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Csenki JT, Tóth BL, Béke F, Varga B, P. Fehér P, Stirling A, Czégény Z, Bényei A, Novák Z. Synthesis of Hydrofluoroolefin‐Based Iodonium Reagent via Dyotropic Rearrangement and Its Utilization in Fluoroalkylation. Angew Chem Int Ed Engl 2022; 61:e202208420. [PMID: 35876269 PMCID: PMC9540448 DOI: 10.1002/anie.202208420] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Indexed: 11/25/2022]
Abstract
[1,2]‐shift of atoms in alkyl fragments belongs to the class of dyotropic rearrangements. Various atoms, including halogens can be involved in the migration, however participation of iodine is unprecedented. Herein, we report our experimental and DFT studies on the oxidation triggered dyotropic rearrangement of iodo and chloro functions via butterfly‐type transition state to demonstrate the migrating ability of λ3‐iodane centre. With the exploitation of dyotropic rearrangement we designed and synthesized a novel fluoroalkyl iodonium reagent from industrial feedstock gas HFO‐1234yf. We demonstrated that the hypervalent reagent serves as an excellent fluoroalkylation agent for various amines and nitrogen heterocycles.
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Affiliation(s)
- János T. Csenki
- ELTE “Lendület” Catalysis and Organic Synthesis Research Group DepartmentInstitute of ChemistryEötvös Loránd UniversityPázmány Péter stny. 1/A1117BudapestHungary
| | - Balázs L. Tóth
- ELTE “Lendület” Catalysis and Organic Synthesis Research Group DepartmentInstitute of ChemistryEötvös Loránd UniversityPázmány Péter stny. 1/A1117BudapestHungary
| | - Ferenc Béke
- ELTE “Lendület” Catalysis and Organic Synthesis Research Group DepartmentInstitute of ChemistryEötvös Loránd UniversityPázmány Péter stny. 1/A1117BudapestHungary
| | - Bálint Varga
- ELTE “Lendület” Catalysis and Organic Synthesis Research Group DepartmentInstitute of ChemistryEötvös Loránd UniversityPázmány Péter stny. 1/A1117BudapestHungary
| | - Péter P. Fehér
- Research Centre for Natural SciencesEötvös Loránd Research NetworkMagyar Tudósok körútja 21117BudapestHungary
| | - András Stirling
- Research Centre for Natural SciencesEötvös Loránd Research NetworkMagyar Tudósok körútja 21117BudapestHungary
- Department of ChemistryEszterházy Károly Catholic UniversityLeányka u. 63300EgerHungary
| | - Zsuzsanna Czégény
- Research Centre for Natural SciencesEötvös Loránd Research NetworkMagyar Tudósok körútja 21117BudapestHungary
| | - Attila Bényei
- Department of Physical ChemistryUniversity of DebrecenEgyetem tér 14032DebrecenHungary
| | - Zoltán Novák
- ELTE “Lendület” Catalysis and Organic Synthesis Research Group DepartmentInstitute of ChemistryEötvös Loránd UniversityPázmány Péter stny. 1/A1117BudapestHungary
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2
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Csenki JT, Tóth BL, Béke F, Varga B, Fehér PP, Stirling A, Czégény Z, Bényei A, Novák Z. Synthesis of Hydrofluoroolefin‐based Iodonium Reagent via Dyotropic Rearrangement and Its Utilization in Fluoroalkylation. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202208420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- János Tivadar Csenki
