Determination of interfacial co-ion concentration in ionic micelles by chemical trapping: Halide concentration at the interface of sodium dodecyl sulfate micelles

被引:27
作者
Cuccovia, IM
AgostinhoNeto, A
Wendel, CMA
Chaimovich, H
Romsted, LS
机构
[1] UNIV ESTADUAL PAULISTA,IBILCE,INST FIS,S JOSE RIO PR,SP,BRAZIL
[2] RUTGERS STATE UNIV,DEPT CHEM,WRIGHT & RIEMAN LABS,NEW BRUNSWICK,NJ 08903
关键词
D O I
10.1021/la970389c
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Products from the spontaneous reaction of a long-chain arenediazonium salt, 2,6-dimethyl-4-hexadecylbenzenediazonium tetrafluoroborate(16-ArN2BF4), in aqueous micellar solutions of sodium dodecyl sulfate (SDS)? are used to estimate the local concentration of chloride and bromide ions at the micellar surface. The arenediazonium ion, 16-ArN2+, which is totally bound to the SDS micelle, reacts by rate-determining loss of N-2 to give an aryl cation that traps available nucleophiles, i,e., H2O, Cl-, and Br-, to give stable phenol, 16-ArOH, and halobenzene products, 16-ArCl and 16-ArBr, respectively. Product yields, determined by HPLC, are related to local concentrations using calibration curves obtained from independent standards. The local concentrations determined by this method are consistent with co-ion concentrations calculated, using a cell model, by numerical integration of the Poisson-Boltzmann equation (PBE) taking into account salt-induced micellar growth. The salt dependence of the intel facial concentrations of Cl- and Br- are identical. indicating no specific interactions in the interfacial co-ion compartment. PBE calculations predict that, in micellar SDS, increasing the concentration of a particular halide salt (NaX) at constant concentration of another halide (NaY) should result in an increase in the local concentrations of both co-ions. Using this chemical-trapping method, this prediction was demonstrated experimentally.
引用
收藏
页码:5032 / 5035
页数:4
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