NOTES
4558
sibly SiO) must diffuse in the opposite direction. Since there is no silicon loss from the charge it does not seem likely that Si0 is the rate-determining species. The experimental observations are consistent with a model where the rate-determining step in the oxidation is CO diffusion controlled. An apparent activation energy of oxidation, 151 kcal/mole, was calculated using rate constants derived from a simple parabolic expression. This is more than twice the highest value6 reported for the diffusion of oxygen in silica. (6) E. W. Sucov, J . A m . Chem. SOC.46, 14(1963).
lH and 19FNuclear Magnetic Resonance Spectra of Tris(pfluoropheny1)phosphine Oxide and Dimethyl p-Fluorophenylphosphonate by C. E. Griffin, J. J. Burke, F. E. Dickson, 11.Gordon,’ H. H. Hsieh, R. Obrycki, and M. P. Williamson Department of Chemistry, University of Pittsburgh, and Mellon Institute, Carnegk-Mellon University, Pittsburgh, Pennsylvania 16616 (Received June 18, 1967)
The chemical shift differences (a2 - 6,) for the aromatic protons of a number of phenylphosphine oxides (1)*and phenylphosphonates (2)314possessing a variety of para substituents are sufficiently large so that wellresolved quartets are observed for both H2 and Ha. Although the spin systems of 1 and 2 are of the A2B2X
a, X =
F; b, X
=
C1; c, X = Br
type, coupling constants (J12, J 1 3 , J 2 3 ) and chemical shifts (62, 63) could be obtained readily by utilizing an Jw,etc.) between ABX appro~imation;~ couplings (JZ2j, meta and pura protons were not normally resolved in the spectra of 1 and 2.*p6 However, three cases (lb,2 2b,4 2c4)have been observed in which no such analysis was possible. In each of these compounds, the aromatic proton resonances consist of two broadened singlets corresponding to the deceptively simple ABX case in which 6~ - 6~ = 0 and JAB - Jax) < JAB.^ No further studies of the spectra of lb, 2b, and 2c were attemped since the expected complexity of the X (”P) resonances would preclude the determination of the line sepThe Journal of Physical Chemistry
arations necessary for complete a n a l y ~ i s . ~The 31Presonances of 2b and 2c would comprise the X portions of A2B21L’I& spectra as a result of coupling with both aromatic and ester protons; the corresponding resonance of l b would be the X portion of an spectrum resulting from coupling with the aromatic protons of all three rings. In an effort to obtain a complete analysis of a similar system which might be expected to give rise to a deceptively simple spectrum, the spectra of the corresponding fluoro compounds (la and 2a) have been examined. Although the ‘H spectra of l a and 2a would be further complicated by coupling with the lgF nucleus (A2BZY systems would be involved), the expected lesser complexity of the lgF resonance as compared to that of the 31Presonance might allow a complete analysis.
Experimental Section The ‘H spectra were recorded using a Varian Associates A-60 spectrometer; double-resonance experiments were carried out with an NilIR Specialties SD-GOB heteronuclear spin decoupler using irradiation frequencies of 24.3 (”P) and 56.4 MHz (19F). For both normal and decoupled spectra, three spectra were recorded for each sweep direction; the coupling constants cited in Table I are the averages of all values derived from these spectra. The 19Fspectra were recorded at 94.1 RlHz using a Varian Associates HA-100 spectrometer. One spectrum was recorded’ for each sweep direction. The spectra were essentially first order; J14 is seen nine times, while and J34each occur twelve times. The coupling constants cited in Table I are the averages of all values derived from both spectra. The 19Fspectrum of l a was also recorded at 56.4 IIHe; the coupling constant values agreed with those obtained a t 94.1 MHz within experimental error. The HA-100 was frequency swept in the HA mode using CFC13 as an internal lock. In order to operate the instrument in this manner, the “manual oscillator’’ was replaced by a General Radio Type 1161-A frequency synthesizer. It was necessary (1) National Science Foundation Cooperative Graduate Fellow, 1961-1964. (2) C. E. Griffin, Tetrahedron, 20, 2399 (1964). (3) M. Gordon, Ph.D. Thesis, University of Pittsburgh, 1965. (4) R. Obrycki, Ph.D. Thesis, University of Pittsburgh, 1966. ( 5 ) (a) T. Schaefer and W. G. Schneider, Can. J . Chem., 37, 2078 (1959): (b) R. J. Abraham and H. J. Bernstein, ibid., 39, 905 (1961); (c) details of this analysis as applied to the spectra of 1 and 2 are given in ref 2. (6) An exact AzBzX analysis of the spectra of representative 1 and 2 in which cross-ring couplings are observable has been carried out and it has been shown that no appreciable differences exist between the values obtained for J12, Jia, J z a , 8 2 , and 63 by the different analyses. (7) R. J. Abraham and H. J. Bernstein, Can. J . Chem., 39,216 (1961).
NOTES
4559
Table I: Nmr Parameters for p-Fluorophenyl Phosphoryl Compoundso Compound
. -Data eourceb---
a-l. 7--
Ja J13
Jt3 J24
Jar Jl4 82c
Sad
Solvent,
-------28
A
B
,---A--
10.87 2.54 8.97 5.83 9.03
... ...
