Dec., 1963
P.M.R.STUDIESOF ACIDICORGANOPHOSPHORUS COMPOUKDS
prevented formation of complexes with these compounds. Cytosine and thymine are tm-o of the four bases in DKA. The observation that these bases form donor-acceptor complexes with quinone-like compounds implies that DNA replication can be altered very easily by Formation of donor-acceptor compounds ; conversely, the replication process may make use of charge-transfer bonding to hold molecules in place as they are added to the replicate. The observation that the photographic developer, 1-phenyl-3-pyrazolidone (phenidone), forms donoracceptor complexes with quinones and yields a donoracceptor peak suggests that the role of donor-acceptor complexes in the so-called “superadditive development” should be carefully evaluated. Conclusions Donor-acceptor complexes yield ttvo types of e.s.r. spectra, a broad peak which is probably due to oxidatioii-reduction reaction and a sharp intense peak which is invariant with donor and acceptor. This has been provisionally labeled the donor-acceptor peak, and its
2639
exact nature must still be determined. The oxidationreduction peak varies in position with the acceptor. The correlation of the intensity of the donor-acceptor peak or the “oxidation-reduction” peak of donoracceptor complexes with spectral sensitization requires additional investigation. The observation that donoracceptor peaks arise from nucleic acid bases indicates another approach to genetic modification by very mild agents. Superadditive development in photography may involve donor-acceptor complexes. Sensitizing dyes may impart light sensitivity outside the intrinsic absorption range of the photosensitive media and may also react with photographic developer oxidation products to form donor-acceptor complexes which materially increase the developability of the latent image. I n fact, this latter process may be as important as the initjal spectral sensitization. Acknowledgments.-The sensitizing dyes were synthesized by Dr. P. H. Dougherty and Mr. D. E. Bonis. The deseiisitizjng dyes were purified by Dr. S. Schlesinger and Mrs. F. Gallo.
PROTON MAGKETIC RESOXAKCE STUDIES O F ACIDIC ORGANOPHOSPHORUS COMPOUNDS‘ BY J. R. FERRARO AND D. F. PEPPARD Argonne National Laboratory, Argonne, Illinois Received June 7 , 1963 The proton magnetic resonance of 19 organophosphorus acids has been studied as a function of concentration in CClh. The chemical shift of the hydroxyl proton is in the direction of higher field with increasing dilution and increasing temperature. The position of this resonance a t 0.5 F concentration is highest for the acids containing phenyl groups. Higher resonance values are also found for the stronger acids. The data are interpreted in terms of polymer-dimer-monomer equilibria.
Introduction n’uclea,r magnetic resonance studies of carboxylic acids have been made.2-4 Similar studies with the acidic organo.phosphorus compounds are lacking. Stronger hydrogen bonding has been observed in the acids of the type (GO),PO(OH) (G can be aryl, alkyl, or mixed alkyl-aryl or a substituted variant thereof) , (GO)G’PO(OH), and GzPO(OH) than is found in the carboxylic acids.6a-c,6 Only in extreme dilutions in carbon tetrachloride is there evidence for monomer forma tion. Therefore, p.m.r. studies of these acids would be interesting for comparison with the results for the carboxylic acids. This paper reports on a p.m.r. study of the hydroxyl group, made with 9 acids of the 8 acids of the type (GO)G’PO(OH), type (GO)zPO(~OH), (1) Based on work performed under the auspices of the U. S. At.omio Energy Commission. Presented at the 144th Sational Meeting of the American Cheinical Society, Los Angeles, California, 3Iarch 31-April 5, 1963. (2) C. M. Hugginti, G. C. Pimentel, and J. N. Shoolery, J . Phys. Chern., 60, 1311 (1956). (3) L. W. Reeves and W-.G. Schneider, Tians. Faraday Sac., 64, 1314 (1958). (4) J. C. Davis, Jr., UCRL-8909 (1969). ( 5 ) (a) D. F. Peppard, J. R. Ferraro, and G. W.MaRon, J. I?%ar#.Nucl, Ch,~m., 7 , 231 (1958); (b) ibid,,1 2 , 60 (1959): (c) ihid., 16, 246 (1961). (6) (a) D. F. Peppard, J. R. Perraro, and G. W. Mason, ibid., 4 , 371 (1967); (b) ibid., 22, 285 (1961). (7) L. C. Thomas, R. A. Chittenden, and H. E. R. Hartley, h’ature, 192, 1283 (1961).
