Gas-phase Reactions of Glycine, Alanine, Valineand theirN-Methyl Derivatives with theNitrosonium Ion, NO+
✍ Scribed by Freitas, Michael A.; O’Hair, Richard A. J.; Schmidt, Joseph A. R.; Tichy, Shane E.; Plashko, Bruce E.; Williams, Todd D.
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 660 KB
- Volume
- 31
- Category
- Article
- ISSN
- 1076-5174
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✦ Synopsis
The gas-phase reactions of the nitrosonium ion, NO+ with the amino acids glycine, alanine and valine and their N-methyl derivatives were investigated under chemical ionization mass spectrometric (CIMS) conditions. Two products were observed in all cases: the formation of the iminium ion and the formation of an [ M -H ] + ion. The latter product is consistent with a reaction channel involving hydride abstraction by NO+, and was confirmed by (i) examining the Ar+CI mass spectra of the same amino acids under similar source conditions and (ii) examining the unimolecular fragmentation reactions of the [ M + H] + ions of the N-nitrosc+N-methyl derivatives of each of the amino acids in a tandem mass spectrometer. Further insights into the reaction of glycine with NO+ were obtaiped by performing ab initiu calculations (at the MP2/6-31G*//HF/6-31G* level). These results indicate that four reactions are thermodynamically viable for glycine: (i) hydride abstraction; (5) iminium ion formation (with concomitant loss of HONO and CO); (iii) diazonium ion formation; and (iv) diazonium ion formation followed by loss of N,. Possible reasons why reactions (iii) and (iv) are not observed are discussed, and comparisons with solution reactivity and the gas-phase reactivity of NO+ are also made.