Standard Reference Data, National Institute of Standards and
Technology, 1993.
Computational procedures
Density functional theory (DFT)26 calculations were per-
formed using the GAUSSIAN94-D4 package27 on an IBM
RISK/6000 workstation. For the geometry optimization and
frequency calculations for chroman and BD, the B3LYP func-
tionals were employed on the 6-31G(d) basis set. A factor
of 0.97 for the calculated vibrational frequencies was used to
correct for the anharmonicity of the molecular vibrations.28
14 M. M. Suryan, S. A. Kafafi and S. E. Stein, J. Am. Chem. Soc., 1989,
111, 1423.
15 S. E. Stein, J. M. Rukkers and R. L. Brown, NIST Structures and
Properties Database version 2.0, Gaithersburg, NIST Standard
Reference Data, National Institute of Standards and Technology,
1994.
16 J. Berkowitz, G. Barney Ellison and D. Gutman, J. Phys. Chem.,
1994, 98, 2744.
17 O. V. Dorofeeva, Thermochim. Acta, 1992, 200, 121.
18 F. G. Bordwell and X. Zhang, J. Am. Chem. Soc., 1994, 116, 973.
19 F. G. Bordwell, T. Gallagher and X. Zhang, J. Am. Chem. Soc., 1991,
114, 3495.
20 D. M. Golden, G. N. Spokes and S. W. Benson, Angew. Chem.,
Int. Ed. Engl., 1973, 12, 534; D. A. Robaugh and S. E. Stein,
Int. J. Chem. Kinet., 1981, 13, 445; M. Rossi and D. M. Golden,
Int. J. Chem. Kinet., 1979, 11, 715.
21 R. G. Gilbert and S. C. Smith, Theory of Unimolecular and
Recombination Reactions, Blackwell Scientific Publications, Oxford,
1990.
22 J. A. Walker and W. Tsang, J. Phys. Chem., 1990, 94, 3324.
23 G. Farina and G. Zecchi, Synthesis, 1977, 755.
24 M. L. Poutsma, in Free Radicals, ed. J. K. Kochi, Wiley, New York,
1973, vol. 2, p. 211; J. G. Traynham and Y. S. Lee, J. Am. Chem. Soc.,
1974, 96, 3590; W. Offerman and F. J. Vögtle, Org. Chem., 1978, 44,
710.
25 I. C. Calder, R. B. Johns and J. M. Desmarchelier, Org. Mass
Spectrom., 1970, 4, 121; K. K. Deb, J. E. Bloor and T. C. Cole, Org.
Magn. Res., 1970, 2, 431.
26 Density Functional Methods in Chemistry, ed. J. K. Labanowski and
J. Andzelm, Springer, New York, 1991; R. G. Parr and W. Yang,
Density Functional Theory of Atoms and Molecules, Oxford
University Press, Oxford, 1989; T. Ziegler, Chem. Rev., 1991, 91, 651;
R. O. Jones and O. Gunnarsson, Rev. Mod. Phys., 1989, 61, 689;
J. M. Seminario and P. Politzer, Modern Density Functional Theory:
A Tool for Chemistry, Elsevier, Amsterdam, 1995.
Acknowledgements
The authors would like to thank Roel Gronheid for performing
the DFT calculations, Enrico Boels, Jacco Luijendijk and Cris
Cannegieter for their contributions to the experimental work,
and Jeff Manion (NIST, Gaithersburg, USA) for the use of the
shock tube setup.
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Paper 8/00189H
Received 6th January 1998
Accepted 2nd March 1998
1178
J. Chem. Soc., Perkin Trans. 2, 1998