The relationship of structure to properties in surfactants: VII. Synthesis and properties of some sodium 1,4-and 2,6-alkoxynaphthalenesulfonates

A number of surface-active alkoxynaphthalenesulfonates, ROC₁₀H₆SO3Na, have been synthesized, and some of their surface properties determined. The synthesis involved a Williamson reaction of an alkyl halide with the disodium salt of a naphtholsulfonic acid. The Krafft points, surface tension-log concentration curves, critical micelle concentrations, and areas/ molecule at the air/liquid interface of the purified and characterized alkoxynaphthalenesulfonates have been determined. Their surface areas/molecule indicate that the oxynaphthalenesulfonate portion of these compounds is lying flat in the air/liquid interface with the alkyl group vertical to the plane of the naphthalene. Their surface tension reduction efficiencies and critical micelle concentrations indicate that an α- or β-naphthoxy gruop in the hydrophobic portion of the molecule at 60 C is equivalent to about eight carbons in a straight alkyl chain and about six carbons at 25 C. These compounds, in contrast to other surfactants without an aryl ether linkage in the molecule, show greater efficiency and effectiveness in surface tension reduction with increase in temperature. Abstracted in part from a thesis for the Master of Arts degree presented by Chang-Chin Kwan to the graduate faculty of Brooklyn College, City University of New York, May 1977.