Application of the temperature dependence of vicinal spin‐spin coupling constants to the investigation of the configuration of substituents in saturated 5‐membered rings

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Abstract
Temperature dependence of cis‐ and trans‐vicinal spin‐spin coupling constants of substituted cyclic 5‐membered compounds is discussed. The temperature dependence of trans‐vicinal coupling constants is shown to be essentially stronger than that of cis‐vicinal coupling constants if the energies of the conformers corresponding to potential energy curve minima are different. The temperature dependence of 33 vicinal spin‐spin coupling constants has been studied for di‐ and trisubstituted thiophanes with a known configuration of substituents. Experimentally determined changes of trans‐vicinal coupling constants with temperature are markedly larger than those for cis‐vicinal coupling constants, whose values, in most cases, are practically temperature independent. Differences in the temperature dependence of cis and trans‐vicinal spin‐spin coupling constants can be applied for the determination of the configuration of substituents in saturated 5‐membered rings.