Kinetics of the Rapid Base Catalyzed Iodination of Imidazole and 2‐Methylimidazole by Molecular Iodine in Aqueous Medium: pH Effect

The study provides a quantitative framework for the assessment of the relative reactivity of thiazole and its two methyl derivatives namely 2-methylthiazole and 4-methylthiazole towards iodination reaction. Thiazole and its derivatives have a wide range of industrial and medicinal applications attributed to the ability of thiazole to manifest substituents around the core scaffold. The kinetic study of the iodination reactions of these substrates helps in the above applications since kinetics is an important investigational tool in configuring the mechanism of the reaction. In the present work, molecular iodine (I 2 ) and iodine monochloride (ICl) were used as reagents for the iodination of thiazole, 2-methylthiazole, and 4-methylthiazole in aqueous medium. The iodination reactions are rapid electrophilic substitution reactions and hence special technique known as hydrodynamic voltammetry was employed for the kinetic study. Iodine is the only electro-reducible species in the reactions. As the solution is devoid of iodide ions, a decrease in the concentration of iodine is measured in terms of diffusion current using a rotating platinum electrode with a saturated calomel electrode (SCE) as a reference electrode. The reactivity correlation of substrates towards iodination reaction was quantitively assessed by determining the reaction rate constants and thermodynamic parameters. The study shows overall rate of iodination of 4-methylthiazole is faster than 2-methylthiazole which is faster than thiazole. The study helps to develop a mechanistic approach considering the effect of substituent present on the thiazole ring. The order of reactivity of the reagents was determined based on obtained rate constants and explained owing to the nature of the reagent.

Section: Resultsmentioning

confidence: 99%

Section: Rate Law For the Iodination Reactionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Comparative quantitative kinetic study of rapid iodination of thiazole and its methyl derivatives in aqueous medium

Kad

Bhadane

Walke

2022

“…Halogenations of aromatic substrates in aqueous solution are pH‐dependent reactions 15 . Hence, a constant pH 7 has been used in the iodination of the regioisomers of nitroaniline by molecular iodine in aqueous medium devoid of iodide ions.…”

Section: Resultsmentioning

confidence: 99%

A novel ternary approach to quantitatively assess the reactivity of nitroaniline regioisomers by investigation of rapid iodination kinetics using hydrodynamic voltammetry, reduction propensities from polarography, and binding affinities from molecular docking simulations

Borkar

2021

A novel ternary approach to assess the reactivity of nitroaniline regioisomers on a quantitative scaffold has been manifested on the basis of three complementary tenets: kinetics, polarography, and molecular docking. Data from investigation of rapid iodination kinetics of nitroaniline regioisomers by hydrodynamic voltammetry in aqueous medium, reduction propensities of these regioisomers from polarography, and their binding affinities with hypoxanthine‐guanine phophoribosyltransferase (HPRT1) from molecular docking simulations lead to inferences regarding their reactivity that agree in entirety. The experimentally determined magnitudes of the specific reaction rates, energies of activation, collision frequencies, entropies of activation from kinetic studies, and reduction propensities of nitroaniline regioisomers from polarograms when complemented with in silico binding energies of these regioisomer ligands with the receptor enzyme, assess their relative reactivities in unison on a quantitative scaffold. This novel ternary approach unambiguously assesses the reactivity of the regioisomers of nitroaniline as 4‐nitroaniline > 2‐nitroaniline > 3‐nitroaniline.

“…Halogenations of aromatic substrates in aqueous solution are pH dependent reactions. 16 Hence, constant pH 7 has been used in the chlorination of the regioisomers of xylenol by molecular chlorine in aqueous solution. Molecular chlorine undergoes hydrolysis in aqueous solutions forming hydrogen ions, chloride ions and hypochlorous acid.…”

Section: Optimization Of the Reaction Conditionsmentioning

confidence: 99%

A quantitative assessment of the reactivity of the regioisomers of xylenol by investigation of rapid chlorination kinetics in aqueous solution employing hydrodynamic voltammetry complemented by molecular docking with acetylcholinesterase: A two‐pronged approach

Borkar¹

2020

Kinetic data is an elegant tool to quantitatively assess structure-reactivity correlation of organic substrates in reactions and is immaculate if endorsed with complementary information. Halogenations of aromatic substrates in aqueous medium are rapid reactions necessitating special techniques for their study. Their rates depend on nature of the reagents, nucleophilicity of the substrates, and steric compulsions involved. Herein, the rapid uncatalyzed chlorination kinetics of six regioisomers of xylenol by aqueous chlorine has been investigated using hydrodynamic voltammetry. These data have been supported with those obtained from molecular docking studies of the xylenol regioisomers with acetylcholinesterase in this two-pronged approach. The magnitudes of the velocity constants, energies of activation, frequency factors, and entropy of activation in these six reactions assess, quantitatively and unambiguously, the reactivity of the regioisomers of xylenol when complemented with the binding energy data obtained from molecular docking.