title: Sub- and post-micellar catalytic and inhibitory effects of cetyltrimethylammonium bromide in the permanganate oxidation of phenylalanine.
abstract: The kinetics of phenylalanine (phe) oxidation by permanganate has been investigated in absence and presence of cetyltrimethylammonium bromide (CTAB) using conventional spectrophotometric technique. The rate shows first- and fractional-order dependence on [MnO(4)(-)] and [phe] in presence of CTAB. At lower values of [CTAB] (< or =10.0x10(-4)moldm(-3)), the catalytic ability of CTAB aggregates are strong. In contrast, at higher values of [CTAB] (> or =10.0x10(-4)moldm(-3)), the inhibitory effect was observed in absence of H(2)SO(4). We find that anions (Br(-), Cl(-) and NO(3)(-)) in the form of sodium salts are strong inhibitors for the CTAB catalyzed oxidation. Kinetic and spectrophotometric evidences for the formation of an intermediate complex and an ion-pair complex between phe and MnO(4)(-), CTAB and MnO(4)(-), respectively, are presented. A mechanism consistent with kinetic results has been discussed. Complex formation constant (K(c)) and micellar binding constant (K(s)) were calculated at 30 degrees C and found to be K(c)=319mol(-1)dm(-3) and K(s)=1127mol(-1)dm(-3), respectively.
authors.affiliation: Department of Chemistry, Aligarh Muslim University, UP, India.
authors.forename: Zoya
authors.initials: Z
authors.lastname: Zaheer
authors.lastname: Rafiuddin
mesh_terms: D002384:Catalysis; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000494:pharmacology*; D017895:Manganese Compounds / Q000737:chemistry; D008823:Micelles; D010084:Oxidation-Reduction / Q000187:drug effects; D010087:Oxides / Q000737:chemistry; D010649:Phenylalanine / Q000737:chemistry*
chemical_list: D002593:Cetrimonium Compounds; D017895:Manganese Compounds; D008823:Micelles; D010087:Oxides; C048856:permanganic acid; D010649:Phenylalanine; D000077286:Cetrimonium