2002
DOI: 10.1021/ja011897i
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Conformation-Dependent Reaction Thermochemistry:  Study of Lactones and Lactone Enolates in the Gas Phase

Abstract: 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 36… Show more

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Cited by 22 publications
(25 citation statements)
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“…However, related experiments of others lead us to favor this explanation. Using gas phase measurement of α-proton acidity in butyrolactone as a guide, we estimate that the p K a of L is ∼22 (53). Hence, regardless of the structure of the copper species responsible for elimination, it (they) must significantly lower the p K a of the lactone.…”
Section: Resultsmentioning
confidence: 99%
“…However, related experiments of others lead us to favor this explanation. Using gas phase measurement of α-proton acidity in butyrolactone as a guide, we estimate that the p K a of L is ∼22 (53). Hence, regardless of the structure of the copper species responsible for elimination, it (they) must significantly lower the p K a of the lactone.…”
Section: Resultsmentioning
confidence: 99%
“…See DOI: 10.1039/b915419a calculations and may not be fully satisfactory. 11 C-H acidity differences 14,15 and an increased basicity of lactones 16 may point towards weak hydrogen bond effects, 17,18 but of course all these aspects are interrelated and call for a detailed and systematic cluster study.…”
Section: Introductionmentioning
confidence: 99%
“…We first examine the dipole-dipole interaction theory for explaining the origin of the abnormal acidity of Meldrum's acid. 7,8,22 Experimentally, Meldrum's acid (I) was found to be 5.24 kcal mol −1 more acidic than dimedone (III), i.e., deprotonation of III is 5.24 kcal mol −1 more endothermic than deprotonation of I in DMSO at 25 o C (δ∆G o = 5.24 kcal mol −1 ). The corresponding values in the gas phase obtained in the present work are δ∆G o = 5.3, 3.1 and 4.2 kcal mol −1 at the MP2/6-31+G*, B3LYP/6-311++G (3df,2p) and G3(+)(MP2) level respectively.…”
Section: Resultsmentioning
confidence: 99%