MeOH2

MeOH2 is the shorthand notation for the protonated methanol cation, CH3OH2+. It represents the conjugate acid of methanol, formed when a methanol molecule accepts a proton, typically at the oxygen atom. In this ion, the oxygen bears a positive charge, and the structure is commonly described as an oxonium-type center with a trigonal pyramidal geometry, having the methyl group and two hydrogens attached to oxygen and one lone pair.

MeOH2+ is most commonly encountered in gas-phase ion chemistry and in strongly acidic or superacid environments. It is generated by protonation of methanol with strong acids, via proton transfer in mass spectrometry experiments, or by reactions in proton-rich media. It is less stable in aqueous solution, where solvent molecules compete for protons; in solution it exists transiently only under high acidity.

In reactivity, MeOH2+ acts as a strong electrophile and a source of protons for further chemistry. It can undergo dehydration to yield other species and participates in proton transfer reactions with bases or nucleophiles. Its exact properties, including acidity, binding behavior, and fragmentation patterns, are topics of study in physical organic chemistry and astrochemistry, where protonated alcohols can be formed in interstellar environments.

Common synonyms include protonated methanol, methanolium, and methyloxonium. The term MeOH2 is often used in computational and spectrometric contexts to refer to this cation.