Stable [C2H7O2]+ isomers: Experimental and theoretical evidence for the existence of protonated peroxides and proton-bound dimers in the gas phase

Evidence is presented for the gas phase generation of at least eight stable isomeric [C₂H₇O₂]⁺ ions. These include energy-rich protonated peroxides (ions documentclass{article}pagestyle{empty}begin{document}$ {rm CH}_{rm 3} {rm CH}_2 {rm O}mathop {rm O}limits^{rm + } {rm H}_{rm 2} $end{document} (e), documentclass{article}pagestyle{empty}begin{document}$ {rm CH}_{rm 3} {rm CH}_{rm 2} mathop {rm O}limits^{rm + } {rm (H)OH} $end{document} (f) and documentclass{article}pagestyle{empty}begin{document}$ {rm CH}_{rm 3} {rm O}mathop {rm O}limits^{rm + } {rm (H)CH}_{rm 3} {rm (g)),} $end{document} (g)), proton-bound dimers (ions documentclass{article}pagestyle{empty}begin{document}$ {rm CH}_{rm 3} {rm CH = O} cdot cdot cdot mathop {rm H}limits^{rm 3} cdot cdot cdot {rm OH}_{rm 2} $end{document} (h) and documentclass{article}pagestyle{empty}begin{document}$ {rm CH2 = O} cdot cdot cdot mathop {rm H}limits^{rm + } cdot cdot cdot {rm HOCH}_{rm 3} $end{document} (i)) and hydroxy-protonated species (ions documentclass{article}pagestyle{empty}begin{document}$ {rm CH}_{rm 2} {rm (OH)CH}_{rm 2} mathop {rm O}limits^{rm + } {rm H}_{rm 2} (a), $end{document} documentclass{article}pagestyle{empty}begin{document}$ {rm CH}_{rm 3} {rm CH(OH)}mathop {rm O}limits^{rm + } {rm H}_{rm 2} $end{document} (b) and documentclass{article}pagestyle{empty}begin{document}$ {rm CH}_{rm 3} {rm OCH}_{rm 2} mathop {rm O}limits^{rm + } {rm H}_{rm 2} $end{document} (c)). The important points of the present study are (i) that these ions are prevented by high barriers from facile interconversion and (ii) that both electron-impact- and proton-induced gas phase decompositions seem to proceed via multistep reactions, some of which eventually result in the formation of proton-bound dimers.