TY - DATA T1 - Role of Counterions in the Solubilization of Benzene by Cetyltrimethylammonium Aggregates. A Multinuclear NMR Investigation† PY - 1999/12/10 AU - Giorgio Cerichelli AU - Giovanna Mancini UR - https://acs.figshare.com/articles/journal_contribution/Role_of_Counterions_in_the_Solubilization_of_Benzene_by_Cetyltrimethylammonium_Aggregates_A_Multinuclear_NMR_Investigation_sup_sup_/3730455 DO - 10.1021/la990748z.s001 L4 - https://ndownloader.figshare.com/files/5822229 KW - 1 H chemical shifts KW - 14 N NMR spectroscopy KW - CTAB KW - CTAC KW - CTAN KW - CTAM KW - CTAS KW - CTAX KW - benzene addition KW - CH KW - 1 H NMR headgroup signals N2 - This paper reports about the influence of counterions on the solubilization of benzene in aqueous solutions of cetyltrimethylammonium surfactants (CTAX, X = Br-, Cl-, NO3-, CH3SO3-, and (SO4)2-1/2, CTAB, CTAC, CTAN, CTAMs, and CTAS, respectively) investigated by 1H, 13C, and 14N NMR spectroscopy, at [CTAX] = 0.10 M. Benzene solubility and the size of the aggregates upon benzene addition depend strongly on the nature of counterion. Aqueous CTAC, CTAMs, and CTAS solutions reach benzene saturation up to [benzene]/[CTAX] ∼ 3 without showing any aggregate growth; on the other hand aqueous CTAB and CTAN solutions are able to solubilize a smaller amount of benzene up to [benzene]/[CTAX] ∼ 1 and the solute addition promotes a sphere to rod transition. 1H chemical shifts of the headgroup signals, namely, the trimethylammonium and four methylenes of the aliphatic chain, undergo a more relevant upfield shift upon benzene addition with respect to the hydrophobic chain signals. 1H NMR headgroup signals correlate to [benzene] through cubic equations, while the other signals do not show any simple correlation to [benzene]. A qualitative model in which benzene displaces water from the clefts which characterize the surface of the micellar aggregates is in agreement with all the experimental data. ER -