Über Arsen-haltige Heterocylen. V. Konformative Gleichgewichte in 8gliedrigen Heterocyclen des Arsens und Antimons

On Heterocyclic Systems Containing Arsenic. V. Conformational Equilibria in Eight-Membered Heterocycles of Arsenic and Antimony ¹H- and ¹³C-NMR spectra were measured at and below room temperature and analysed quantitatively for two arsocanes and two stibocanes. Chemical shifts and coupling constants could be assigned and correlated with torsion angles starting from the known conformations in the solid. There are equilibria in solution between a chair-chair conformation and the two enantiomers of a boat-chair conformation at room temperature. These transitions turn infrequent at lower temperature. The amount of the two conformations is different for the four compounds. Transition states are discussed.