13C NMR studies of conformational dynamics in α-tocopherol esters in solution and solid state

Molecular dynamics in esters of alpha-tocopherol were studied by means of dynamic C-13 NMR in solution and C-13 CP MAS NMR in solid phase. The coalescence of C2a, C3 and C1' carbon signals was monitored and discussed in terms of hindered rotation around the C-O-ester bond. The dynamic parameters (k, DeltaG(double dagger)) were determined. The barrier was described by the interplay of steric and electronic effects of the ester residue. The molecular interaction of the 2,2,6,6-tetramethylpiperidinyloxyl radical as a spin probe with alpha-tocopheryl acetate at low temperature (263 K) was also investigated. The regiospecicity towards free radical approach was observed.