1
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Prado Merini M, Schleif T, Sander W. Heavy-Atom Tunneling in Bicyclo[4.1.0]hepta-2,4,6-trienes. Angew Chem Int Ed Engl 2023; 62:e202309717. [PMID: 37698374 DOI: 10.1002/anie.202309717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Revised: 09/11/2023] [Accepted: 09/12/2023] [Indexed: 09/13/2023]
Abstract
Heavy-atom tunneling limits the lifetime and observability of bicyclo[4.1.0]hepta-2,4,6-triene, a key intermediate in the rearrangement of phenylcarbene. Bicyclo[4.1.0]hepta-2,4,6-triene had been proposed as the primary intermediate of the rearrangement of phenylcarbene, but despite many efforts evaded its characterization even in cryogenic matrices. By introducing fluorine substituents into the ortho-positions of the phenyl ring of phenylcarbene, the highly strained cyclopropene 1,5-difluorobicyclo[4.1.0]hepta-2,4,6-triene becomes stable enough to be characterized in argon matrices. However, even at 3 K this cyclopropene is only metastable and rearranges via heavy-atom tunneling to the corresponding cycloheptatetraene. Calculations suggest that fluorination is necessary to slow down the tunneling rearrangement of the bicycloheptatriene. The parent bicycloheptatriene rapidly rearranges via heavy-atom tunneling and therefore cannot be detected under matrix isolation conditions.
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Affiliation(s)
- Melania Prado Merini
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Universitätsstraße 150, 44801, Bochum, Germany
| | - Tim Schleif
- Department of Chemistry, Yale University, 225 Prospect St., New Haven, CT 06520, USA
| | - Wolfram Sander
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Universitätsstraße 150, 44801, Bochum, Germany
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2
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Bégué D, Dargelos A, Wentrup C. Rearrangements of Nitrile Imines: Ring Expansion of Benzonitrile Imines to Cycloheptatetraenes and Ring Closure to 3-Phenyl-3 H-diazirines. J Org Chem 2019; 84:8668-8673. [PMID: 31244156 DOI: 10.1021/acs.joc.9b01183] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nitrile imines are important intermediates in 1,3-dipolar cycloaddition reactions, and they are also known to undergo efficient, unimolecular rearrangements to carbodiimides via 1 H-diazirines and imidoylnitrenes under both thermal and photochemical reaction conditions. We now report a competing rearrangement, revealed by CASPT2(14,12) and B3LYP calculations, in which C-phenylnitrile imines 8 undergo ring expansion to 1-diazenyl-1,2,4,6-cycloheptatetraenes 12 akin to the phenylcarbene-cycloheptatetraene rearrangement. Amino-, hydroxy-, and thiol-groups in the meta positions of C-phenylnitrile imine lower the activation energies for this rearrangement so that it becomes potentially competitive with the cyclization to 1 H-diazirines and hence rearrange to carbodiimides. The diazenylcycloheptatetraenes 12 thus formed can evolve further to cycloheptatetraene 30 and 2-diazenyl-phenylcarbene 16 over modest activation barriers, and the latter carbenes cyclize very easily to 2 H- and 3 H-indazoles, from which 6-methylenecyclohexadienylidene, phenylcarbene, fulvenallene, and their isomers are potentially obtainable. Moreover, another new rearrangement of benzonitrile imine forms 3-phenyl-3 H-diazirine, which is a precursor of phenyldiazomethane and hence phenylcarbene. This reaction is competitive with the ring expansion. The new rearrangements predicted here should be experimentally observable, for example, under matrix photolysis or flash vacuum pyrolysis conditions.
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Affiliation(s)
- Didier Bégué
- CNRS/Université de Pau et des Pays de l'Adour/E2S UPPA, Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Matériaux, UMR5254 , Pau 64000 , France
| | - Alain Dargelos
- CNRS/Université de Pau et des Pays de l'Adour/E2S UPPA, Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Matériaux, UMR5254 , Pau 64000 , France
| | - Curt Wentrup
- School of Chemistry and Molecular Biosciences , The University of Queensland , Brisbane , Queensland 4072 , Australia
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3
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Xu J, Mieres-Perez J, Sanchez-Garcia E, Lee JK. Gas-Phase Deprotonation of Benzhydryl Cations: Carbene Basicity, Multiplicity, and Rearrangements. J Org Chem 2019; 84:7685-7693. [PMID: 31008604 DOI: 10.1021/acs.joc.9b00496] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Many fundamental properties of carbenes, particularly basicity, remain poorly understood. Herein, an experimental and computational examination of the deprotonation of a series of benzhydryl cations has been undertaken. These studies represent the first attempt at providing experimental values for diarylcarbene basicities. Pathways to deprotonation, including whether the singlet or triplet carbene is formed, are probed. Because diarylcarbenes are expected to be among the strongest organic bases known, assessing the energetics of protonation of these species is of fundamental importance for a wide range of chemical processes.
