The ionic isomerization [HCOH] [rad]+ → [CH 2O] [rad]+ : proton-transport catalysis by CO and CO 2

Abstract

Mass spectrometry based experiments show that CH 2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 CH 2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 ions HCOH + do not isomerize into CH 2O + but the CO or CO 2 molecule in the above complexes catalyzes this transformation prior to dissociation. CO is the better catalyst because its proton affinity is closer to the criterion for efficient proton-transport catalysis.