Barrier to Rotation about Sulfur-Sulfur Bonds in Homocyclic Sulfur Molecules [1]

It is shown that the distances (d) of the 19 longest bonds in 9 homocyclic sulfur rings of type Sn (n = 6-20) depend on the torsional angles (r) which vary between 0° and 140°. The function d = f (r) is smallest for r = 90-100° and largest for r = 0°; the corresponding bond distance variation amounts to 13 pm or 6%. The height of the torsional cis-barrier is estimated from the enthalpy of formation of gaseous S7 as equal to or smaller than 24 kJ/mol.