Vibrational spectra and molecular conformation of propargyl ethyl ether

Abstract

The infrared absorption spectra of propargyl ethyl ether (CH₃CH₂OCH₂CCH) in the vapour, liquid and solid states have been examined. Vapour phase spectra indicate that the dominant rotamer in this phase has the methyl substituent in the trans position and the acetylenic group in a gauche position. However, liquid phase spectra suggest the presence of at least two other rotameric forms in this phase, together with the more stable t(CH₃)g(CCH) conformation. At low temperatures, two different types of spectra were observed for propargyl ethyl ether in the crystalline solid phase. These correspond to two different rotameric forms of the molecule, being the more stable t(CH₃)g(CCH) conformation in one case and probably a heavy-atom planar t(CH₃)t(CCH) structure in the other.