Transient intermediates in the laser flash photolysis of ketoprofen in aqueous solutions: Unusual photochemistry for the benzophenone chromophore

Journal of the American Chemical Society

Volumn 119, Issue 45, 1997, Pages 11066-11070

  Martinez L J ^a   Scaiano, J C ^a  

^a UNIVERSITY OF OTTAWA   (Canada)

Author keywords

[No Author keywords available]

Indexed keywords

BENZOPHENONE DERIVATIVE; KETOPROFEN;

AQUEOUS SOLUTION; ARTICLE; CHROMATOPHORE; LASER; PHOTOCHEMISTRY; PHOTOLYSIS;

EID: 0030682401     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja970818t     Document Type: Article

References (47)

1. Scaiano, J. C. J. Photochem. 1973/74, 2, 81.
2. Turro, N. J. Modern Molecular Photochemistry, Benjamin/Cummings Publishing Co.: Menlo Park, 1978; p 628.
3. Scaiano, J. C.; Selwyn, J. C. Can. J. Chem. 1981, 59, 2368.
4. Scaiano, J. C.; Abuin, E. B.; Stewart, L. C. J. Am. Chem. Soc. 1982, 104, 5673.
5. Bensasson, R. V.; Gramain, J.-C. J. Chem. Soc., Faraday Trans. 1 1980, 76, 1801.
6. Beckett, A.; Porter, G. Trans. Faraday Soc. 1963, 59, 2051.
7. Dormán, G.; Prestwich, G. D. Biochemistry 1994, 33, 5661.
8. Schallreuter, K. U.; Wood, J. M.; Farwell, D. W.; Moore, J.; Edwards, H. G. M. J. Invest. Dermatol. 1996, 106, 583.
9. Silva, R.; Almeida, L. M. S.; Brandao, F. M. Contact Dermatitis 1995, 32, 176.
10. Alomar, A.; Gerda, M. T. Contact Dermatitis 1989, 20, 74.
11. Szczurko, C.; Dompmartin, A.; Michel, M.; Moreau, A.; Leroy, D. Photodermatol., Photoimmunol. Photomed. 1994, 10, 144.
12. Bell, J. A.; Linschitz, H. J. Am. Chem. Soc. 1963, 85, 528.
13. Elisei, F.; Favaro, G.; Görner, H. J. Photochem. Photobiol. A: Chem. 1991, 59, 243.
14. Boscá, F.; Miranda, M. A.; Carganico, G.; Mauleön, D. Photochem. Photobiol. 1994, 60, 96.
15. Constanze, L. L.; De Guidi, G.; Condorelli, G.; Cambria, A.; Fama, M. Photochem. Photobiol. 1989, 50, 359.
16. Budac, D.; Wan, P. J. Photochem. Pholobiol. A: Chem 1992, 67, 135.
17. Studies in cellular systems suggest free radical involvement: Chignell, C. F.; Sik, R. H. Photochem. Photobiol. 1995, 62, 205.
18. While this manuscript was being reviewed we became aware of similar studies conducted by S. Monti (Monti, S.; Sortino, S.; De Guidi, G.; Marconi, G. J. Chem. Soc., Faraday Trans. Submitted for publication).
19. Other aspects of the system are similar to those described earlier: Scaiano, J. C. J. Am. Chem. Soc. 1980, 102, 7747. Scaiano, J. C.; Tanner, M.; Weir, D. J. Am. Chem. Soc. 1985, 107, 4396.
20. Other aspects of the system are similar to those described earlier: Scaiano, J. C. J. Am. Chem. Soc. 1980, 102, 7747. Scaiano, J. C.; Tanner, M.; Weir, D. J. Am. Chem. Soc. 1985, 107, 4396.
21. Hug, G. L. Optical Spectra of Nonmetallic Inorganic Transient Species in Aqueous Solution; National Bureau of Standards: Washington, 1981; NSRDS-NBS 69, p 160.
22. Carmichael, I.; Hug, G. L. J. Phys. Chem. Ref. Data 1986, 15, 1.
23. The differences observed in organic solvents could be related to the protonation state of this propionic acid. This is currently under investigation.
24. Lachish, U.; Shafferman, A.; Stein, G. J. Chem. Phys. 1976, 64, 4205.
25. Sauberlich, J.; Brede, O.; Beckert, D. J. Phys. Chem. 1996, 100, 18101.
26. Sauberlich, J.; Beckert, D. J. Phys. Chem. 1995, 99, 12520.
27. Baral-Tosh, S.; Chattopadhyay, S. K.; Das, P. K. J. Phys. Chem. 1984, 88, 1404.
28. Chatgilialoglu, C. In Handbook of Organic Photochemistry; Scaiano, J. C., Ed.; CRC Press: Boca Raton, FL, 1989; Vol. II, p 3.
