Pentadienyl radicals and their 3-methyl and 3-hydroxy derivatives were generated from the corresponding 1,4-pentadienes. The rates of hydrogen abstraction were studied by laser flash photolysis, and the bisallylic C-H bond dissociation energies were determined by photoacoustic calorimetry. Pentadienyl radicals were also generated by monoenergetic electron bombardment of 3-tert-butyl-1,4-pentadiene, and the radical's enthalpy of formation was deduced from the appearance energy of the tert-butyl cation. Evaluation of all recent data leads to recommended values of DELTA-H(f)-degrees (pentadienyl) = 49.8 +/- 1.0 kcal mol-1 and DH-degrees ((CH2 = CH)2CH) = 76.6 +/- 1.0 kcal mol-1. The EPR spectra of 3-methylpentadienyl and several other radicals were also examined. The effect of substituents on the stabilization energy of pentadienyl radicals was assessed, and pentadienyl radicals were compared with other delocalized polyenyl radicals.

AbstractThe charge‐stripping mass spectra of the ten C5H10 isomers and of cyclopropane and propene have been re‐evaluated. Oxygen is the preferred collision gas for the former group and helium for the latter pair. A con bined study of the low‐energy mass spectra, charge‐stripping mass spectra and appearance energy measurements had to the conclusion that loss of H2O from ionized pentan‐1‐ol and loss of HCl from ionized 1‐chloropentane both predominantly produce ionized ethylcyclopropane as the fragment ion. For the alcohol, a 1,4‐elimination followed by an energetically favoured 1,2‐H shift is involved, whereas for the halide a direct 1,3‐elimination obtains.

AbstractThe energetics of olefin loss from ionized alkyl phenyl ethers have been determined by ionization and appearance energy measurements. It is concluded that the reaction is governed by one or more of three features: (i) the strength of the bond between the phenoxy radical and the alkyl ion; (ii) the ease of isomerization of the alkyl ions, chiefly by H‐shifts therein, and (iii) the strength of the CH bond (primary, secondary and tertiary) involved in the H transfer to oxygen which precedes the olefin loss. The possible participation in the reaction of distonic ions and proton bound radical‐molecule pairs is also discussed.

ChemInformVolume 20, Issue 7 Article ChemInform Abstract: Heats of Formation and Bond Dissociation Energies in Halogen-Substituted Methyl and Ethyl Radicals. J. L. HOLMES, J. L. HOLMES Dep. Chem., Univ. Ottawa, Ottawa, Ont. K1N 6N5, Can.Search for more papers by this authorF. P. LOSSING, F. P. LOSSING Dep. Chem., Univ. Ottawa, Ottawa, Ont. K1N 6N5, Can.Search for more papers by this author J. L. HOLMES, J. L. HOLMES Dep. Chem., Univ. Ottawa, Ottawa, Ont. K1N 6N5, Can.Search for more papers by this authorF. P. LOSSING, F. P. LOSSING Dep. Chem., Univ. Ottawa, Ottawa, Ont. K1N 6N5, Can.Search for more papers by this author First published: February 14, 1989 https://doi.org/10.1002/chin.198907083AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume20, Issue7February 14, 1989 RelatedInformation

Hydrogen atom affinities of even-electron ions have been shown to be dissimilar to homolytic bond dissociation energies in analogous neutral molecules. The proton affinities of free radicals are, in general, not the same as those of appropriate neutral molecules (each being protonated at the same functional group). These results are discussed with respect to their utility in estimating ionic heats of formation.

Electron impact ionization of tetrachloromethane has been shown to produce stable [CCl4]+· ions; their heat of formation is ⩽ 237 kcal mol−1. The ylid isomer, [Cl2CClCl]+·, generated upon dissociative ionization of Cl3CCOCl, is remarkably more stable; ΔH0f([Cl2CClCl]+·) < 224 kcal mol−1. The values for both isomers are significantly lower than calculated values. The corresponding neutrals, CCl4 and Cl2CClCl, are not stable on the time and energy scale of neutralization—re-ionization experiments. Although [Cl2CClCl]2+, was calculated to be stable, it was not present in the charge-stripping mass spectrum of the ylid ion.

