The Protonation Site of 2‐Methoxyethanol Under Chemical Ionization. An Experimental and Theoretical Study

Abstract

The mass spectral behavior of 2-methoxyethanol was studied under chemical ionization conditions with methane, isobutane, acetone and 3-pentanone as reagent gases. The protonated ion, [M+H]+, was of high abundance in the case of methane, isobutane and acetone chemical ionization. The ion decomposed readily by loss of water. However, using acetone or 3-pentanone chemical ionization, a number of adduct ions were produced, including the ions [M+43]+ and [M+59]+, or [M+57]+ and [M+87]+, respectively. The most probable protonation site of 2-methoxyethanol and different conformations of the structures were studied by theoretical ab initio calculations. Together, six different low-energy conformers, where the proton is situated either on the ether oxygen or on the hydroxyl oxygen, were located.