Abstract
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.
Highlights
Surfactants contain a polar head and a non-polar
Spectra on the rate constant of histidine and ninhydrin in pure water and surfactants were measured after completion of reaction over a wavelength range 350–650 nm using a quartz cuvette with 1 cm path length
The influence of pH on kψ on ninhydrin and histidine reaction was seen at several pH varying from 4.0 to 6.0 at constant histidine, ninhydrin and temperature (343 K) in gemini system ([16-s-16] = 30 × 10−5 mol dm−3). kψ increases with pH up to 5.0
Summary
Surfactants contain a polar head (hydrophilic group) and a non-polar (hydrophobic hydrocarbon tail). They have been employed in several aspects of chemical, biological and industrial processes [1,2,3,4,5]. Surfactants aggregate frequently and catalyse the chemical reactions, but they inhibit reactions. Micelles affect reaction rate owing to numerous aspects [6]. A little alteration in the structure of micelle induces variations in surface properties and rigidity of micelles; it alters the reactants’ activity [7,8,9]. Micelles offer several unusual media for different parts of the reactants. Solubilization of micellar environment could serve as a key part in micellar catalysis of a chemical royalsocietypublishing.org/journal/rsos R.
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