1
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Trends in oxygenate/hydrocarbon selectivity for electrochemical CO (2) reduction to C 2 products. Nat Commun 2022; 13:1399. [PMID: 35302055 PMCID: PMC8931056 DOI: 10.1038/s41467-022-29140-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 02/17/2022] [Indexed: 11/08/2022] Open
Abstract
The electrochemical conversion of carbon di-/monoxide into commodity chemicals paves a way towards a sustainable society but it also presents one of the great challenges in catalysis. Herein, we present the trends in selectivity towards specific dicarbon oxygenate/hydrocarbon products from carbon monoxide reduction on transition metal catalysts, with special focus on copper. We unveil the distinctive role of electrolyte pH in tuning the dicarbon oxygenate/hydrocarbon selectivity. The understanding is based on density functional theory calculated energetics and microkinetic modeling. We identify the critical reaction steps determining selectivity and relate their transition state energies to two simple descriptors, the carbon and hydroxide binding strengths. The atomistic insight gained enables us to rationalize a number of experimental observations and provides avenues towards the design of selective electrocatalysts for liquid fuel production from carbon di-/monoxide.
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2
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Kamath D, Mezyk SP, Minakata D. Elucidating the Elementary Reaction Pathways and Kinetics of Hydroxyl Radical-Induced Acetone Degradation in Aqueous Phase Advanced Oxidation Processes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:7763-7774. [PMID: 29923393 DOI: 10.1021/acs.est.8b00582] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Advanced oxidation processes (AOPs) that produce highly reactive hydroxyl radicals are promising methods to destroy aqueous organic contaminants. Hydroxyl radicals react rapidly and nonselectively with organic contaminants and degrade them into intermediates and transformation byproducts. Past studies have indicated that peroxyl radical reactions are responsible for the formation of many intermediate radicals and transformation byproducts. However, complex peroxyl radical reactions that produce identical transformation products make it difficult to experimentally study the elementary reaction pathways and kinetics. In this study, we used ab initio quantum mechanical calculations to identify the thermodynamically preferable elementary reaction pathways of hydroxyl radical-induced acetone degradation by calculating the free energies of the reaction and predicting the corresponding reaction rate constants by calculating the free energies of activation. In addition, we solved the ordinary differential equations for each species participating in the elementary reactions to predict the concentration profiles for acetone and its transformation byproducts in an aqueous phase UV/hydrogen peroxide AOP. Our ab initio quantum mechanical calculations found an insignificant contribution of Russell reaction mechanisms of peroxyl radicals, but significant involvement of HO2• in the peroxyl radical reactions. The predicted concentration profiles were compared with experiments in the literature, validating our elementary reaction-based kinetic model.
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Affiliation(s)
- Divya Kamath
- Department of Civil and Environmental Engineering , Michigan Technological University , Houghton , Michigan 49931 , United States
| | - Stephen P Mezyk
- Department of Chemistry and Biochemistry , California State University , Long Beach , California 90840 , United States
| | - Daisuke Minakata
- Department of Civil and Environmental Engineering , Michigan Technological University , Houghton , Michigan 49931 , United States
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3
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Sarkar S, Mallick S, Kumar P, Bandyopadhyay B. Ammonolysis of ketene as a potential source of acetamide in the troposphere: a quantum chemical investigation. Phys Chem Chem Phys 2018; 20:13437-13447. [DOI: 10.1039/c8cp01650j] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Quantum chemical calculations at the CCSD(T)/CBS//MP2/aug-cc-pVTZ levels of theory have been carried out to investigate a potential new source of acetamide in Earth's atmosphere through the ammonolysis of the simplest ketene.
