AbstractThe high‐resolution proton‐coupled13C NMR spectra of 2‐chloro‐ and 2‐phenyl‐4‐methyl‐1,3,2‐dithiarsolane and 2‐chloro‐ and 2‐phenyl‐1,3,2‐dithiarsolane have been obtained and completely analysed. The spectral analysis has provided all the13C chemical shifts and13C1H coupling constants, including their relative signs. The results of this work are adequately interpreted in terms of two rapidly equilibrating half‐chair conformers with the 4‐methyl pseudo‐axial or pseudo‐equatorial. Thecisisomers appear to be conformationally biased towards the form with the 4‐methyl pseudo‐equatorial. The two one‐bond13C1H coupling constants of the methylene group are distinctly different. For both thecisandtransisomers, the largest one‐bond coupling always involves the methylene proton situatedsynto the substituent at arsenic. The observed variation in the geminal and vicinal13C1H coupling constants are discussed in terms of a stereospecific inductive effect of th