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Anal. Chem. 1982, 54, 1641-1642
and 10” F in NaF. ThLe CMEs were then soaked for about 30 min in triply distilled1water and placed in lo4 F NaF. The amounts of MV2+cont,ained in the polymer films were then determined by quantitatively reducing the films at -0.8 V (vs. SCE) and counting the charge required to reoxidized the reduced films. The results of this study are shown in Table I. The data indicate that the reconstituted films have somewhat diminished exchange capacities. It is very important to point out, however, that 100% of the theoretical maximum number of sites could not be obseirved electrochemically in the 970 ew polymer either (IO). Hence, it seem likely that the apparently diminished exchange capacities are an artifact of the electrochemical measurement rather than a true loss of -SO3- sites from the films. In any event, the film clearly retains a more than ample supply of exchange sites. As a final attempt t o determine whether thermal degradation occurs during dissolution, we have compared the amount of polymer added to the reactor to the amount of polymer present after the dissolution procedure was completed. For this study, 5-mL aliquots of 0.6% solutions were evaporated to dryness and weighed. The observed weights were within 2% of the expected weights in all cases. Given the volatilities of the solvents used, the propensity of the polymer to absorb atmospheric water and the possibility of adsorption of the polymer to the glassware used, these results indicate that no material is lost (e.g., through thermal degradation and volatilization) (18)as a result of the dissolution process. LITIERATURE CITED (1) Oyama, N.; Anson, F. C. J . Electrochem. SOC. 1980, 727, 247. (2) Oyama, N.; Anson, F. C. Anal. Chem. 1980, 52, 1192.
Shigehara, K.; Oyama, N.; Anson, F. C. Inorg. Chem. 1981, 20, 518. Rubenstein, I.; Bard, A. J. J . Am. Chem. SOC. 1980, 702, 6641. Henning, T. P.; White, H. S.;Bard, A. J. J . Am. Chem. SOC.1081, 703, 3937. Rubenstein, I.; Bard, A. J. J . Am. Chem. SOC. 1981, 703, 5007. Buttry. D. A.; Anson, F. C. J . Electroanal. Chem. 1981, 730, 333. Bruce, J. A.; Wrighton, M. S. J . Am. Chem. SOC. 1982, 704, 74. Martin, C. R.; Rubenstein, I.; Bard, A. J. J . Am. Chem. Soc., In press. White, H. S.;Leddy, J.; Bard, A. J. J . Am. Chem. SOC.,in press. Martin, C. R.; Freiser, H. Anal. Chem. 1980, 53, 902. Fisher, Charles, DuPont Co., Wllmington, DE, personal communication. Mattln, C. R., unpublished results. Yeo, R. S. Po&mer 1980, 27, 432. Qierke, T. D. Presented to the 152nd National Meeting of the Electrochemical Society, Atlanta, QA, Oct 1977. Lee, P. C.; Meisei, D. J . Am. Chem. SOC. 1980, 120, 5477. Morrison, R. T.; Boyd, R. N. “Organic Chemistry”; Ailyn and Bacon: Boston, MA, 1973; Voi. 3, p 554. “Nafion Perfluorosuifonic AcM Products, Safety in Handilng and Use”; Brochure E-24084; DuPont Co., Plastic Products and Resins Depattment: Wllmington, DE.
Charles R. Martin* Teresa A. Rhoades James A. Ferguson Department of Chemistry Texas A&M University College Station, Texas 77843
RECEIVED for review April 2, 1982. Accepted May 17, 1982. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for the support of this research. The authors acknowledge discussions with Allen J. Bard, Keith Wellbourn, and Henry White of the University of Texas a t Austin.
Trifluoromethanesulforiyl Chloride for Identification of Oxygen, Nitrogen, and Sulfur Functional Groups by Fluorine-19 Nuclear Magnetic Resonance Spectrometry Sir: NMR spectrometry has been a powerful tool for determination of organic structure and fiunctionality. A summary of ”, I3C, and I9F NMR methods for organic functional group analysis has been reported (1). ?3i NMR has also been employed recently foi. hydroxy functional group characterization by silylation (2). ?F’ NMR appears to have the greatest potential utility for functional group determination due to its high sensitivity and wide chemical shift range. The fluorine reagents used have been hexafluoroacetone (3-7), trifluoroacetic anhydride (8),and trifluoroacetyl chloride (9) for derivatization of active hydrogen containing compounds (e.g., alcohols, amines, and thiols) and p-fluorophenol (I) for hydrogen bonding with blasic nitrogen compounds. In this paper, we wish to introduce a new fluorine reagent, trifluoromethanesulfonyl chloride, which not only yields sulfonation products with active hydrogen containing compounds but also forms stable complexes with tertiary nitrogen bases. The 19F chemical shifts for the trifluoromethanesulfonyl derivatives of selected model compounds are presented and discussed in relation to structural effects.