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Affiliation(s)
- Saptarshi Sarkar
- Department of Chemistry
- Malaviya National Institute of Technology Jaipur
- Jaipur
- India
| | - Subhasish Mallick
- Department of Chemistry
- Malaviya National Institute of Technology Jaipur
- Jaipur
- India
| | - Pradeep Kumar
- Department of Chemistry
- Malaviya National Institute of Technology Jaipur
- Jaipur
- India
| | - Biman Bandyopadhyay
- Department of Chemistry
- Malaviya National Institute of Technology Jaipur
- Jaipur
- India
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4
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Louie MK, Francisco JS, Verdicchio M, Klippenstein SJ, Sinha A. Hydrolysis of Ketene Catalyzed by Formic Acid: Modification of Reaction Mechanism, Energetics, and Kinetics with Organic Acid Catalysis. J Phys Chem A 2015; 119:4347-57. [DOI: 10.1021/jp5076725] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Matthew K. Louie
- Department
of Chemistry and Biochemistry, University of California−San Diego, La Jolla, California 92093-0314, United States
| | - Joseph S. Francisco
- Department
of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, United States
| | - Marco Verdicchio
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439-4837, United States
| | - Stephen J. Klippenstein
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439-4837, United States
| | - Amitabha Sinha
- Department
of Chemistry and Biochemistry, University of California−San Diego, La Jolla, California 92093-0314, United States
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5
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Allen AD, Tidwell TT. Structure and Mechanism in Ketene Chemistry. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2014. [DOI: 10.1016/b978-0-12-800256-8.00004-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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6
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Nguyen TL, Xue BC, Ellison GB, Stanton JF. Theoretical Study of Reaction of Ketene with Water in the Gas Phase: Formation of Acetic Acid? J Phys Chem A 2013; 117:10997-1005. [DOI: 10.1021/jp408337y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Thanh Lam Nguyen
- Department
of Chemistry & Biochemistry, The University of Texas at Austin, Austin, Texas 78712-0165, United States
| | - Bert C. Xue
- Department
of Chemistry & Biochemistry, The University of Texas at Austin, Austin, Texas 78712-0165, United States
| | - G. Barney Ellison
- Department
of Chemistry and Biochemistry, University of Colorado at Boulder, 215 UCB, Boulder, Colorado 80309, United States
| | - John F. Stanton
- Department
of Chemistry & Biochemistry, The University of Texas at Austin, Austin, Texas 78712-0165, United States
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7
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Kao JPY, Muralidharan S. Characterizing caged molecules through flash photolysis and transient absorption spectroscopy. Methods Mol Biol 2013; 995:57-77. [PMID: 23494372 DOI: 10.1007/978-1-62703-345-9_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Caged molecules are photosensitive molecules with latent biological activity. Upon exposure to light, they are rapidly transformed into bioactive molecules such as neurotransmitters or second messengers. They are thus valuable tools for using light to manipulate biology with exceptional spatial and temporal resolution. Since the temporal performance of the caged molecule depends critically on the rate at which bioactive molecules are generated by light, it is important to characterize the kinetics of the photorelease process. This is accomplished by initiating the photoreaction with a very brief but intense pulse of light (i.e., flash photolysis) and monitoring the course of the ensuing reactions through various means, the most common of which is absorption spectroscopy. Practical guidelines for performing flash photolysis and transient absorption spectroscopy are described in this chapter.