12.38 12.30 3.19 3.24 8.83 8.91 5.71 5.66 8.87 8.93
... 7.70 7.35 ... DMSOc
5.66 8.99 1.95
... 101.16 Acetonee
B
c
... ... ...
12.36 3.18 8.82 5.64 5.68 8.97 8.87 ... . . . 1.54 . . . 7.80 7.83 ... 7.80 7.27 7.33 . . . 7.27 ... . , , 99.75 . . . Neat C C k Neat Neat
Coupling constants are given in hertz. b A, from alp and decoupled spectra; B, from 19F spectrum; C, from normal spectrum. c In ppm downfield from internal TMS. d In ppm Concentration ea. 50% w/v. upfield from inter1i:tl CFCls. 0
19F
to use a simple phase shifter to correct the phase of the signal going to the reference input of the analytical phase detector. A low-pass filter was also used to eliminate multiples of the analytical reference frequency which affected the sample input of the analytical phase detector. Tris(p-fluoropheny1)phosphine oxide (la) was prepared by the reaction of the aryl Grignard reagent with phosphorus oxychloride ;* the preparation of dimethyl p-fluorophenylphosphonate (2a) has been reported previously.
Results and Discussion Despite these expectations, the 'H spectra of la and 2a were not deceptively simple at 60 RIHe; ie., b2 -
83 # 0, and no solvents were found in which deceptively simple spectra resulted for either compound. Fourteen of the sixteen lines expected for the ABXY approximation were cleanly observable for la, but coupling and chemical shift parameters could only be estimated because of line coincidences and overlap of the Hz and HI portions of the spectrum. However, double-resonance experiments (independent irradiations of 31P and 19F)resulted in simplification of the spectrum to that of the iiB portion of an ABX system; all of the coupling and chemical shift data (Table I) were obtained from the decoupled spectra by the previously employed approximation.2 The IH spectrum of 2a was essentially first order in character and all pameters (Table I) could be obtained directly from the normal spectrum. The chemical shift difference ( 6 2 1 5 ~ )is sufficiently large so that the Hz and H3 resonances
show no overlap and the spectrum is of the AzM&Y type. The eight expected lines are observed for the H2 resonance, while the near equivalence of J3*and J Z 3 results in a six-line multiplet for H3. The magnitudes and identities of the parameters derived from the normal spectrum were confirmed by 31Fand 19F decoupling. Further confirmation of the lH-ISF parameters obtained from the lH spectra of la and 2a was obtained by examination of the 19F spectra of these compounds. These spectra were essentially first order in appearance, and, in addition to J2* and J34, the 1gF-31P coupling (J14) is observable. Agreement in the magnitudes of parameters obtained by these diff ererit methods was within the limits of experimental error. The changes in the 'H spectra of the two series of compounds (la-c and 2a-c) provide an illustration of the differences in shielding ability of the three halogens. In the phosphine oxide series, S2 - 83 = - 16 He for the bromo compound (IC), HB being the more deshielded proton.2 The greater shielding ability of chlorine is indicated by the observation of 82 - 83 E 0 for lb.2 The further increase in shielding ability for fluorine results in a reversal of chemical shifts for the fluoro analog (la) relative to the bromo compound (IC); in la,8,is the more shielded proton and 62 - J3 = +21 He. A similar progression is observed for the phosphonates (2). The 8 2 - 6 3 values show an approximate correlation with the ugo values for the halogens,1° indicating that the chemical shift of H3 is determined to a large degree by the mesomeric interaction of the halogen with the ring.ll Examination of the complete series of p-halophenylphosphoryl structures was not possible; a number of attempts to prepare the iodo analogs of 1 and 2 were unsuccessful. The various parameters determined for la and 2a fall within the ranges observed for analogous compounds: triarylphosphine oxides,*J12= 10.5-11.5 Hz, JI3 = 2.1-3.4 He; phenylpho~phonates,~,~ Jlz = 12.2-12.9 Hz, J 1 3 = 3.2-4.2 Hz. The magnitudes of the observed lH-19F coupling constants are also normal for para-substituted fluorobenzenes; e.g., J3* = 8.7 He (8) For details of this preparation, see H. H. Hsieh, Ph.D. Thesis, University of Pittsburgh, 1964. (9) R. Obrycki and C. E. Griffin, Tetrahedron Letters, 5049 (1966). (10) R.W . Taft, E. Price, I. R. Fox, I. C. Lewis, K. K. Anderson, and G . T. Davis, J. Am. Chem. Soc., 8 5 , 3146 (1963). (11) This correlation yields the correct trend for SZ - 61, but is not exact since the near equivalence of the uROvalues'0for bromine (0.16)and chlorine (0.18)would indicate that 62 - 63 should be approximately the same for Ib and IC. Similar considerations hold for a correlation of 6 2 - 63 with ~1.10 However, 01 values indicate fluorine to be more strongly electron withdrawing than either bromine or ch1orine;'O if an inductive effect were operative in the shielding of Hx, 62 - 6a for l a would be predicted t o be the most negative of the series, a prediction contrary to experimental fact.