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Affiliation(s)
- Jiahui Xu
- Department of Chemistry and Chemical Biology , Rutgers, The State University of New Jersey , New Brunswick , New Jersey 08901 , United States
| | - Joel Mieres-Perez
- Computational Biochemistry, Center of Medical Biotechnology , University of Duisburg-Essen , D-45141 Essen , Germany
| | - Elsa Sanchez-Garcia
- Computational Biochemistry, Center of Medical Biotechnology , University of Duisburg-Essen , D-45141 Essen , Germany
| | - Jeehiun K Lee
- Department of Chemistry and Chemical Biology , Rutgers, The State University of New Jersey , New Brunswick , New Jersey 08901 , United States
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4
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Ghafarian Shirazi R, Neese F, Pantazis DA. Accurate Spin-State Energetics for Aryl Carbenes. J Chem Theory Comput 2018; 14:4733-4746. [DOI: 10.1021/acs.jctc.8b00587] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Reza Ghafarian Shirazi
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Frank Neese
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Dimitrios A. Pantazis
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
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5
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Henkel S, Pollok CH, Schleif T, Sander W. Azulenylcarbenes: Rearrangements on the C11H8Potential Energy Surface. Chemistry 2016; 22:12479-86. [DOI: 10.1002/chem.201601390] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Indexed: 11/09/2022]
Affiliation(s)
- Stefan Henkel
- Lehrstuhl für Organische Chemie II; Ruhr-Universität Bochum; 44780 Bochum Germany
| | - Corina H. Pollok
- Lehrstuhl für Organische Chemie II; Ruhr-Universität Bochum; 44780 Bochum Germany
| | - Tim Schleif
- Lehrstuhl für Organische Chemie II; Ruhr-Universität Bochum; 44780 Bochum Germany
| | - Wolfram Sander
- Lehrstuhl für Organische Chemie II; Ruhr-Universität Bochum; 44780 Bochum Germany
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6
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Gryn'ova G, Coote ML, Corminboeuf C. Theory and practice of uncommon molecular electronic configurations. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2015; 5:440-459. [PMID: 27774112 PMCID: PMC5057308 DOI: 10.1002/wcms.1233] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 09/15/2015] [Accepted: 09/17/2015] [Indexed: 11/10/2022]
Abstract
The electronic configuration of the molecule is the foundation of its structure and reactivity. The spin state is one of the key characteristics arising from the ordering of electrons within the molecule's set of orbitals. Organic molecules that have open-shell ground states and interesting physicochemical properties, particularly those influencing their spin alignment, are of immense interest within the up-and-coming field of molecular electronics. In this advanced review, we scrutinize various qualitative rules of orbital occupation and spin alignment, viz., the aufbau principle, Hund's multiplicity rule, and dynamic spin polarization concept, through the prism of quantum mechanics. While such rules hold in selected simple cases, in general the spin state of a system depends on a combination of electronic factors that include Coulomb and Pauli repulsion, nuclear attraction, kinetic energy, orbital relaxation, and static correlation. A number of fascinating chemical systems with spin states that fluctuate between triplet and open-shell singlet, and are responsive to irradiation, pH, and other external stimuli, are highlighted. In addition, we outline a range of organic molecules with intriguing non-aufbau orbital configurations. In such quasi-closed-shell systems, the singly occupied molecular orbital (SOMO) is energetically lower than one or more doubly occupied orbitals. As a result, the SOMO is not affected by electron attachment to or removal from the molecule, and the products of such redox processes are polyradicals. These peculiar species possess attractive conductive and magnetic properties, and a number of them that have already been developed into molecular electronics applications are highlighted in this review. WIREs Comput Mol Sci 2015, 5:440-459. doi: 10.1002/wcms.1233 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Ganna Gryn'ova
- Institut des Sciences et Ingénierie Chimiques Ecole polytechnique fédérale de Lausanne Lausanne Switzerland
| | - Michelle L Coote
- Australian Research Council Centre of Excellence for Electromaterials Science, Research School of Chemistry Australian National University Canberra Australia
| | - Clemence Corminboeuf
- Institut des Sciences et Ingénierie Chimiques Ecole polytechnique fédérale de Lausanne Lausanne Switzerland
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7
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Mebel AM, Kaiser RI. Formation of resonantly stabilised free radicals via the reactions of atomic carbon, dicarbon, and tricarbon with unsaturated hydrocarbons: theory and crossed molecular beams experiments. INT REV PHYS CHEM 2015. [DOI: 10.1080/0144235x.2015.1075280] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Alexander M. Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Ralf I. Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA
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8
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Kvaskoff D, Lüerssen H, Bednarek P, Wentrup C. Phenylnitrene, Phenylcarbene, and Pyridylcarbenes. Rearrangements to Cyanocyclopentadiene and Fulvenallene. J Am Chem Soc 2014; 136:15203-14. [DOI: 10.1021/ja506151p] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- David Kvaskoff
- School
of Chemistry and Molecular
Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Holger Lüerssen
- School
of Chemistry and Molecular
Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Pawel Bednarek
- School
of Chemistry and Molecular
Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Curt Wentrup
- School
of Chemistry and Molecular
Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
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9
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Moss RA, Cang H, Krogh-Jespersen K. The nucleophilicity of adamantanylidene: a Hammett study. Tetrahedron Lett 2014. [DOI: 10.1016/j.tetlet.2014.06.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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10
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McKee ML, Reisenauer HP, Schreiner PR. Combined ab Initio Molecular Dynamics and Experimental Studies of Carbon Atom Addition to Benzene. J Phys Chem A 2014; 118:2801-9. [DOI: 10.1021/jp501107b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Hans Peter Reisenauer
- Institute
of Organic Chemistry, Justus-Liebig University, Heinrich-Buff-Ring 58, 35392 Giessen, Germany
| | - Peter R. Schreiner
- Institute
of Organic Chemistry, Justus-Liebig University, Heinrich-Buff-Ring 58, 35392 Giessen, Germany
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11
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Høj M, Kvaskoff D, Wentrup C. Nitrene-Carbene-Carbene Rearrangement. Photolysis and Thermolysis of Tetrazolo[5,1-a]phthalazine with Formation of 1-Phthalazinylnitrene, o-Cyanophenylcarbene, and Phenylcyanocarbene. J Org Chem 2013; 79:307-13. [DOI: 10.1021/jo402448u] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Martin Høj
- School
of Chemistry and Molecular
Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - David Kvaskoff
- School
of Chemistry and Molecular
Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Curt Wentrup
- School
of Chemistry and Molecular
Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
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12
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Régimbald-Krnel MJ, Wentrup C. Laser-induced carbene-carbene rearrangement in solution: the diphenylcarbene-fluorene rearrangement. J Org Chem 2013; 78:8789-95. [PMID: 23941300 DOI: 10.1021/jo401607m] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Diphenylcarbene (DPC) generated by high-intensity laser photolysis of diphenyldiazomethane rearranges to fluorene (FL) by two distinct mechanisms as revealed by methyl-group labeling. Thus, excimer laser irradiation of p,p'-dimethyldiphenyldiazomethane generates 3,6-dimethylfluorene (3,6-DMF) and 2,7-dimethylfluorene (2,7-DMF), which were identified by fluorescence measurements as well as GC-MS and comparison with authentic materials. 3,6-DMF corresponds to direct bond formation between ortho positions in DPC, referred to as ortho,ortho' coupling. 2,7-DMF corresponds to a carbene-carbene rearrangement, whereby DPC undergoes ring expansion to phenylcycloheptatetraene (PhCHT) followed by ring contraction to o-biphenylylcarbene (o-BPC), which then cyclizes to FL. The carbene-carbene rearrangement dominates over the ortho,ortho' coupling under all conditions employed. The ortho,ortho' coupling must take place in a higher excited state (most likely S2 or T1) of DPC, because it is not observed at all under thermolysis conditions, where only S1 and T0 are populated. The carbene-carbene rearrangement may take place either in a hot S1 state or more likely in a higher excited state (S2 or T1).
