Volume 57 (1984) Issue 9 Pages 2391-2395
The energy difference between the two rotational isomers, i.e., Cs and C1, of isopropyl methyl ether has been elucidated from the observed vicinal 13C-1H coupling constant. The conventional Gutowsky method based on the simple rotational isomeric state model tends to give an underestimate, especially when the energy difference is large. A more elaborate treatment, which takes account of the overall profile of the torsional potential energy curve, has been attempted. Adoption of JT=11.0–12.0 Hz for the trans coupling gave a value of 2.2±0.2 kcal mol−1 for the energy difference Ecs–Ec1. This result is consistent with the range (2.4±0.6 kcal mol−1) estimated by the matrix-isolation method as reported by Nakata et al.