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Article: Comparison between protonation, lithiation, and argentination of 5-oxazolones: A study of a key intermediate in gas-phase peptide sequencing

TitleComparison between protonation, lithiation, and argentination of 5-oxazolones: A study of a key intermediate in gas-phase peptide sequencing
Authors
Issue Date2000
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/jpca
Citation
Journal Of Physical Chemistry A, 2000, v. 104 n. 22, p. 5335-5342 How to Cite?
AbstractMolecular orbital calculations at B3LYP/6-31++G(d,p) are reported for bases 2-(aminomethyl)-5-oxazolone, 2-(aminomethyl)-4-methyl-5-oxazolone, 2-phenyl-5-oxazolone, and 2-phenyl-4 methyl-5-oxazolone and for the cations formed by protonation of these bases on their imino nitrogens. Structures and relative energies for isomers generated by protonation at each of the four heteroatoms of 2-(aminomethyl)-5-oxazolone are reported. Lithium and silver cations both add to 2-(aminomethyl)-5-oxazolone, but unlike the proton, they bind with two heteroatoms simultaneously. For both the lithiated and argentinated 2-(aminomethyl)-5-oxazolone cations the lowest energy isomers have the metal coordinated with the two nitrogen atoms. Proton affinities of these bases are in the range 217.0-221 kcal mol -1, with the methyl group at C4 increasing the proton affinity by ~3 kcal mol -1. Single-point calculations were performed at MP4(fc)/6-31 l++G(2df,p)//B3LYP/6-31++G-(d,p) for 2-(aminomethyl)-5-oxazolone, diketopiperazine, glycine, and alanine and their conjugate acids. The proton affinities from this level of theory are lower by as much as 2.7 kcal mol -1 than those calculated at B3LYP/6-31++G(d,p). Enthalpies of formation calculated at B3LYP/6-31++G(d,p) from isodesmic reactions for glycine, alanine, and their conjugate acids are all within l kcal mol -1 of the experimental values, but those calculated at MP4 deviate by as much as 4.8 kcal mol -1. Enthalpies of formation from atomization reactions at the MP4 level are in larger disagreement with experimental values. © 2000 American Chemical Society.
Persistent Identifierhttp://hdl.handle.net/10722/167639
ISSN
2015 Impact Factor: 2.883
2015 SCImago Journal Rankings: 1.231
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorRodriquez, CFen_US
dc.contributor.authorShoeib, Ten_US
dc.contributor.authorChu, IKen_US
dc.contributor.authorMichael Siu, KWen_US
dc.contributor.authorHopkinson, ACen_US
dc.date.accessioned2012-10-08T03:09:21Z-
dc.date.available2012-10-08T03:09:21Z-
dc.date.issued2000en_US
dc.identifier.citationJournal Of Physical Chemistry A, 2000, v. 104 n. 22, p. 5335-5342en_US
dc.identifier.issn1089-5639en_US
dc.identifier.urihttp://hdl.handle.net/10722/167639-
dc.description.abstractMolecular orbital calculations at B3LYP/6-31++G(d,p) are reported for bases 2-(aminomethyl)-5-oxazolone, 2-(aminomethyl)-4-methyl-5-oxazolone, 2-phenyl-5-oxazolone, and 2-phenyl-4 methyl-5-oxazolone and for the cations formed by protonation of these bases on their imino nitrogens. Structures and relative energies for isomers generated by protonation at each of the four heteroatoms of 2-(aminomethyl)-5-oxazolone are reported. Lithium and silver cations both add to 2-(aminomethyl)-5-oxazolone, but unlike the proton, they bind with two heteroatoms simultaneously. For both the lithiated and argentinated 2-(aminomethyl)-5-oxazolone cations the lowest energy isomers have the metal coordinated with the two nitrogen atoms. Proton affinities of these bases are in the range 217.0-221 kcal mol -1, with the methyl group at C4 increasing the proton affinity by ~3 kcal mol -1. Single-point calculations were performed at MP4(fc)/6-31 l++G(2df,p)//B3LYP/6-31++G-(d,p) for 2-(aminomethyl)-5-oxazolone, diketopiperazine, glycine, and alanine and their conjugate acids. The proton affinities from this level of theory are lower by as much as 2.7 kcal mol -1 than those calculated at B3LYP/6-31++G(d,p). Enthalpies of formation calculated at B3LYP/6-31++G(d,p) from isodesmic reactions for glycine, alanine, and their conjugate acids are all within l kcal mol -1 of the experimental values, but those calculated at MP4 deviate by as much as 4.8 kcal mol -1. Enthalpies of formation from atomization reactions at the MP4 level are in larger disagreement with experimental values. © 2000 American Chemical Society.en_US
dc.languageengen_US
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/jpcaen_US
dc.relation.ispartofJournal of Physical Chemistry Aen_US
dc.titleComparison between protonation, lithiation, and argentination of 5-oxazolones: A study of a key intermediate in gas-phase peptide sequencingen_US
dc.typeArticleen_US
dc.identifier.emailChu, IK:ivankchu@hku.hken_US
dc.identifier.authorityChu, IK=rp00683en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1021/jp000036d-
dc.identifier.scopuseid_2-s2.0-0033746906en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0033746906&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume104en_US
dc.identifier.issue22en_US
dc.identifier.spage5335en_US
dc.identifier.epage5342en_US
dc.identifier.isiWOS:000088943500024-
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridRodriquez, CF=7004085075en_US
dc.identifier.scopusauthoridShoeib, T=6603516521en_US
dc.identifier.scopusauthoridChu, IK=7103327484en_US
dc.identifier.scopusauthoridMichael Siu, KW=8967015800en_US
dc.identifier.scopusauthoridHopkinson, AC=15067169300en_US

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