Roh2

ROH2 is a shorthand notation used in organic chemistry to denote a protonated alcohol, formally the oxonium ion ROH2+. In strong acid media the neutral alcohol ROH accepts a proton to form ROH2+, a highly reactive intermediate that is typically short-lived and not isolable under ordinary conditions. The positive charge resides mainly on the oxygen atom, giving a three-coordinate, highly energized species that participates readily in further acid-catalyzed processes.

In practice, ROH2+ is formed when alcohols are exposed to strong Brønsted acids (for example sulfuric acid or superacids) or in gas-phase protonation during mass spectrometry. The most important reaction of ROH2+ in classic organic chemistry is its role in dehydration to form alkenes. Through unimolecular loss of water, ROH2+ generates a carbon-centered carbocation intermediate (R+). Subsequent deprotonation yields an alkene. The rate and outcome of this pathway depend on the stability of the resulting carbocation (tertiary > secondary > primary) and on the reaction environment, which can influence rearrangements before dehydration.

ROH2+ can also engage in other proton-transfer or nucleophilic capture events, especially on acid sites of catalysts or in solvent systems with competing nucleophiles. Spectroscopically, ROH2+ is typically too transient for routine isolation, but its formation and decay can be inferred from reaction kinetics, carbocation formation, and characteristic mass-spectral fragmentation patterns. Overall, ROH2+ is best understood as a reactive intermediate that governs key steps in acid-catalyzed alcohol dehydration and related transformations.