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 [ CH,0CHz6Hz (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 h e r s .

Anab InitioComputational Molecular Orbital Study of Radical, Protonated Radical (Radical Cation), and Carbocation Species That Have Been Proposed in Mechanisms for the Transfer Process in the Enzyme−Coenzyme B12-Catalyzed Dehydration of 1,2-Dihydroxyethane

“… a (i) from ref , (ii) from ref and , (iii) from ref −32, (iv) from ref . b Energies calculated at level A , but with the thermal energy corrections obtained from frequency analyses 14 using the RHF/6-31G* basis set. …”

Gas‐phase basicities of polyfunctional molecules. Part 2: Saturated basic sites

“…Its strength is, however, limited by steric and electrostatic constraints, as attested by a nonlinear O–H$\cdots $ O arrangement. According to a FAB study, protonation of ethylene glycol gives rise to an ion of the type ${\rm HO(CH}_{{\rm 2}} {\rm )}_{{\rm 2}} {\rm OH}_{{\rm 2}}^{{\rm + }} $ (Van Driel et al, 1985). …”

“…The proton affinity of ethyl hydroperoxide has not been experimentally determined, but its protonation sites have been studied theoretically. HF/3‐21G calculations have shown that protonation of the internal oxygen is favored by 15 kJ/mol (Van Driel et al, 1985). Our G3 calculations lead to a value of 27 kJ/mol and a proton affinity of 749 kJ/mol, and underline the greater stabilization effect of the ethyl group compared to the methyl group.…”

“…Our G3 calculations lead to a value of 27 kJ/mol and a proton affinity of 749 kJ/mol, and underline the greater stabilization effect of the ethyl group compared to the methyl group. According to calculations (Van Driel et al, 1985), the two protonated forms are separated by a high‐energy barrier. Consequently, if both ions were generated they should not interconvert.…”

“…In the case of dimethylperoxide, the two oxygen atoms are equivalent. It has been shown (Van Driel et al, 1985; Schalley et al, 1997) that protonation of CH 3 OOCH 3 under CH 4 or H 2 chemical ionization induces, to some extent, the formation of ${\rm CH}_{{\rm 3}} {\rm (OH)OCH}_{{\rm 3}}^{{\rm + }} $ ion even if dissociation mostly proceeds via a methanol/formaldehyde proton bound complex. Schalley et al (1997) also estimated its proton affinity by DFT calculations and obtained a value of 748.5 kJ/mol, while a value of 754 kJ/mol is obtained at the G3 level.…”