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Martínez AG, Siehl HU, de la Moya S, Gómez PC. Easy and accurate computation of energy barriers for carbocation solvation: an expeditious tool to face carbocation chemistry. Phys Chem Chem Phys 2023; 25:31012-31019. [PMID: 37938916 DOI: 10.1039/d3cp03544a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
An expeditious procedure for the challenging computation of the free energy barriers (ΔG≠) for the solvation of carbocations is presented. This procedure is based on Marcus Theory (MT) and the popular B3LYP/6-31G(d)//PCM method, and it allows the easy, accurate and inexpensive prediction of these barriers for carbocations of very different stability. This method was validated by the fair mean absolute error (ca. 1.5 kcal mol-1) achieved in the prediction of 19 known experimental barriers covering a range of ca. 50 kcal mol-1. Interestingly, the new procedure also uses an original method for the calculation of the required inner reorganization energy (Λi) and free energy of reaction (ΔG). This procedure should pave the way to face computationally the pivotal issue of carbocation chemistry and could be easily extended to any bimolecular organic reaction.
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Affiliation(s)
- Antonio G Martínez
- Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040, Madrid, Spain.
| | - Hans-Ulrich Siehl
- Abteilung Organische Chemie I, Universität Ulm, Albert Einstein Alee 11, 89069 Ulm, Germany
| | - Santiago de la Moya
- Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040, Madrid, Spain.
| | - Pedro C Gómez
- Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040, Madrid, Spain.
- Departamento de Química Física, Universidad Complutense de Madrid, Facultad de Ciencias Químicas, 28040 Madrid, Spain.
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Meng Y, Gnanamani E, Zare RN. Direct C(sp 3)–N Bond Formation between Toluene and Amine in Water Microdroplets. J Am Chem Soc 2022; 144:19709-19713. [DOI: 10.1021/jacs.2c10032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yifan Meng
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Elumalai Gnanamani
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667, India
| | - Richard N. Zare
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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Kumar A, Mondal S, Sandeep, Venugopalan P, Kumar A, Banerjee S. Destabilized Carbocations Caged in Water Microdroplets: Isolation and Real-Time Detection of α-Carbonyl Cation Intermediates. J Am Chem Soc 2022; 144:3347-3352. [PMID: 35179907 DOI: 10.1021/jacs.1c12644] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Over the last 50 years, proposals of α-carbonyl cation intermediates have been driven by chemical intuition and indirect evidence. Recently, wide interest in α-carbonyl cation chemistry has opened new gates to prepare α-functionalized carbonyl compounds. Though these intrinsically unstable carbocations are formed under forcing conditions (e.g., in a strong acid medium), their fleeting existence prohibits direct observation or spectroscopic measurement. We report that high-speed aqueous microdroplets can directly capture α-carbonyl cation intermediates from various reactions (Friedel-Crafts arylation, deoxygenation, and azidation) upon bombarding with the corresponding reaction aliquots. The α-carbonyl cations caged in water droplets are then desorbed to the gas phase, allowing their successful measurement by mass spectrometry. This has also enabled us to simultaneously monitor the relative abundance of the associated precursor, α-carbonyl cation intermediate, and product during the progress of the reaction.
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Affiliation(s)
- Anubhav Kumar
- Department of Chemistry, Indian Institute of Science Education and Research Tirupati, Tirupati 517507, India
| | - Supratim Mondal
- Department of Chemistry, Indian Institute of Science Education and Research Tirupati, Tirupati 517507, India
| | - Sandeep
- Department of Applied Sciences, University Institute of Engineering and Technology, Panjab University, Chandigarh 160014, India.,Department of Chemistry, Panjab University, Chandigarh 160014, India
| | | | - Anil Kumar
- Department of Applied Sciences, University Institute of Engineering and Technology, Panjab University, Chandigarh 160014, India
| | - Shibdas Banerjee
- Department of Chemistry, Indian Institute of Science Education and Research Tirupati, Tirupati 517507, India
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Kumar A, Mondal S, Banerjee S. Aqueous Microdroplets Capture Elusive Carbocations. J Am Chem Soc 2021; 143:2459-2463. [DOI: 10.1021/jacs.0c12512] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anubhav Kumar
- Department of Chemistry, Indian Institute of Science Education and Research Tirupati, Tirupati 517507, India
| | - Supratim Mondal
- Department of Chemistry, Indian Institute of Science Education and Research Tirupati, Tirupati 517507, India
| | - Shibdas Banerjee
- Department of Chemistry, Indian Institute of Science Education and Research Tirupati, Tirupati 517507, India
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de la Moya Cerero S, Siehl HU, Martínez AG. About the Existence of Organic Oxonium Ions as Mechanistic Intermediates in Water Solution. J Phys Chem A 2016; 120:7045-50. [PMID: 27552494 DOI: 10.1021/acs.jpca.6b06216] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Santiago de la Moya Cerero
- Departamento de Química Orgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid , Ciudad Universitaria s/n, E-28040 Madrid, Spain
| | - Hans-Ullrich Siehl
- Abteilung Organische Chemie I, Universität Ulm , Albert Einstein Allee 11, D-89069 Ulm, Germany
| | - Antonio García Martínez
- Departamento de Química Orgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid , Ciudad Universitaria s/n, E-28040 Madrid, Spain
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Abstract
It has been shown recently that many supposed reaction intermediates in aqueous media do not have lifetimes long enough for them to serve this purpose. Among these are oxygen-protonated species where the positive charge is not delocalized, primary and secondary carbocations, and the commonly written species H3O+ and HO–. This means that the mechanisms for many of the organic reactions that take place in aqueous media are in need of revision. This paper concerns the acid hydrolysis of simple ethers, many of which cannot form carbocations stable enough to exist in water. Rather than an A1 process in which an oxygen-protonated species dissociates into an alcohol and a carbocation, which is then quenched by water, or an A2 process in which a water molecule or another nucleophilic species assists in this, the mechanism for most ethers is a general-acid-catalyzed process in which proton transfer to oxygen is concerted with C–O bond cleavage in cases where a stable carbocation can exist, or additionally concerted with nucleophilic attack for those cases in which stable carbocation formation is not possible. All of the cases for which rate constant data could be found in the literature are analyzed and discussed in this paper, with the exception of the hydrolyses of several azoethers, where additional hydrolysis mechanisms are possible. These will be discussed in a subsequent paper.
