Tautomerization Equilibria in Aqueous Micellar Solutions:  A Spectrophotometric and Factor-Analytical Study

Abstract

The keto-enol equilibria of benzoylacetone (BZA) as a model for 1,3-dicarbonyl compounds are studied in aqueous acid and cationic micellar solution. Evolving factor analysis (EFA), multivariate curve resolution-alternating least-squares (MCR-ALS), and rank annihilation factor analysis (RAFA) are used for complete resolving of measured spectrophotometric data. The acidity constants of the enolic, KaE, and ketonic, KaK, forms of BZA and also the tautomerization constant, Kt, and its related thermodynamic parameters have been determined by using EFA and MCR-ALS methods and spectral variation of BZA solutions in various pHs and temperatures. The concentration and spectral profiles of all species were calculated without any assumption about chemical models. The spectral variation of BZA solutions as a function of cationic micelle concentration sufficiently beyond its critical micelle concentration is analyzed according to the partition model for distribution between water and micellar pseudo-phase and RAFA. The outputs of using RAFA on measured rank deficient data are the spectrum of enolic form in the micellar pseudo-phase, free from contribution of the enolic form in the aqueous phase, the partition coefficient of enolic form, KdE, between the micelle and water phases, and the tautomerization constant in the micellar pseudo-phase, Ktm.

Electronic effects on keto–enol tautomerism of p-substituted aryl-1,3-diketone malonates

“…when X ¼ H a DH lowest value results in À0.9019 kcal/mol and the highest difference is found when X ¼ Ph group (À1.4644 kcal/mol). These results are in good agreement with the experimental value of À2.0 kcal/mol for the keto-enol equilibria of benzoylacetone in an aqueous and liquid-micellar phase obtained by Abdollahi and Vahideh Mahdavi [33]. In terms of DS (Table 8), the calculated values for the tautomerization process of diketone malonates 1e9 are in the range of À1.03 to À2.5 e.u., which are close to the values (3.31e6.66 e.u.)…”

Chemometrics: An important tool for monitoring interactions of vitamin B7 with bovine serum albumin with the aim of developing an efficient biosensing system for the analysis of protein

“…Abdollahi and Mahdavi illustrate how concentration profiles obtained from EFA may be used as initial estimates for the concentration matrix input in the constrained ALS optimization [18]. PCA, an alternative approach to EFA, is a common chemometrics tool; it yields the number and direction of the relevant sources of variation in a bilinear data set [19].…”

A perspective on the growth of chemometrics in Iran: a glance into activities between 2005 and 2012

“…They published these two works in one of the top chemistry journals, Analytical Chemistry [3,4]. The research group of Abdollahi has developed different factor analysis-based curve resolution methods to resolve different chemical systems [27][28][29][30][31]. Tautomerization equilibria in aqueous micellar solutions and acid dissociation equilibria in mixed solvent media were studied using factor analysis methods by this group [27,29,32].…”