“01. 5 , No. 5, May 1966
RADIOSULFUR-EXCHANGE REACTIONS IN LIQUIDH,S
911
CONTRIBUTION FROM THE DEPARTMENT OF CHEMISTRY, OREGON STATEUNIVERSITY, CORVALLIS, OREGON
Radiosulfur-Exchange Reactions in Liquid Hydrogen Sulfide. F2 BY J. R. MICKELSEN, T. H. NORRIS, AND R. c. SMITH3
Received August 2, 1965 Sulfur-35 has been used to study a number of solute-solvent exchange reactions in the solvent liquid hydrogen sulfide. In neutral solution the exchange rate is negligible or exceedingly slow with sulfur, carbon disulfide, dimethyl sulfide, or ethyl mercaptan. In basic, triethylamine-containing solutions, however, arsenic and antimony tri- and pentasulfides, carbon disulfide, and sulfur all show rapid exchange; phosphorus pentasulfide gives a moderate rate (apparently related to slow attainment of equilibrium among solute species), while ethyl mercaptan again shows no significant exchange. The results are interpreted as generally supporting the concept of the formation of thio anionic species in the basic solutions in those cases where moderate to fast exchange occurs.
Extending similar work with other nonaqueous solvents, we have carried out some exploratory radiosulfur-exchange studies between the solvent liquid hydrogen sulfide and a variety of solutes. The solvent properties of this relatively low dielectric constant medium (8.04 a t -61.206) have been reviewed by Wilkinsona and Jander.’ Among other phenomena, Jander describes the amphoterism of arsenic trisulfide; the material, insoluble in neutral solution, reportedly dissolving on addition of either hydrogen chloride or triethylamine. The basic solution is presumed to contain thioarsenite, formed by reaction with ( (C2H6)3NH) SH87 AszS~4- 6((CzH6)3NH)SH = ~ ( ( C Z H ~ ) ~ N H ) f ~ A3HzS S S ~ (1)
If reactions of type 1 occur, arsenic trisulfide and related materials should, on being dissolved and later recovered from triethylamine-containing solutions, show a t least partial sulfur exchange with the solvent (rapid exchange between ((CzH6)aNH)SH and solvent being assumed). Depending on the rate of solventthio anion exchange, the net observed exchange might or might not be complete. Analogous isotopic oxygen exchanges between oxy anions and water have been found very slow in some cases and in others relatively rapid.l0 I n view of the interest of this matter, exchange experiments with various possible thio anion (1) This research has been supported by the U. S. Atomic Energy Commission under Contract AT(45-1)-244. Report N o . RLO-244-1. (2) Presented a t the 136th National Meeting of the American Chemical Society, Atlantic City. N . J., Sept. 1959. (3) Taken from the Ph.D. Thesis of J. R. Mickelsen and the M.S. Thesis of R. C. Smith, Oregon State University, June 1956 and June 1952. (4) Cf.R. R. Wiggle and T. H. Norris, Inovg. Chem., 3, 539 (1964). (5) S . Havriliak, R. W. Swenson, and R. H . Cole, J. Chem. Phys., 2 3 , 134 (1955). (6) J. A. Wilkinson, Chem. Rev., 8, 237 (1931). (7) G. Jander, “Die Chemie in Wasserahnlichen Losungsmitteln,” Springer-Verlag, Berlin, 1949, pp 77-119. (8) Jander’s visualization of triethylamine in liquid hydrogen sulfide as ((C2Hl)aNH)SH dates from a time when analogous aqueous hydroxide species were commonly so written. Although present knowledge indicates the actual dominance in water systems of the free amine bases, it does seem possible, in view of the relative stability of amine hydrosulfides,a that a substantial conversion of amine to a hydrosulfide (ion paired) may occur in the present medium. The validity of this assumption, however, is not especially material to the interpretation of the present results. (9) M. Achterhof, R. F. Conaway, and C. E. Boord, J. A m . Chem. SOL, 63,2682 (1931). (10) (a) A. I. Brodskii and L. V. Sulima, Dokl. A k a d . Nauk S S S R , 92, 589 (1953); (b) N . F. Hall and 0. R. Alexander, J. A m . Chem. Soc., 62, 3455 (1940).
forming solutes have had a central place in the present work. Experimental Section Preliminary Observations.-Very little solubility in neutral hydrogen sulfide was found for the group V sulfides here studied (estimated 6h cszc 2 2 . 0 f 0.6" >Ih 14-384 CzH6SHC 25 (CHa)zSc 20 144 1 0 f 0.5' >2h a Concentrations: Sa,0.012 or 0.015 m; CzHsSH, 6.9 m; (CH~)ZS, 9.3 m; CS2, 1.32 m. * Sulfur initially labeled. Solvent initially labeled. d Durations of individual experiments were distributed over indicated range of times; no evident trend with time except possibly for sulfur a t 25". e Averages and experimental standard deviations of individual experiments. f Uncertainty based on estimated uncertainty of counting data. 0 From least-squares McKay plot. Maximum McKay slope based on estimated exchange uncertainties.
SSb Sab
TABLE I1 RADIOSULFUR EXCHANGE IN TRIETHYLAMINE-CONTAINING HYDROGEN SULFIDE Temp, Solute
oc
Reaction No. of times? min expts
Exch,i
%
Estd min
11 96 f 3