- Eötvös Loránd Tudományegyetem: Eotvos Lorand Tudomanyegyetem Institute of Chemistry HUNGARY
| | - Balázs László Tóth
- Eötvös Loránd Tudományegyetem: Eotvos Lorand Tudomanyegyetem Institute of Chemistry HUNGARY
| | - Ferenc Béke
- Eötvös Loránd Tudományegyetem: Eotvos Lorand Tudomanyegyetem Institute of Chemistry HUNGARY
| | - Bálint Varga
- Eötvös Loránd Tudományegyetem: Eotvos Lorand Tudomanyegyetem Institute of Chemistry HUNGARY
| | - Péter Pál Fehér
- Research Centre for Natural Sciences: Termeszettudomanyi Kutatokozpont Research Centre for Natural Sciences: Termeszettudomanyi Kutatokozpont HUNGARY
| | - András Stirling
- Research Centre for Natural Sciences: Termeszettudomanyi Kutatokozpont Research Centre for Natural Sciences: Termeszettudomanyi Kutatokozpont HUNGARY
| | - Zsuzsanna Czégény
- Research Centre for Natural Sciences: Termeszettudomanyi Kutatokozpont Research Centre for Natural Sciences: Termeszettudomanyi Kutatokozpont HUNGARY
| | - Attila Bényei
- University of Debrecen: Debreceni Egyetem Department of Physical Chemistry HUNGARY
| | - Zoltán Novák
- Eotvos Lorand Tudomanyegyetem Institute of Chemistry Pázány Péter stny 1/a 1117 Budapest HUNGARY
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Brown TM, Gillespie BR, Rothrock MM, Ranieri AJ, Schueneman MK, Heard GL, Setser DW, Holmes BE. Unimolecular HBr and HF Elimination Reactions of Vibrationally Excited C 2H 5CH 2Br and C 2D 5CHFBr: Identification of the 1,1-HBr Elimination Reaction from C 2D 5CHFBr and Search for the C 2D 5(F)C:HBr Adduct. J Phys Chem A 2019; 123:8776-8786. [PMID: 31513404 DOI: 10.1021/acs.jpca.9b07029] [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
Chemical activation experiments and computational methods have been used to study the unimolecular reactions of C2H5CH2Br and C2D5CHFBr with 90 and 93 kcal mol-1 of vibrational energy, respectively. The four-centered elimination reactions of HBr and DBr are the dominant reactions; however, 2,1-DF, 1,1-HBr, and 1,1-HF reactions are also observed from C2D5CHFBr. The main focus was to search for the role of the C2D5(F)C:HBr adduct in the 1,1-HBr elimination for comparison with carbene adducts in 1,1-HX(Y) elimination from RCHXY (X,Y = Cl and F) molecules. Models of transition states and molecules from electronic structure calculations were used in statistical calculations of the rate constants to assign threshold energies for each reaction based on the experimental rate constants. The threshold energy for 2,1-HBr elimination from 1-bromopropane is 50 kcal mol-1, which is in basic agreement with thermal activation experiments. Comparison of the 2,1-DBr and 2,1-HBr rate constants permits discussion of the kinetic isotope effects and the effect of F atom substitution on the threshold energy for 2,1-HBr elimination. Although CD3CD═CDF from 1,1-HBr elimination of C2D5CHFBr followed by D atom migration is an experimentally observed product, dissociation of the C2D5(F)C:HBr adduct may be the rate-limiting step rather than crossing the barrier associated with the transition state for 1,1-HBr elimination. The calculated dissociation energies of C2H5(X)C:HF adducts are 9.9, 9.3, and 9.0 kcal mol-1 for X = F, Cl, and Br, and the values for C2H5(F)C:HX are 9.9, 6.4, and ∼4.9 kcal mol-1.
