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Um IH, Moon HJ, Shin YH, Dust JM. Medium effect on the α-effect for nucleophilic substitution reactions of p-nitrophenyl acetate with benzohydroxamates and m-chlorophenoxide in DMSO–H2O mixtures as contrasts with MeCN–H2O mixtures: comparing two very different polar aprotic solvent components. CAN J CHEM 2018. [DOI: 10.1139/cjc-2018-0103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A kinetic study is reported on nucleophilic substitution reactions of p-nitrophenyl acetate (1a) with three α-effect nucleophiles, benzohydroxamate (BHA–), p-methylbenzohydroxamate (MBHA–), and p-methyl-N-methylbenzohydroxamate (M2BHA–), and a reference nucleophile, m-chlorophenoxide (m-ClPhO–), in DMSO–H2O mixtures of varying compositions at 25.0 ± 0.1 °C. Second-order rate constants for the reactions with BHA– and MBHA– decrease upon addition of DMSO to the reaction medium up to 60 mol % DMSO and then increase thereafter only a little. In contrast, M2BHA– and m-ClPhO– become much more reactive as the DMSO content in the medium increases. Such contrasting medium effects on reactivity are consistent with the report that hydroxamic acids behave as OH acids in H2O but as NH acids in dipolar aprotic solvents (e.g., DMSO and MeCN). It has been concluded that BHA– and MBHA– form an equilibrium of a reactive form I with less reactive species II in DMSO–H2O mixtures and the position of the equilibrium is dependent on solvent compositions. BHA– and MBHA– exhibit the α-effect in H2O but not in in 90 mol % DMSO. In contrast, the α-effect yielded by M2BHA– increases steeply up to 70 mol % DMSO and then levels off thereafter.
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Affiliation(s)
- Ik-Hwan Um
- Department of Chemistry, Ewha Womans University, Seoul 03767, Korea
| | - Hyun-Jung Moon
- Department of Chemistry, Ewha Womans University, Seoul 03767, Korea
| | - Young-Hee Shin
- Department of Chemistry, Seoul National University, Seoul 08826, Korea
| | - Julian M. Dust
- Departments of Chemistry and Environmental Science, Grenfell Campus-Memorial University of Newfoundland, Corner Brook, NL A2H 5G4, Canada
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Hamlin TA, Swart M, Bickelhaupt FM. Nucleophilic Substitution (S N 2): Dependence on Nucleophile, Leaving Group, Central Atom, Substituents, and Solvent. Chemphyschem 2018; 19:1315-1330. [PMID: 29542853 PMCID: PMC6001448 DOI: 10.1002/cphc.201701363] [Citation(s) in RCA: 118] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Indexed: 11/12/2022]
Abstract
The reaction potential energy surface (PES), and thus the mechanism of bimolecular nucleophilic substitution (SN 2), depends profoundly on the nature of the nucleophile and leaving group, but also on the central, electrophilic atom, its substituents, as well as on the medium in which the reaction takes place. Here, we provide an overview of recent studies and demonstrate how changes in any one of the aforementioned factors affect the SN 2 mechanism. One of the most striking effects is the transition from a double-well to a single-well PES when the central atom is changed from a second-period (e. g. carbon) to a higher-period element (e.g, silicon, germanium). Variations in nucleophilicity, leaving group ability, and bulky substituents around a second-row element central atom can then be exploited to change the single-well PES back into a double-well. Reversely, these variations can also be used to produce a single-well PES for second-period elements, for example, a stable pentavalent carbon species.
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Affiliation(s)
- Trevor A. Hamlin
- Department of Theoretical Chemistry andAmsterdam Center for Multiscale Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081 HVAmsterdamThe Netherlands
| | - Marcel Swart
- Department of Theoretical Chemistry andAmsterdam Center for Multiscale Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081 HVAmsterdamThe Netherlands
- Institut de Química Computacional I Catàlisi and Department de QuímicaUniversitat de Girona17003GironaSpain
- ICREAPg. Lluís Companys 2308010BarcelonaSpain
| | - F. Matthias Bickelhaupt
- Department of Theoretical Chemistry andAmsterdam Center for Multiscale Modeling (ACMM)Vrije Universiteit AmsterdamDe Boelelaan 10831081 HVAmsterdamThe Netherlands
- Institute of Molecules and Materials (IMM)Radboud UniversityHeyendaalseweg 1356525 AJNijmegenThe Netherlands
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3
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Han LL, Li SJ, Fang DC. Theoretical estimation of kinetic parameters for nucleophilic substitution reactions in solution: an application of a solution translational entropy model. Phys Chem Chem Phys 2016; 18:6182-90. [PMID: 26847838 DOI: 10.1039/c5cp07803b] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The kinetic parameters, such as activation entropy, activation enthalpy, activation free-energy, and reaction rate constant, for a series of nucleophilic substitution (SN) reactions in solution, are investigated using both a solution-phase translational entropy model and an ideal gas-phase translational entropy model. The results obtained from the solution translational entropy model are in excellent agreement with the experimental values, while the overestimation of activation free-energy from the ideal gas-phase translational entropy model is as large as 6.9 kcal mol(-1). For some of the reactions studied, such as and in methanol, and and in aqueous solution, the explicit + implicit model, namely, a cluster-continuum type model, should be employed to account for the strong solvent-solute interactions. In addition, the explicit + implicit models have also been applied to the DMSO-H2O mixtures, which would open up a door to investigate the reactions in a mixed solvent using density functional theory (DFT) methods.
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Affiliation(s)
- Ling-Li Han
- College of Chemistry, Beijing Normal University, Beijing, 100875, China. and Department of Chemistry and Chemical Engineering, Jining University, Qufu, 273155, Shandong, China
| | - Shi-Jun Li
- College of Chemistry, Beijing Normal University, Beijing, 100875, China.
| | - De-Cai Fang
- College of Chemistry, Beijing Normal University, Beijing, 100875, China.
