NMR parameters of two tricyclododecadienes--strained hydrocarbons with close distance between perpendicularly or parallelly arranged double bonds.
Quantum chemical calculations of the hypothetical tricyclo[5.5.0.0(4, 10)]dodeca-1(7),4(10)-diene with a perpendicular arrangement of double bonds and of the known tricyclo[4.2.2.2(2, 5)]dodeca-1,5-diene isomer with the parallel arrangement yield, in agreement with expectations, greater stability of the latter molecule. They reproduce the available experimental results for chemical shifts and coupling constants for the latter molecule. Large calculated values of sigma(Csp2) and those of (1)J(C=C) for both dienes are not due to nonplanar distortions on the double bonds but due to the close distances between them. The calculated NMR parameters of the hypothetical diene could be useful for its future identification as the calculated values of the parameters for 1 are larger than those for 2.
Dodziuk
Helena
H
Ostrowski
Maciej
M
Marchwiany
Maciej E
ME