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Affiliation(s)
- Timothy M Brown
- Department of Chemistry , University of North Carolina-Asheville , One University Heights, Asheville , North Carolina 28804-8511 , United States
| | - Blanton R Gillespie
- Department of Chemistry , University of North Carolina-Asheville , One University Heights, Asheville , North Carolina 28804-8511 , United States
| | - Mallory M Rothrock
- Department of Chemistry , University of North Carolina-Asheville , One University Heights, Asheville , North Carolina 28804-8511 , United States
| | - Anthony J Ranieri
- Department of Chemistry , University of North Carolina-Asheville , One University Heights, Asheville , North Carolina 28804-8511 , United States
| | - Melinda K Schueneman
- Department of Chemistry , University of North Carolina-Asheville , One University Heights, Asheville , North Carolina 28804-8511 , United States
| | - George L Heard
- Department of Chemistry , University of North Carolina-Asheville , One University Heights, Asheville , North Carolina 28804-8511 , United States
| | - Donald W Setser
- Kansas State University , Manhattan , Kansas 66506 , United States
| | - Bert E Holmes
- Department of Chemistry , University of North Carolina-Asheville , One University Heights, Asheville , North Carolina 28804-8511 , United States
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Fu Y, Li QZ, Xu QS, Hügel H, Li MP, Du Z. NaI-Catalyzed Oxidative Amination of Aromatic Sodium Sulfinates: Synergetic Effect of Ethylene Dibromide and Air as Oxidants. European J Org Chem 2018. [DOI: 10.1002/ejoc.201801386] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Ying Fu
- College of Chemistry and Chemical Engineering; Northwest Normal University; 730070 Lanzhou China
| | - Quan-Zhou Li
- College of Chemistry and Chemical Engineering; Northwest Normal University; 730070 Lanzhou China
| | - Qin-Shan Xu
- College of Chemistry and Chemical Engineering; Northwest Normal University; 730070 Lanzhou China
| | - Helmut Hügel
- College of Science, Engineering & Health; School of Science, ACES; RMIT University; 3001 Melbourne Australia
| | - Ming-Peng Li
- College of Chemistry and Chemical Engineering; Northwest Normal University; 730070 Lanzhou China
| | - Zhengyin Du
- College of Chemistry and Chemical Engineering; Northwest Normal University; 730070 Lanzhou China
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5
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Brown TM, Gillespie BR, Smith CA, Nestler MJ, Heard GL, Setser DW, Holmes BE. Analysis of the Five Unimolecular Reaction Pathways of CD 2ClCHFCl with Emphasis on CD 2Cl(F)C: and CD 2Cl(Cl)C: Formed by 1,1-HCl and 1,1-HF Elimination. J Phys Chem A 2018; 122:8446-8457. [PMID: 30261723 DOI: 10.1021/acs.jpca.8b06680] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The five unimolecular HX and DX (X = F, Cl) elimination pathways of CD2ClCHFCl* were examined using a chemical activation technique; the molecules were generated with 92 kcal mol-1 of vibrational energy in a room-temperature bath gas by a combination of CD2Cl and CHFCl radicals. The total unimolecular rate constant was 9.7 × 107 s-1, and branching fractions for each channel were 0.52 (2,1-DCl), 0.29 (1,1-HCl), 0.10 (2,1-DF), 0.07 (1,1-HF), and 0.02 (1,2-HCl). Comparison of the individual experimental rate constants to calculated statistical rate constants gave threshold energies for each process as 63, 72, 66, 73, and 70 kcal mol-1, listed in the same order as the branching fractions. The 1,1-HCl and 1,1-HF reactions gave carbenes, CD2Cl(F)C: and CD2Cl(Cl)C:, respectively, as products, which have hydrogen-bonded complexes with HCl or HF in the exit channel of the potential energy surface. These carbenes have energy in excess of the threshold energy for D atom migration to give CDCl═CDF and CDCl═CDCl, and the subsequent cis-trans isomerization rates of the dihaloethenes can provide information about energy disposal by the 1,1-HX elimination reactions. Electronic structure calculations provide information for transition states of CD2ClCHFCl and hydrogen-bonded complexes of carbenes with HF and HCl. In addition, D atom migration in both free carbenes and in complexes formed by the carbene hydrogen bonding to HCl or HF is explored.
