RAMAN SPECTRA OF ARSENIC TRICHLORIDE IN WATER AND ALCOHOLS AND SPECTRUM OF ARSENIC TRIBROMIDE

Liquid AsCl3 and its solutions in a number of solvents [H2O, D2O, CH3OH, C2H5OH, CH3CHOHCH3, (CH3CH2)2O] have been investigated with Raman spectroscopy. Although the stretching frequencies of AsCl3 are strongly affected by all solvents except diethyl ether, the Raman spectra can be interpreted as being consistent with a pyramidal structure of C3T symmetry. New lines were observed at 710 cm-1 in H2O solution, at 690 cm-1 in D2O, and between 620 and 660 cm-1 in alcohols, along with a lower frequency line at ca. 240 cm-1 in all of these solutions. These data are interpreted as indicative of the formation of aquo and alcohol complexes with AsCl3. There is little evidence for the loss of Cl- or formation of As(III) species with fewer than three chlorides until ASjOe is precipitated upon complete hydrolysis. A species H2OAsCl3 is believed in equilibrium with HOAsCl3~ because the intensity of the 710-cm-1 line increases upon dilution with H2O and this equilibrium is reversed with acid concentrations of ca. 3 M. Finally, the Raman spectrum of AsBr3(1) has been reinvestigated. The existence of four Raman lines is demonstrated with their proper polarizations for C3v symmetry. The assignments given are: v1 (A1) 272 ± 3 cm-1, polarized; v3 (E) 287 ± 3 cm-1, depolarized; v2 (A1) 130 ± 1 cm-1, polarized; v4 (E) 100 ± 1 cm-1, depolarized. In ether solution, the positions of v1 and v3 are reversed. © 1969, American Chemical Society. All rights reserved.