Abstract
The gas-phase reactions of negative ions (O-., NH −2 , C2H5NH−, (CH3)2N−, C6H t-5 , and CH3SCH −2 ) with fluorobenzene and 1,4-difluorobenzene have been studied with Fourier transform ion cyclotron resonance mass spectrometry. The O−. ion reacts predominantly by (1) proton abstraction, (2) formal H +.2 abstraction, and (3) attack on an unsubstituted carbon atom. In addition to these processes, attack on a fluorine bearing carbon atom yielding F− and C6H4FO− ions occurs with 1,4-difluorobenzene. Site-specific deuterium labeling reveals the occurrence of competing 1,2-, 1,3-, and 1,4-H +.2 abstractions in the reaction of O−. with fluorobenzene. Attack of the O−. ion on the 3- and 4-positions in fluorobenzene with formation of the 3- and 4-fluorophenoxide ions, respectively, is preferred to reaction at the 2-position, as indicated by the relative extent of loss of a hydrogen and a deuterium atom in the reactions with labeled fluorobenzenes. The NH −2 , C2H5NH−, (CH3)2N−, C6H −5 , and CH3SCH −2 anions react with fluoroberuene and 1,4-difluorobenzene only by proton abstraction. The relative importance of H+ and D+ abstraction in the reaction of these anions with labeled fluorobenzenes indicates that the 2-position in fluorobenzene is more acidic than the 3- and 4-positions, suggesting that the literature value of the gas-phase acidity of this compound (ΔH oacid = 1620 ± 8 kJ mol−1) refers to the former site. Based on the occurrence of reversible proton transfer between the CH3O− ion and 1,4-difluorobenzene, the ΔH oacid of this compound is redetermined to be 1592 ± 8 kJ mol−1.
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References
Harrison, A. G. Chemical Ionization Mass Spectromety; CRC: Boca Raton, FL, 1983.
Busch, K. L.; Glish, G. L.; McLuckey, S. A. Mass Specfrmtry/Mass Spectromtey; Verlag Chemie: Weinheim, 1988.
Nibbering, N. M. M. Adv. Phys. Org. Chem. 1988, 24, 1–53.
Bruins, A. P.; Ferrer-Correia, A. J. V.; Harrison, A. G.; Jennings, K.R.; Mitchum, R. K. Adv. Mass Spectrom. 1978, 7A, 355–358.
Leopold, D. G.; Miller, A. E. S.; Lineberger, W. C. J. Am. Chem. Soc. 1986, 108, 1379–1384.
Matimba, H. E. K.; Crabbendam, A. M.; Ingemann, S.; Nibbering, N. M. M. J. Chem. Soc. Chem, Commun. 1991, 644-645.
Guo, Y.; Grabowski, J. J. J. Am. Chem. Soc. 1991, 213, 5923–5931.
VanOrden, S. L.; Malcomson, M. E.; Buckner, S. W. Anal. Chim. Acta. 1991, 246, 199–210.
Dawson, J. H. J.; Nibbering, N. M. M. J. Am. Chem. Soc. 1978, 100, 1928–1929.
Guo, Y.; Grabowski, J. J. Int. J. Mass Spectrom. Ion Processes 1990, 97, 253–264.
Dawson, J. H. J.; Nibbering, N. M. M. Int. J. Mass Spectrom. Ion Processes 1980, 33, 3–19.
Grabowski, J. J.; Melly, S. J. Int. J. Muss Spectrom. Ion Processes 1987, 81, 147–164.
Matimba, H. E. K.; Crabbendam, A. M.; Ingemann, S.; Nibbering, N. M. M. Int. J. Mass Spectrom. Ion Processes 1992, 114, 85–97.
van der Wel, H.; Nibbering, N. M. M. Int. J. Mass Spectrom. Ion Processes 1986, 72, 145–153.
van der Wel, H.; Nibbering, N. M. M. Recl. Trav. Chim. Pays-Bas 1988, 107, 479–490.
Marshall, A.; Tkaczyk, H.; Harrison, A. G. J. Am. Soc. Mass Spectrom. 1991, 2, 292–298.
Dawson, J. H. J.; Noest, A. J.; Nibbering, N. M. M. Int. J. Mass Spectrom. Ion Processes 1979, 30, 189–191.
Meot-Ner (Mautner), M.; Kafafi, S. A. J. Am. Chum. Soc., 1988, 110, 6297–6303.
Wenthold, P. G.; Paulino, J. A.; Squires, R. R. J. Am. Chem. Soc. 1991, 113, 7414–7415.
Marshall, A. G.; Verdun, F. R. Fourier Transforms in NMR, Optical and Muss-Spectrometry; Elsevier: Amsterdam, 1990.
Koning, L. J. de; Kort, C. W. F.; Pinkse, F. A.; Nibbering, N. M. M. Int. J. Mass Spectrom. Ion Processes 1989, 95, 71–92, and references cited therein.
Peerboom, R. A. L.; Ingemann, S.; Nibbering, N. M. M.; Liebman, J. F. J. Chem. Soc. Perkin Trans. 2 1990, 1825–1828, and references cited therein.
Chantry, P. J. J. Phys. Chem. 1969, 51, 3369–3379.
Bak, B. J. Org. Chem. 1956, 22, 797–798.
Vogel, A. I., Vogel’s Textbook of Practical Organic Chemistry, 5th ed.; Longman: New York, 1989.
Lias, S. G.; Bartmess, J. E.; Liebman, J. F.; Holmes, J. L.; Levin, R. D.; Mallard, W. G. J. Phys. Chem. Ref. Data 1988, 17, Suppl. 1.
Briscese, S. M. J.; Riveros, J. M. J. Am. Chem. Soc. 1975, 97, 230–231.
Ingemann, S.; Nibbering, N. M. M.; Sullivan, S. A.; DePuy, C. H. J. Am. Chem. Soc. 1982, 104, 6520–6527.
Ingemann, S.; Nibbering, N. M. M. J. Org. Chem. 1983, 48, 183–191.
Grabowski, J. J.; DePuy, C. H.; Doren, J. M. van; Bierbaum, V. M. J. Am. Chem. Soc. 1985, 107, 7384–7389.
Bartmess, J, E.; McIver, Jr., R. T. In Gas Phase ion Chemistry, Vol. 2; Bowers, M. T., Ed.; Academic Press: New York, 1979; p 87.
Cumming, J. B.; Kebarle, P. Can. J. Chem. 1978, 56, 1–9.
Marcus, R. A.; Sutin, N. Biochim. Biophys. Acta 1985, 811, 265–322.
Han, C. C.; Brawnan, J. I. J. Am. Chem. Soc. 1989, 112, 6491–6496.
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Matimba, H.E.K., Ingemann, S. & Nibbering, N.M.M. Gas-phase reactions between O−. and C6H5F: On the acidity of fluorobenzene and 1,4-difluorobenzene. J Am Soc Mass Spectrom 4, 73–81 (1993). https://doi.org/10.1016/1044-0305(93)85045-Y
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DOI: https://doi.org/10.1016/1044-0305(93)85045-Y