Isoformyl cation

A calculational study of the formyl cation to isoformyl cation (H—0=C) rearrangement reveals that the latter is much the less stable of the two.52... 

According to a recent ab initio molecular dynamic simulation study639 formation of formyl cation 328 is optimally favored in the 1 1 HF-SbF5 solution. No evidence, however, was found for the formation of the isoformyl cation 329 and diprotonated CO. The fast proton exchange observed earlier was suggested to occur between HCO+ and HF(HF) or SbF6. ... 

It is noteworthy that CAD of 9, ll" and 12 -15 generates inter alia) prominent fragments by cleavage of the triple bond ". This decomposition yields long-sought organic cations, such as C=0 H (isoformyl cation) from 9", C=N H2 from ll" and C=0 CH3 (O-methylated CO) from all of which are of potential interest in interstellar chemistry . MS/MS/MS experiments confirm that these ions exist as distinct species hence, they must be separated by considerable barriers from the more stable isomers HC O", HC NH" and CH3C=0 , respectively. 

Whereas the formyl cation could not be directly observed by NMR spectroscopy its intermediacy has been well established in aromatic formylation reactions In order to account for the failure to observe the formyl cation, it has been suggested that CO is protonated in acid media to generate protosolvated formyl cation a very reactive electrophile. Protosolvation of the carbonyl oxygen allows facile deprotonation of the methine proton, thus resulting in rapid exchange via involvement of the isoformyl cation. 

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