Polyethylene Glycol–Cationic Surfactant Interactions and Their Influence on the Hydrolytic Behavior of Bis (4‐Nitrophenyl) Phosphate

ABSTRACT

The micelle‐mediated hydrolysis of bis(4‐nitrophenyl) phosphate (BNPP) with butane 2,3‐dione oxime (BDMO) and benzohydroxamic acid (BHA) in cationic surfactant systems that are cetyldiethylethanolammonium bromide (CDEEAB) and cetyldimethylethanolammonium bromide (CDMEAB) in the presence of various polyethylene glycols (PEG 400–6000) has been investigated at pH 11.0. The observed rate constants ( k _obs ) were analyzed as functions of increasing surfactant concentration at fixed concentrations (1% and 5%) of PEG with both surfactants. Variations in PEG (400–6000) molecular weight modulate micellar organization and binding efficiency, thereby modulating the micellar rate constant. The study demonstrated that the kinetic hydrolysis of BNPP with BDMO and BHA in CDEEAB and CDMEAB exhibited an enhanced reaction rate with larger molecular weights of PEG, specifically 6000 and 4000, compared to lower molecular weights of 400 and 600. The synergistic effects of micellar binding and PEG‐dependent modulation of micellar microviscosity result in significant rate enhancement, reflected by increased pseudo‐first‐order rate constants. The kinetic data were fitted to the pseudo‐phase micellar model.