The ionic isomerization [HCOH]+→[CH2O]+: proton-transport catalysis by CO and CO2

Mass spectrometry based experiments show that CH2O+ is cleanly generated in the spontaneous decarbonylation of low energy glyoxal ions, OCHCHO+. Likewise, glyoxilic acid ions, OCHC(OH)O+, decarboxylate into CH2O+, but in admixture with some HCOH+. A mechanistic analysis using the CBS-QB3 model chemistry shows that the above ions first rearrange into hydrogen bridged radical cations, HCOH+⋯CO and HCOH+⋯OCO, respectively. Solitary …