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Um IH, Kim MY, Cho HJ, Dust JM, Buncel E. The α-effect in the SNAr reaction of 1-(4-nitrophenoxy)-2,4-dinitrobenzene with anionic nucleophiles: effects of solvation and polarizability on the α-effect. CAN J CHEM 2015. [DOI: 10.1139/cjc-2015-0073] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A kinetic study on SNAr reactions of 1-(4-nitrophenoxy)-2,4-dinitrobenzene (1a) with various anionic nucleophiles in 80 mol% water – 20 mol% DMSO at 25.0 °C is reported. The Brønsted-type plot for the reaction of 1a with a series of substituted phenoxides and HOO− results in an excellent linear correlation with βnuc = 1.17. However, OH− exhibits dramatic negative deviation from the Brønsted-type plot, while N3−, C6H5S−, and butane-2,3-dione monoximate (Ox−) deviate positively from linearity. HOO− is 680-fold more reactive than OH− but does not exhibit the α-effect. In contrast, Ox− is 166-fold more reactive than isobasic 4-Cl−C6H4O− and exhibits the α-effect. Differential solvation effects have been suggested to be responsible for the α-effect in this study, i.e., Ox− exhibits the α-effect, since it is 5.7 kcal/mol less strongly solvated than 4-Cl−C6H4O− in the reaction medium, while HOO− does not show the α-effect due to a strong requirement for partial desolvation before nucleophilic attack. The highly enhanced reactivity of polarizable N3− and C6H5S− and extremely decreased reactivity of nonpolarizable OH− are in accord with the hard–soft acid and base principle.
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Affiliation(s)
- Ik-Hwan Um
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Min-Young Kim
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Hyo-Jin Cho
- Department of Chemistry, Duksung Women’s University, Seoul 132-714, Korea
| | - Julian M. Dust
- Departments of Chemistry and Environmental Science, Grenfell Campus, Memorial University of Newfoundland, Corner Brook, NL A2H 5G4, Canada
| | - Erwin Buncel
- Department of Chemistry, Queen’s University, Kingston, ON K7L 3N6, Canada
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Singh N, Karpichev Y, Sharma R, Gupta B, Sahu AK, Satnami ML, Ghosh KK. From α-nucleophiles to functionalized aggregates: exploring the reactivity of hydroxamate ion towards esterolytic reactions in micelles. Org Biomol Chem 2015; 13:2827-48. [DOI: 10.1039/c4ob02067g] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydroxamate ions as α-nucleophiles for esterolytic reactions in water and micelles.
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Affiliation(s)
- Namrata Singh
- School of Studies in Chemistry
- Pt. Ravishankar Shukla University
- Raipur (C.G)
- India
- Department of Psychiatry
| | - Yevgen Karpichev
- L.M. Litvinenko Institute of Physical Organic and Coal Chemistry
- Donetsk
- Ukraine
- Center for Basic and Advanced Research
- Faculty of Informatics and Management
| | - Rahul Sharma
- School of Studies in Chemistry
- Pt. Ravishankar Shukla University
- Raipur (C.G)
- India
| | - Bhanushree Gupta
- School of Studies in Chemistry
- Pt. Ravishankar Shukla University
- Raipur (C.G)
- India
| | - Arvind K. Sahu
- School of Studies in Chemistry
- Pt. Ravishankar Shukla University
- Raipur (C.G)
- India
| | - Manmohan L. Satnami
- School of Studies in Chemistry
- Pt. Ravishankar Shukla University
- Raipur (C.G)
- India
| | - Kallol K. Ghosh
- School of Studies in Chemistry
- Pt. Ravishankar Shukla University
- Raipur (C.G)
- India
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Um IH, Kim MY, Bae AR, Dust JM, Buncel E. Evidence for a Catalytic Six-Membered Cyclic Transition State in Aminolysis of 4-Nitrophenyl 3,5-Dinitrobenzoate in Acetonitrile: Comparative Brønsted-Type Plot, Entropy of Activation, and Deuterium Kinetic Isotope Effects. J Org Chem 2014; 80:217-22. [PMID: 25438168 DOI: 10.1021/jo502303f] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ik-Hwan Um
- Department
of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Min-Young Kim
- Department
of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Ae-Ri Bae
- Department
of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Julian M. Dust
- Departments
of Chemistry and Environmental Science, Grenfell Campus, Memorial University of Newfoundland, Corner Brook, Newfoundland
and Labrador A2H 5G4, Canada
| | - Erwin Buncel
- Department
of Chemistry, Queen’s University, Kingston, Ontario K7L 3N6, Canada
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Kim MY, Kim TE, Lee J, Um IH. The α-Effect in Hydrazinolysis of 4-Chloro-2-Nitrophenyl X-Substituted-Benzoates: Effect of Substituent X on Reaction Mechanism and the α-Effect. B KOREAN CHEM SOC 2014. [DOI: 10.5012/bkcs.2014.35.8.2271] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Cho HJ, Um IH. The α-Effect in S NAr Reaction of 1-Fluoro-2,4-dinitrobenzene with Hydrazine: Ground-State Destabilization versus Transition-State Stabilization. B KOREAN CHEM SOC 2014. [DOI: 10.5012/bkcs.2014.35.8.2371] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Cho HJ, Kim MY, Um IH. The α-Effect in SNAr Reaction of Y-Substituted-Phenoxy-2,4-Dinitrobenzenes with Amines: Reaction Mechanism and Origin of the α-Effect. B KOREAN CHEM SOC 2014. [DOI: 10.5012/bkcs.2014.35.8.2448] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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