The heats of formation, ΔH0f, of a series of halogen-substituted alkyl ions have been determined by appearance energy measurements with energy selected electrons. Halogen substitution at the formal charge site significantly reduces the heterolytic bond strength D[R+H−], the effect being not greatly different for Cl, Br and I. The β-substituted halo-ethyl ions clearly show stabilization resulting from the formation of bridged halonium ions but this effect is absent in the propyl and butyl analogues.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHeats of formation and bond dissociation energies in halogen-substituted methyl and ethyl radicalsJohn L. Holmes and F. P. LossingCite this: J. Am. Chem. Soc. 1988, 110, 22, 7343–7345Publication Date (Print):October 1, 1988Publication History Published online1 May 2002Published inissue 1 October 1988https://pubs.acs.org/doi/10.1021/ja00230a012https://doi.org/10.1021/ja00230a012research-articleACS PublicationsRequest reuse permissionsArticle Views300Altmetric-Citations87LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHeats of formation of alkyl radicals from appearance energiesJohn L. Holmes, F. P. Lossing, and Allan. MaccollCite this: J. Am. Chem. Soc. 1988, 110, 22, 7339–7342Publication Date (Print):October 1, 1988Publication History Published online1 May 2002Published inissue 1 October 1988https://pubs.acs.org/doi/10.1021/ja00230a011https://doi.org/10.1021/ja00230a011research-articleACS PublicationsRequest reuse permissionsArticle Views154Altmetric-Citations56LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

AbstractThe following isomers of the ethyl halide molecular ions have all been shown to be stable species in the gas phase: [CH2CH2FH]+˙; [CH3ClCH2]+˙ (ΔHf° = 1012 kJ mol−1); [CH3CHClH]+˙ (ΔHf° = 971 kJ mol−1); [CH2CH2ClH]+˙; [CH3BrCH2]+˙ (ΔHf° = 1058 KJ mol−1); [CH3CHBrH]+˙ (ΔHf° = 995 kJ mol−1) and [CH2CH2BrH]+˙.Neutralization–reionization mass spectrometry, employing Xe as the electron transfer target gas and O2 as the target gas for reionization, indicated that the ylides CH3ClCH2 and CH3BrCH2 could not be generated by such means. However, the species CH3CHClH, CH2CH2ClH and CH2CH2BrH (and possibly CH3CHBrH) were unambiguously identified.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCharacterizing the 2-norbornyl cation in the gas phaseMarcia C. Blanchette, John L. Holmes, and F. P. LossingCite this: J. Am. Chem. Soc. 1987, 109, 5, 1392–1395Publication Date (Print):March 1, 1987Publication History Published online1 May 2002Published inissue 1 March 1987https://pubs.acs.org/doi/10.1021/ja00239a019https://doi.org/10.1021/ja00239a019research-articleACS PublicationsRequest reuse permissionsArticle Views97Altmetric-Citations10LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

ChemInformVolume 18, Issue 28 Preparative Organic Chemistry ChemInform Abstract: Characterizing the 2-Norbornyl Cation in the Gas Phase M. C. BLANCHETTE, M. C. BLANCHETTE Chem. Dep., Univ. Ottawa, Ottawa, Ont., Can. K1N 9B4Search for more papers by this authorJ. L. HOLMES, J. L. HOLMES Chem. Dep., Univ. Ottawa, Ottawa, Ont., Can. K1N 9B4Search for more papers by this authorF. P. LOSSING, F. P. LOSSING Chem. Dep., Univ. Ottawa, Ottawa, Ont., Can. K1N 9B4Search for more papers by this author M. C. BLANCHETTE, M. C. BLANCHETTE Chem. Dep., Univ. Ottawa, Ottawa, Ont., Can. K1N 9B4Search for more papers by this authorJ. L. HOLMES, J. L. HOLMES Chem. Dep., Univ. Ottawa, Ottawa, Ont., Can. K1N 9B4Search for more papers by this authorF. P. LOSSING, F. P. LOSSING Chem. Dep., Univ. Ottawa, Ottawa, Ont., Can. K1N 9B4Search for more papers by this author First published: July 14, 1987 https://doi.org/10.1002/chin.198728133Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume18, Issue28July 14, 1987 RelatedInformation

