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

Abstract Evidence is presented for the gas phase generation of at least eight stable isomeric [C 2 H 7 O 2 ] + ions. These include energy‐rich protonated peroxides (ions $$ {\rm CH}_{\rm 3} {\rm CH}_2 {\rm O}\mathop {\rm O}\limits^{\rm + } {\rm H}_{\rm 2} $$ ( e ), $$ {\rm CH}_{\rm 3} {\rm CH}_{\rm 2} \mathop {\rm O}\limits^{\rm + } {\rm (H)OH} $$ ( f ) and $$ {\rm CH}_{\rm 3} {\rm O}\mathop {\rm O}\limits^{\rm + } {\rm (H)CH}_{\rm 3} {\rm (g)),} $$ ( g )), proton‐bound dimers (ions $$ {\rm CH}_{\rm 3} {\rm CH = O} \cdot \cdot \cdot \mathop {\rm H}\limits^{\rm 3} \cdot \cdot \cdot {\rm OH}_{\rm 2} $$ ( h ) and $$ {\rm CH2 = O} \cdot \cdot \cdot \mathop {\rm H}\limits^{\rm + } \cdot \cdot \cdot {\rm HOCH}_{\rm 3} $$ ( i )) and hydroxy‐protonated species (ions $$ {\rm CH}_{\rm 2} {\rm (OH)CH}_{\rm 2} \mathop {\rm O}\limits^{\rm + } {\rm H}_{\rm 2} (a), $$ $$ {\rm CH}_{\rm 3} {\rm CH(OH)}\mathop {\rm O}\limits^{\rm + } {\rm H}_{\rm 2} $$ ( b ) and $$ {\rm CH}_{\rm 3} {\rm OCH}_{\rm 2} \mathop {\rm O}\limits^{\rm + } {\rm H}_{\rm 2} $$ ( 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.