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Affiliation(s)
- Michèle J Régimbald-Krnel
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
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13
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Glock C, Younis FM, Ziemann S, Görls H, Imhof W, Krieck S, Westerhausen M. 2,6-Diisopropylphenylamides of Potassium and Calcium: A Primary Amido Ligand in s-Block Metal Chemistry with an Unprecedented Catalytic Reactivity. Organometallics 2013. [DOI: 10.1021/om4001007] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Carsten Glock
- Institut für Anorganische
und Analytische Chemie, Friedrich-Schiller-Universität Jena, Humboldtstrasse 8, D-07743 Jena, Germany
| | - Fadi M. Younis
- Institut für Anorganische
und Analytische Chemie, Friedrich-Schiller-Universität Jena, Humboldtstrasse 8, D-07743 Jena, Germany
| | - Steffen Ziemann
- Institut für Anorganische
und Analytische Chemie, Friedrich-Schiller-Universität Jena, Humboldtstrasse 8, D-07743 Jena, Germany
| | - Helmar Görls
- Institut für Anorganische
und Analytische Chemie, Friedrich-Schiller-Universität Jena, Humboldtstrasse 8, D-07743 Jena, Germany
| | - Wolfgang Imhof
- Institut für Integrierte Naturwissenschaften,
Abteilung Chemie, Universität Koblenz-Landau, Universitätsstrasse 1, D-56070 Koblenz, Germany
| | - Sven Krieck
- Institut für Anorganische
und Analytische Chemie, Friedrich-Schiller-Universität Jena, Humboldtstrasse 8, D-07743 Jena, Germany
| | - Matthias Westerhausen
- Institut für Anorganische
und Analytische Chemie, Friedrich-Schiller-Universität Jena, Humboldtstrasse 8, D-07743 Jena, Germany
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14
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Ishikawa A, Tanimura Y, Nakao Y, Sato H, Sakaki S. Complicated Electronic Process of C–C σ-Bond Activation of Cyclopropene by Ruthenium and Iridium Complexes: Theoretical Study. Organometallics 2012. [DOI: 10.1021/om300811g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Atsushi Ishikawa
- Department
of Molecular Engineering,
Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Yudai Tanimura
- Department
of Molecular Engineering,
Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Yoshihide Nakao
- Fukui Institute for Fundamental
Chemistry, Kyoto University, Nishihiraki-cho
34-4, Takano, Sakyo-ku, Kyoto 606-8103, Japan
| | - Hirofumi Sato
- Department
of Molecular Engineering,
Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Shigeyoshi Sakaki
- Fukui Institute for Fundamental
Chemistry, Kyoto University, Nishihiraki-cho
34-4, Takano, Sakyo-ku, Kyoto 606-8103, Japan
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15
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Gerbig D, Ley D. Computational methods for contemporary carbene chemistry. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2012. [DOI: 10.1002/wcms.1124] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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16
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17
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Peuronen A, Hänninen MM, Tuononen HM. Pyrazolium- and 1,2-Cyclopentadiene-Based Ligands as σ-Donors: a Theoretical Study of Electronic Structure and Bonding. Inorg Chem 2012; 51:2577-87. [DOI: 10.1021/ic202546a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Anssi Peuronen
- Department of Chemistry,
P.O. Box 35, University of Jyväskylä, FI-40014 Jyväskylä,
Finland
| | - Mikko M. Hänninen
- Department of Chemistry,
P.O. Box 35, University of Jyväskylä, FI-40014 Jyväskylä,
Finland
| | - Heikki M. Tuononen
- Department of Chemistry,
P.O. Box 35, University of Jyväskylä, FI-40014 Jyväskylä,
Finland
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18
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Affiliation(s)
- Daniela Polino
- Department Chimica, Materiali e Ingegneria Chimica “G. Natta”, Politecnico di Milano, via Mancinelli 7, 20131 Milano, Italy
| | - Carlo Cavallotti
- Department Chimica, Materiali e Ingegneria Chimica “G. Natta”, Politecnico di Milano, via Mancinelli 7, 20131 Milano, Italy
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19
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Polino D, Famulari A, Cavallotti C. Analysis of the Reactivity on the C7H6 Potential Energy Surface. J Phys Chem A 2011; 115:7928-36. [DOI: 10.1021/jp2019236] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Daniela Polino
- Dipartimento di Chimica, Materiali e Ingegneria chimica “G. Natta”, Politecnico di Milano, via Mancinelli 7, 20131 Milano, Italy
| | - Antonino Famulari
- Dipartimento di Chimica, Materiali e Ingegneria chimica “G. Natta”, Politecnico di Milano, via Mancinelli 7, 20131 Milano, Italy
| | - Carlo Cavallotti
- Dipartimento di Chimica, Materiali e Ingegneria chimica “G. Natta”, Politecnico di Milano, via Mancinelli 7, 20131 Milano, Italy
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20
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Cui G, Fang W. Channels to Singlet and Triplet Phenylcarbenes in Phenyldiazomethane: A CASSCF and MRCI Study. Chemphyschem 2011; 12:1689-96. [DOI: 10.1002/cphc.201100025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2011] [Revised: 03/11/2011] [Indexed: 11/07/2022]
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21
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Borden WT. With a Little Help from My Friends: Forty Years of Fruitful Chemical Collaborations. J Org Chem 2011; 76:2943-64. [PMID: 21452841 DOI: 10.1021/jo200213x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Weston Thatcher Borden
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling, University of North Texas, 1155 Union Circle #305070, Denton, Texas 76203-5017, United States
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22
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Gronert S, Keeffe JR, More O’Ferrall RA. Stabilities of Carbenes: Independent Measures for Singlets and Triplets. J Am Chem Soc 2011; 133:3381-9. [DOI: 10.1021/ja1071493] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Scott Gronert
