Study of metal-amino acid [Cr(III)-Trp]²⁺ complex and ninhydrin reaction: role of gemini micellar solution on rate constant

Abstract

In this article, the study of metal-amino acid complex and ninhydrin reaction was examined in gemini micellar solution using a UV-visible spectrophotometric measurement. The role of varying amounts of gemini micellar systems on rate constant of the study was investigated. Initially, rate constant (k_ψ) enhances, below cmc and levelling-off areas are, then, noticed up to 400 × 10⁻⁵ mol dm⁻³. Later, gemini offers a third region of fast enhancement k_ψ above 400 × 10⁻⁵ mol dm⁻³. Gemini surfactant series provided more efficient implications on the study than pure water and their monomeric traditional surfactant system. The values of rate constant, k_ψ, were determined under a set of different experimental reaction situations with the help of a computer-based procedure. Such unfamiliar behaviour developed by gemini micellar solutions was treated by pseudo-phase model of micellar activity. An electrical conductometric measurement was employed to measure critical micellar concentration (cmc) of pure gemini micellar solutions and mixed systems. Several activation parameters were also determined by Eyring’s equation and different constants. Data obtained confirmed that lower values of activation enthalpy (ΔH^#) with large negative activation entropy (ΔS^#) were attained in gemini than aqueous. A plausible reaction mechanism of the study has been discussed and proposed.

GRAPHICAL ABSTRACT

KEYWORDS:

• Gemini surfactants
• interfacial phenomenon
• micellar activity
• ninhydrin
• rate constant

Acknowledgement

This project was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, Saudi Arabia under grant no. (KEP-51-130-38). The authors, therefore, acknowledge with thanks DSR technical and financial support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This project was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, Saudi Arabia under grant no. (KEP-51-130-38). The authors, therefore, acknowledge with thanks DSR technical and financial support.