and 2 acids of the type G2PO(OH). The hydroxyl proton resonance was measured as a function of concentration in carbon tetrachloride. Experimental The acid phosphates and phosphonates used in this study were prepared as previously reported.i They were of a purity of 99% or better as determined by alkali titration and elemental analysesj and were dried on a vacuum line just prior to use. The method of preparing the two phosphinic acids will be discussed in a forthcoming paper. The CCI, used was spectral grade from Matheson Colernan and Bell and was found to be anhydrous by the Karl Fischer method. Results with this CC14were the same as those obtained for CC14 which was twice distilled from anhydrous calcium sulfate. The p.m.r. spectra were obtained with a Varian Associates Model A-60 n.m.r. spectrometer, kept in a room controlled a t 25 rt 1”. Spectra were scanned at rates of 120-240 c.p.s./min. The side-band t e c h n i q ~ ewas ~ ~ used ~ ~ ~ to measure the shift wherever possible, using a Hewlett-Packard audio oscillator Model 200 C in conjunction with a Beckman counter Model 5210B, using tetramethylsilane, from Anderson Chem. Div., as the internal standard. The accuracies are estimated to be about 10.5 C.P.S. I n very dilute solutions, the average of several measurements was used to obtain the shift (OH-CH~,TM~). Data are reported in ternis of the field independent unit 6 &.p.m.
= (v
- YTMS)/GO
where the frequency for tetramethylsilane is arbitrarily h k e n as (8) C. >I. Huggins, G. C. Pimentel, and J. N. Shoolery, J . Chern. P h y s . . 23, 1244 (1955). (9) J. T. Arnold and &‘IE. . Paokard, ibid., 19, 1608 (1951).
J. R. FERRARO AND D. F. PEPPARD
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CHEMICAL SHIFTOF
THE
Vol. 67
TABLE I HYDROXYL PROTOX IS VARIOUS ORGANOPHOSPHORUS ACIDSAS 9 FCNCTION OF COKCENTRATIOK IN CCh AT 25' Phosphoric acids
Bis(2-ethylhexyl)
12.90(0.408)," 12.85(0.320), 12.75(0.154),12.61(0.114), 12.70(0.087),12.53(0.062),12.37(0.032), 12.22(0.023), 12.17(0.018), 12.32(0.017), 12.05(0.015), ll.95(0.011), 11.80(0.O O i ) , 11.70(0.0056), 11.32(0.0054), 11.17(0.0033), 10.90(0.0028) 12.83(0.444), 12.70(0.244),12.58(0.161), 12.03(0.017), 11.80(0.O l l ) , 11.72(0.009), 11.40(0.006), 11.05(0.003) 12.65(0.046), 12.21(0.O l O ) , l l . l l ( 0 . 0 0 5 ) 13.08(0,009),12,90(0.004), too insoluble for more concentrated solutions 13.24(0.046), 12.70(0.010), 12.46(0.007) 12.37(0.051), 11.65(0.009), 11.41(0.006), 10.95(0.003) 11.47(0.055), 11.00(0.012), 10.32(0.004) 12.37(0.046), 11.70(0.010), ll.Ol(O.005) l2.66(0.030), 12.24(0.010), 11.50(0.005)
Bis-m-tolyl Bis-n-butyl Bisphenyl Bis-o-tolyl Bis-yphenylprop yl Bisbutoxyethyl Biscyclohexyl Bis-6-phenylethyl
Hydrogen phosponates 2-Ethylhesyl2-ethylhexyl n-Butyl n-butyl %-Hexyl n-hexyl n Octyl chloromethyl 2-Ethylhexyl chloromethyl Beneyl phenyl Phenyl phenyl Butyl phenyl
12.92(0.464), 12.75(0.277),12.45(0.212), 12.43(0.051)! 12.18(0.017),12.13(0.012),11.88(0.007), 11.63(0.006), ll,10(0.004), 10.92(,0.005),10.88(0.003), 10.07(0.002) 11.75(0.050), 11.42(0.009), 11.12(0.005) 12.60(0.049), 12.20(0.009),11.58(0.004) 12.27(0.050), 11.56(0.008), ll.lO(O.005) 12.86(0.054), 12.45(0.009), 12.17(0.004) 13.57(0.05l), 12.83(0.O l O ) , 12.37(0.0O6) 13.41 (0,005), too insoluble for more concentrated solutions 12.92(0.046), 12.33(0.009), l1.83(0.004) Phosphinates
12.38(0.016), 12.31(0.013), 12.17(0.010), 12 .03(0.008), 11.78(0.006), 11.38(0.004), Biscyclohexyl 11.40(0.0040),11,12(0.003),10.42(0.0020),10.07(0.0016),too insoluble for more concentratedsolutions 12,37(0.OlO), 11,89(0.005),too insoluble for more concentrated solutions Cyclohexyl phenyl a Kumbers in parentheses are in units of mole fraction.
