The dissociation chemistry of low-energy N-formylethanolamine ions: Hydrogen-bridged radical cations as key intermediates

作者：Jobst Karl J; Bowen Richard D; Terlouw Johan K^*

来源：International Journal of Mass Spectrometry, 2011, 306(1): 9-26.

DOI：10.1016/j.ijms.2011.05.011

• Tandem mass spectrometry
• CBS-QB3 model chemistry
• C(3)H(5)NO ion structures
• Conformers
• Quid-pro-quo catalysis

Tandem mass spectrometry experiments show that N-formylethanolamine molecular ions HOCH(2)CH(2)NHC(H)=O(center dot+) (FE1) lose C(2)H(3)O(center dot), CH(2)O and H(2)O to yield m/z 46 ions HC(OH)NH(2)(+), m/z 59 ions (center dot)CH(2)N(H)CHOH(+), and m/z 71 N-vinylformamide ions CH(2)=C(H)N(H)CHO(center dot+).
A detailed mechanistic study using the CBS-QB3 model chemistry reveals that the readily generated 1,5-H shift isomer HOCHCH(2)N(H)C(H)OH(center dot+). (FE2) and hydrogen-bridged radical cations (HBRCs) act as key intermediates in a 'McLafferty + 1' type rearrangement that yields the m/z 46 ions. The co-generated C(2)H(3)O(center dot) neutrals are predicted to be vinyloxy radicals CH(2)=CHO(center dot) in admixture with CH(3)C=O(center dot) generated by quid-pro-quo (QPQ) catalysis.
A competing C-C bond cleavage in FE1 leads to HBRC[CH(2)N(H)C(H=O-...H...O=CH(2)](center dot+) as the direct precursor for CH(2)O loss.
In addition, ion FE2 also communicates with a myriad of ion-molecule complexes of vinyl alcohol and formimidic acid whose components may recombine to form distonic ion FE3, HOCH(CH(2))N(H)C(H)OH(center dot+), which loses H(2)O after undergoing a 1,5-H shift. Further support for these proposals comes from experiments with D- and (18)O-labelled isotopologues.
Previously reported proposals for the H(2)O and CO losses from protonated N-formylethanolamine are briefly re-examined.

• 出版日期2011-9-1