Reactions of Charged Phenyl Radicals with Aliphatic Amino Acids in the Gas Phase
| Autor: | Hilkka I. Kenttämaa, Leo Guler, Yiqun Huang, Jenny L. Heidbrink |
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| Rok vydání: | 2005 |
| Předmět: |
Models
Molecular Reaction mechanism Fourier Analysis Free Radicals Stereochemistry Chemistry Radical General Chemistry Hydrogen atom abstraction Photochemistry Ion cyclotron resonance spectrometry Biochemistry Mass Spectrometry Catalysis Structure-Activity Relationship Colloid and Surface Chemistry Electron affinity (data page) Nucleophile Electrophile Benzene Derivatives Reactivity (chemistry) Gases Amino Acids |
| Zdroj: | Journal of the American Chemical Society. 127:3973-3978 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | Gas-phase reactivity of five differently substituted positively charged phenyl radicals was examined toward six amino acids by using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR). The reactivity of the radicals studied was determined by the electrophilicity of the radical, which can be characterized by the radical's electron affinity (EA). The larger the electron affinity of the radical, the higher the overall reaction rate. In addition to the expected H-atom abstraction, several unprecedented reaction pathways were observed, including NH2 abstraction, SH abstraction, and SCH3 abstraction. These reaction pathways dominate for the most electrophilic radicals, and they may not follow radical but rather nucleophilic addition-elimination mechanisms. Hydrogen abstraction from glycine was also investigated theoretically. The results indicate that hydrogen abstraction from alphaC of glycine is both kinetically and thermodynamically favored over the NH2 group. The ordering of transition state energies for hydrogen abstraction from the alphaC and NH2 groups was found to reflect the radicals' EA ordering. |
| Databáze: | OpenAIRE |
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