Volume '71, Number I d
December 1967
NOTES
4560
and Jz4= 5.8 Hz for p-fluorotoluene.6” The 19F31P couplings (J14) are of the same order of magnitude as the corresponding coupling constants in a variety of pentafluorophenylphosphorus derivatives.l 2 Acknowledgment. We wish to thank Mr. D. E. Wisnosky for his invaluable technical assistance in modifying the HA-100 spectrometer. This work was performed using, in part, instrumentation provided by a grant (FR 00292) from the National Institutes of Health. ~
~~
~
~~
(12) M. G. Barlow, M. Green, R. N. Haszeldine, and H. G. Higson, J . Chem. Soc., Sect. B , 1025 (1966); M. G. Hogben, R. S. Gay, and W. A . G. Graham, J . A m . Chem. SOC.,88, 3457 (1966).
Radiation Decomposition of Solid Chlorates by C. E. Burchill, P. F. Patrick, and K. J. McCallum Departmen lof Chemistry and Chemical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan (Received June 19, 1987)
The decomposition of solid chlorates by ionizing radiation has been reported by several authors. 1-6 These studies, however, have not resulted in complete agreement regarding the identity of the decomposition products or their yields. I n the present work, irradiation of crystalline sodium, potassium, and barium chlorates by Cow y rays followed by solution in water was found t o lead t o the formation of oxygen, chlorine dioxide, and perchlorate, chlorite,, hwochlorite, and chloride ions. ” *
Experimental Section The purified salts were irradiated in Pyrex test tubes a t room temperature in a Gammacell 220 unit manufactured by Atomic Energy of Canada Ltd. Dosimetry measurements were made with the Fricke dosimeter, using a G value of 15.5 for the production of ferric ion. Dose rates in the solid sample were corrected on the basis of Compton absorption in sodium and potassium chlorates, with an additional small contribution from photoelectric absorption in barium chlorate. The yield of oxygen on solution of the irradiated crystals was determined chromatographically on Linde Riolecular Sieve Type 5A using either helium or argon as the carrier gas. A correction for the small amount of oxygen which remained dissolved in the solution was made by polarographic measurement. When argon was used as the carrier gas, it was possible to detect and measure the production of a small amount of hydrogen. The Journal of Physical Chemistry
I n some experiments, volumetric estimations of gas yields were made, giving results in agreement with those obtained chromatographically. The aqueous solution obtained when the irradiated salt was dissolved was analyzed for products containing chlorine in all of the oxidation states stable in solution. Perchlorate ion produced in the solution was determined by measuring the optical density of the methylene blue complex at 665 mp.’ The yield of chloride ion was measured mercurimetrically in neutral solution, using sodium nitroprusside indicator.8 The yields of chlorine dioxide, hypochlorite, and chlorite were determined using a modification of the procedure due to White.g The total number of oxidizing equivalents of these products was determined iodimetrically in acetic acid solutions. Chlorine dioxide was estimated from the decrease in the number of oxidation equivalents following disproportionation of this species in basic solution to chlorate and chlorite. In another aliquot the arsenious oxide methodlo was used to determine hypochlorite after the interfering chlorine dioxide was removed by treatment with base. Finally, the amount of chlorite present was calculated by difference.
Results and Discussion The G values for the yields of products, measured at a dose rate of 7 X 10l6ev/g min, are given in Table I. The deviations quoted in this table represent the standard deviations of individual points on the dose-yield curves. The yields of products were found to increase linearly with increasing dose over the range examined (up t o loz1ev/g). The G values were found to be independent of dose rate over the range 1.4 X 10’6 to 7 X 1016ev/gmin. The general features of the product yields of the three chlorates are very similar, suggesting that the same general mechanism is operative. The decomposition scheme proposed by Heal4is consistent with the (1) G. Hennig, R. Lees, and M.S. Matheson, J . Chem. Phys., 21, 664 (1953). (2) L. J. Sharman and K. J. McCallum, ibid., 23, 597 (1955). (3) T . P. V. Bakerkin, Dokl. Akad. S a u k SSSR, Otd. Khim. Sauk, 167 (1957). (4) H . G. Heal, Can. J . Chem., 37, 979 (1959). (5) C. J. Hochanadel, J . Phys. Chem., 67, 2229 (1963). (6) P. F. Patrick and K . J. McCallum, Sature, 194, 776 (1962). (7) D. F. Boltz and W. J. Holland in “Colorimetric Determination of Nonmetals,” D. F. Boltz, Ed., Interscience Publishers, Inc., New York, N. Y.,1958, p 176. (8) 1. M. Kolthoff and V. A. Stenger, “Volumetric Analysis,” Vol. 11, 2nd revised ed, Interscience Publishers, Inc., New Tork, N. Y., 1947, p 331. (9) J. F. White, A m . Dyestuff Reptr., 31, 484 (1942). (10) I. M. Kolthoff, “Textbook of Quantitative Inorganic Analysis,” 3rd ed, The Macmillan Co., New Tork, N. T.,1952, p 597.