- Department of Chemistry, Virginia Commonwealth University, 1001 W. Main Street, Richmond, Virginia 23284, United States
| | - James R. Keeffe
- Department of Chemistry and Biochemistry, San Francisco State University, 1600 Holloway Avenue, San Francisco, California 94132, United States
| | - Rory A. More O’Ferrall
- School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
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23
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Mahlokozera T, Goods JB, Childs AM, Thamattoor DM. Crystal Structure of a Cyclotetramer from a Strained Cyclic Allene. Org Lett 2009; 11:5095-7. [DOI: 10.1021/ol902177b] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - John B. Goods
- Department of Chemistry, Colby College, Waterville, Maine 04901
| | - Adam M. Childs
- Department of Chemistry, Colby College, Waterville, Maine 04901
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24
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Wijeratne NR, Fonte MD, Ronemus A, Wyss PJ, Tahmassebi D, Wenthold PG. Photoelectron Spectroscopy of Chloro-Substituted Phenylnitrene Anions. J Phys Chem A 2009; 113:9467-73. [PMID: 19655776 DOI: 10.1021/jp9039594] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Neloni R. Wijeratne
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47906, and Department of Chemistry, Indiana University−Purdue University Fort Wayne, Fort Wayne, Indiana 46805
| | - Maria Da Fonte
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47906, and Department of Chemistry, Indiana University−Purdue University Fort Wayne, Fort Wayne, Indiana 46805
| | - Alan Ronemus
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47906, and Department of Chemistry, Indiana University−Purdue University Fort Wayne, Fort Wayne, Indiana 46805
| | - Phillip J. Wyss
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47906, and Department of Chemistry, Indiana University−Purdue University Fort Wayne, Fort Wayne, Indiana 46805
| | - Daryoush Tahmassebi
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47906, and Department of Chemistry, Indiana University−Purdue University Fort Wayne, Fort Wayne, Indiana 46805
| | - Paul G. Wenthold
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47906, and Department of Chemistry, Indiana University−Purdue University Fort Wayne, Fort Wayne, Indiana 46805
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25
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Rzepa HS. Wormholes in chemical space connecting torus knot and torus link pi-electron density topologies. Phys Chem Chem Phys 2009; 11:1340-1345. [PMID: 19224034 DOI: 10.1039/b810301a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Möbius aromaticities can be considered as deriving from cyclic delocalized pi-electron densities rho(r)(pi) which have the topological form of either a two-component torus link or a single-component torus knot. These two topological forms are distinguished by their (non-zero) linking number L(k), which describes how many times the two components of a torus link cross each other or the single component of a torus knot crosses with itself. The special case of Hückel or benzenoid aromaticity is associated with a pi-electron density that takes the form of a two-component torus link for which the linking number is zero. A class of molecule has been identified which here is termed a Janus aromatic, and which bears the characteristics of both a two-component torus link and a single-component torus knot in the topology of the pi-electron density. This is achieved by the formation of one (or more) wormholes or throats in the pi-electron density connecting the two torus forms, which can impart a Janus-like dual personality to the aromaticity of the system. The impact of such wormholes on the overall pi-delocalized aromaticity of such molecules is approximately estimated using a NICS(rcp) index, and subdivides into two types; those where the forms of aromaticity associated with a torus link and a torus knot cooperate and those where they oppose.
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Affiliation(s)
- Henry S Rzepa
- Department of Chemistry, Imperial College London, South Kensington Campus, London, UKSW7 2AY
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Azenkeng A, Laumb JD, Jensen RR, Olson ES, Benson SA, Hoffmann MR. Carbene proton attachment energies: theoretical study. J Phys Chem A 2008; 112:5269-77. [PMID: 18491844 DOI: 10.1021/jp7115214] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The geometries and electronic energies of six singlet carbenes, with methyl and phenyl substituents, and the corresponding carbenium ions were obtained using several density functional theory (DFT) variants and the second-order Møller-Plesset method for electron correlation and compared with G3 results, with the aim to determine a relatively low-cost computational protocol that is sufficiently accurate for the specific molecules and ions of interest. Some additional calculations were performed at the CCSD(T) level. Results for diphenylcarbene, methylphenylcarbene, and their cations, which were not previously investigated by ab initio methods, are reported as are calculations on methylene, methylcarbene, dimethylcarbene, and phenylcarbene. The MPW3LYP/6-311+G(d,p) hybrid DFT level was found to give results that were in close agreement with those obtained using G3 theory, with a mean absolute deviation (MAD) of 1.76 kcal/mol for the calculated proton attachment energies (PAEs). Equilibrium geometries obtained with this method were compared with those obtained at the MP2/6-311G(d,p) level of theory, and bond lengths and bond angles had MADs of 0.005 A and 1.0 degrees, respectively. Harmonic vibrational frequencies of all the carbene molecules and the corresponding ions were computed to verify that the stationary points were true minima, to obtain zero-point corrected energies, to assist in infrared studies of the molecules. The recommended combination of method and basis set is expected to be a useful framework that uses modest amounts of computer resources to obtain usable thermochemical data on moderate-sized hydrocarbons and hydrocarbon cations, including coal-mimetic species.