-
t-
=
0 LL
-
Bis- ( c y c I o h e x y l ) p h o s p h i n i c o c i d (t)
/
131 12
-
E
Bis-(m-tolyl)-phosphoric
2 - e t h y l hexyl
0
-
0.005
0.010
cc14
o c i d (X)
hydrogen 2 - e t h y l hexyl phosphonote
0.015
0.020
MOLE
0.025
(n)
0.030
0.035
0.040
0.045
FRACTION
Fig. 1.-Chemical shifts for the hydroxyl proton in several organophosphorus acids in CC14 a t low mole fractions of the acids. zero, and frequency increases in the direction of decreasing magnetic field strength. Spectra a t 60" were made by Dr. Donald P. Hollis a t Varian Associates, since a high temperature probe was not available to us.
Results and Discussion 1. Hydrogen Resonance of the Hydroxyl Group.
A. Concentration and Temperature Dependency.In all the measurements made, o d y one absorption band was found for the hydroxyl proton. This is in agrcrnient with invest igations of other hydrogalboiided systeiiisl" and indicates a rapid excliangc (IO) li. S.Gutouvky and A. Saika, J . Chem I'hys., 21, 1688 (1953).
between the protons of the various polymeric species. I n addition, the hydroxyl proton does not exhibit spin-spin coupling due to the presence of P31, as do the hydrogens on the a-CHPO-groups. These acids are predominantly dimeric and form an eight-membered ring, in which the hydroxyl hydrogens are rapidly exchanging between both of the oxygens in the bond aiid causing spin decoupliiig Kith P31. The resonance shows both a temperature and conceiitration dependency, and the hydroxyl proton shii't in both instalices is in the directiou of' the high-field sidc as the temperature increases and as the concenlratioll ie
Dee., 1963
P.M.R.STUDIES OF ACIDICORGANOPHOSPHORUS COMPOUNDS
decreased. Results for the 19 acids a t different concentrations are tabulated in Table I. The chemical shifts for several acids vs. the mole fraction of the acids in carbon tetrachloride a t 25' are plotted in Fig. 1. Typical spectra for several acids are presented in Fig. 2. The acids appear to behave similarly, and two main slopes are observed. From about 0.01 mole fraction to higher eoncentrations a shallow slope is obtained, while a t lower concentrations a rery steep slope is found. The shape of the dilution curve is similar to that observed for ethyl alcohol and phenols2S1l and to that obtained in recent work on monocarboxylic acids.4 Although extensive temperature studies were not done, it appears that a similar dependency exists with temperature. The shift to high field with dilution and with an increase in temperature must be the result of the breaking of hydrogen bonds. The protons attached to carbon atoms show no appreciable shifts with dilution or temperature increases. The initial shallow slope is probably due to the equilibria of dimers and higher aggregates. The actual amount of higher polymer must be very small. Infrared studies indicate only a single broad hydroxyl absorption, and this has been ascribed to the absorption of the dimeric species in CCI,. No infrared absorption has been reported for higher ~ p e c i e s . ~However, isopiestic studies do indicate6b average molecular weights greater than the dimer stage for some of these acids. The steep slope is probably due to the equilibria between dimers and monomers and actually occurs a t mole fractions of less than 0.005. The lowest points obtained on this slope are at the limits of the minimum concentrations measured by the A-60. B. Effect of Electronegative Groups on the Hydroxyl Proton Frequency.-At intermediate concentrations, the position of the hydroxyl proton resonance is a t about 11.5-13.6 p.p.m. In hydrogen-bonded polymers, the position of the proton resonance is determined by the state of aggregation and the strength of of the hydrogen bond. Infrared datal2 have indicated that these two factors are interdependent, and that as the size of the hydrogen-bonded polymer increases the hydrogen bonds become stronger. It has been observed that ithe acidic organophosphorus cornpounds containing phenyl groups are more highly aggregated than the dimer state.6b A tabulation of the hydroxyl hydrogen resonance for several acids at about 0.5 F solution in carbon tetrachloride is made in Table 11, and the phenyl-containing compounds do have higher yalues. It is
