SPECTRA OF PERFLUOROALKYL DERIVATIVES OF SULFUR HEXAFLUORIDE
March 5 , 1957
that although these reactions are more prominent a t high fiH values, they are important over the entire pH range studied. T o account for the observed phenomena the following mechanism is proposed. Let us consider that the first initial activity in the water layer is due to the partition of iodine and to reactions between iodine and water.
Jr + € 1 2 0 J_ Iz.Hz0
(1) (2)
IPtHnO)
I2(CC!c)
12
A t low concentrations reaction 2 would lie far to the right. To calculate the exact effect of this reaction on the distribution coefficient, the equilibrium constant would have to be known. However, the effect of this reaction would be seen a t all fiH values, which corresponds to the data obtained. Secondly, the slow rise in activity of the aqueous phase with time could be caused by the following dissociation of the water-iodine complex. 12.H20 J _ H201f I(3)
41'
+ +
HOI +
Hf
The end products of the above reactions would be HOI and 13-. Since no iodate is found in the solutions, even after standing, apparently HOI is stable a t these concentrations. The above mechanism would explain the gradual appearance of 13- and the increase in conductance with time in freshly prepared aqueous iodine solutions. A similar explanation has been given for the rise in conductance of iodine-pyridine solutions with time. 1a,14 This mechanism is also consistent with the results obtained by Benesi and HildebrandI6 in a study of iodine-acetone solutions. They found that 1 3 - was formed immediately when iodine was added to acetone. After observing the behavior and characteristics of these solutions they concluded that the following reactions were occurring 0 OH
/I
CHI-C-CHI OH
I
CHs-C=CHz
I r'CHa-C=CH2
(4)
0
I1 + +CHa-C-CH21 12
+ I- + H + (5)
12
I-
.If
+ 1%
18-
(6)
Equation 5 may be written stepwise to show complete analogy to eq. 3.
13-
This equilibrium would be FH dependent due to the decomposition of H201+. Thus the equilibrium concentrations of HOI and Is- should decrease with a decrease in PH. This also is consistent with the data shown in Fig. 1.
[CONTRIBUTION FROM THE
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PHYSICAL
(13) L. F. Audrieth and E. J. Birr, TRISJOURNAL, 66, 668 (1933). (14) G.Kortiim and H. Wilski, 2. physik. Chcm., 202, 35 (1953). (15) H. A. Benesi and J. H. Hildebrand, TEISJOURNAL, 72, 2273 (1950).
BATONROUGE3, LA.
RESEARCH DIVISION,CHEMICAL WARFARE LABORATORIES]
Nuclear Magnetic Resonance Spectra of Some Perfluoroalkyl Derivatives of Sulfur Hexafluoride BY NORBERT MULLER,~ PAUL C. LAUTERBUR AND GEORGE F. SVATOS RECEIVED SEPTEMBER 17, 1956 High-resolution F19 NMR spectra have been obtained for several perfluoroalkyl derivatives of sulfur hexafluoride of the types RFSF~ and ( R p ) z S F d . Indirect spin-spin coupling leads t o an unusually complex resonance multiplet for the Flu nuclei of the -SF6 group. Calculations show that the observed fine structure is consistent with the assumption that these fluorines form a square pyramid. The resonance of the -SFr group is a single line if the CS-C angle is near 180°,and a characteristic pair of triplets if the C-S-C angle is near 90'.
Introduction plet of the SF, group, using the method of reference 4; this required more precise calculations than the Compounds of the types R F S F ~and ( R F ) ~ S F ~ give F19 NMR signals in two, well-separated re- customary first-order approximation. The results gions. One of these contains the resonances of the are compatible with the supposition that the five fluorine nuclei in the perfluoroalkyl (RF) radical, fluorine atoms form a square pyramid. The patwhich may be used to identify this radical. The tern obtained for -SF4- groups was found to deother contains the resonances of fluorine bonded t o pend characteristically on whether the C-S-C angle the sulfur atom. A study of the multiplet patterns is near 90' or near 180'. in this S-F region constitutes an interesting apExperimental plication of the theory of indirect spin-spin couAll materials used in these studies were prepared in these ling.^-^ We made a detailed analysisof the multi- laboratories; methods of synthesis and purification are. be(1) Department of Chemistry, Purdue University, Lafayette, Ind. (2) E. L. Hahn and D. E. Maxwell, P h y s . Rev., 88, 1070 (1952). (3) M . K. Banerjee, T. P. Das and A. K. Saha, Proc. R o y . Sac. (London), 2268, 490 (1954). (4) H. M. McConnell, A. D. McLean and C. A. Reilly, J. Chem. Phys., 23 1152 (1955).
ing published elsewhere.' The absence of NMR signals other than those which can be accounted for on the basis of the structures assumed for the materials indicates that no more than a few per cent. of fluorine-containing impurities can have been present in any of the samples. (5) F. W. Hoffmann, T.C. Simmons, ef al., to be published.
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NORBERT MULLER,P. C. LAUTERBUR AND G. F. SVATOS
Vol. 79
TABLE I RESULTSOF F19 CHEMICAL SHIFTMEASUREMENTS All entries are values of 6 = (ETo - H..)/H, X lo6, referred to CFICOOH. Group
CiFaSFi
CaFSFa
CiFpSF,
5.3
5.0 18.8 50.7
5.2 18.0 46.5 49.5
(CnFdzSF,
(CSFI)ZSFI
O