as well as nondeuterated solvents were used) in 5-mm NMR tubes. Reactions were carried out in the presence, or absence, of tertiary nitrogen base catalysts at room temperture or 0 “C depending on the reaction rates. The entire reaction can be completed in minutes or hours depending on individual compounds. A Varian T-60 NMR spectrometer was used to obtain 19FNMR spectra at 54.6 MHz. lPF chemical shifta were reported in parts per million in reference to the trifluoromethanesulfonyl chloride signal with a positive sign indicating a downfield shift from trifluoromethanesulfonyl chloride.
RESULTS AND DISCUSSION The 19Fchemical shift data for various trifluoromethanesulfonyl derivatives of model compounds are presented in Table I. With the exception of tertiary nitrogen bases (sample no. 14-17), the I9F chemical shift of all the trifluoromethanesulfonyl derivatives shows little or no solvent effect (the value for chemical shifts is generally lower than 0.01). Tertiary nitrogen bases interact with trifluoromethansulfonyl chloride presumably by a Lewis acid-Lewis base complexation mechanism as shown below:
EXPERIMENTAL SECTION Trifluoromethanesulfonylchloride purchased from Aldrich was kept in a desiccator under nitrogen. Samples were prepared with an approximate 2:l ratio of trifluoromethanesulfonyl chloride/ substrate in various solvents (e.g., dimethylformamide,dimethyl sulfoxide, tetrahydroban and chloroform, perdeuterated solvents 0003-2700/82/0354-1641$01.25/0
F,CSO,
The 19Fchemical shift of the complex increases as the solvent 0 1982 American Chemical Society
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Anal. Chem. 1982, 5 4 , 1642-1644
Table I. 19FChemical Shifts of Trifluoromethanesulfonyl Derivatives of Model Compounds chemical shift,a sample compound no. PPm 1 tert-butyl alcohol -8.18 2 -4.56 sec-butyl alcohol 3 -3.72 n-butyl alcohol 4 -3.70 isobutyl alcohol methanol 5 -3.20 6 -2.60 benzyl alcohol a -naphthol 7 t 1.72 8 t2.12 phenol a-naphthol 9 t 2.66 10 -2.72 sec-butylamine 11 n-butylamine -1.72 N-methylaniline -0.90 12 13 aniline -0.36 -2.64 (in CDCl,), 14 triethylamine -2.36 (in DMF) 15 pyridine -2.58 (in CDCl,), -2.26 (in DMF) quinoline 16 -2.52 (in CDCl,), -2.14 (in DMF) -2.44 (in CDCl,), acridine 17 -2.06 (in DMF) pyrrole 18 -8.80b indole 19 -8.40,b t 3.74' t 8.20 carbazole 20 thiophenol -1.94 21 a Both DMF and DMF-d, as well as CDCl, have been used, shifts are smaller than 0.01. For the C-2 sulfoFor the N-sulfonated product. nated product.
