Configuration and conformation of substituted 1,3,2-dioxaarsenanes

Abstract

The configuration and conformations often 2-, 4-, and 5-substituted 1,3,2-dioxaarsenanes were studied from their PMR spectra. Inversion of the shielding constants of protons in the 4, 6, and 5 positions and of methyl groups in the 5 position was established, and the axial orientation of the As-Cl and As-OR bonds, the equatorial orientation of the 4-CH₃ group, and the chair conformation of the six-membered heteroring were proved. The anisotropies of the diamagnetic susceptibility were estimated for the first time: $\Delta _{\chi _{{\text{As - O}}} } = 4.67 \cdot 10^{ - 6}$ and $\Delta _{\chi _{{\text{As - Cl}}} } = 5.13 \cdot 10^{ - 6} {\text{cm}}^{\text{3}} \cdot {\text{mole}}^{{\text{ - 1}}}$ (dipole approximation); $\Delta _{\chi _{{\text{As - O}}} } = 0.9 \cdot 10^{ - 6}$ and $\Delta _{\chi _{{\text{As - Cl}}} } = 6.8 \cdot 10^{ - 6} {\text{cm}}^{\text{3}} \cdot {\text{mole}}^{{\text{ - 1}}}$ (nondipole approximation). The cyclic torsion angle (ψ= 58°) as found for 2-chloro-1,3,2-dioxaarsenane by the “R-factor” method. Conclusions regardiwng the conformation of the ring and substituents were confirmed by a study of the specific effect of an aromatic solvent on the position of the resonance lines.