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Affiliation(s)
- Timothy M Brown
- Department of Chemistry , University of North Carolina-Asheville , One University Heights , Asheville , North Carolina 28804 , United States
| | - Blanton R Gillespie
- Department of Chemistry , University of North Carolina-Asheville , One University Heights , Asheville , North Carolina 28804 , United States
| | - Caleb A Smith
- Department of Chemistry , University of North Carolina-Asheville , One University Heights , Asheville , North Carolina 28804 , United States
| | - Matthew J Nestler
- Department of Chemistry , University of North Carolina-Asheville , One University Heights , Asheville , North Carolina 28804 , United States
| | - George L Heard
- Department of Chemistry , University of North Carolina-Asheville , One University Heights , Asheville , North Carolina 28804 , United States
| | - D W Setser
- Kansas State University , Manhattan , Kansas 66506 , United States
| | - Bert E Holmes
- Department of Chemistry , University of North Carolina-Asheville , One University Heights , Asheville , North Carolina 28804 , United States
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6
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Van Hoomissen DJ, Vyas S. 1,2-Fluorine Radical Rearrangements: Isomerization Events in Perfluorinated Radicals. J Phys Chem A 2017; 121:8675-8687. [DOI: 10.1021/acs.jpca.7b08895] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
| | - Shubham Vyas
- Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401, United States
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7
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Brown TM, Nestler MJ, Rossabi SM, Heard GL, Setser DW, Holmes BE. Characterization of the 1,1-HCl Elimination Reaction of Vibrationally Excited CD3CHFCl Molecules and Assignment of Threshold Energies for 1,1-HCl and 1,2-DCl plus 1,1-HF and 1,2-DF Elimination Reactions. J Phys Chem A 2015; 119:9441-51. [PMID: 26291380 DOI: 10.1021/acs.jpca.5b06638] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Vibrationally excited CD3CHFCl molecules with 96 kcal mol(-1) of energy were generated by the recombination of CD3 and CHFCl radicals in a room-temperature bath gas. The four competing unimolecular decomposition reactions, namely, 1,1-HCl and 1,2-DCl elimination and 1,1-HF and 1,2-DF elimination, were observed, and the individual rate constants were measured. The product branching fractions are 0.60, 0.27, 0.09, and 0.04 for 1,2-DCl, 1,1-HCl, 1,2-DF, and 1,1-HF elimination, respectively. Electronic structure calculations were used to define models of the four transition states. The statistical rate constants calculated from these models were compared to the experimental rate constants. The assigned threshold energies with ±2 kcal mol(-1) uncertainty are 60, 72, 65, and 74 kcal mol(-1) for the 1,2-DCl, 1,1-HCl, 1,2-DF, and 1,1-HF reactions, respectively. The loose structure of the 1,1-HX transition states, which is exemplified by the order of magnitude larger pre-exponential factor relative to the 1,2-HX elimination reactions, compensates for the high threshold energy; thus, the 1,1-HX elimination reaction rates can compete with the 1,2-HX elimination reactions for high levels of vibrational excitation in CD3CHFCl. The 1,1-HCl and 1,1-HF reactions are observed via the CD2═CDF and CD2═CDCl products formed from isomerization of the CD3CF and CD3CCl carbenes. These D-atom migration reactions are discussed, and the possibility of tunneling is evaluated. The transition states developed from the 1,1-HCl and 1,1-HF reactions of CD3CHFCl are compared to models for the HCl and HF elimination reactions of CHF2Cl, CHFCl2, and CH2FCl.