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Affiliation(s)
- Alexander Azenkeng
- Department of Chemistry, University of North Dakota, P. O. Box 9024, Grand Forks, North Dakota 58202, USA
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Gicquel M, Heully JL, Lepetit C, Chauvin R. Carbo-[3]oxocarbon and its isomers: evaluation of the stability and of the electron delocalization. Phys Chem Chem Phys 2008; 10:3578-89. [DOI: 10.1039/b718817j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Lazzaroni S, Dondi D, Fagnoni M, Albini A. Geometry and Energy of Substituted Phenyl Cations. J Org Chem 2007; 73:206-11. [DOI: 10.1021/jo7020218] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Simone Lazzaroni
- Department of Organic Chemistry and Department of General Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy
| | - Daniele Dondi
- Department of Organic Chemistry and Department of General Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy
| | - Maurizio Fagnoni
- Department of Organic Chemistry and Department of General Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy
| | - Angelo Albini
- Department of Organic Chemistry and Department of General Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy
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Qi SF, Yang ZZ. Modeling Mechanisms of Unusual Benzene Imine N6 Adduct Formation in Carcinogenic Reactions of Arylnitrenium Ions with Adenosine. J Org Chem 2007; 72:10058-64. [DOI: 10.1021/jo701980y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Shi-Fei Qi
- Chemistry and Chemical Engineering Faculty, Liaoning Normal University, Dalian 116029, People's Republic of China
| | - Zhong-Zhi Yang
- Chemistry and Chemical Engineering Faculty, Liaoning Normal University, Dalian 116029, People's Republic of China
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Woodcock HL, Moran D, Brooks BR, Schleyer PVR, Schaefer HF. Carbene Stabilization by Aryl Substituents. Is Bigger Better? J Am Chem Soc 2007; 129:3763-70. [PMID: 17326641 DOI: 10.1021/ja068899t] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The geometries and relative stabilities of the singlet and triplet states of phenyl- (Cs), diphenyl- (C2), 1-naphthyl- (Cs), di(1-naphthyl)- (C2), and 9-anthryl-substituted (Cs) carbenes were investigated at the B3LYP/6-311+G(d,p) + ZPVE level of density functional theory. The singlet-triplet energy separations (DeltaEST), 2.7, 2.9, 3.4, 3.7, and 5.7 kcal/mol, respectively, after including an empirical correction (2.8 kcal/mol) based on the error in the computed singlet-triplet gap for methylene versus experiment, are in good agreement with available experimental values. Consistent with literature reports, triplet di(9-anthryl)carbene has a linear, D2d symmetrical, allene structure with 1.336 A C=C bond lengths and considerable biradical character. B3LYP favors such cumulene biradical structures and triplet spin states and predicts a large (>15 kcal/mol) "di(9-anthryl)carbene" singlet-triplet (biradical) energy gap. The resonance stabilization of both singlet and triplet carbenes increases modestly with the size of the arene substituent and overall, (di)arylcarbenes, both singlet and triplet, are better stabilized by bigger substituents. For example, methylene is stabilized more by a naphthyl than a phenyl group (singlets, 26.6 versus 24.4; and triplets, 20.9 versus 18.1 kcal/mol, respectively). The carbene geometries are affected by both steric effects and arene-carbene orbital interactions (sigma-p and p-pi). For instance, the central angles at the carbene are widened by a second arene group, which leads to increased s-character and shorter carbene bond lengths (i.e., C-C, C-H). In general, the aromaticity of the substituted rings in triplet carbenes is most affected by the presence of the unpaired electrons.
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Affiliation(s)
- H Lee Woodcock
- Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602-2525, USA.
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DePinto JT, deProphetis WA, Menke JL, McMahon RJ. Triplet 1,3-diphenylpropynylidene (Ph-C-C-C-Ph). J Am Chem Soc 2007; 129:2308-15. [PMID: 17279747 DOI: 10.1021/ja066300j] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Photolysis (lambda>571 nm) of 1,3-diphenyldiazopropyne (9) affords triplet 1,3-diphenylpropynylidene (3), as characterized by IR, UV/vis, and EPR spectroscopy in low-temperature matrices. Two conformational isomers of triplet 3 are spectroscopically distinguishable. The initially formed, non-relaxed conformer is believed to reflect the geometry of the diazo precursor, as enforced by the rigid matrix. Annealing the matrix permits the structure to relax to the equilibrium D2d geometry. The highly symmetric equilibrium structure of 3 is best envisioned as a 1,3-allenic diradical. Density functional theory calculations suggest that the equilibrium structure does not exhibit a bond-localized structure that would be characteristic of an acetylenic carbene. Chemical trapping with O2, however, affords products that are familiar as carbene trapping products: carbonyl oxide 10, ketone 11, and dioxirane 12. Irradiation (lambda>261 nm) of triplet 1,3-diphenylpropynylidene (3) results in cyclization to singlet diphenylcyclopropenylidene (6), a process that is photochemically reversible at lambda=232 nm. Diphenyl-1,2-propadienylidene (7) was not observed under any irradiation conditions.
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Affiliation(s)
- Jeffrey T DePinto
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706-1396, USA
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Bally T, Borden WT. Calculations on Open-Shell Molecules: A Beginner's Guide. REVIEWS IN COMPUTATIONAL CHEMISTRY 2007. [DOI: 10.1002/9780470125908.ch1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
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Affiliation(s)
| | - Udo H. Brinker
- Institut für Organische Chemie, Universität Wien, Währinger Straße 38, 1090 Wien, Austria, Fax: +43‐1‐4277‐52140
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Wang X, Yang Z, Wang J, Zhang J, Cao W. Computational study of the rearrangement reaction mechanism of phenylcarbene in a molecular container: Cram's hemicarcerand. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.theochem.2006.04.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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35
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Enyo T, Arai N, Nakane N, Nicolaides A, Tomioka H. o-Phenylene Halocarbenonitrenes and o-Phenylene Chlorocarbenocarbene: A Combined Experimental and Computational Approach. J Org Chem 2005; 70:7744-54. [PMID: 16149808 DOI: 10.1021/jo0512204] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
[reaction: see text] Computations find that o-phenylene(halo)carbenonitrenes 2-XN, X = F, Cl, Br, have quinoidal singlet biradical ground states such as the parent o-phenylenecarbenonitrene (2-HN). Compared to the parent 2-HN, halogen substitution stabilizes the A'' states relative to the A' ones. Halogen substitution also affects the barrier and exothermicity of the ring-opening reaction (to form unsaturated nitriles 4-XN, X = F, Cl, Br), but it has a smaller effect on the ring-closing reaction (to form benzo(aza)cyclobutadiene 3-XN, X = F, Cl, Br). Attempts to generate and observe the o-phenylene(halo)carbenonitrenes 2-XN, X = F, Cl, Br, using matrix isolation spectroscopy under conditions similar to those of the successful observation of 2-HN failed. Instead, the observed photoproducts were a mixture of 3-XN and 4-XN. In each case, the major product of the mixture appears to be the thermodynamically more stable one. In the case of X = Br, the observed mixture contains an additional component that is postulated to be Z-6-BrN. o-Phenylenechlorocarbenocarbene is also computed to have a quinoidal singlet biradical ground state and relatively stabilized A'' excited states. Attempts to generate the biscarbene under matrix isolation conditions led to the detection of benzochlorocyclobutadiene (3-ClC), small amounts of the ring-open product (dienediyne 4-ClC), and cycloalkyne 5-ClC. Computations suggest that the formation of 5-ClC implies the generation of Z-6-ClC, which is analogous to the formation of Z-6-BrN from 2-BrN.
