Abstract
The primayy step of the o-nitrobenzaldehyde-o-nitrosobenzoic acid photorearrangement in solution has been studied by flash absorption with 35 ps 355 nm light pulses. Flash photolysis of o-nitrobenzaldehyde in acetonitrile or THF solutions produces a transient absorption with a maximum at ca. 440 nm. Formation of the transient was < 35 ps, the laser pulse width, and within experimental error, no furthrr buildup was observed. The transient which decayed at nanosccond times is attributed to a remarkably reactive ketene intermediate formed by H abstraction of the aldehydic hydrogen by the excited state of the nitro group. Decay of the ketene was more rapid in water-acetonitrile, methanol-acetonitrile, tert-butyl alcohol and in THF than in acetonitrile solution. It is suggested that the intramolecular reaction of the ketene intermediate is enhanced in THF relative to acetonitrile because of the ability of THF to faciliaate proton transfer associated with the reaction.
The addition of the triplet quencher cis-piperylene to a solution of o-nitrobenzaldehyde in THF did not accelerate decay of the transient nor reduce its yield. The n,π* triplet excited state band observed in the 625–650 nm region for a number of the nitroaromatic compounds was not observed in the case of o-nitrobenzaldehyde. The results provide evidence that in the direct irradiation on o-nitrobenzaldehyde in THF or acetonitrile solutions, the intramolecular reaction occurs from the singlet rather than the triplet excited state.
Similar content being viewed by others
References
For early publications on the mechanism, see a) P.A. Leighton and F.A. Lucy, J. Chem. Phys., 2(1934)756; b) F.A. Lucy and P.A. Leighton, ibid., 3(1934)760; c) J.N. Pitts, Jr., J.K.S. Wan, and E.A. Schuck, J. Am. Chem. Soc, 86(196430006; d) P. de Mayo and S.T. Reid, Quar. Rev., 15(1961)39.
G. Ciamician and P. Silber, Chem. Ber., 34(1901)2040; Ibid., 35(190219992.
D. Döpp, Top. Curr. Chem., 55(1975)40.
The meta- and para-substituted nitrobenzyl derivatives which do not possess hydrognn atoms for intramolecular abstraction undergo instead photoredox reactions (see for instance, P. Wan and K. Yates, J. Org. Chem., 48(1983)136).
R. Dessaurr and J.P. Paris in W.A. Noyes, Jr., G.S. Hammond, and J.N. Pitts (Eds.), Advancss in Photochemistry, Interscience, New York, 1963, Vol. 1, p. 275.
a) J. Hébert and D. Gravel, Can. J. Chem., 52(1974)1887; b) D. Gravel, J. Hébert and D. Thoraval, Can. J. Chem., 61(1983400; c) D. Gravel, S. Murray, and G. Ladouceur, Chem. Commun., (1985)182; d) For excellent reviews see B. Amit, U. Zehavi, and A. Patchornik, Israel J. Chem., 12(1974)103; W.N.R. Pillai, Synthesis, (1980)1.
a) E. Reichmanis, R. Gooden, C.W. Wilkins, Jr., and H.J. Schonhorn, J. Polym. Sci., Chem. Ed., 21(1983)1075; b) H. Barzynski, D. Sanger, Angew. Makromol., 93(1981)131.
R.W. Yip, D.K. Sharma, R. Giasson, and D. Gravel, J. Phys. Chem., 88(1984)5770.
R.W. Yip, D.K. Sharma, R. Giasson, and D. Gravel, J. Phys. Chem., 89(1985)5328.
M.V. George and J.C. Scaiano, J. Phys. Chem., 84(1980)492.
W.G. Filby and K. Günther, Z. Physik. Chem., N.F., 95(1975)289.
The kinetics of the transient was treated using a quasi-4-level kinetic scheme (see R. Le Sage, K.L. Sala, R.W. Yip, and C.L. Langford, Can. J. Chem., 61(1983)2761) in which changes in the ground state population were neglected, and vibrational relaxation of the Franck-Condon state initially populated by the excitation flash was assumed fast. Erross in the rate constant for decay of the transient was estimated using the method reported by Nagakuaa and coworkess (Bull. Chem. Soc. Jpn., 53(1980)43).
Sensitization resulss places the triplet energy of o-nitrobenzaldehyde at ca. 60 kcal mol-1. See W.G. Filby and K. Gunther, Z. Physik. Chem. N.F., 125(1981)21.
When samples containing methanol were subjected to extensive photolysis, a small amount of a species which possessed a broad absorption in the 425–600 nm region was observed from 500 ps to 10 ns, the limit of our optical delay.
a) S.K. Chattopadhyay and B.B. Craig, J. Phys. Chem., 91(1987)323; b) S.J. Atherton and B.B. Craig, Chem. Phys. Lett., 127(1986)7; c) B.B. Craig and S.J. Atherton in A.B. Harvey (Ed.)., Appiications of Laser Chemistry and Diagnostics, SPIE, 482(1984)96.
a) J.D. Margerum, L.J. Miller, E. Saito, M.S. Brown, and H.S. Mosher, J. Phys. Chem., 66(1962)2434; b) G. Wettermark, J. Phys. Chem., 66(1962) 2560; c) G. Wettermark and R. Ricci, J. Chem. Phys., 39(1963)1218; d) M.E. Langmuir, L. Dogliotti, E.D. Black, and G. Wettermark, J. Am. Chem. Soc, 91(1969)2204.
H. Schupp, W.K. Wong, and W. Schnabel, J. Photochem., 36(1987)85.
S.L. Murov, Handbook of Photochemistry, Marcel Dekker, New York, 1973.
For nucleophilic attack of ketenes, see for instance, A.D. Allen, J. Kresge, N.P. Schepp, and T.T. Tidwell, Can. J. Chem., 65(1987)1719.
R.W. Yip, D. Gravel, and R.G. Giasson, to be published.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Yip, R.W., Sharma, D.K. The reactive state in the photo-rearrangement of o-nitrobenzaldehyde. Res Chem Intermed 11, 109–116 (1989). https://doi.org/10.1163/156856789X00014
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1163/156856789X00014