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Affiliation(s)
- Timothy M Brown
- Department of Chemistry, University of North Carolina-Asheville , One University Heights, Asheville, North Carolina 28804-8511, United States and
| | - Matthew J Nestler
- Department of Chemistry, University of North Carolina-Asheville , One University Heights, Asheville, North Carolina 28804-8511, United States and
| | - Samuel M Rossabi
- Department of Chemistry, University of North Carolina-Asheville , One University Heights, Asheville, North Carolina 28804-8511, United States and
| | - George L Heard
- Department of Chemistry, University of North Carolina-Asheville , One University Heights, Asheville, North Carolina 28804-8511, United States and
| | - D W Setser
- Kansas State University , Manhattan, Kansas 66506, United States
| | - Bert E Holmes
- Department of Chemistry, University of North Carolina-Asheville , One University Heights, Asheville, North Carolina 28804-8511, United States and
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8
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Wormack LN, McGreal ME, McClintock CE, Heard GL, Setser DW, Holmes BE. Characterization of the 1,1-HF Elimination Reaction from the Competition between the 1,1-HF and 1,2-DF Unimolecular Elimination Reactions of CD3CD2CHF2. J Phys Chem A 2015; 119:3887-96. [DOI: 10.1021/acs.jpca.5b01129] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | | | | | | | - D. W. Setser
- Kansas State University, Manhattan Kansas 66506, United States
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9
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McClintock CE, Smith KC, Heard GL, Setser DW, Holmes BE. Effects of CF3 and CH3 Groups on the Threshold Energy for the Unimolecular Interchange Reaction of Cl- and F-Atoms in CF3CHFCH2Cl and CH3CHFCH2Cl. J Phys Chem A 2014; 118:2886-96. [DOI: 10.1021/jp412299p] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Corey E. McClintock
- Department
of Chemistry, University of North Carolina at Asheville, One University
Heights, Asheville, North
Carolina 28804-8511, United States
| | - Kylie C. Smith
- Department
of Chemistry, University of North Carolina at Asheville, One University
Heights, Asheville, North
Carolina 28804-8511, United States
| | - George L. Heard
- Department
of Chemistry, University of North Carolina at Asheville, One University
Heights, Asheville, North
Carolina 28804-8511, United States
| | - D. W. Setser
- Kansas State University, Manhattan, Kansas 66506, United States
| | - Bert E. Holmes
- Department
of Chemistry, University of North Carolina at Asheville, One University
Heights, Asheville, North
Carolina 28804-8511, United States
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Tucker MK, Rossabi SM, McClintock CE, Heard GL, Setser DW, Holmes BE. Unimolecular isomerization of CH2FCD2Cl via the interchange of Cl and F atoms: assignment of the threshold energy to the 1,2-dyotropic rearrangement. J Phys Chem A 2013; 117:6717-23. [PMID: 23837645 DOI: 10.1021/jp4032767] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The room-temperature gas-phase recombination of CH2F and CD2Cl radicals was used to prepare CH2FCD2Cl molecules with 91 kcal mol(-1) of vibrational energy. Three unimolecular processes are in competition with collisional deactivation of CH2FCD2Cl; HCl and DF elimination to give CHF═CD2 and CH2═CDCl plus isomerization to give CH2ClCD2F by the interchange of F and Cl atoms. The Cl/F interchange reaction was observed, and the rate constant was assigned from measurement of CHCl═CD2 as a product, which is formed by HF elimination from CH2ClCD2F. These experiments plus previously published results from chemically activated CH2ClCH2F and electronic structure and RRKM calculations for the kinetic-isotope effects permit assignment of the three rate constants for CH2FCD2Cl (and for CH2ClCD2F). The product branching ratio for the interchange reaction versus elimination is 0.24 ± 0.04. Comparison of the experimental rate constant with the RRKM calculated rate constant permitted the assignment of a threshold energy of 62 ± 3 kcal mol(-1) for this type-1 dyotropic rearrangement. On the basis of electronic structure calculations, the nature of the transition state for the rearrangement reaction is discussed. The radical recombination reactions in the chemical system also generate vibrationally excited CD2ClCD2Cl and CH2FCH2F molecules, and the rate constants for DCl and HF elimination were measured in order to confirm that the photolysis of CD2ClI and (CH2F)2CO mixtures was giving reliable data for CH2FCD2Cl.
