| Popis: |
With the use of a previously developed method [1] based on (temperature dependent) shift parameters of AB spin systems, the thermodynamic quantities controlling conformational equilibria in trans-4-Me-6-alkyl-1,3-thioxanes have been computed (table 1). The conformations with axial substitution next to the sulphur atom are always in excess. The total energy differences are the result of each time a constant enthalpy, but a variable entropy contribution, the latter in disadvantage of the conformation with the (hindered) axial substituent at the oxygen side. These results are discussed in the light of the previously reported special ring shape of thioxanes [6]. |
