David J. McAdoo

The University of Texas Medical Branch at Galveston

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Charles E. Hudson

The University of Texas at Austin

John C. Traeger

La Trobe University

Lawrence L. Griffin

Texas A&M University at Galveston

Claire E. Hulsebosch

The University of Texas Health Science Center at Houston

Michael G. Hughes

Cardiff Metropolitan University

Fred W. McLafferty

Cedars-Sinai Medical Center

C. S. Giam

Texas A&M University at Galveston

Guoying Xu

The University of Texas Medical Branch at Galveston

Karin N. Westlund

University of New Mexico

William D. Willis

National Institute of Environmental Health Sciences

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The University of Texas Medical Branch at Galveston

129

Galveston College

Baylor College of Medicine

The University of Texas at Austin

Cornell University

Texas A&M University at Galveston

University of Arizona

The University of Texas Health Science Center at Houston

National Institutes of Health

Combat Capabilities Development Command Soldier Center

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Why Do Losses of Polyatomic Fragments Strongly Dominate Losses of Atoms at High Internal Energies? Methyl versus Cl^• Loss from the 2-Chloropropane Cation

The Journal of Physical Chemistry A (2003)

Charles E. Hudson John C. Traeger Lawrence L. Griffin David J. McAdoo

Previous work demonstrates that rates of H• losses generally increase much less rapidly with increasing internal energy than do those of losses of polyatomic fragments. To determine whether this is also the case for the losses of other atoms, the dependencies of the rates of Cl• and CH3• losses from CH3CHClCH3+• on ion internal energy are compared. These dependencies were established experimentally by photoionization mass spectrometry. The reactant ion and the transition states were characterized by B3LYP/6-31G(d), B3LYP/6-311G(d,p), and MP2/6-31G(d) theories. The transition states located are at very long bond lengths and close in energy to the corresponding dissociation products. Rate constants as a function of internal energy were obtained by RRKM theory. According to both experiment and theory, above its onset, methyl loss increases much more rapidly with internal energy than does loss of Cl•. This stems from three vibrational frequencies being substantially lowered in the transition state for the former but not in the latter reaction as they are being transformed into rotations of the separated products. This produces a much more rapid increase in the RRKM sum of states for the transition state to CH3CHCl+ + CH3•, and thus also in the rate of that reaction. This, together with previous work, establishes that losses of polyatomic fragments from ions in the gas phase generally increase much faster with increasing internal energy than do losses of atoms.

Polyatomic ion

Internal energy

Transition state

Transition state theory

Bond-dissociation energy

10.1021/jp021740s

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Citations (3)

Energy randomization is complete in [C5H10O]+˙ ions with the oxygen on the middle carbon

Organic Mass Spectrometry (1983)

David J. McAdoo Charles E. Hudson

Abstract The relative intensities of the losses of ethyl groups from opposite sides of the 3‐pentanone ion formed by isomerization from its enol isomer are shown to be equal when corrections for protonated acrolein formation, isotope effects, and overlapping ethane losses are made. Thus the ion decomposes symmetrically, implying ergodic behavior, as concluded by Depke and Schwarz.

Acrolein

Carbon fibers

10.1002/oms.1210180406

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An ab Initio Study of Substituent Effects in [1,3]-Hydrogen Shifts

The Journal of Organic Chemistry (2003)

Charles E. Hudson David J. McAdoo

Reports in the literature place the TS for the [1,3]-H shift in propene comparable to or higher in energy than loss of the allylic H. However, [1,3]-H shifts have been repeatedly observed experimentally in enolates. We used GAUSSIAN 98 to examine the origin of this apparent contradiction. We found the first TS for an antarafacial [1,3]-H shift that is clearly lower in energy than simple dissociation of the migrating H. This occurs in the [1,3]-H shift in the acetone enolate. Symmetrical substituents (H, O(-), ethynyl) have TSs with C(2) symmetry, implying that they, and probably most [1,3]-H shift TSs, are antarafacial. Conjugating substituents at C2 lower the energy of [1,3]-H shifts and raise the energy of dissociation by loss of a hydrogen atom from C3, increasing the likelihood of the former type of reaction. Strongly electron-donating and electron-withdrawing substituents are more effective than neutral substituents in lowering the energy requirement of [1,3] shifts. Our best calculations predict that a [1,3]-H shift is lower in energy than dissociation by loss of the H by 27.8 kJ/mol in 2-methyl-1-butene-3-yne, by 36.8 kJ/mol in isoprene, by 55.9 kJ/mol in 2-aminopropene, by 114.5 kJ/mol in the acetone enolate, and by 120.8 kJ/mol in the 1-methylacryloyl cation. Thus, there is a chance of experimental observation of [1,3] shifts in conjugated alkenes and related species.

