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Lowe B, Cardona AL, Bodi A, Mayer PM, Burgos Paci MA. The Unimolecular Chemistry of Methyl Chloroformate Ions and Neutrals: A Story of Near-Threshold Decomposition. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:2831-2839. [PMID: 38008918 DOI: 10.1021/jasms.3c00334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2023]
Abstract
The near-threshold dissociation of ionized and neutral methyl chloroformate (CH3COOCl, MCF) was explored with imaging photoelectron photoion coincidence spectroscopy. The threshold photoelectron spectrum (TPES) for MCF was acquired for the first time; the large geometry changes upon ionization of MCF result in a broad, poorly defined TPES. Franck-Condon simulations are consistent with an adiabatic ionization energy (IE) of 10.90 ± 0.05 eV. Ionized MCF dissociates by chlorine atom loss at a measured 0 K appearance energy (AE) of 11.30 ± 0.01 eV. Together with the above IE, this AE suggests a reaction barrier of 0.40 ± 0.05 eV, consistent with the SVECV-f12 computational result of 0.41 eV. At higher internal energies, the loss of CH3O• becomes competitive due to its lower entropy of activation. Pyrolysis of neutral MCF formed the anticipated major products CH3Cl + CO2 (R1) and the minor products HCl + CO + CH2O (R2). The thermal decomposition products were identified by their photoion mass-selected threshold photoelectron spectrum (ms-TPES). Possible reaction pathways were explored computationally to confirm the dominant ones: R1 proceeds by a concerted Cl atom migration via a four-membered transition state in agreement with the mechanism proposed in the literature. R2 is a two-step reaction first yielding 2-oxiranone by HCl loss, which then decomposes to CH2O and CO. Kinetic modeling of the neutral decomposition could simulate the observed reactions only if the vibrational temperature of the MCF was assumed not to cool in the expansion.
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Affiliation(s)
- Bethany Lowe
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Canada K1N 6N5
| | - Alejandro L Cardona
- INFIQC - CONICET, Departamento fisicoquímica, Universidad Nacional de Córdoba, Córdoba, Argentina X5000HUA
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Paul M Mayer
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Canada K1N 6N5
| | - Maxi A Burgos Paci
- INFIQC - CONICET, Departamento fisicoquímica, Universidad Nacional de Córdoba, Córdoba, Argentina X5000HUA
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Xia H, Zhang Y, Attygalle AB. Experimental and Theoretical Studies on Gas-Phase Fragmentation Reactions of Protonated Methyl Benzoate: Concomitant Neutral Eliminations of Benzene, Carbon Dioxide, and Methanol. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:1601-1610. [PMID: 29881998 DOI: 10.1007/s13361-018-1997-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Revised: 05/07/2018] [Accepted: 05/13/2018] [Indexed: 06/08/2023]
Abstract
Protonated methyl benzoate, upon activation, fragments by three distinct pathways. The m/z 137 ion for the protonated species generated by helium-plasma ionization (HePI) was mass-selected and subjected to collisional activation. In one fragmentation pathway, the protonated molecule generated a product ion of m/z 59 by eliminating a molecule of benzene (Pathway I). The m/z 59 ion (generally recognized as the methoxycarbonyl cation) produced in this way, then formed a methyl carbenium ion in situ by decarboxylation, which in turn evoked an electrophilic aromatic addition reaction on the benzene ring by a termolecular process to generate the toluenium cation (Pathway II). Moreover, protonated methyl benzoate undergoes also a methanol loss (Pathway III). However, it is not a simple removal of a methanol molecule after a protonation on the methoxy group. The incipient proton migrates to the ring and randomizes to a certain degree before a subsequent transfer of one of the ring protons to the alkoxy group for the concomitant methanol elimination. The spectrum recorded from deuteronated methyl benzoate showed two peaks at m/z 105 and 106 for the benzoyl cation at a ratio of 2:1, confirming the charge-imparting proton is mobile. However, the proton transfer from the benzenium intermediate to the methoxy group for the methanol loss occurs before achieving a complete state of scrambling. Graphical Abstract ᅟ.
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Affiliation(s)
- Hanxue Xia
- Center for Mass Spectrometry, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Yong Zhang
- Center for Mass Spectrometry, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Athula B Attygalle
- Center for Mass Spectrometry, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ, 07030, USA.