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Affiliation(s)
- Joseph P Y Kao
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA
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8
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Theoretical study on the role of cooperative solvent molecules in the neutral hydrolysis of ketene. Theor Chem Acc 2010. [DOI: 10.1007/s00214-010-0738-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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9
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Acton A, Allen AD, Fedorov AV, Henry-Riyad H, Tidwell TT. Aminoxyl radical addition to arylketenes. J PHYS ORG CHEM 2007. [DOI: 10.1002/poc.1036] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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10
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Rode JE, Dobrowolski JC. An ab Initio Study on the Allene−Isocyanic Acid and Ketene−Vinylimine [2 + 2] Cycloaddition Reaction Paths. J Phys Chem A 2006; 110:3723-37. [PMID: 16526656 DOI: 10.1021/jp055073p] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reaction paths of [2 + 2] cycloadditions of allene (H2C=C=CH2) to isocyanic acid (HN=C=O) and ketene (H2C=C=O) to vinylimine (H2C=C=NH), leading to all the possible 14 four-membered ring molecules, were investigated by the MP2/aug-cc-pVDZ method. In the two considered reactions, the 2-azetidinone (beta-lactam) ring compounds were predicted to be the most stable thermodynamically in the absence of an environment. Although 4-methylene-2-azetidinone is the most stable product of the ketene-vinylimine cycloaddition, its activation barrier is higher than that for 4-methylene-2-iminooxetane by ca. 6 kcal/mol. Therefore, the latter product can be obtained owing to kinetic control. The activation barriers in the allene-isocyanic acid reactions are quite high, 50-70 kcal/mol, whereas in the course of the ketene-vinylimine cycloaddition they are equal to ca. 30-55 kcal/mol. All the reactions studied were found to be concerted and mostly asynchronous. Simulation of the solvent environment (toluene, tetrahydrofuran, acetonitrile, and water) by using Tomasi's polarized continuum model with the integral equation formalism (IEF-PCM) method showed the allene-isocyanic reactions remained concerted, yet the activation barriers were somewhat higher than those in the gas phase, whereas the ketene-vinylimine reactions became stepwise. The larger the solvent dielectric constant, the lower the activation barriers found. The lowest-energy pathways in the gas phase and in solvent were confirmed by intrinsic reaction coordinate (IRC) calculations. The atoms in molecules (AIM) analysis of the electron density distribution in the transition-state (TS) structures allowed us to distinguish pericyclic from pseudopericyclic from nonplanar-pseudopericyclic types of reactions.
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Affiliation(s)
- Joanna E Rode
- Industrial Chemistry Research Institute, 01-793 Warsaw, 8 Rydygiera Street, Poland
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11
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12
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Wu H, Loeppky RN, Glaser R. Nitrosation Chemistry of Pyrroline, 2-Imidazoline, and 2-Oxazoline: Theoretical Curtin−Hammett Analysis of Retro-Ene and Solvent-Assisted C−X Cleavage Reactions of α-Hydroxy-N-Nitrosamines. J Org Chem 2005; 70:6790-801. [PMID: 16095298 DOI: 10.1021/jo050856s] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The results are presented of a theoretical study of the nitrosation chemistry of pyrroline 1 (X = CH2), imidazoline 2 (X = NH), and 2-oxazoline 3 (X = O). Imines 1-3 are converted to the alpha-hydroxy-N-nitrosamines 7-9 via the N-nitrosoiminium ions 4-6. The NN-cis isomers of 7-9 may undergo retro-ene reactions to the delta-oxoalkyl diazotic acids 10-12. With the opportunity for microsolvation, C-X cleavage becomes possible for 8 and 9 and leads to the formation of N-(2-aminoethyl)- and N-(2-hydroxyethyl)-N-nitrosoformamides 15 and 16, respectively. The NN-isomerization barriers are comparable to the barriers for the ring-opening reactions, and the consideration of two Curtin-Hammett scenarios is required: CH-I for the NN-trans-rotamers of 7-9 to undergo C-X cleavage or NN-isomerization and CH-II for the NN-cis-rotamers to undergo C-X cleavage, C-N cleavage, or NN-isomerization. We determined all stereoisomers of the substrates, the products, and of all transition states structures for the retro-ene reactions of 7-9, the C-X cleavages of microsolvated 8 and 9, and the NN-isomerizations of 8 and 9. The potential energy surfaces were explored at the B3LYP/6-31G level, and the results are discussed with emphasis on the comparison of the kinetics and thermodynamics of C-N versus C-X cleavage. The study shows all decompositions to be very fast with activation barriers below 21 kcal.mol(-1), and the comparative analysis predicts that the chemical toxicologies of 1 and 3 should be similar and remarkably different from that of 2.