Propene

Hydrogen atom

Bond-dissociation energy

10.1021/jo020624i

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Citations (17)

Competing dissociation of and bond formation between CH3CHOH+ and .CH2CH3 formed by bimolecular processes

International Journal of Mass Spectrometry and Ion Processes (1994)

Mohammed Ahmed C. S. Giam David J. McAdoo

10.1016/0168-1176(93)03869-n

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Citations (10)

The formation of [CH₃CH₂C(OH)CH₂]^+˙ from 1‐hepten‐3‐ol

Organic Mass Spectrometry (1981)

David J. McAdoo Charles E. Hudson

Abstract The [C 4 H 8 O] +˙ ion in the mass spectrum of 1‐hepten‐3‐ol is shown to be \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{3}} {\rm{CH}}_{\rm{2}} {\rm{C(= }}\mathop {\rm{O}}\limits^{\rm{ + }} {\rm{H}})\mathop {\rm{C}}\limits^{\rm{.}} {\rm{H}}_{\rm{2}} $\end{document} by collisional activation spectra, appearance energies and comparison of the ratios of the intensities of metastable decompositions. [C 4 H 8 O] +˙ appears to be formed by rearrangement of ionized 1‐hepten‐3‐ol to \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{3}} \mathop {\rm{C}}\limits^{\rm{.}} {\rm{HC(= }}\mathop {\rm{O}}\limits^{\rm{ + }} {\rm{H)CH}}_{\rm{2}} {\rm{CH}}_{\rm{2}} {\rm{CH}}_{\rm{2}} {\rm{CH}}_{\rm{3}} $\end{document} followed by γ‐hydrogen rearrangement‐β‐cleavage.

Metastability

10.1002/oms.1210160704

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Citations (4)

Amino acid uptake and incorporation into cell-specific peptides and evidence for intracellular peptide pools in Aplysia neurons R3–R14

Comparative Biochemistry and Physiology Part B Comparative Biochemistry (1989)

Cheng-Yie Lin Michael G. Hughes David J. McAdoo

Aplysia

10.1016/0305-0491(89)90327-1

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Citations (5)

Unimolecular Decompositions of Ionized Isopropyl Methyl Ether: An ab Initio and RRKM Study

Journal of the American Chemical Society (1995)

Santiago Olivella Albert Solé David J. McAdoo Lawrence L. Griffin

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUnimolecular Decompositions of Ionized Isopropyl Methyl Ether: An ab Initio and RRKM StudySantiago Olivella, Albert Sole, David J. McAdoo, and Lawrence L. GriffinCite this: J. Am. Chem. Soc. 1995, 117, 9, 2557–2564Publication Date (Print):March 1, 1995Publication History Published online1 May 2002Published inissue 1 March 1995https://pubs.acs.org/doi/10.1021/ja00114a019https://doi.org/10.1021/ja00114a019research-articleACS PublicationsRequest reuse permissionsArticle Views82Altmetric-Citations18LEARN 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-AlertscloseSupporting Info (2)»Supporting Information Supporting Information Get e-Alerts

Isopropyl

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10.1021/ja00114a019

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Citations (18)

Reaction of ionized propene with methanol: Comparison with CH₃OH₂⁺ formation from ionized 2‐methylpropanol

Organic Mass Spectrometry (1994)

David J. McAdoo Zhao Guohong Mohammed Ahmed Charles E. Hudson C. S. Giam

Abstract Methanol exchanges its hydroxyl hydrogen with deuteriums in ionized propene during the formation of protonated methanol. This exchange is attributed to the interconversion [CH 3 CHCH 2 +. HOCH 3 ⇌][CH 2 ⋅CHCH 2 + H 2 OCH 3 ] in single collisions. The exchange in this ion‐molecule reaction is analogous to that observed in the formation of protonated methanol from ionized 2‐methylpropanol, supporting the intermediacy of ion‐neutral complexes in the final step of the latter reaction. Ion‐molecule reactions were studied using a Fourier transform mass spectrometer.

Propene

10.1002/oms.1210290806

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Citations (1)

GAS CHROMATOGRAPHIC–MASS SPECTROMETRIC ANALYSIS OF BIOGENIC AMINES IN IDENTIFIED NEURONS AND TISSUES OF HIRUDO MEDICINALIS

Journal of Neurochemistry (1976)

David J. McAdoo R. E. Coggeshall

Abstract —Previous workers have reported that the colossal cells of Retzius in the segmental ganglia of the medicinal leech contain about 2.3 pmol of 5‐hydroxytryptamme (5‐HT)/cell body. We verify the identify of 5‐HT in the Retzius cells by gas chromatography‐mass spectrometry and derive concentrations of 1.3–4.1 pmol/neuron by analyses of eight individually dissected Retzius cell bodies. The Retzius cell bodies contain about 30% of the 5‐HT in each ganglion. An average of 25 pmol 5‐HT/mg tissue, a concentration about 500 times lower than that in the Retzius cell, was found in the fibrous, pigmented tissue surrounding the leech nervous system. We could not detect γ‐aminobutyric acid, octopamine, dopamine or norepinephrine in the Retzius cells, in the pigmented tissue, or, with the possible exception of dopamine (±0.4 pmol/ganglion), in whole ganglia. Furthermore, we could not detect 5‐HT in pooled samples of 100 non‐chromaffin control neurons.

Hirudo medicinalis

Octopamine (neurotransmitter)

Biogenic amine

10.1111/j.1471-4159.1976.tb04452.x

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Citations (93)

ChemInform Abstract: KENNZEICHEN METASTABILER IONEN 21. MITT. ISOMERISIERUNGS‐ UND ZERS.‐RK. VON C4H8O(.+)‐IONEN

Chemischer Informationsdienst (1972)

David J. McAdoo Fred W. McLafferty T. E. PARKS

10.1002/chin.197221090

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