| Popis: |
The proton magnetic resonance spectra of a series of 2-alkoxytetrahydropyrans of general formula have been measured. R represents a variety of groups, including para-, meta-, and ortho-substituted phenyl, and several alkyl substituents. The geminal coupling constant, JAB, has been determined in each ether, from the AB pattern produced by the magnetically non-equivalent methylene protons in the alkoxy group. JAB has been found to be dependent on the nature of the substituent. A study of the solvent dependence of JAB in benzyl 2-tetrahydropyranyl ether has shown an opposite trend in the variation of JAB to that previously reported in the literature. The proton magnetic resonance spectrum of the 2-tetrahydropyranyl ether of 2,2,2-trifluoroethanol has been measured in several different solvents and at several temperatures. Analysis of the ABX3 pattern produced by the trifluoroethyl group revealed that the vicinal coupling constants JAX and JBX had different magnitudes. This difference is interpreted as evidence that the C-HA and C-HB bonds of the trifluoroethyl group differ electronically. In contrast to the above result, the 2-tetrahydropyranyl ether of ethanol showed equal vicinal proton-proton coupling constants in the ethyl group. |