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Affiliation(s)
- Hong Wu
- Department of Chemistry, University of Missouri-Columbia, Columbia, MO 65211, USA
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13
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Allen AD, Fedorov AV, Tidwell TT, Vukovic S. Hydration of Pyridylketenes: Formation of Acid Enol and Dihydropyridine (Eneaminone) Transients. J Am Chem Soc 2004; 126:15777-83. [PMID: 15571401 DOI: 10.1021/ja047623n] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
2-, 3-, and 4-Pyridylketenes 4 formed in water by photochemical Wolff rearrangements using flash photolysis undergo rapid hydration forming transient intermediates observed by UV spectroscopy. 3-Pyridylketene (3-4) formed the acid enol intermediate 3-10 which was converted to the acid 3-11, and phenylketene gave similar behavior. 4-Pyridylketene (4-4) reacted with a similar initial rate constant of 5.0 x 10(4) s(-1) for decay of an absorption at 275 nm, with concomitant formation of a strong absorption at 370 nm with the same rate constant. The intermediate absorbing at 370 nm decayed with a lifetime 2.4 x 10(3) fold longer than that of the ketene, and is identified as 4-(carboxymethylene)-1,4-dihydropyridine (4-13), resulting from conjugate 1,6-addition of H(2)O to 4-4. 2-Pyridylketene (2-4) underwent hydration with a similar rate constant of 1.1 x 10(4) s(-1) forming a transient with a UV absorption with maxima at 310 and 380 nm that decayed with biexponetial kinetics, with rate constants slower than the rate of formation by factors of 5.2 and 110, respectively. These results are interpreted as indicating the presence of two species, namely Z- and E-2-(carboxymethylene)-1,2-dihydropyridines (2-13), resulting from conjugate 1,4-addition of H(2)O to 2-4. The identifications of the 1,2- and 1,4-(carboxymethylene)dihydropyridines 2- and 4-13 were confirmed by comparison of their UV spectra with those of the corresponding N-methyl derivatives. The amination of 2-pyridylketene in CH(3)CN was reinvestigated, and spectroscopic evidence, computational studies, and preparation of the N-methyl analogue demonstrated formation of the 1,2-dihydropyridine Z-2-8f as the long-lived intermediate.
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Affiliation(s)
- Annette D Allen
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6 Canada
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14
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Rayat S, Wu Z, Glaser R. Nitrosative Guanine Deamination: Ab Initio Study of Deglycation of N-Protonated 5-Cyanoimino-4-oxomethylene-4,5-dihydroimidazoles. Chem Res Toxicol 2004; 17:1157-69. [PMID: 15377149 DOI: 10.1021/tx0499416] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
5-Cyanoimino-4-oxomethylene-4,5-dihydroimidazoles (1) (R at N1) have been discussed as possible intermediates in nitrosative guanine deamination, which are formed by dediazoniation and deprotonation of guaninediazonium ion. The parent system 1 (R = H) and its N1 derivatives 2 (R = Me) and 3 (R = MOM) are considered here. Protonation of 1-3, respectively, may occur either at the cyano-N to form cations 4 (R = H), 6 (R = Me), and 8 (R = MOM) or at the imino-N to form cations 5 (R = H), 7 (R = Me), and 9 (R = MOM), respectively. This protonation is the first step in the acid-catalyzed water addition to form 5-cyanoimino-imidazole-4-carboxylic acid, which then leads to oxanosine. There also exists the option of a substitution reaction by water at the R group of 6-9, and this dealkylation forms N-[4-(oxomethylene)-imidazol-5-yl]carbodiimide (10) and N-[4-(oxomethylene)-imidazol-5-yl]cyanamide (11). In the case of DNA, the R group is a deoxyribose sugar, and attack by water leads to deglycation. To explore this reaction option, the S(N)1 and S(N)2 reactions of 6-9 with water were studied at the MP2/6-31G*//RHF/6-31G* and CCSD/6-31G*//RHF/6-31G* levels, with the inclusion of implicit solvation at the IPCM(MP2/6-31G*)//RHF/6-31G* level, and the electron density distributions of tautomers 1, 10, and 11 were analyzed. The low barriers determined for the MOM transfer show that the deglycation could occur at room temperature but that the process cannot compete with water addition.
