Position of the equilibrium during the migration of double bonds in the pyrazoline ring |
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Authors: | B V Ioffe N B Burmanova |
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Institution: | 1. A. A. Zhdanov Leningrad State University, USSR
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Abstract: | Data characterizing the position of the equilibrium between Δ2- and Δ1-pyrazolines with alkyl substituents in different positions, which is established under the influence of potassium tertbutoxide in tert-butyl alcohol at 90°C, were obtained. 3-Alkyl-Δ2-pyrazolines are thermodynamically more stable than their isomers with different positions of the double bond, so that the fraction of the latter in equilibrium mixtures does not exceed 1–2%, and they are practically completely isomerized to the 3-Alkyl-Δ2-substituted derivatives. If the position of the side chains excludes the possibility of the formation of 3-alkyl-Δ2-pyrazolines by migration of the double bond (4-alkyl- and 5,5-dialkyl-substituted compounds), the fraction of Δ1-pyrazolines in the equilibrium rises appreciably and reaches 12% for 3,3-diethyl-Δ1-pyrazoline. |
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