Study of Methionine and Cumene Hydroperoxide Reaction Kinetics in the Presence of Nonionic Surfactant

The kinetics of the reaction methionine+cumene hydroperoxide in the presence of nonionic surfactant was studied both in the pre-micellar and post-micellar regions at different temperatures by iodometry. It was established that the rate of the methionine + cumene hydroperoxide reaction depends on the molecular/ionic/micellar form of surfactant in the reaction system. In the post-micellar region the rate of methionine+cumene hydroperoxide reaction slows down due to solubilization of the reacting substances in the micelles. Quantification of solubilization of cumene hydroperoxide and methionine in the micelles has been studied by HPLC analysis. It was obtained that about 30% of cumene hydroperoxide, which is more hydrophobic than methionine, is solubilized in the micelles, as a result the concentration of cumene hydroperoxide in the reaction environment decreases and the rate of reaction in the post-micellar region also decreases. Based on the kinetic studies the reaction rate constant was determined and the value of activation energy was obtained.

Kinetic study of the metal-dipeptide complex with ninhydrin facilitated by gemini (m-s-m) surfactant micelles

The three Gemini (m-s-m; m (head group) = 16 and s (spacer) = 4, 5, 6) surfactants have been synthesized and their impact on reaction of zinc(II)-glycylleucine complex ([Zn(II)-Gly-Leu]⁺) and ninhydrin were studied at temperature (343 K) and pH (5.0) using spectroscopic method. Influence of several factors, viz., [Zn(II)-Gly-Leu]⁺, [ninhydrin], temperature and pH were also carried out on title reaction in geminis. Rates of reaction are the first-order path in concentration of [Zn(II)-Gly-Leu]⁺ complex and fractional order path in concentration of ninhydrin. The catalysis of gemini 16-s-16 surfactant micelles was investigated below and above their critical micelle concentration (cmc) value and detailed elaboration were provided in the text. In the present case, rate constants, k_ψ, increased on increasing geminis ([gemini] are below their cmc, region I) and stayed nearly constant (region II). The shape of (region I and II) surfactants ([gemini] = 0 to 400 × 10^-5 mol dm^-3) are similar to a cetyltrimethylammonium bromide, CTAB (single hydrophilic head group and hydrophobic part). Later, a sharp increment in rate was observed with higher [gemini] (region III, (Fig. 5). The study was catalyzed and accelerated quite enough by geminis (at concentrations below their cmc) compared to aqueous. An appropriate mechanism has been proposed for accounting for the distribution of reactants between aqueous and micellar pseudo phases. Resulting kinetic data were used to determine the binding constants of micelle-substrate (K_B) and micelle-ninhydrin (K_Nin).

Catalytic influence of 16-s-16 gemini surfactants on the rate constant of histidine and ninhydrin

The present paper reports the catalytic influence of 16-s-16 (spacer (s) = 4, 5, 6) gemini surfactants on the rate constant of histidine and ninhydrin at 343 K and pH 5.0 using the spectrophotometric technique. The effect of varying amounts of geminis was made on the rate constant of histidine and ninhydrin keeping other constituents constant. Characteristics of the rate constant (kψ ) versus [gemini] depict the effect of surfactants on the rate constant. A systematic explanation about the effect of surfactants is revealed and discussed in the text. The influence of different parameters that includes [reactants], temperature and pH has also been performed on the study. In order to determine the critical micelle concentration (cmc) of pure surfactants and their solution mixtures, conductivity measurement was employed. By using the Eyring equation, activation parameters at different temperatures have been obtained. The resultant data of kψ versus [gemini] plot were rationalized with the pseudo-phase model of micelles.

Influence of Cationic Cetyltrimethylammonium Bromide on Rate of Zn(II)-Histidine Complex and Ninhydrin

Paper analyses the influence of cationic cetyltrimethylammonium bromide on rate of Zn(II)-histidine and ninhydrin. UV-visible spectroscopy was applied to note absorbance of Zn(II)-histidine complex with ninhydrin at the end of reaction in the two systems. Rate constant, k_obs, (in aqueous) and rate constant, k_ψ, (in cetyltrimethylammonium bromide, CTAB) were determined by computer software. Reactions depict first-order in Zn(II)-histidine concentration and fractional-order in ninhydrin concentration in aqueous and micellar media. The results achieved indicate that the reactions take place principally by the same reaction mechanism in both the media. Critical micelle concentration of CTAB surfactant was calculated by recording the conductivity as a function of surfactant concentrations. Influence of various amounts of surfactant on Zn(II)-histidine complex and ninhydrin reaction was performed under different reaction conditions. Reaction was catalyzed and accelerated efficiently by surfactant medium compared to aqueous medium. The observed influence of surfactant on rate has been mentioned in details and their quantitative treatment of kinetic results have been deduced by the means of Menger and Portnoy model for micellar catalysis.

Application of Oxidative Fatty Acid Esters in Amino Acid Surfactants

The amino acid surfactants were synthesized by using natural fatty acid esters (FAE) as raw materials, but FAE with a high iodine value has thermal and oxidative instabilities in chemical reactions. The oxidation of FAE by peroxyacetic acid generated was studied under various conditions, then the oxidized FAE and different amino acids (glycine, glutamic acid and aspartic acid) were used to form sodium N-acyl amino acids in glycerol. By the surface tension method, the relationship between temperature and critical micelle concentration (CMC) has been researched. The CMC value, the surface tension at the CMC (γCMC), and the maximum surface excess concentration Γmax were calculated, respectively. For different amino acids surfactants, the surface tension of the solution was greatly reduced at the low CMC value, and the γCMC constantly decreases with rising temperature.

Study of Zinc-glycylglycine Complex with Ninhydrin in Aqueous and Cationic Micellar Media: A Spectrophotometric Technique

Studies of the interaction between the zinc-peptide complex ([Zn(II)-Gly-Gly]+) and ninhydrin in aqueous and CTAB surfactant media were executed by the means of UV-visible spectrophotometry. The reaction rates (k obs and k ψ) were determined in both media by varying different parameters such as pH, temperature and the concentration of the reactants and CTAB. The micellar binding constants and activation parameters were also calculated. The catalytic activity in the CTAB medium was found to be better than in the aqueous medium on the title reaction. The catalysis by CTAB is treated quantitatively by applying the model of the kinetic pseudo-phase of the micelle. Variation of the rate constant with the change of the CTAB concentration was used for the calculation of several kinetic parameters such as the binding constants (K B and K Nin) and the micellar rate constant k m. On basis of the experimental results, a probable mechanism is proposed.

Study of the reaction of ninhydrin with tyrosine in gemini micellar media

This paper reports the study of the ninhydrin and l-tyrosine (Tyr) reaction in gemini micellar media. The aim of the study was to see the influence of different parameters on the reaction rate, including the influence of reactant concentration, temperature and pH. Spectrophotometric and conductometric techniques were employed to record the absorption of the product formed and cmc values as a function of the surfactants, respectively. The effect of varied surfactant concentrations on the reaction rate was also investigated. The quantitative treatment of the rate constant (k_ψ) vs. surfactant concentration was carried out on the basis of the pseudo-phase model suggested by Martinek et al., Menger and Portnoy, and established by Bunton. Micellar binding parameters and thermodynamic parameters have been calculated and are discussed in detail. A plausible reaction mechanism that is consistent with observed kinetic data has been proposed.

The importance of the study increased due to the use of a very small quantity of gemini surfactant required to perform the reaction.