A study on interaction between benzyl alcohol and cationic surfactant micelles by ¹H NMR

Abstract

Solubilization of benzyl alcohol in aqueous micellar solution of 3-alkoxy-2-hydroxypropyl trimethyl ammonium bromides (C_nH_2n+1OCH₂CH(OH)CH₂N(CH₃)₃⁺ Br^-, abbreviated as C_nNBr, (<i>n</i>=8, 12, 14, 16) has been studied by high resolution ¹H NMR. Results indicate that the alkyl chain length of the surfactant affects the solubility of benzyl alcohol in the micellar solution. The peak of methylenes in long chain surfactant splits into an upfield signal and a down field signal when the solubilization system is at high

molar ratio of benzyl alcohol to surfactant. The solubility of benzyl alcohol in micelle solutions of different surfactants (<i>n</i>=8, 12, 14 and 16)at the same concentration (3.00×10^-2mol L^-1) are 0.1125, 0.1470, 0.1755 and 0.2100 mol L^-1, respectively. The transfer free energy of benzyl alcohol from aqueous phase to micellar phase is – 18.45, - 18.59, - 18.72 and - 18.80 kJ mol^-1 for <i>n</i> = 8, 12, 14 and 16, respectively.