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

Abstract

Molecular dynamics in esters of α-tocopherol were studied by means of dynamic ¹³C NMR in solution and ¹³C 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, ΔG^‡) 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 α-tocopheryl acetate at low temperature (263 K) was also investigated. The regiospecificity towards free radical approach was observed.