Conclusions
-
1)
1-Methyldicyclopentadiene (I) and 8-methyldicyclopentadiene (II) undergo a reversible thermal isomerization at 120–130°, leading to a mixture containing 56.2% (I) and 43.8% (II).
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2)
The kinetics of the isomerization of (I) ⇋ (II) were studied in the given temperature range. The Arrhenius activation energies and preexponential factors for the forward and reverse reaction were calculated [for (I)→(II) e1=28.8±0.4 kcal/mole, log Z1=11.67±0.15; for (II)→(I) E2=29.0±0.4 kcal/mole, log Z2=11.89±0.15].
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3)
The rate of the isomerization (I) ⇌ (II) is not changed by the action of acids, bases or Lewis acids and does not depend on the nature of the surface of the flask and on the presence of dissolved oxygen.
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4)
The reversible thermal isomerization (I) ⇌(II) is a variation of the retrodiene process, and occurs through a biradical mechanism with breakage of only one diene-dienophile bond.
-
5)
Depending on the nature of the diene and the dienophile, the diene synthesis can occur by two distinct mechanisms: one-stage and two-stage.
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Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 859–866, April, 1968.
For communication 24 see [1].
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Mironov, V.A., Fadeeva, T.M., Stepanyants, A.U. et al. Cyclic unsaturated compounds. Russ Chem Bull 17, 821–827 (1968). https://doi.org/10.1007/BF00905762
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DOI: https://doi.org/10.1007/BF00905762