THE STRUCTURE OF CYCLOHEXANE, F-CYCLOHEXANE, CL-CYCLOHEXANE, BR-CYCLOHEXANE AND I-CYCLOHEXANE

The ground state, r(0), and the average, r, structures of cyclohexane were determined from the recently reported rotational constants for s everal isotopic species of cyclohexane. These structures provide a bet ter description of the heavy atom skeleton in cyclohexane than the r, structure and allow an accurate prediction of the rotational constants for C6H12 and C6D12 The new structure for cyclohexane was combined wi th ab initio calculations to redetermine the key structural features o f F-, Cl-, Br- and I-cyclohexane, and it is found that while the equat orial CX bond lengths are comparable with those for secondary substitu tion in propane, the axial bond lengths are all longer and halfway bet ween those for secondary and tertiary substitution.