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Affiliation(s)
- Tomonori Enyo
- Chemistry Department for Materials, Faculty of Engineering, Mie University, Tsu, Mie 514-8507 Japan
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Cremeens ME, Hughes TS, Carpenter BK. Mechanistic Studies on the Cyclization of (Z)-1,2,4-Heptatrien-6-yne in Methanol: A Possible Nonadiabatic Thermal Reaction. J Am Chem Soc 2005; 127:6652-61. [PMID: 15869286 DOI: 10.1021/ja0445443] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Myers et al. pyrolyzed (Z)-1,2,4-heptatrien-6-yne (1) in methanol at 100 degrees C and observed benzylmethyl ether (2) as a major product and 2-phenylethanol (3) as a minor product. If a biradical intermediate, such as the open-shell singlet state of alpha,3-didehydrotoluene (4), was the only intermediate generated by the cyclization, then reaction with methanol might be expected to afford 2-phenylethanol as the principal product. The question that has been of interest since its first discovery is the origin of the principal product of the title reaction, benzylmethyl ether. This report considers three mechanisms for formation of the benzylmethyl ether: direct methanol participation in the cyclization of the reactant, partial ether formation from the biradical 4, or involvement of the closed-shell zwitterionic state of alpha,3-didehydrotoluene (5). A fourth mechanism, involving a cyclic allene intermediate, has been ruled out by earlier studies. In the present work, the first two mechanisms are ruled out by experiment and/or calculation. The remaining one, involving the zwitterion, is shown to be consistent with experimental and computational data only if a component of the reaction follows a nonadiabatic course.
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Affiliation(s)
- Matthew E Cremeens
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA
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Xie SY, Peng Y, Chen M, Huang RB, Chow YL, Zheng LS. On assembling polychlorinated aromatic hydrocarbons from carbon tetrachloride via dichlorocarbene intermediary by a solvothermal reaction: a reaction pattern from carbene-ylide interconversion. J Org Chem 2005; 70:1400-7. [PMID: 15704976 DOI: 10.1021/jo048190+] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[reaction: see text] The forced one-electron reduction of carbon tetrachloride with sodium in a sealed steel vessel is shown to have a narrow window of conditions to arrest the reaction at the polychlorinated aromatic hydrocarbons (PCAHs), as well as to prevent the reaction from proceeding all the way to the final stage of graphite and other carbon solids. The intermediates are quenched with toluene or benzene to give electrophilic substitution products and with water to give a quinomethine as the major product. The product pattern leads us to propose the carbene, perchlorobenzo[c,d]pyren-6-ylidene, or its reversible dimer as the major intermediate among others, that survives the severe conditions until coming into contact with these nucleophiles. Mainly from aromatic resonance stabilization, the carbene is proposed to have a delocalized singlet state analogous to a ylide electronic structure and, thus, undergoes observed ionic reactions instead of typical carbene reactions. This work serves as a mechanistic link on the structural evolution of carbon networks between molecular chemistry and nanomaterial chemistry.
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Affiliation(s)
- Su-Yuan Xie
- State Key Laboratory for Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
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Trindle C. Post-Hartree−Fock Studies on the Structure of Bis(ortho-substituted phenyl)methylenes. J Phys Chem A 2005; 109:898-904. [PMID: 16838962 DOI: 10.1021/jp0473467] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Long-lived triplet bisarylmethylenes are now well-known. Experimental data (primarily ESR hyperfine parameters) suggest that the carbon framework of long-lived bisarylmethylenes approaches D(2)(d)() symmetry, as ortho-substitution forces the central angle to approach 180 degrees . According to DFT modeling, the approach of the central angle to 180 degrees is accompanied by a dramatic shortening of the central CC bonds and severe quinoid distortion of the phenyl rings. In contrast, X-ray investigation of bis(2,4,6-trichlorophenyl)methylene shows a structure closer to the carbene valence bond representation with less seriously distorted phenyl rings, a more acute central angle, and a longer bond from the methylene carbon to the aryl substituent. We address the difficulty of achieving a balance of cumulene and carbene character, treating the model systems diethynylmethylene, dicyanomethylene, and diisocyanomethylene by post-Hartree-Fock methods CAS and CCSD as well as DFT models, and applying the perturbation-corrected CAS methods to the chloro and methyl ortho-substituted bisphenyl carbenes.
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Affiliation(s)
- Carl Trindle
- Chemistry Department, University of Virginia, Charlottesville, Virginia 22904, USA
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Carbenes generated within cyclodextrins and zeolites. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2005. [DOI: 10.1016/s0065-3160(05)40001-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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41
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Rodrı́guez E, Caballol R, Reguero M. Ab initio study of the singlet–triplet relative stability of 2,6-dibromo-2′,6′-bistrifluoromethyl-diphenylmethylene. Chem Phys 2004. [DOI: 10.1016/j.chemphys.2004.05.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Winter AH, Falvey DE, Cramer CJ. Effect of meta Electron-Donating Groups on the Electronic Structure of Substituted Phenyl Nitrenium Ions. J Am Chem Soc 2004; 126:9661-8. [PMID: 15291569 DOI: 10.1021/ja047677x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Density functional theory (UB3LYP/6-31G(d,p)) was used to determine substituent effects on the singlet-triplet-state energy gap for 21 meta-substituted phenylnitrenium ions. It was found that strongly electron-donating substituents stabilize the triplet state relative to the singlet state. With sufficiently strong meta electron donors (e.g., m,m'-diaminophenylnitrenium ion) the triplet is predicted to be the ground state. Analysis of equilibrium geometries, Kohn-Sham orbital distributions, and Mulliken spin densities for the triplet states of this series of nitrenium ions leads to the conclusion that there are two spatially distinct types of low-energy triplet states. Simple arylnitrenium ions such as phenylnitrenium ions as well as those having electron-withdrawing or weakly donating meta substituents have lowest-energy triplet states that are n,pi in nature. That is, one singly occupied molecular orbital is orthogonal to the plane of the phenyl ring and one is coplanar. These n,pi triplets are generally characterized by large ArNH bond angles (ca. 130-132 degrees ) and an NH bond that is perpendicular to the plane of the phenyl ring. In contrast, meta donor arylnitrenium ions have a lowest-energy triplet state best described as pi,pi. That is, both singly occupied molecular orbitals are orthogonal to the aromatic ring. Such pi,pi states are characterized by NH bonds that are coplanar with the phenyl ring and have ArNH bond angles that are more acute (ca. 110-111 degrees ). These triplet nitrenium ions have electronic structures analogous to those of meta-benzoquinodimethane derivatives.