29. 2 we believe that decarboxylation following the direct excitation of KP occurs within the duration of the laser pulse. (a) Wang, J.; Itoh, H.; Tsuchiya, M.; Tokumaru, K.; Sakuragi, H. Tetrahedron 1995, 57, 11967. (b) Wang, J.; Tateno, T.; Sakuragi, H.; Tokumaru, K. Tetrahedron 1995, 92, 53.
30. 2 we believe that decarboxylation following the direct excitation of KP occurs within the duration of the laser pulse. (a) Wang, J.; Itoh, H.; Tsuchiya, M.; Tokumaru, K.; Sakuragi, H. Tetrahedron 1995, 57, 11967. (b) Wang, J.; Tateno, T.; Sakuragi, H.; Tokumaru, K. Tetrahedron 1995, 92, 53.
31. -1). Therefore, we can only provide a lower limit for the decarboxylation process.
32. The estimate is in line with similar lower limits obtained for other acyl radicals leading to benzylic radical centers: Steenken, S.; Warren, C. J.; Gilbert, B. C. J. Chem. Soc., Perkin Trans. 2 1990, 335.
33. -1 (Hilborn, J. W.; Pincock, J. A. J. Am. Chem. Soc. 1991, 113, 2683). The only absolute measurement corresponds to the radical derived from 9-methylfluorene-9-carboxylate with a lifetime of ca. 55 ps: Falvey, D. E.; Schuster, G. B. J. Am. Chem. Soc. 1986, 108, 7419.
34. -1 (Hilborn, J. W.; Pincock, J. A. J. Am. Chem. Soc. 1991, 113, 2683). The only absolute measurement corresponds to the radical derived from 9-methylfluorene-9-carboxylate with a lifetime of ca. 55 ps: Falvey, D. E.; Schuster, G. B. J. Am. Chem. Soc. 1986, 108, 7419.
35. Ross, A. B.; Mallard, W. G.; Helman, W. P.; Bielski, B. H. J.; Buxton, G. V.; Cabelli, D. A.; Greenstock, C. L.; Huie, R. E.; Neta, P. NDRL/NIST Solution Kinetics Database: Ver. 1, 1.0 ed.; NIST, U.S. Department of Commerce: Gaithersburg, MD, 1992.
36. Hayon, E.; Ibata, T.; Lichtin, N. N.; Simic, M. J. Phys. Chem. 1972, 76, 2072.
37. a of the benzophenone ketyl radical anion has been reported to be 9.2 (see ref 28).
38. Small, R. D.; Scaiano, J. C. J. Phys. Chem. 1977, 81, 828.
39. Small, R. D., Jr.; Scaiano, J. C. J. Phys. Chem. 1977, 81, 2126.
40. Caldwell, R. A.; Dhawan, S. N.; J. Am. Chem. Soc. 1985, 107, 5163.
41. The rate constant is below diffusion control, but somewhat faster than comparable isoenergetic triplet energy migration as expected for a slightly exothermic transfer: Encinas, M. V.; Scaiano, J. C. Chem. Phys. Lett. 1979, 63, 305.
42. Naturally, the precursor process (sensitization) needs to be faster than the decay of the intermediate of interest for this species to be detectable. For the 600-nm transient this would require such high concentrations of KP that selective excitation of the sensitizer would be impossible. The experiments do show the absence of KP triplet in the time scale available through sensitization.
43. The 1-azaxanthone triplet is a much better electron acceptor than the electron rich triplet of 4-methoxyacetophenone.
44. Alternatively, the KP carbanion could be the species involved in the electron transfer reaction. It is well documented that carbanions that are not resonance stabilized can transfer an electron to photoexcited aromatic hydrocarbons. Budac, D.; Wan, P. Adv. Carbohydr. Chem. 1996, 2, 147.
45. A seminal study of the carbanion derived fron p-nitrophenyl acetate has been reported: Craig, B. B.; Weiss, R. G.; Atherton, S. J. J. Phys. Chem. 1987, 91, 5906.
46. Thiols were among the earliest reported biradical scavengers: Wagner, P. J.; Kelso, P. A.; Zepp, R. G. J. Am. Chem. Soc. 1972, 94, 7480.
47. Bockrath, B. a. L. M. D. J. Am. Chem. Soc. 1974, 96, 5708.