1985 Volume 58 Issue 6 Pages 1690-1695
The 400 MHz 1H NMR spectrum of the title compound at −100 °C in dichloromethane revealed the presence of two isomers in a ratio of 88 : 12, which results from restricted rotation about the triptycyl–oxygen single bond. The major isomer was assigned to the ap rotamer on the basis of the low temperature 13C NMR spectrum. Dynamic NMR studies gave the activation parameters for the ap→±sc conversion: ΔH\ eweq=11.9±0.5 kcal/mol (1 calth=4.184 J), ΔS\ eweq=2.6±2.5 eu, ΔG\ eweq200K=11.4 kcal/mol. Results of molecular mechanics calculations on the compound are discussed.
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