The conformation of non‐aromatic ring compounds. XX: The dipole moments and NMR spectra of some 2‐substituted 1,3‐dithianes

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Abstract
The conformation of several 2‐substituted 1,3‐dithianes is studied by means of dipole moments and NMR spectra. The value of the dipole moments of all compounds having only hydrocarbon substituents is 2.0 ± 0.1 D., indicating that in all these compounds the six‐membered ring is in the same conformation. From the dipole moments of the 1,3‐dithianes studied it may be concluded that in solution the dithiane ring has the same geometry (chair conformation) as that found by X‐ray analysis of 2‐phenyl‐1,3‐dithiane2. The NMR spectra of 2‐methyl‐2‐phenyl‐, 2,2‐diphenyl‐ and 2‐p‐chlorophenyl‐2‐methyl‐1,3‐dithiane show that a phenyl group at atom 2 in axial position gives rise to two absorption peaks, one due to the ortho protons and one to the meta (and para) protons. The same effect is seen with the axial phenyl group in α‐trithiobenzaldehyde. The protons of an equatorial phenyl substituent give only one band. These phenomena are discussed.

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