solutions in the combined presence of sodium salts of aromatic acids (sodium salicylate, NaSal; sodium benzoate, NaBen; sodium anthranilate, NaAn) and organic additives (1-hexanol, C 6 OH; n-hexylamine, C 6 NH 2 ) at 30°C. On addition of C 6 OH or C 6 NH 2 , the viscosity of 25 mM CTAB solution remained nearly constant without salt as well as with a lower salt concentration. This is due to low CTAB concentration which is not sufficient to produce structural changes in this concentration range of salts. However, as the salt concentration was increased further, the effect of C 6 OH/C 6 NH 2 addition was different with different salts: The viscosity first increased; then a decrease was observed with the former while with C 6 NH 2 a decrease followed by constancy appeared in plots of relative viscosities (η r ) vs. organic additive concentrations. At further higher salt concentration, the magnitude of η r was much higher. The viscosity increase is explained in terms of micellar growth and the decrease in terms of swollen micelle formation (due to interior solubilization of organic additive) or micellar disintegration (due to formation of water + additive pseudophase).Paper no. S1267 in JSD 5, 55-59 (January 2002).Numerous studies have been carried out on the effect of salts (1-3) and organic additives (4-6) on the micellar structural transitions in aqueous medium. Recently, we reported a kind of "synergism" (e.g., significant increase in viscosity) in such systems when salts and organic additives are present concurrently in the micellar solutions (7-11). In these studies the nature of salts and additives was found to play a crucial role toward such synergisms.Micelles of quaternary ammonium halides [e.g., cetyltrimethylammonium bromide (CTAB)] grow from spherical to rod-shaped on the addition of different counterions (12). Halide anions associate only moderately with surfactant headgroups, and micellar growth is gradual. However, with anions that associate strongly, such as aromatic salt anions (e.g., salicylate, Sal − ), rod-shaped micelles grow rapidly even at low surfactant and salt concentrations (13), and the solutions exhibit a remarkable viscosity increase (14,15).Aqueous micelles are capable of solubilizing organic molecules with quite distinct polarities and degrees of hydrophobicity (16). The addition of different types of molecules leads to large deviations of packing parameters in micellar assembly (17). Many counterions and organic additives are strongly adsorbed at the micellar interface, and depending on the degree of penetration, this may change the mean distance between polar headgroups or may increase the volume of the micellar core. The aromatic acid counterions are most efficient with cationic micelles. 1 H nuclear magnetic resonance (NMR) studies have shown that the Sal − anion orients in such a way that the negatively charged site (COO − group) stands perpendicular to the CT...