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Affiliation(s)
- Sundeep Rayat
- Department of Chemistry, University of Missouri-Columbia, Columbia, Missouri 65211, USA
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15
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Acton AW, Allen AD, Antunes LM, Fedorov AV, Najafian K, Tidwell TT, Wagner BD. Amination of pyridylketenes: experimental and computational studies of strong amide enol stabilization by the 2-pyridyl group. J Am Chem Soc 2002; 124:13790-4. [PMID: 12431108 DOI: 10.1021/ja027347h] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Laser flash photolyses of 2-, 3-, and 4-diazoacetylpyridines 8 give the corresponding pyridylketenes 7 formed by Wolff rearrangements, as observed by time-resolved infrared spectroscopy, with ketenyl absorptions at 2127, 2125, and 2128 cm(-1), respectively. Photolysis of 2-, 3-, and 4-8 in CH(3)CN containing n-BuNH(2) results in the formation of two transients in each case, as observed by time-resolved IR and UV spectroscopy. The initial transients are assigned as the ketenes 7, and this is confirmed by IR measurements of the decay of the ketenyl absorbance. The ketenes then form the amide enols 12, whose growth and decay are monitored by UV. Similar photolysis of diazoacetophenone leads to phenylketene (5), which forms the amide enol 17. For 3- and 4-pyridylketenes and for phenylketene, the ratios of rate constants for amination of the ketene and for conversion of the amide enol to the amide are 3.1, 7.7, and 22, respectively, while for the 2-isomer the same ratio is 1.8 x 10(7). The stability of the amide enol from 2-7 is attributed to a strong intramolecular hydrogen bond to the pyridyl nitrogen, and this is supported by the DFT calculated structures of the intermediates, which indicate this enol amide is stabilized by 12.8 kcal/mol relative to the corresponding amide enol from phenylketene. Calculations of the transition states indicate a 10.9 kcal/mol higher barrier for conversion of the 2-pyridyl amide enol to the amide as compared to that from phenylketene.
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Affiliation(s)
- Austin W Acton
- Department of Chemistry, University of Toronto, Toronto, Ontario, M5S 3H6 Canada
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16
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A theoretical study of the addition reactions of HF, H2O, H2S, NH3 and HCN to carbodiimide and related heterocumulenes. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s0166-1280(00)00515-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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17
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18
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Andraos J. Bimolecular Kinetics at Low Temperatures Using FTIR Matrix Isolation Spectroscopy: Some Caveats. Thermokinetic Parameters for the Reaction of Fulvenones with Pyridine in Pyridine Matrixes. J Phys Chem A 2000. [DOI: 10.1021/jp993648a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- John Andraos
- The University of Queensland, Department of Chemistry, Brisbane, Queensland, 4072 Australia
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19
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Nguyen MT, Raspoet G, Vanquickenborne LG. Contrasting mechanism of the hydration of carbon suboxide and ketene. A theoretical study. J PHYS ORG CHEM 2000. [DOI: 10.1002/(sici)1099-1395(200001)13:1<46::aid-poc195>3.0.co;2-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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20
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Abstract
New insights into the detailed mechanism of the hydration of ketene yielding acetic acid (H2C=C=O + H2O →> CH3COOH) were obtained by theoretical methods in both gas phase and solution. While gas phase calculations were performed using ab initio molecular orbital theory, bulk solvent effects were included using the self-consistent reaction field method (SCRF) and the polarizable continuum model (PCM). The hydration modeled by attack of water clusters containing two, three, and four water molecules confirms that a two-step addition of water to the ketene C=O bond, yielding a 1,1-enediol intermediate as initially demonstrated in 1984, is energetically, slightly but consistently, preferred over a concerted addition across the C=C bond leading directly to the acid product. Attempts to locate a zwitterion intermediate in solution were not successful. At least a cluster of three hydrogen-bonded water molecules is present in the gas phase supersystem to facilitate the proton transfer. Further incorporation of active water molecules in the catalytic water chain induces rather minor energetic improvements on the proton relay, which indicates a certain saturation of the cluster when reaching 3-4 water molecules. Effects of the surrounding solvent bulk do not change qualitatively the facts found in gas phase. The C=O addition mechanism is in better agreement with recent experimental developments in identifying enols of carboxylic acids than other mechanisms involving either a zwitterion or a direct C=C addition, as proposed for years in the literature.Key words: ketene, ketene hydration, hydration mechanism, solvent effect, ab initio calculations.