ChemInformVolume 18, Issue 15 Physical Organic Chemistry ChemInform Abstract: Theory and Experiment in Concert; the CH3O-C+=O Ion and Its Isomers M. C. BLANCHETTE, M. C. BLANCHETTE Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this authorJ. L. HOLMES, J. L. HOLMES Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this authorC. E. C. A. HOP, C. E. C. A. HOP Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this authorF. P. LOSSING, F. P. LOSSING Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this authorR. POSTMA, R. POSTMA Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this authorP. J. A. RUTTINK, P. J. A. RUTTINK Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this authorJ. K. TERLOUW, J. K. TERLOUW Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this author M. C. BLANCHETTE, M. C. BLANCHETTE Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this authorJ. L. HOLMES, J. L. HOLMES Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this authorC. E. C. A. HOP, C. E. C. A. HOP Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this authorF. P. LOSSING, F. P. LOSSING Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this authorR. POSTMA, R. POSTMA Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this authorP. J. A. RUTTINK, P. J. A. RUTTINK Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this authorJ. K. TERLOUW, J. K. TERLOUW Chem. Dep., Univ. Ottawa, Ottawa, Ont. K1N 9B4, Can.Search for more papers by this author First published: April 14, 1987 https://doi.org/10.1002/chin.198715050Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume18, Issue15April 14, 1987 RelatedInformation

Organic Mass SpectrometryVolume 21, Issue 10 p. 729-731 Oms Letter The mass spectrometric generation of neutral ethynamine HCCNH2 and other C2H3N isomers John M. Buschek, Corresponding Author John M. Buschek Chemistry Department, University of Ottawa, Ottawa, Ontario, Canada K1N 9B4Chemistry Department, University of Ottawa, Ottawa, Ontario, Canada K1N 9B4Search for more papers by this authorJohn L. Holmes, Corresponding Author John L. Holmes Chemistry Department, University of Ottawa, Ottawa, Ontario, Canada K1N 9B4Chemistry Department, University of Ottawa, Ottawa, Ontario, Canada K1N 9B4Search for more papers by this authorF. P. Lossing, F. P. Lossing Chemistry Department, University of Ottawa, Ottawa, Ontario, Canada K1N 9B4Search for more papers by this author John M. Buschek, Corresponding Author John M. Buschek Chemistry Department, University of Ottawa, Ottawa, Ontario, Canada K1N 9B4Chemistry Department, University of Ottawa, Ottawa, Ontario, Canada K1N 9B4Search for more papers by this authorJohn L. Holmes, Corresponding Author John L. Holmes Chemistry Department, University of Ottawa, Ottawa, Ontario, Canada K1N 9B4Chemistry Department, University of Ottawa, Ottawa, Ontario, Canada K1N 9B4Search for more papers by this authorF. P. Lossing, F. P. Lossing Chemistry Department, University of Ottawa, Ottawa, Ontario, Canada K1N 9B4Search for more papers by this author First published: October 1986 https://doi.org/10.1002/oms.1210211021Citations: 14AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume21, Issue10October 1986Pages 729-731 RelatedInformation

Chemischer InformationsdienstVolume 17, Issue 26 Article ChemInform Abstract: Heats of Formation and Homolytic Bond Dissociation Energies i-n the Keto - Enol Tautomers C2H4O, C3H6O J. L. HOLMES, J. L. HOLMESSearch for more papers by this authorF. P. LOSSING, F. P. LOSSINGSearch for more papers by this authorJ. K. TERLOUW, J. K. TERLOUWSearch for more papers by this author J. L. HOLMES, J. L. HOLMESSearch for more papers by this authorF. P. LOSSING, F. P. LOSSINGSearch for more papers by this authorJ. K. TERLOUW, J. K. TERLOUWSearch for more papers by this author First published: July 1, 1986 https://doi.org/10.1002/chin.198626084Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume17, Issue26July 1, 1986 RelatedInformation

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTheory and experiment in concert: the [MeOC:O]+ ion and its isomersM. C. Blanchette, J. L. Holmes, C. E. C. A. Hop, F. P. Lossing, R. Postma, P. J. A. Ruttink, and J. K. TerlouwCite this: J. Am. Chem. Soc. 1986, 108, 24, 7589–7594Publication Date (Print):November 1, 1986Publication History Published online1 May 2002Published inissue 1 November 1986https://doi.org/10.1021/ja00284a024RIGHTS & PERMISSIONSArticle Views79Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (728 KB) Get e-Alerts Get e-Alerts

AbstractThe kinetic energy release for methyl loss from the molecular ion of 2‐methylpentane increases c. twofold over the time‐range 1–15 μs. This result from a mixture of secondary and tertiary pentyl cations. The appearance energy showed that at threshold (and long times) only tertiary ions are formed. The molecular ion of 2‐methylhexane produces tertiary hexyl ions by loss of methyl at threshold, but in the μs time‐frame only secondary hexyl ions appear to be formed, because the kinetic energy release is small and independent of the observation time.

The heats of formation of eighteen organic radicals have been measured from appearance energies for fragmentations in which the daughter ion structure and heat of formation are known. The agreement with values obtained from kinetic measurements is generally good.