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Affiliation(s)
- Mary K Tucker
- Department of Chemistry, University of North Carolina-Asheville, One University Heights, Asheville, North Carolina 28804-8511, USA
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Damrauer R, Stanton JF. Studies of 1,2-Dihalo Shifts in Carbon–Carbon, Carbon–Silicon, and Silicon–Silicon Systems: A Computational Study. Organometallics 2012. [DOI: 10.1021/om301019s] [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)
- Robert Damrauer
- Chemistry Department, University of Colorado Denver, Campus Box 137, P.O. Box 173364, Denver, Colorado
80217-3364, United States
| | - John F. Stanton
- Chemistry and Biochemistry Department, University of Texas at Austin, Austin, Texas 78712-0165,
United States
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12
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Solaka SA, Boshamer SE, Parworth CL, Heard GL, Setser DW, Holmes BE. Isomerisation of CF2ClCH2Cl and CFCl2CH2F by Interchange of Cl and F Atoms with Analysis of the Unimolecular Reactions of Both Molecules. Chemphyschem 2012; 13:869-78. [DOI: 10.1002/cphc.201100568] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2011] [Revised: 12/07/2011] [Indexed: 11/08/2022]
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Enstice EC, Duncan JR, Setser DW, Holmes BE. Unimolecular reactions in the CF3CH2Cl ↔ CF2ClCH2F system: isomerization by interchange of Cl and F atoms. J Phys Chem A 2011; 115:1054-62. [PMID: 21244059 DOI: 10.1021/jp108955m] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The recombination of CF(2)Cl and CH(2)F radicals was used to prepare CF(2)ClCH(2)F* molecules with 93 ± 2 kcal mol(-1) of vibrational energy in a room temperature bath gas. The observed unimolecular reactions in order of relative importance were: (1) 1,2-ClH elimination to give CF(2)═CHF, (2) isomerization to CF(3)CH(2)Cl by the interchange of F and Cl atoms and (3) 1,2-FH elimination to give E- and Z-CFCl═CHF. Since the isomerization reaction is 12 kcal mol(-1) exothermic, the CF(3)CH(2)Cl* molecules have 105 kcal mol(-1) of internal energy and they can eliminate HF to give CF(2)═CHCl, decompose by rupture of the C-Cl bond, or isomerize back to CF(2)ClCH(2)F. These data, which provide experimental rate constants, are combined with previously published results for chemically activated CF(3)CH(2)Cl* formed by the recombination of CF(3) and CH(2)Cl radicals to provide a comprehensive view of the CF(3)CH(2)Cl* ↔ CF(2)ClCH(2)F* unimolecular reaction system. The experimental rate constants are matched to calculated statistical rate constants to assign threshold energies for the observed reactions. The models for the molecules and transition states needed for the rate constant calculations were obtained from electronic structures calculated from density functional theory. The previously proposed explanation for the formation of CF(2)═CHF in thermal and infrared multiphoton excitation studies of CF(3)CH(2)Cl, which was 2,2-HCl elimination from CF(3)CH(2)Cl followed by migration of the F atom in CF(3)CH, should be replaced by the Cl/F interchange reaction followed by a conventional 1,2-ClH elimination from CF(2)ClCH(2)F. The unimolecular reactions are augmented by free-radical chemistry initiated by reactions of Cl and F atoms in the thermal decomposition of CF(3)CH(2)Cl and CF(2)ClCH(2)F.