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Affiliation(s)
- Arthur H Winter
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742-2021, USA
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Abstract
We use electronic structure modeling, mainly density functional methods, to characterize a variety of long-lived bisaryl triplet carbenes. The bisaryl systems have a triplet ground state, favored by a substantial delocalization of the spin into the aromatic rings. One can imagine two extreme cases of the bonding in these species, representable as valence isomers. In the first case, spin delocalization is minor and incidental; the spin is predominantly located on the central carbene carbon. In the second case, spins are separated by large distances and are found primarily on the aromatic rings; the rings are linked by an allenic bridge. The bisphenyl carbenes tend toward the first limit. They can be kinetically stabilized by ortho substituents which shield the reactive center and para substituents which protect that site which has substantial spin density. The bond angle at carbene is opened from about 142 degrees (the B3LYP/6-31G value for the parent bis(phenyl)carbene) to 160 degrees or more by these substituents. Bisanthryl carbenes illustrate the second extreme, favoring a D(2)(d)() structure and possessing a low-lying open shell singlet state. A hypothetical phenyl-9-anthrylcarbine lies between the carbine and diradical extemes. The same principle which guides the design of stabilized diphenylcarbene carbenes and substitution of reactive sites by bulky protective groups serves to stabilize the bis-9-anthrylcarbene biradical.
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Affiliation(s)
- Carl Trindle
- Chemistry Department, University of Virginia, Charlottesville, Virginia 22904, USA.
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Rosenberg MG, Brinker UH. Inter- and innermolecular reactions of chloro(phenyl)carbene. J Org Chem 2003; 68:4819-32. [PMID: 12790587 DOI: 10.1021/jo026521h] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Supramolecular photolyses of 3-chloro-3-phenyl-3H-diazirine (8) were performed within cyclodextrin (CyD) hosts to determine whether these toroidal inclusion compounds could alter the reactivity of the ensuing carbene reaction intermediate, chloro(phenyl)carbene (9). Remarkably, no intramolecular products stemming from carbene 9 could be detected. Instead, modified CyDs were formed via so-called innermolecular reactions. Hence, diazirine 8 was photolyzed in various conventional solvents to gauge the intermolecular reactivity of carbene 9. Relevant results were used to rationalize the CyD innermolecular reaction products.
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Affiliation(s)
- Murray G Rosenberg
- Institut für Organische Chemie, Universität Wien, Währinger Strasse 38, A-1090 Vienna, Austria
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Ananikov VP. Competing nature of intramolecular [4 + 2] and [3 + 2] cycloaddition reactions: a theoretical study. J PHYS ORG CHEM 2003. [DOI: 10.1002/poc.613] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Kerdelhué JL, Langenwalter KJ, Warmuth R. Mapping the potential energy surface of the tolylcarbene rearrangement in the inner phase of a hemicarcerand. J Am Chem Soc 2003; 125:973-86. [PMID: 12537496 DOI: 10.1021/ja027831k] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Photolysis of p-tolyldiazirine (6) in the inner phase of a hemicarcerand with four butane-1,4-dioxy linker groups (5) in C(6)D(5)CD(3) at 77 K yields the 5-methylcycloheptatetraene hemicarceplex 5 circle 3b in 41% together with innermolecular reaction products resulting from an insertion of transient p-tolylcarbene (1b) into an acetal C-H or linker C-O bond of 5 and from the addition of 1b to an aryl unit of 5. The yield of incarcerated 3b increased up to 67% if 6 is photolyzed inside a hemicarcerand with deuterated spanners and butane-1,4-dioxy linker groups (d(48)-5). Hemicarceplex 5 circle 3b is not formed if the photolysis is carried out in CDCl(3). Incarcerated 3b is stable at room temperature in the absence of oxygen and is characterized by 1D and 2D NMR spectroscopy. In the presence of oxygen, 3b reacts quantitatively to yield toluene and CO(2). Upon heating solutions of d(48)-5 circle 3b in C(6)D(5)CD(3), 3b rearranges to 1b and m-tolylcarbene (18). Both tolylcarbenes immediately react with the surrounding host. From a product analysis and the measured rate constants for the thermal decomposition of d(48)-5 circle 3b in the temperature range 70-102 degrees C, the activation parameters for the 3b to 1b and 3b to 18 rearrangements are calculated (3b to 1b: DeltaG(373)++ = 27.3 +/- 1.4 kcal/mol, DeltaH(373)++ = 26.4 +/- 1.0 kcal/mol, TDeltaS(373)++ = -0.9 +/- 1.0 kcal/mol; 3b to 18: DeltaG(373)++ = 27.8 +/- 1.4 kcal/mol, DeltaH(373)++ = 19.7 +/- 1.0 kcal/mol, TDeltaS(373)++ = 8.1 +/- 1.0 kcal/mol). These values are compared with those calculated by Geise and Hadad at the B3LYP/6-311+G** level of theory (Geise, C. M.; Hadad, C. M. J. Org. Chem. 2002, 67, 2532-2540). The slightly higher inner phase activation free energy of the 3b to 18 rearrangement is explained through steric constraints imposed by the surrounding hemicarcerand on the transition state. The enthalpy-entropy compensation observed for the 3b to 18 rearrangement is discussed and interpreted as a result of a hemicarcerand and solvent reorganization along the reaction coordinate. It is taken as indirect evidence for the intermediacy of 2-methylbicyclo[4.1.0]hepta-2,4,6-triene in the 3b to 18 rearrangement.
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Affiliation(s)
- Jean-Luc Kerdelhué
- Department of Chemistry, Kansas State University, Manhattan, KS 66506-3701, USA
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Bonvallet PA, Todd EM, Kim YS, McMahon RJ. Access to the naphthylcarbene rearrangement manifold via isomeric benzodiazocycloheptatrienes. J Org Chem 2002; 67:9031-42. [PMID: 12467426 DOI: 10.1021/jo020304z] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Irradiation (lambda = 670 or >613 nm) of 4,5-benzodiazocycloheptatriene (15), matrix isolated in argon at 10 K, produces primarily 2,3-benzobicyclo[4.1.0]hepta-2,4,6-triene (9) accompanied by small amounts of triplet 4,5-benzocycloheptatrienylidene (2) and 2-naphthylcarbene (10). A reversible photoequilibrium is established in which 9 is converted to 10 at lambda = 290 nm and then regenerated at lambda = 360 nm. Similarly, matrix-isolated 2,3-benzodiazocycloheptatriene (16) produces 4,5-benzobicyclo[4.1.0]hepta-2,4,6-triene (11) at lambda = 670 or >613 nm, but without detection of 2,3-benzocycloheptatrienylidene (4). Irradiation of 11 at lambda = 290 nm induces ring opening to triplet 1-naphthylcarbene (12), which, in turn, cyclizes back to 11 at lambda = 342 or >497 nm. The diazo compounds and photoproducts are characterized by IR, UV/visible, and ESR spectroscopy, where appropriate, and by comparison of the experimental and B3LYP/6-31G calculated IR spectra for each species. Alternate rearrangement products such as allenes 6, 7, and 8 are not detected in the photolysis of either diazo compound.
