Effect of Ethanol on Micellization and on Decarboxylation of 6-Nitrobenzisoxazole-3-carboxylate in Aqueous Cationic Micelles

• Published in: Journal of colloid and interface science Vol. 247; no. 2; pp. 429 - 436
• Main Authors: Brinchi, Lucia, Di Profio, Pietro, Germani, Raimondo, Savelli, Gianfranco, Spreti, Nicoletta
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 15.03.2002; Elsevier
• Subjects: Chemistry; Colloidal state and disperse state; decarboxylation; ethanol; Exact sciences and technology; General and physical chemistry; micelles; Micelles. Thin films; micelles; ethanol; decarboxylation; Nitro compound; Five membered ring; Ethanol; Cationic surfactant; Micelle; Alcohol; Quaternary ammonium compound; Micellar critical concentration; Decarboxylation; Alkanol; Carboxylate; Bicyclic compound; Aromatic compound; Oxygen nitrogen heterocycle; Micellization
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.2001.8053

The effects of ethanol on the critical micellar concentration (cmc) and the rates of decarboxylation of 6-nitrobenzisoxazole-3-carboxylate (6-NBIC) have been investigated in aqueous cationic surfactants of the cetyltrialkylammonium family with bromide [CT(R)ABr], chloride [CT(R)ACl], and nitrate [CT(R)ANO3] counterions, and methyl (CTAX), n-propyl (CTPAX), and n-butyl (CTBAX) as the head group alkyl moieties. Effects upon cmc and reactivity are similar, featuring a break at the ethanol mole fraction, xEtOH, of ca. 0.055; these effects have been related to changes in solvent structure, with formation of a clathrate at xEtOH=0.055. Rate data in CTBABr were further investigated and fitting of raw kinetic data to the pseudophase model is possible up to xEtOH=0.1, showing an unexpected decrease of rate constant values in the micellar pseudophase, k′M, as ethanol content increases: a significant variation of micellar ionization degree could account for this kinetic effect.