Linked Life Data

11982386

Source:http://linkedlifedata.com/resource/pubmed/id/11982386

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
18
pubmed:dateCreated
2002-5-1
pubmed:abstractText
Gas-phase acidities (Delta H degrees (acid)) of lactones with ring sizes from four to seven have been measured on a Fourier transform ion cyclotron resonance mass spectrometer. Electron affinities (EAs) of the corresponding lactone enolate radicals were measured on a continuous-wave ion cyclotron resonance mass spectrometer, and the bond dissociation energies (BDEs) of the alpha C-H bonds were derived. In order of increasing ring size, Delta H degrees (acid) = 368.7 +/- 2., 369.4 +/- 2.2, 367.3 +/- 2.2, and 368.3 +/- 2.2 kcal/mol and BDE = 99.4 +/- 2.3, 94.8 +/- 2.3, 89.2 +/- 2.3, and 92.8 +/- 2.4 kcal/mol for beta-propiolactone, gamma-butyrolactone, delta-valerolactone, and epsilon-caprolactone, respectively. For their corresponding enolate radicals, EA = 44.1 +/- 0.3, 38.8 +/- 0.3, 35.3 +/- 0.3, and 37.9 +/- 0.6 kcal/mol. All of these lactones are considerably more acidic than methyl acetate, consistent with a dipole repulsion model. Both BDEs and EAs show a strong dependence on ring size, whereas Delta H degrees (acid) does not. These findings are discussed, taking into account differential electronic effects and differential strain between the reactant and product species in each reaction.
pubmed:language
eng
pubmed:journal
pubmed:status
PubMed-not-MEDLINE
pubmed:month
May
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
8
pubmed:volume
124
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
5213-21
pubmed:dateRevised
2003-11-3
pubmed:year
2002
pubmed:articleTitle
Conformation-dependent reaction thermochemistry: study of lactones and lactone enolates in the gas phase.
pubmed:affiliation
Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA.
pubmed:publicationType
Journal Article