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Wu X, Zhou X, Hemberger P, Bodi A. Dissociative Photoionization of Dimethyl Carbonate: The More It Is Cut, the Bigger the Fragment Ion. J Phys Chem A 2017; 121:2748-2759. [DOI: 10.1021/acs.jpca.7b00544] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xiangkun Wu
- Hefei
National Laboratory for Physical Sciences at the Microscale and Department
of Chemical Physics, National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Xiaoguo Zhou
- Hefei
National Laboratory for Physical Sciences at the Microscale and Department
of Chemical Physics, National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Patrick Hemberger
- Laboratory
for Femtochemistry and Synchrotron Radiation, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Andras Bodi
- Laboratory
for Femtochemistry and Synchrotron Radiation, Paul Scherrer Institute, 5232 Villigen, Switzerland
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Piekarski DG, Delaunay R, Maclot S, Adoui L, Martín F, Alcamí M, Huber BA, Rousseau P, Domaracka A, Díaz-Tendero S. Unusual hydroxyl migration in the fragmentation of β-alanine dication in the gas phase. Phys Chem Chem Phys 2015; 17:16767-78. [DOI: 10.1039/c5cp01628b] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Experimental and theoretical investigations show that hydroxyl migration leads to unexpected fragmentation dynamics of β-alanine dication in the gas phase.
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Affiliation(s)
| | - Rudy Delaunay
- CIMAP (UMR 6252) - CEA
- CNRS
- ENSICAEN
- Unicaen
- 14070 Caen Cedex 5
| | - Sylvain Maclot
- CIMAP (UMR 6252) - CEA
- CNRS
- ENSICAEN
- Unicaen
- 14070 Caen Cedex 5
| | - Lamri Adoui
- CIMAP (UMR 6252) - CEA
- CNRS
- ENSICAEN
- Unicaen
- 14070 Caen Cedex 5
| | - Fernando Martín
- Departamento de Química
- Módulo 13
- Universidad Autónoma de Madrid
- 28049 Madrid
- Spain
| | - Manuel Alcamí
- Departamento de Química
- Módulo 13
- Universidad Autónoma de Madrid
- 28049 Madrid
- Spain
| | - Bernd A. Huber
- CIMAP (UMR 6252) - CEA
- CNRS
- ENSICAEN
- Unicaen
- 14070 Caen Cedex 5
| | | | | | - Sergio Díaz-Tendero
- Departamento de Química
- Módulo 13
- Universidad Autónoma de Madrid
- 28049 Madrid
- Spain
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Hu N, Tu YP, Jiang K, Pan Y. Intramolecular Charge Transfer in the Gas Phase: Fragmentation of Protonated Sulfonamides in Mass Spectrometry. J Org Chem 2010; 75:4244-50. [DOI: 10.1021/jo100761k] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Nan Hu
- Department of Chemistry, Zhejiang University, 38 Zheda Road, Hangzhou, Zhejiang 310027, China
| | - Ya-Ping Tu
- Drug Metabolism and Pharmacokinetics, Infectious Diseases Center of Excellence for Drug Discovery, GlaxoSmithKline, 5 Moore Drive, Research Triangle Park, North Carolina 27709
| | - Kezhi Jiang
- Department of Chemistry, Zhejiang University, 38 Zheda Road, Hangzhou, Zhejiang 310027, China
| | - Yuanjiang Pan
- Department of Chemistry, Zhejiang University, 38 Zheda Road, Hangzhou, Zhejiang 310027, China
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Chai Y, Jiang K, Pan Y. Hydride transfer reactions via ion-neutral complex: fragmentation of protonated N-benzylpiperidines and protonated N-benzylpiperazines in mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2010; 45:496-503. [PMID: 20301171 DOI: 10.1002/jms.1731] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
An ion-neutral complex (INC)-mediated hydride transfer reaction was observed in the fragmentation of protonated N-benzylpiperidines and protonated N-benzylpiperazines in electrospray ionization mass spectrometry. Upon protonation at the nitrogen atom, these compounds initially dissociated to an INC consisting of [RC(6)H(4)CH(2)](+) (R = substituent) and piperidine or piperazine. Although this INC was unstable, it did exist and was supported by both experiments and density functional theory (DFT) calculations. In the subsequent fragmentation, hydride transfer from the neutral partner to the cation species competed with the direct separation. The distribution of the two corresponding product ions was found to depend on the stabilization energy of this INC, and it was also approved by the study of substituent effects. For monosubstituted N-benzylpiperidines, strong electron-donating substituents favored the formation of [RC(6)H(4)CH(2)](+), whereas strong electron-withdrawing substituents favored the competing hydride transfer reaction leading to a loss of toluene. The logarithmic values of the abundance ratios of the two ions were well correlated with the nature of the substituents, or rather, the stabilization energy of this INC.
