title: Acid-catalyzed hydrolysis of sodium dodecyl sulfate.
abstract: The acid-catalyzed hydrolysis of sodium dodecyl sulfate (1) and the effect of 1-dodecanol (2) on this hydrolysis were investigated. The rate of hydrolysis was followed by measuring the rate of production of HSO-4 using a pH-stat. The rate constant (kH+) below the critical micelle concentration (CMC) increased with increasing concentrations of 2, up to a mole ratio of 0.5 for 2 to 1, after which the hydrolysis rate was independent of the concentration of 2. These results suggest the possible formation of a complex between 1 and 2. A micellar solution of pure sodium dodecyl sulfate (20 mM) hydrolyzed 50 times faster than that of a premicellar solution at the same pH. Plots of log k versus pH were linear with a slope of -1 at pH less than 4.3. At a constant pH, the addition of NaCl resulted in a decrease in the rate of hydrolysis of a micellar solution. This is probably due to the reduction of concentration of protons at the micelle surface. Furthermore, kH+ was also decreased by the addition of 2 in the region where 2 is solubilized in the micelle; again, this was probably due to the reduction of the charge density (sigma) on the surface of the micelle.
mesh_terms: D002384:Catalysis; D007851:Dodecanol / Q000032:analysis; D004573:Electrolytes; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008823:Micelles; D012967:Sodium Dodecyl Sulfate / Q000032:analysis*; D012995:Solubility
chemical_list: D004573:Electrolytes; D008823:Micelles; D007851:Dodecanol; D012967:Sodium Dodecyl Sulfate