The double tert-butyl rotation in solid cis-2-tert-butyl-5-(tert-butylsulphonyl)-1,3-dioxane

cis-2-tert-Butyl-5-(tert-butylsulphonyl)-1,3-dioxane displays a double tert-butyl coalescence at low temperatures in its C-13 CP/MAS NMR spectrum associated with slowing down of the rotation of both tert-butyl groups. The overlap of the resonances precluded the measurement of rates of rotation from Lineshape analyses. However, C-13 T-1 rho measurements above coalescence allowed rates of rotation and activation parameters for the rotations of both groups to be derived. The C-tert-butyl group has Delta H-double dagger = 26.3 +/- 3.6 kJ mol(-1) and Delta S-double dagger - 13 +/- 14 J K-1 mol(-1). The S-tert-butyl group has Delta H-double dagger = 31.8 +/- 2.2 kJ mol(-1) and Delta S-double dagger - 9 J K-1 mol(-1). (C) 1997 by John Wiley & Sons, Ltd.