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Affiliation(s)
- Yunfeng Chai
- Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
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Tu YP, Huang Y, Atsriku C, You Y, Cunniff J. Intramolecular transacylation: fragmentation of protonated molecules via ion-neutral complexes in mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2009; 23:1970-1976. [PMID: 19504483 DOI: 10.1002/rcm.4108] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
An intramolecular transacylation reaction was observed in the mass spectrometry of molecules containing both benzoyl and carboxymethyl groups on an aromatic heterocyclic core. The reaction is triggered by a dissociative protonation on the heterocyclic ring at the atom (carbon or nitrogen) that bonds to the benzoyl group, leading to an intermediate ion-neutral complex. The incipient benzoyl cation in the complex migrates to attack the carboxyl group of the neutral partner at the carbonyl or hydroxyl oxygen under thermodynamic or kinetic control, respectively. Elimination of benzoic acid followed by loss of carbon monoxide takes place as a result of the transacylation.
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Affiliation(s)
- Ya-Ping Tu
- Drug Metabolism and Pharmacokinetics, Genelabs Technologies, Inc., 505 Penobscot Drive, Redwood City, CA 94063, USA.
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Decker BK, Babcock LM, Adams NG. Selected Ion Flow Tube Studies of S+(4S) Reactions with Small Oxygenated and Sulfurated Organic Molecules. J Phys Chem A 2000. [DOI: 10.1021/jp992470p] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Brian K. Decker
- Department of Chemistry, The University of Georgia, Athens, Georgia 30602
| | - Lucia M. Babcock
- Department of Chemistry, The University of Georgia, Athens, Georgia 30602
| | - Nigel G. Adams
- Department of Chemistry, The University of Georgia, Athens, Georgia 30602
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Ruttink PJA, Burgers PC, Fell LM, Terlouw JK. G2 Theory and Experiment in Concert: Enthalpy of Formation of CH3O−CO+ and Its Isomers Revisited. J Phys Chem A 1999. [DOI: 10.1021/jp984015j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Paul J. A. Ruttink
- Theoretical Chemistry Group, Department of Chemistry, University of Utrecht, Padualaan 14, 3584 CH Utrecht, The Netherlands
| | - Peter C. Burgers
- Hercules European Research Center BV, P.O. Box 252, 3770 AG Barneveld, The Netherlands
| | - Lorne M. Fell
- Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - Johan K. Terlouw
- Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1, Canada
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Harrison AG, Malát J. An electron impact and chemical ionization study of some diethyl dicarboxylates. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s0168-1176(97)00073-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Suh D, Kingsmill CA, Ruttink PJ, Burgers PC, Terlouw JK. ClH⋯O and O⋯H⋯O bonded intermediates in the dissociation of low energy methyl glycolate radical cations. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0168-1176(95)04192-n] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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12
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Cordero MM, Wesdemiotis C. Tandem mass spectrometry of peptides: Mechanistic aspects and structural information based on neutral losses. II—Tri- and larger peptides. ACTA ACUST UNITED AC 1994. [DOI: 10.1002/oms.1210290709] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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13
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Schröder D, Hrušák J, Tornieporth-Oetting IC, Klapötke TM, Schwarz H. Definitiver Beweis für die Existenz von AuF. Angew Chem Int Ed Engl 1994. [DOI: 10.1002/ange.19941060223] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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14
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The effects of methyl substitution on the structure and thermochemistry of the cyanomethyl radical and cation. Chem Phys Lett 1993. [DOI: 10.1016/0009-2614(93)87121-i] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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15
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On the generation and identification of dimethoxycarbene and 2-oxazolidinylidene in the rarefied gas phase of the mass spectrometer. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/0168-1176(92)85030-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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17
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Holmes JL, Lossing F. Bond strengths in even-electron ions and the proton affinities of free radicals. ACTA ACUST UNITED AC 1989. [DOI: 10.1016/0168-1176(89)83022-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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