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22
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Chiang Y, Kresge AJ, Popik VV, Schepp NP. The Mandelic Acid Keto−Enol System in Aqueous Solution. Generation of the Enol by Hydration of Phenylhydroxyketene and Phenylcarboxycarbene. J Am Chem Soc 1997. [DOI: 10.1021/ja971774r] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Y. Chiang
- Contribution from the Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - A. J. Kresge
- Contribution from the Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - V. V. Popik
- Contribution from the Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - N. P. Schepp
- Contribution from the Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
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24
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Birney DM, Xu X, Ham S, Huang X. Chemoselectivity in the Reactions of Acetylketene and Acetimidoylketene: Confirmation of Theoretical Predictions. J Org Chem 1997; 62:7114-7120. [PMID: 11671814 DOI: 10.1021/jo971083d] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Acetylketene (1) was generated by flash pyrolysis of 2,2,6-trimethyl-4H-1,3-dioxin-4-one (6). The selectivities of 1 toward a number of representative functional groups were measured for the first time in a series of competitive trapping reactions. The trend in reactivities toward 1 follows the general order amines > alcohols >> aldehydes approximately ketones and can be rationalized by considering both the nucleophilicity and the electrophilicity of the reacting species. Alcohols show significant selectivity based on steric hindrance, with MeOH approximately 1 degrees > 2 degrees > 3 degrees. These selectivities are consistent with the activation energies and the pseudopericyclic transition structure previously calculated for the addition of water to formylketene. The results, presented here, of ab initio transition structure calculations for the addition of ammonia to formylketene are qualitatively consistent with the experimental trends as well. N-Propylacetacetimidoylketene (2) was generated by the solution pyrolysis of tert-butyl N-propyl-3-amino-2-butenoate (9a) and showed similar selectivity toward alcohols as opposed to ketones and similar steric discrimination toward alcohols. This is again in agreement with previous ab initio calculations. Taken together, these experimental trends in the reactivities of both 1 and 2 toward a variety of reagents provide strong, although indirect support for the planar, pseudopericyclic transition structures for these reactions which are predicted by ab initio calculations.
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Affiliation(s)
- David M. Birney
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061
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25
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Andraos J, Chiang Y, Kresge AJ, Popik VV. Flash Photolysis of 10-Diazo-9(10H)-phenanthrenone in Aqueous Solution. Hydration of Fluorenylideneketene and the Fluorene-9-carboxylic Acid Keto−Enol System. J Am Chem Soc 1997. [DOI: 10.1021/ja971381s] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- J. Andraos
- Contribution from the Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Y. Chiang
- Contribution from the Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - A. J. Kresge
- Contribution from the Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - V. V. Popik
- Contribution from the Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
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26
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Frey J, Rappoport Z. Generation and Detection of a Relatively Persistent Carboxylic Acid Enol2,2-Bis(2‘,4‘,6‘-triisopropylphenyl)ethene-1,1-diol. J Am Chem Soc 1996. [DOI: 10.1021/ja9601090] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Joseph Frey
- Contribution from the Department of Organic Chemistry, The Hebrew University, Jerusalem 91904, Israel
| | - Zvi Rappoport
- Contribution from the Department of Organic Chemistry, The Hebrew University, Jerusalem 91904, Israel
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