title: Diffusion of organic solutes in squalane.
abstract: The translational diffusion constants, D, of 26 hydrocarbons have been determined in squalane (2,6,10,15,19,23-hexamethyltetracosane) at room temperature using capillary flow techniques. These new data and previously published room-temperature D values for the same solutes in some (or all) of the n-alkanes n-C(6)-n-C(16) constitute a study of solute diffusion in media spanning a 100-fold change in viscosity; at 23 °C, η = 0.31 cP for n-C(6), 3.2 cP for n-C(16), and 30 cP for squalane. The D values in the n-alkanes and squalane show deviations from the Stokes-Einstein relation, D = k(B)T/(6πηr); the values of r, a solute's hydrodynamic radius, decrease as the viscosity increases. The deviations increase as the solute size decreases and are analyzed by fitting the diffusion constants to the modified Stokes-Einstein equation, D/T = A(SE)/η(p). Fits involving the n-alkane-only and combined n-alkane-squalane D values give comparable results with values of p < 1 that increase as the solute size increases; p = 1 for the Stokes-Einstein limit. The deviations from Stokes-Einstein behavior also are discussed in terms of the relative sizes of the solutes, the n-alkanes, and squalane.
authors.affiliation: Department of Chemistry, Saint Louis University, 3501 Laclede Avenue, St. Louis, Missouri 63103, United States. kowertba@slu.edu
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Kowert
authors.forename: Michael B
authors.initials: MB
authors.lastname: Watson
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D004058:Diffusion; D017022:Flow Injection Analysis; D015394:Molecular Structure; D012997:Solvents / Q000737:chemistry*; D013185:Squalene / Q000031:analogs & derivatives* / Q000737:chemistry; D013696:Temperature; D014783:Viscosity
chemical_list: D000473:Alkanes; D012997:Solvents; D013185:Squalene; C019556:squalane