polarity increases. Since only one 19FNMR signal is observed in a mixture of tertiary nitrogen bases, rapid exchange of the bases for the electrophilic sulfonyl center must occur. The 19F chemical shifts for the trifluoromethanesulfonyl derivatives of aliphatic alcohols (sample no. 1-5) cover a range of -5 ppm indicating a prominent sensitivity to structural variations. This may provide an alternative method of differentiating primary, secondary, and tertiary alcohols. A distinct separation between the 19Fchemical shifts of the trifluoromethanesulfonyl derivatives of aliphatic alcohols and phenols is also noted. The IgF chemical shifts of primary and secondary amines (sample no. 10-13) follow the same trends as those of alcohols and phenols. In general, alkyl substitution increases the fluorine shielding and phenyl substitution de-
creases the fluorine shielding. The reactions of pyrrolic-ring compounds with trifluoromethanesulfonyl chloride are more complicated. For pyrrole, trifluoromethanesulfonyl chloride reacts by a C-2 sulfonation mechanism in the presence, or absence, of the tertiary nitrogen base catalyst. The reaction of indole with trifluoromethanesulfonyl chloride occurs to yield either the C-2 or the N-sulfonated product depending on the absence, or presence, of the tertiary nitrogen base. N-Sulfonation is favored in the presence of the base. For cabazole, since a C-2 position is not available, reactions occur slowly due to steric hindrance to give the normal N-sulfonated product only in the presence of the base catalyst. The unusually low fluorine shielding for the trifluoromethanesulfonyl derivatives of carbazole has yet to be explained. The limited data for the series of the pyrrolic-ring compounds do not allow us to draw any conclusions as to the trends of the fluorine shielding. Trifluoromethanesulfonyl chloride has been pointed out as being both a sulfonating and chlorinating reagent (10). Chlorination would produce trifluoromethanesulfonic acid with a 19FNMR signal at -11.5 ppm which was not observed for model compounds studied. The present work gives only the qualitative results for limited compounds. Further studies will be directed toward the quantitative aspects of the reaction of trifluoromethanesulfonyl chloride with a variety of compounds. LITERATURE CITED (1) Martin, T. F.; Snape, C. E.: Bartle, K. D. Prep. Pap.-Am. Chem. SOC.,Dlv. Fuel Chem. 1980, 25 (4),79. (2) Coleman, W. M., 111; Boyd, A. R. Anal. Chem. 1982, 54, 133. (3) Leader, G. R. Anal. Chem. 1970, 42, 16. (4) Leader, G. R. Anal. Chem. 1973, 45, 1700. (5) Ho, F. F A . Anal. Chem. 1973, 45, 603. (6) Ho, F. F.-L. Anal. Chem. 1974, 4 6 , 496. (7) Ho, F. F.-L.; Kohier, R. R. Anal. Chem. 1974, 46, 1302. (6) Manatt, S.L. J . Am. Chem. SOC. 1986, 88, 1323. (9) Sleevl, P.; Galss, T. E.; Dorn, H. C. Anal. Chem. 1979, 51, 1931. ( I O ) Haklmelakl, G. H.; Just, G., Tetrahedron Lett. 1979, 3643.
Feng F a n g S h u e Teh Fu Yen* Department of Chemical Engineering University of Southern California Los Angeles, California 90007 RECEIVED for review March 8,1982. Accepted April 29,1982. Support from U S . Department of Energy Contract No. 79EV10017.000 is acknowledged.
Room-Temperature Phosphorescence of Nitrogen Heterocycles and Aromatic Amines Sir: Room-temperature phosphorescence (RTP) has generated considerable interest over the past several years (1-10). Reviews have also appeared on the subject (11-14). Several materials have been used to induce R T P from a variety of compounds. However, there is still a need to test additional materials and experimental conditions for R T P so the maximum sensitivity and selectivity can be obtained. In this work, three solid surfaces and several experimental conditions were tested for RTP of nitrogen heterocycles and aromatic amines. Nitrogen heterocycles and aromatic amines are an important class of compounds as shown by work in areas such as environmental research and coal liquefaction research (15, 16). EXPERIMENTAL SECTION Apparatus. All RTP intensity data were obtained with a Schoeffel SD3000 spectrodensitometer equipped with a SDC 300
density computer (Schoeffel Instruments, Westwood, NJ) and a phosphoroscope accessory. Details of instrumental setup were reported previously ( I 7). Relative RTP signals were measured with the spectrodensitometer with the inlet and exit slits set at 2 mm and 3 mm, respectively. A 150-W Xe lamp (Conrad Hanovia Inc., Newark, NJ) and R928 photomultiplier tube (Hamamatsu Corp., Middlesex, NJ) were employed in the spectrodensitometer. Reagents. Ethanol was purified by distillation. All nitrogen heterocycles and aromatic amines were recrystallized from ethanol. The plastic-backed silica gel chromatoplates (EM Laboratories, Elmsford, NY) and filter paper (Whatman No. 1)were developed in distilled ethanol to concentrate impurities at one end. Polyacrylic acid (PAA)-sodium chloride mixtures (0.5%w/w) were prepared by grinding to a homogeneous powder in a ball-mill. Procedure. Stock solutions of all compounds in distilled ethanol were used to prepare four different spotting solutions (neutral, 0.1 M HC1, 0.1 M HBr, and 0.1 M NaOH) of each
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