Experimental studies of allene, methylacetylene, and the propargyl radical: Bond dissociation energies, gas-phase acidities, and ion-molecule chemistry

Marin S Robinson, Mark L. Polak, Veronica M. Bierbaum, Charles H. DePuy, W. C. Lineberger

Research output: Contribution to journalArticle

142 Citations (Scopus)

Abstract

Electron affinities and ΔHacid are combined in a thermochemical cycle to arrive at bond dissociation energies for allene, methylacetylene, and the propargyl radical: D0(CH2=C=CH-H) = 88.7 ± 3 kcal mol-1, D0(H-CH2C≡CH) = 90.3 ± 3 kcal mol-1, D0(CH3C≡C-H) = 130.2 ± 3 kcal mol-1, and D0(CH2=C=C-H) = 100 ± 5 kcal mol-1. Electron affinity measurements were determined using negative ion photoelectron spectroscopy and yielded the following for the propargyl, 1-propynyl, and propadienylidene radicals: EA(CH2=C=CH) = 0.918 ± 0.008 eV, EA(CH3C≡C) = 2.718 ± 0.008 eV, and EA(CH2=C=C̈) = 1.794 ± 0.008 eV. Gas-phase acidity measurements were made using proton transfer kinetics in a flowing afterglow/selected-ion flow tube and yielded the following for allene, methylacetylene, and the propargyl radical: ΔGacid(CH2=C=CH-H) = 372.8 ± 3 kcal mol-1, ΔGacid(H-CH2C=CH) = 374.7 ± 3 kcal mol-1, ΔGacid(CH3C≡C-H) = 373.4 ± 2 kcal mol-1, and ΔGacid(CH2=C=CH) = 364 ± 5 kcal mol-1. ΔGacid was converted to ΔHacid by employing ΔSacid: ΔHacid(CH2=C=CH-H) = 381.1 ± 3 kcal mol-1, ΔHacid(H-CH2C≡CH) = 382.7 ± 3 kcal mol-1, ΔHacid(CH3C≡C-H) = 381.1 ± 3 kcal mol-1, and ΔHacid(CH2=C=CH) = 372 ± 5 kcal mol-1. Evidence is provided for the isomerization of the allenyl anion (CH2=C=CH-) to the 1-propynyl anion (CH3C≡C-) in the proton transfer reactions of CH2=C=CH- with CH3OH and CH3CH2OH. This complexity limits the precision of experimental measurements. This study explores the intricacies of determining gas phase acidity values by proton transfer reactions for systems in which isomerization can occur.

Original languageEnglish (US)
Pages (from-to)6766-6778
Number of pages13
JournalJournal of the American Chemical Society
Volume117
Issue number25
StatePublished - Jun 28 1995
Externally publishedYes

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Proton transfer
Acidity
Protons
Electron affinity
Negative ions
Gases
Ions
Isomerization
Molecules
Anions
Electrons
Photoelectron Spectroscopy
Pipe flow
Photoelectron spectroscopy
Kinetics
propadiene
methylacetylene

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Experimental studies of allene, methylacetylene, and the propargyl radical : Bond dissociation energies, gas-phase acidities, and ion-molecule chemistry. / Robinson, Marin S; Polak, Mark L.; Bierbaum, Veronica M.; DePuy, Charles H.; Lineberger, W. C.

In: Journal of the American Chemical Society, Vol. 117, No. 25, 28.06.1995, p. 6766-6778.

Research output: Contribution to journalArticle

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title = "Experimental studies of allene, methylacetylene, and the propargyl radical: Bond dissociation energies, gas-phase acidities, and ion-molecule chemistry",
abstract = "Electron affinities and ΔHacid are combined in a thermochemical cycle to arrive at bond dissociation energies for allene, methylacetylene, and the propargyl radical: D0(CH2=C=CH-H) = 88.7 ± 3 kcal mol-1, D0(H-CH2C≡CH) = 90.3 ± 3 kcal mol-1, D0(CH3C≡C-H) = 130.2 ± 3 kcal mol-1, and D0(CH2=C=C-H) = 100 ± 5 kcal mol-1. Electron affinity measurements were determined using negative ion photoelectron spectroscopy and yielded the following for the propargyl, 1-propynyl, and propadienylidene radicals: EA(CH2=C=CH) = 0.918 ± 0.008 eV, EA(CH3C≡C) = 2.718 ± 0.008 eV, and EA(CH2=C=C̈) = 1.794 ± 0.008 eV. Gas-phase acidity measurements were made using proton transfer kinetics in a flowing afterglow/selected-ion flow tube and yielded the following for allene, methylacetylene, and the propargyl radical: ΔGacid(CH2=C=CH-H) = 372.8 ± 3 kcal mol-1, ΔGacid(H-CH2C=CH) = 374.7 ± 3 kcal mol-1, ΔGacid(CH3C≡C-H) = 373.4 ± 2 kcal mol-1, and ΔGacid(CH2=C=CH) = 364 ± 5 kcal mol-1. ΔGacid was converted to ΔHacid by employing ΔSacid: ΔHacid(CH2=C=CH-H) = 381.1 ± 3 kcal mol-1, ΔHacid(H-CH2C≡CH) = 382.7 ± 3 kcal mol-1, ΔHacid(CH3C≡C-H) = 381.1 ± 3 kcal mol-1, and ΔHacid(CH2=C=CH) = 372 ± 5 kcal mol-1. Evidence is provided for the isomerization of the allenyl anion (CH2=C=CH-) to the 1-propynyl anion (CH3C≡C-) in the proton transfer reactions of CH2=C=CH- with CH3OH and CH3CH2OH. This complexity limits the precision of experimental measurements. This study explores the intricacies of determining gas phase acidity values by proton transfer reactions for systems in which isomerization can occur.",
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T1 - Experimental studies of allene, methylacetylene, and the propargyl radical

T2 - Bond dissociation energies, gas-phase acidities, and ion-molecule chemistry

AU - Robinson, Marin S

AU - Polak, Mark L.

