Infrared and Raman spectroscopic studies of conformations in liquid and solid triethyl-, diethyl(methyl)- and ethyldimethyl-amines, -phosphines, and -arsines

Abstract

Infrared and Raman spectra of YMe₃, YEt₃, YMeEt₂, and YMe₂Et (Y = N, P, or As) have been recorded for the liquids and the solids. Study of the YC₃ stretching bands indicates that the liquids (except YMe₃) contain a mixture of conformational isomers. The solids are simpler. All the YEt₃ compounds on crystallization adopt a C₃ configuration, and YMe₂Et also crystallize to a single form. The compounds YMeEt₂, solidify to glasses containing one or two conformers, depending on the conditions. The vapour-phase i.r. spectrum of NMe₂Et has been analyzed to ascertain its structure. It is suggested that the preferred conformations in the solids have all the C–Me groups gauche to the lone pair of the central atom.