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Affiliation(s)
- Robin A. Cox
- 16 Guild Hall Drive, Scarborough, ON M1R 3Z8, Canada
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Fang D, Ren W, Lü H, Yang H. Partial amination of cationic exchange resins and its application in the hydration of butene. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/s1003-9953(11)60370-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Brooner REM, Widenhoefer RA. Stereochemistry and mechanism of the Brønsted acid catalyzed intramolecular hydrofunctionalization of an unactivated cyclic alkene. Chemistry 2011; 17:6170-8. [PMID: 21506179 DOI: 10.1002/chem.201003128] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2010] [Indexed: 11/06/2022]
Abstract
Through employment of deuterium-labeled substrates, the triflic acid catalyzed intramolecular exo addition of the X-H(D) (X=N, O) bond of a sulfonamide, alcohol, or carboxylic acid across the C=C bond of a pendant cyclohexene moiety was found to occur, in each case, with exclusive formation (≥90%) of the anti-addition product without loss or scrambling of deuterium as determined by (1)H and (2)H NMR spectroscopy and mass spectrometry analysis. Kinetic analysis of the triflic-acid-catalyzed intramolecular hydroamination of N-(2-cyclohex-2'-enyl-2,2-diphenylethyl)-p-toluenesulfonamide (1a) established the second-order rate law: rate=k(2)[HOTf][1a] and the activation parameters ΔH(++)=(9.7±0.5) kcal mol(-1) and ΔS(++)=(-35±5) cal K(-1) mol(-1). An inverse α-secondary kinetic isotope effect of k(D)/k(H) =(1.15±0.03) was observed upon deuteration of the C2' position of 1a, consistent with partial C-N bond formation in the highest energy transition state of catalytic hydroamination. The results of these studies were consistent with a mechanism for the intramolecular hydroamination of 1a involving concerted, intermolecular proton transfer from an N-protonated sulfonamide to the alkenyl C3' position of 1a coupled with intramolecular anti addition of the pendant sulfonamide nitrogen atom to the alkenyl C2' position.
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Niggemann M, Meel M. Calcium-Catalyzed Friedel-Crafts Alkylation at Room Temperature. Angew Chem Int Ed Engl 2010; 49:3684-7. [DOI: 10.1002/anie.200907227] [Citation(s) in RCA: 177] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Niggemann M, Meel M. Calcium-katalysierte Friedel-Crafts-Alkylierung bei Raumtemperatur. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.200907227] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Nelson DJ, Brammer C, Li R. Substituent effects in acid-catalyzed hydration of alkenes, measured under consistent reaction conditions. Tetrahedron Lett 2009. [DOI: 10.1016/j.tetlet.2009.08.128] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Jia ZS, Ottosson H, Zeng X, Thibblin A. The role of ion-molecule pairs in solvolysis reactions. Nucleophilic addition of water to a tertiary allylic carbocation. J Org Chem 2002; 67:182-7. [PMID: 11777457 DOI: 10.1021/jo016162a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The acid-catalyzed solvolysis of 2-methoxy-2-phenyl-3-butene (1-OMe) in 9.09 vol % acetonitrile in water provides 2-hydroxy-2-phenyl-3-butene (1-OH) as the predominant product under kinetic control along with the rearranged alcohol 1-hydroxy-3-phenyl-2-butene (2-OH) and a small amount of the rearranged ether 2-OMe. The more stable isomer 2-OH is the predominant product after long reaction time, K(eq) = [2-OH](eq)/[1-OH](eq) = 16. The ether 2-OMe reacts to give 2-OH and a trace of 1-OH. Solvolysis of 1-OMe in (18)O-labeled water/acetonitrile shows complete incorporation of (18)O in the product 1-OH, confirming that the reaction involves cleavage of the carbon-oxygen bond to the allylic carbon. A completely solvent-equilibrated allylic carbocation is not formed since the solvolysis of the corresponding chloride 1-chloro-3-phenyl-2-butene (2-Cl) yields a larger fraction of 1-OH. This may be attributed to a shielding effect from the chloride leaving group. Quantum chemical calculations of the geometry and charge distribution show that the cation should rather be described as a vinyl-substituted benzyl cation than as an allyl cation, which is in accord with its higher reactivity at the tertiary carbon.
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Affiliation(s)
- Zhi Sheng Jia
- Institute of Chemistry, University of Uppsala, P.O. Box 531, SE-751 21 Uppsala, Sweden
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Cox RA. Excess acidities. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2000. [DOI: 10.1016/s0065-3160(00)35011-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
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