296
Chapter 22 Free-Radical and Spin-Paired Diradical Reactions
10. R. Huisgen, (a) Angewandte. Chemie (Int. Ed.), 2, 565, 633 (1963); (b) J. Org. Chem.,
33, 2291 (1968); (c) ibid, 41, 404 (1976).
11. R.D. Harcourt, J. Mol. Structure, 12, 351 (1972).
12. R.D. Harcourt and W. Roso, Canad. J. Chem., 56, 1093 (1978).
13. P.C. Hiberty and C. Leforestier, J. Amer. Chem. Soc., 100, 2012 (1978).
14. R.D. Harcourt, Tetrahedron, 34, 3125 (1978), 35, 901 (1979).
15. R.D. Harcourt and J.F. Sillitoe, Aust. J. Chem., 27, 691 (1974).
16. S.P. Walch and W.A. Goddard III, J. Amer. Chem. Soc., 97, 5319 (1975).
17. R.A. Firestone, (a) J. Org. Chem., 33, 2285 (1968); J. Chem. Soc. A, 1570 (1970); (c) J.
Org. Chem., 37, 2181 (1972); (d) Tetrahedron, 33, 3009 (1977).
18. G. Leroy, M. Sana, L.A. Burke and M.-T. Nguyen, Quantum Theory of Chemical
Reactions, Vol. 1, (R. Daudel, A. Pullman, L. Salem and A. Veillard, eds.) Reidel
(1980), p. 91.
19. S. Patai and Y. Gotshal, T. Chem. Soc. Β, 489 (1966).
20. R.A. Abramovitch, Chem. Soc. Special Publication 24, 323 (1970).
Addendum Chapter 22
1.
In Refs. 21-24, increased-valence formulations are presented for:
a) metal-ion catalysed dehydrogenation reactions with O 2 and azide compounds
as oxidants.
b) the four electron reduction of O 2 to H 2 O in acid and alkaline solutions;
c) the reaction of HbO 2 with NO to form metHb + NO 3
-
;
d) the formation and decomposition of N 2 O 5 .
2.
Further consideration for the singlet-diradical mechanism for 1,3-dipolar cycloadditions is provided in Refs. 25a-c. It is to be noted that, as discussed for S N 2
reactions in the Chapter 21 Addendum, a constribution from the singlet-diradical
structure to the valence-bond resonance scheme is needed in order that the
cycloaddition reaction be concerted. This occurs in the valence-bond formulations
of both (31) → (28) and (34) →(36), but not for (24) → (25).
Spin coupled valence-bond formulations of the cycloaddition involve one fourorbital configuration for the active space electrons
26
, and use HC N O and
H 2 C N N as the valence –bond structures for HCNO and CH 2 NN.
Chapter 22 Free-Radical and Spin-Paired Diradical Reactions
10. R. Huisgen, (a) Angewandte. Chemie (Int. Ed.), 2, 565, 633 (1963); (b) J. Org. Chem.,
33, 2291 (1968); (c) ibid, 41, 404 (1976).
11. R.D. Harcourt, J. Mol. Structure, 12, 351 (1972).
12. R.D. Harcourt and W. Roso, Canad. J. Chem., 56, 1093 (1978).
13. P.C. Hiberty and C. Leforestier, J. Amer. Chem. Soc., 100, 2012 (1978).
14. R.D. Harcourt, Tetrahedron, 34, 3125 (1978), 35, 901 (1979).
15. R.D. Harcourt and J.F. Sillitoe, Aust. J. Chem., 27, 691 (1974).
16. S.P. Walch and W.A. Goddard III, J. Amer. Chem. Soc., 97, 5319 (1975).
17. R.A. Firestone, (a) J. Org. Chem., 33, 2285 (1968); J. Chem. Soc. A, 1570 (1970); (c) J.
Org. Chem., 37, 2181 (1972); (d) Tetrahedron, 33, 3009 (1977).
18. G. Leroy, M. Sana, L.A. Burke and M.-T. Nguyen, Quantum Theory of Chemical
Reactions, Vol. 1, (R. Daudel, A. Pullman, L. Salem and A. Veillard, eds.) Reidel
(1980), p. 91.
19. S. Patai and Y. Gotshal, T. Chem. Soc. Β, 489 (1966).
20. R.A. Abramovitch, Chem. Soc. Special Publication 24, 323 (1970).
Addendum Chapter 22
1.
In Refs. 21-24, increased-valence formulations are presented for:
a) metal-ion catalysed dehydrogenation reactions with O 2 and azide compounds
as oxidants.
b) the four electron reduction of O 2 to H 2 O in acid and alkaline solutions;
c) the reaction of HbO 2 with NO to form metHb + NO 3
-
;
d) the formation and decomposition of N 2 O 5 .
2.
Further consideration for the singlet-diradical mechanism for 1,3-dipolar cycloadditions is provided in Refs. 25a-c. It is to be noted that, as discussed for S N 2
reactions in the Chapter 21 Addendum, a constribution from the singlet-diradical
structure to the valence-bond resonance scheme is needed in order that the
cycloaddition reaction be concerted. This occurs in the valence-bond formulations
of both (31) → (28) and (34) →(36), but not for (24) → (25).
Spin coupled valence-bond formulations of the cycloaddition involve one fourorbital configuration for the active space electrons
26
, and use HC N O and
H 2 C N N as the valence –bond structures for HCNO and CH 2 NN.