AU - Bierbaum, Veronica M.

AU - DePuy, Charles H.

AU - Lineberger, W. C.

PY - 1995/6/28

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N2 - Electron affinities and ΔHacid are combined in a thermochemical cycle to arrive at bond dissociation energies for allene, methylacetylene, and the propargyl radical: D0(CH2=C=CH-H) = 88.7 ± 3 kcal mol-1, D0(H-CH2C≡CH) = 90.3 ± 3 kcal mol-1, D0(CH3C≡C-H) = 130.2 ± 3 kcal mol-1, and D0(CH2=C=C-H) = 100 ± 5 kcal mol-1. Electron affinity measurements were determined using negative ion photoelectron spectroscopy and yielded the following for the propargyl, 1-propynyl, and propadienylidene radicals: EA(CH2=C=CH) = 0.918 ± 0.008 eV, EA(CH3C≡C) = 2.718 ± 0.008 eV, and EA(CH2=C=C̈) = 1.794 ± 0.008 eV. Gas-phase acidity measurements were made using proton transfer kinetics in a flowing afterglow/selected-ion flow tube and yielded the following for allene, methylacetylene, and the propargyl radical: ΔGacid(CH2=C=CH-H) = 372.8 ± 3 kcal mol-1, ΔGacid(H-CH2C=CH) = 374.7 ± 3 kcal mol-1, ΔGacid(CH3C≡C-H) = 373.4 ± 2 kcal mol-1, and ΔGacid(CH2=C=CH) = 364 ± 5 kcal mol-1. ΔGacid was converted to ΔHacid by employing ΔSacid: ΔHacid(CH2=C=CH-H) = 381.1 ± 3 kcal mol-1, ΔHacid(H-CH2C≡CH) = 382.7 ± 3 kcal mol-1, ΔHacid(CH3C≡C-H) = 381.1 ± 3 kcal mol-1, and ΔHacid(CH2=C=CH) = 372 ± 5 kcal mol-1. Evidence is provided for the isomerization of the allenyl anion (CH2=C=CH-) to the 1-propynyl anion (CH3C≡C-) in the proton transfer reactions of CH2=C=CH- with CH3OH and CH3CH2OH. This complexity limits the precision of experimental measurements. This study explores the intricacies of determining gas phase acidity values by proton transfer reactions for systems in which isomerization can occur.

AB - Electron affinities and ΔHacid are combined in a thermochemical cycle to arrive at bond dissociation energies for allene, methylacetylene, and the propargyl radical: D0(CH2=C=CH-H) = 88.7 ± 3 kcal mol-1, D0(H-CH2C≡CH) = 90.3 ± 3 kcal mol-1, D0(CH3C≡C-H) = 130.2 ± 3 kcal mol-1, and D0(CH2=C=C-H) = 100 ± 5 kcal mol-1. Electron affinity measurements were determined using negative ion photoelectron spectroscopy and yielded the following for the propargyl, 1-propynyl, and propadienylidene radicals: EA(CH2=C=CH) = 0.918 ± 0.008 eV, EA(CH3C≡C) = 2.718 ± 0.008 eV, and EA(CH2=C=C̈) = 1.794 ± 0.008 eV. Gas-phase acidity measurements were made using proton transfer kinetics in a flowing afterglow/selected-ion flow tube and yielded the following for allene, methylacetylene, and the propargyl radical: ΔGacid(CH2=C=CH-H) = 372.8 ± 3 kcal mol-1, ΔGacid(H-CH2C=CH) = 374.7 ± 3 kcal mol-1, ΔGacid(CH3C≡C-H) = 373.4 ± 2 kcal mol-1, and ΔGacid(CH2=C=CH) = 364 ± 5 kcal mol-1. ΔGacid was converted to ΔHacid by employing ΔSacid: ΔHacid(CH2=C=CH-H) = 381.1 ± 3 kcal mol-1, ΔHacid(H-CH2C≡CH) = 382.7 ± 3 kcal mol-1, ΔHacid(CH3C≡C-H) = 381.1 ± 3 kcal mol-1, and ΔHacid(CH2=C=CH) = 372 ± 5 kcal mol-1. Evidence is provided for the isomerization of the allenyl anion (CH2=C=CH-) to the 1-propynyl anion (CH3C≡C-) in the proton transfer reactions of CH2=C=CH- with CH3OH and CH3CH2OH. This complexity limits the precision of experimental measurements. This study explores the intricacies of determining gas phase acidity values by proton transfer reactions for systems in which isomerization can occur.

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