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Affiliation(s)
- Erin C Enstice
- Department of Chemistry, University of North Carolina-Asheville, Asheville, North Carolina 28804-8511, USA
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14
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Duncan JR, Heard GL, Holmes BE. Theoretical investigation of 1,2-interchange of a chlorine atom and methyl group in 1,1-dichloroacetone. J Phys Chem A 2010; 114:12992-7. [PMID: 21105681 DOI: 10.1021/jp1072582] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A recent photofragment translational spectroscopy study of 1,1-dichloroacetone at 193 nm reported two primary unimolecular decomposition channels: C-Cl bond cleavage and elimination of HCl in a 9:1 ratio, respectively. The HCl translational energy distribution was bimodal suggesting two distinct decomposition pathways that were assumed to be 1,1-HCl loss forming a carbene and a 1,3-HCl elimination reaction forming a biradical ( Butler , L. J. ; Liu , Y. ; Lau , K. ; McCunn , L. R. ; Fitzpatrick , B. L. ; Bell , J. M. ; Krisch , M. J. J. Phys. Chem. A 2007 , 111 , 5968. ). An alternative two-step mechanism for HCl loss has been proposed involving interchange of a chlorine atom and a CH(3) group converting 1,1-dichloroacetone into 2-chloropropanoyl chloride followed by either a 1,2-HCl or 2,3-HCl elimination reaction. This alternative mechanism was computationally explored with density functional theory using B3PW91/6-31G(d',p') and unimolecular rate constants were calculated. The theoretical rate constant ratio for loss of HCl and the mean HCl translation energy for each elimination channel were in excellent agreement with the experimental results.
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Affiliation(s)
- Juliana R Duncan
- Department of Chemistry, University of North Carolina-Asheville, One University Heights, Asheville, North Carolina 28804-8511, United States
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15
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Lisowski CE, Duncan JR, Ranieri AJ, Heard GL, Setser DW, Holmes BE. Isomerization of neopentyl chloride and neopentyl bromide by a 1,2-interchange of a halogen atom and a methyl group. J Phys Chem A 2010; 114:10395-402. [PMID: 20809644 DOI: 10.1021/jp1047166] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The recombination of chloromethyl and t-butyl radicals at room temperature was used to generate neopentyl chloride molecules with 89 kcal mol(-1) of internal energy. The observed unimolecular reactions, which give 2-methyl-2-butene and 2-methyl-1-butene plus HCl, as products, are explained by a mechanism that involves the interchange of a methyl group and the chlorine atom to yield 2-chloro-2-methylbutane, which subsequently eliminates hydrogen chloride by the usual four-centered mechanism to give the observed products. The interchange isomerization process is the rate-limiting step. Similar experiments were done with CD(2)Cl and C(CH(3))(3) radicals to measure the kinetic-isotope effect to help corroborate the proposed mechanism. Density functional theory was employed at the B3PW91/6-31G(d',p') level to verify the Cl/CH(3) interchange mechanism and to characterize the interchange transition state. These calculations, which provide vibrational frequencies and moments of inertia of the molecule and transition state, were used to evaluate the statistical unimolecular rate constants. Matching the calculated and experimental rate constants, gave 62 ± 2 kcal mol(-1) as the threshold energy for interchange of the Cl atom and a methyl group. The calculated models also were used to reinterpret the thermal unimolecular reactions of neopentyl chloride and neopentyl bromide. The previously assumed Wagner-Meerwein rearrangement mechanism for these reactions can be replaced by a mechanism that involves the interchange of the halogen atom and a methyl group followed by HCl or HBr elimination from 2-chloro-2-methylbutane and 2-bromo-2-methylbutane. Electronic structure calculations also were done to find threshold energies for several related molecules, including 2-chloro-3,3-dimethylbutane, 1-chloro-2-methyl-2-phenylpropane, and 1-chloro-2-methyl-2-vinylpropane, to demonstrate the generality of the interchange reaction involving a methyl, or other hydrocarbon groups, and a chlorine atom. The interchange of a halogen atom and a methyl group located on adjacent carbon atoms can be viewed as an extension of the halogen atom interchange mechanisms that is common in 1,2-dihaloalkanes.
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Affiliation(s)
- Carmen E Lisowski
- Department of Chemistry, University of North Carolina-Asheville, One University Heights, Asheville, North Carolina 28804-8511, USA
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