Evidence of co-operativity in the pre-micellar region in the hydrolytic cleavage of phenyl salicylate in the presence of cationic surfactants of CTAB, TTAB and CPC

Effect of microheterogeneous environments of CTAB, Triton X‐100, and Tween 20 on the oxidative degradation of d‐fructose by nanoparticles of MnO2

“…In the presence of surfactants, hydrophobic and electrostatic interactions occur between the reactants and the surfactant monomers/aggregates, which may either favor or restrict the movement of the attacking reagent and thus the rate of the reaction is either enhanced or retarded . For all the three surfactants, there is an initial decrease of the reaction rate with an increase in [surfactant].…”

“…In case of TX‐100 and Tween 20, there may be interaction between the –OH groups of fructose and the polar oxyethylene groups and the –OH groups of the surfactant monomers through H‐bonding. Such interactions may lead to the formation of small aggregates, called premicelles, which may either sterically or entropically inhibit the approach of the oxidant, thus decreasing the reaction rate. It is evident from Figure that there is either a hump or a maximum near the CMC when both the reactants become associated with the micelle and come in the vicinity of each other, and beyond this point k ψ decreases slowly with further increase of [surfactant], possibly due to lowering of concentrations of both the reactants within the micelle (known as dilution effect).…”

Study on catalytic property of NaOH-cationic surfactant solutions for efficient, green and selective synthesis of flavanone

“…The quaternary ammonium group of QAS can interact with benzaldehyde molecules through carbonyl oxygen (Scheme 5i [5b]) making carbonyl carbon more electrophilic for reaction with enolate ions of HAP. Similarly, the quaternary ammonium group of QAS can also interact with HAP through carbonyl group [15] as well as through phenoxide (PhO − ) oxygen [10] (Scheme 5ii). The interaction of carbonyl group of HAP with positively charged head group of QAS can activate the HAP for enolization [15].…”

“…The intermolecular gape/space can be beneficial in the accommodation of reactant molecules at interface for reaction and also for better accessibility of OH − ions to HAP molecules present in micellar interface. Pratik et al [10] demonstrated lesser interference of the C 16 PQAS molecules than other QASs (C 14 and C 16 surfactants) at interface in the hydrolysis of phenyl acetophenone because of planner pyridinium head group showing less hindrance in approach of water molecules for nucleophilic attack at ester group. This shows that as compared to other QASs, C 16 PQAS micellar system (at 0.25 mM) possesses optimum properties and/or microenvironment (hydrophobicity, intermolecular packing, etc.)…”

“…In premicellar solutions, the reactions are accelerated due to either complexation of the substrate with surfactant monomers or pre-micelles or to substrate induced formation of micelles; and the decreased reaction rate at high surfactant concentration has been ascribed to dissolution/strong binding of reactant molecules in the micelles [9]. Pratik et al [10] reported the inhibition of hydrolysis of phenyl salicylate in the cationic surfactant solutions having surfactant concentration below CMC suggesting a pre-micellar aggregation between the substrate and surfactant monomers, which protects the ester group from water hydrolysis.…”