J. Phys. Chem. 1980, 84, 229-230 R\
R
/
/OS
N-N
‘SR‘
I1
(RSN=O) intermediates, and the subsequent trapping of the NO radical: RSNO + XH RSH + X-NO (1)
+ -
where X = R2:N, tert-butyl, NaO, or C1 RSNO RS- NO. RSNO
+ NO.
(2)
RSN N=O)O* $11
(3)
Paramagnetic species can also be produced from reaction of NO with ferrous iron containing ligands. Results from the ICP optical emission spectroscopy indicated that the thiols in question are almost void of iron impurity ( < 2 ppm). It, was reported3 that thionitrites, in the presence of secondary amines, produce N-nitrosamines. A detailed knowledge of the mechanism of the reaction of nitroso compounds with thiols is pertinent, since it may involve the formation as well as the inhibition of the carcinogenic N-nitrosamines.
Figure 1. Capacity ratio k , of naphthalene as a function of pressure at three supercritical temperatures measured in a chromatographic column filled with silica gel (Perisorb A; surface 14 m2 g-’) as ithe stationary phase and carbon dioxide as the mobile phase.
plbar
Acknowledgment. We thank Drs. E. Ragelis and A. Pohland for helpful discussions and Mr. J. Jones for running samples in the ICP spectrometer. References and Notes (1) B. Saville, Analyst, 83,670 (1958). (2) S. Oae, Y. K:im, D. Fukushima, and T. Takata, Chem. Lett., 833 (197’7). (3) S.Oae, D. Fukushima, and Y. Kim, J. Chem Soc., Chem. Commun., 407 (1977). (4) H. H. Hatt, “Organic Syntheses”, Collect. Vol. 11, Wiley, New York, 1943,p 211 (5) W. A. Waters, J . Chem. Soc., Chem. Commun., 741 (1970). Division of Chemistry and Physics Food and i3rug Administration Washington, D.C. 20204
George C. Yang” Avlnash Joshl
Received July 16, 1979
Flgure 2. Partial molar volumes V,” of naphthalene and fluorene at infinite dilution in supercritical carbon dioxide [(V)naphthalene, stationisry phase Perisorb A; (A) naphthalene, stationary phase Perisorb RP 8; (0) fluorene, stationary phase Perisorb A; (0)fluorene, stationary phase Perisorb RP 8; (--) isothermal compressibility K of pure CO, (from ref
411.
Partial Molar Volumes of Naphthalene and Fluorene at Infinite Dilution in Carbon Dioxide near Its Critical Point Publication costs assisted by the University of Bochum
Sir: Critical phenomena in pure compounds and mixtures are of rapidly increasing interest. In this paper partial molar volumes of organic substances at infinite dilution in carbon dioxide near its critical point are presented. These data have been obtained from supercritical fluid chromatography (SFC); it would have been difficult to determine these data with other (e.g., static) methods. In the chromatographic process the sample (2) is distributed between the supercritical solvent (1, here supercriticitd C02) in the mobile phase (’) and the stationary phase (” here two different adsorbents). The partition coefficient K 2 E: cz/’/c; determines the capacity ratio k z (ci’/ci) (V”/V’) where V” and V’ are the volumes of the stationary phase (that is assumed to be proportional to the surface) and the mobile phase, respectively, with the concentrations of the sample in the two phases being c2” and c2/. The basic chromatographic equation kz -- ( t R 2 - to)/t, (1) 0022-3654/80/2084-0229$01 .OO/O
relates the capacity ratio k z to the retention time tR2of the sample 2 and to the time toan inert particle needs to travel through the column. For the thermodynamic description a model was chosen that was derived for adsorption from solutions.2 Its application on the chromatographic process yields a simple expression for the capacity ratio hz and the pressure dependence is found to bell3
(a In k2/ap)T =: (V2”’- (az/al)Vl*’)/RT(1/ P ’ ) (ap’/ap)?- (2)
Here Vzm’is the partial molar volume of the sample in the solvent at infinite dilution, VI*’ the partial molar volume of the nearly pure solvent, p’ the bulk density of the mobile phase, and thus (l/~’)(ap’/ap)~ the isothermal compressibility K ; al and a2 are the partial molar areas on the surface occupied by species 1 and 2 . In the experiments hz has been determined for naphthalene and fluorene by using two different stationary surfaces (Perisorb A; Perisorb RP8) at three temperatures each over a wide range of pressure. One set of data is shown in Figure 1. From these data the partial molar volumes have been calculated according to eq 2. For VI*’ the molar volume of pure GO2*was uaed and a 2 / a 1was roughly estimated to be the ratio of the molar volumes of the pure soliid 0 1980 American
Chemical Society
230
Communications to the Editor
The Journal of Physical Chemistry, Vol. 84, No. 2, 1980
sample 2 and pure solid COz resulting in a value of approximately 4.5 for both samples (for details see ref 1). The results are presented in Figure 2; details are given in the legend. Only negative Vzm’values are found and the two solutes (naphthalene and fluorene) do not show any remarkable differences in Vzm. The most interesting finding is the strong correlation between Vzm and the isothermal compressibility K of the pure solvent COz that corresponds to the full line in Figure 2. This behavior had already been predicted by Wheeler5 on the basis of a lattice-gas model according to which in the critical region V,- should be dominated by K of the pure solvent. The present results confirm this prediction and support a value of Vzmrunning to negative infinity when approaching the critical point of the solvent. A discussion of similar phenomena with respect to static experiments has been given by Rozen.6
Acknowledgment. Financial support of the Fonds der Chemischen Industrie e.V. is gratefully acknowledged. References and Notes U. van Wasen, Dissertation, University of Bochum, German Federal Republic, 1978. H. D. Everett, Trans. Faraday Soc., 81, 2478 (1965). U. van Wasen, I. Swaid, and G. M. Schneider manuscript in preparation. IUPAC, “International Thermodynamic Tables of the Fluid State, Carbon Dioxide”, Pergamon Press, Oxford, 1976. J. C. Wheeler, Ber. Bunsenges. Phys. Chem., 78, 308 (1972). A. M. Rozen, Russ. J. Phys. Chem., 50,837 (1976). University of Bochum Department of Chemistry Institute of Physical Chemistry Bochum, Federal Republic of Germany Received May 4, 1979
U v a n Wasen G. M. Schneider”