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Affiliation(s)
- Paul A Bonvallet
- Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison 53706-1396, USA
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Enyo T, Nicolaides A, Tomioka H. Halogen derivatives of m-phenylene(carbeno)nitrene: a switch in ground-state multiplicity. J Org Chem 2002; 67:5578-87. [PMID: 12153255 DOI: 10.1021/jo025877q] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
m-Phenylene-coupled carbenonitrenes [(3-nitrenophenyl)methylene (2-H), (3-nitrenophenyl)fluoromethylene (2-F), (3-nitrenophenyl)chloromethylene (2-Cl), (3-nitrenophenyl)bromomethylene (2-Br)] have been investigated computationally (with B3LYP, MCSCF, CASPT2, ROMP2, and QCISD(T) methods) and experimentally (with IR, UV, and ESR spectroscopy). For each species, five electronic states were considered. At the highest level of theory explored, the parent compound (2-H) has a quintet ground state, but its halogen derivatives (2-X, X = F, Cl, and Br) have triplet ground states. A linear relationship between the Q[bond]T energy gap of 2-X and the T-S gap of the corresponding phenylcarbenes 8-X is found, which can be helpful in rationalizing and predicting ground-state multiplicities in m-phenylene-linked carbenonitrenes and similar species. Precursors for the photochemical generation of 2-X (X = H, F, Cl, and Br) were synthesized and photolyzed in matrixes (Ar, triacetin) at low temperatures. IR (Ar, 13 K) and ESR (triacetin, 77 K) data are compatible with the generation of triplet halocarbenonitrenes 2-X, (X = F, Cl, and Br). All four compounds upon further irradiation undergo isomerization to substituted cyclopropenes 5-X (X = H, F, Cl, and Br), as suggested by their IR spectra.
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Affiliation(s)
- Tomonori Enyo
- Chemistry Department for Materials, Faculty of Engineering, Mie University, Tsu, Mie 514-8507, Japan
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Geise CM, Hadad CM. Substituent effects in the interconversion of phenylcarbene, bicyclo[4.1.0]hepta-2,4,6-triene, and 1,2,4,6-cycloheptatetraene. J Org Chem 2002; 67:2532-40. [PMID: 11950298 DOI: 10.1021/jo0162181] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effect of aryl substituents on the interconversion of phenylcarbene (PC), bicyclo[4.1.0]hepta-2,4,6-triene (BCT), and 1,2,4,6-cycloheptatetraene (CHTE) has been studied by density functional theory. It is found that substituents have a large effect on both the thermochemistry and activation energy of these rearrangements. For instance, para-substitution yields a range of overall activation energies for the formation of BCT from PC of 20.3 to 11.7 kcal/mol for the NH(2) and NO(2) substituents, respectively. In the syn-meta-substituted cases, all of the rearrangements to the substituted CHTE species are more exothermic than that of the parent PC. The proximity of the substituent to the carbene center can also affect the overall chemistry as in the case of ortho-substituted species. Here, formation of bicyclic structures and ylides, which can then rearrange to stable structures, can compete with the ring-expansion process. Also, as calculated herein, the ortho substituents can, by a combination of mesomeric and steric interactions with the carbene center, affect the overall barrier to reversible ring expansion. Most notably, in the anti-ortho-substituted species, halogens (F and Cl) raise the activation barrier to ring expansion by approximately 5 kcal/mol. This is reminiscent of the effect of fluorine substitution on the chemistry (inter- and intramolecular) of phenylnitrene.
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Affiliation(s)
- C Michael Geise
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA
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Engels B, Schöneboom JC, Münster AF, Groetsch S, Christl M. Computational assessment of the electronic structures of cyclohexa-1,2,4-triene, 1-oxacyclohexa-2,3,5-triene (3delta(2)-pyran), their benzo derivatives, and cyclohexa-1,2-diene. An experimental approach to 3delta(2)-pyran. J Am Chem Soc 2002; 124:287-97. [PMID: 11782181 DOI: 10.1021/ja011227c] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The six-membered cyclic allenes given in the title have been studied theoretically by means of an MR-CI approach. For all compounds, the allene structures were found to be the ground states in the gas phase. In the cases of cyclohexa-1,2-diene (1), the isobenzene 2, and the isonaphthalene 7, the most stable structures having a planar allene moiety are the diradicals 1b, 2b, and 7b, representing the transition states for the racemization of 1a, 2a, and 7a and being less stable than the latter by 14.1, 8.9, and 11.2 kcal/mol, respectively. At variance with this order, the 3delta(2)-pyran 4 and the chromene 5 have the zwitterions 4c and 5c as the most stable planar structures, which lie only 1.0 and 5.4 kcal/mol above 4a and 5a, respectively. According to the simulation of the solvent effect, 4c even becomes the ground state of 4 in THF solution. The frontier orbitals of the respective states of 2 and 4 suggest different rates and sites for the reaction with nucleophiles. For the first time, the pyran 4 has been generated and trapped. As a precursor for 4, 3-bromo-4H-pyran (9) was chosen, the synthesis of which was achieved on two routes from 4H-pyran. The treatment of 9 with potassium tert-butoxide (KOt-Bu)/18-crown-6 gave 4-tert-butoxy-4H-pyran as the only discernible product, whether styrene or furan was present, indicating the interception of 4 by KOt-Bu. Finally, the disagreement between the experiment and the theory concerning the heat of formation and the electronic nature of the isobenzene 2 is resolved by demonstrating that the experimental data can provide only an upper limit of the DeltaH(f) degrees value.
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Affiliation(s)
- Bernd Engels
- Institut für Organische Chemie and Institut für Physikalische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
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