- Synthesis and Reduction of 2,2-diaryl-1-nitroethylenes by using a chiral and a non chiral NADH model in the pyrrolopyridine series
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Reduction of 2,2-diphenyl-1-nitroethylene (1) and 2-(2-pyridyl)-2-phenyl-1-nitroethylene (5) is achieved by using the NADH model in the pyrrolopyridine series 2a to give 2,2-diphenyl-1-nitroethane (3) and 2-(2-pyridyl)-2-phenyl-1-nitroethane (7) respectively in 40% yield. The asymmetric reduction of 2-(2-pyridyl)-2-phenyl-1-nitroethylene by the chiral NADH model 2b is studied. Thus, 2-(2-pyridyl)-2-phenyl-1-nitroethane (7) is obtained in 15 to 32% yield. The stereocontrol of the reduction proved to be dependent on the amount of magnesium ions.
- Levacher, Vincent,Valque, Claude,Coupa, Sophie,Dupas, Georges,Queguiner, Guy,Bourguignon, Jean
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- Chemical Ionization Mass Spectrometry of Doxylamine and Related Compounds
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The chemical ionization mass spectrometric (CIMS) analysis of doxylamine, N,N-dimethyl-2-ethanamine, and related compounds, using both ammonia and methane as reagent gases, is discussed.The two reagent gases did not produce the same major fragment ion for doxylamine.Mechanisms for the fragmentation of doxylamine under either ammonia or methane CIMS conditions are proposed.The mechanisms explain the obsrevation of an m/z 182 fragment ion for doxylamine analyzed under methane CIMS conditions and an m/z 184 product ion detected under ammonia CIMS conditions.
- Korfmacher, Walter A.,Holder, Claude L.,Freeman, James P.,Mitchum, Ronald K.,Gosnell, Aubrey B.
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- Reactivity Diversification - Synthesis and Exchange Reactions of Cobalt and Iron 2-Alkenylpyridine/-pyrazine Complexes Obtained by Vinylic C(sp2)-H Activation
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Abstract The reactivity of 2-alkenylpyridine derivatives with trimethylphosphane-supported iron- and cobalt-methyl adducts were investigated and provided a series of C,N-cyclometalated complexes through smooth vinyl C(sp2)-H activation. The rea
- Beck, Robert,Camadanli, Sebnem,Fl?rke, Ulrich,Klein, Hans-Friedrich
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- Photoenzymatic Hydrogenation of Heteroaromatic Olefins Using ‘Ene’-Reductases with Photoredox Catalysts
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Flavin-dependent ‘ene’-reductases (EREDs) are highly selective catalysts for the asymmetric reduction of activated alkenes. This function is, however, limited to enones, enoates, and nitroalkenes using the native hydride transfer mechanism. Here we demonstrate that EREDs can reduce vinyl pyridines when irradiated with visible light in the presence of a photoredox catalyst. Experimental evidence suggests the reaction proceeds via a radical mechanism where the vinyl pyridine is reduced to the corresponding neutral benzylic radical in solution. DFT calculations reveal this radical to be “dynamically stable”, suggesting it is sufficiently long-lived to diffuse into the enzyme active site for stereoselective hydrogen atom transfer. This reduction mechanism is distinct from the native one, highlighting the opportunity to expand the synthetic capabilities of existing enzyme platforms by exploiting new mechanistic models.
- Biegasiewicz, Kyle F.,Black, Michael J.,Chung, Megan M.,Hyster, Todd K.,Meichan, Andrew J.,Nakano, Yuji,Sandoval, Braddock A.,Zhu, Tianyu
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p. 10484 - 10488
(2020/04/29)
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- A compound including phenmethyl phenmethyl hydrogen official functional modification of carbon-carbon double bond or carbonyl method (by machine translation)
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The present invention discloses a compound including phenmethyl phenmethyl hydrogen official functional modification of carbon-carbon double bond or carbonyl of the method, the method is under protective atmosphere, including phenmethyl compound and dimethyl sulfoxide, in the ammonium persulfate and sodium methoxide in the presence of a pot of reaction, to obtain a styrene derivative; or, under the environment of air, including phenmethyl compound and dimethyl sulfoxide, in potassium sulfate and sodium methoxide in the presence of a pot of reaction, to obtain the decoloring derivatives; the method in metallic catalytic, moderate reaction conditions by a one-step reaction in including phenmethyl compound on the phenmethyl hydrogen yield, high selectivity modifying carbon-carbon double bond or carbonyl, simple steps, the procedure is short, low cost, and is favorable for industrial production. (by machine translation)
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Paragraph 0043; 0044; 0048
(2018/03/24)
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- Catalytic Enantioselective Synthesis of α-Chiral Azaheteroaryl Ethylamines by Asymmetric Protonation
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The direct enantioselective synthesis of chiral azaheteroaryl ethylamines from vinyl-substituted N-heterocycles and anilines is reported. A chiral phosphoric acid (CPA) catalyst promotes dearomatizing aza-Michael addition to give a prochiral exocyclic aryl enamine, which undergoes asymmetric protonation upon rearomatization. The reaction accommodates a broad range of N-heterocycles, nucleophiles, and substituents on the prochiral centre, generating the products in high enantioselectivity. DFT studies support a facile nucleophilic addition based on catalyst-induced LUMO lowering, with site-selective, rate-limiting, intramolecular asymmetric proton transfer from the ion-paired prochiral intermediate.
- Xu, Chao,Muir, Calum W.,Leach, Andrew G.,Kennedy, Alan R.,Watson, Allan J. B.
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supporting information
p. 11374 - 11377
(2018/08/28)
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- A Lewis Base Catalysis Approach for the Photoredox Activation of Boronic Acids and Esters
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We report herein the use of a dual catalytic system comprising a Lewis base catalyst such as quinuclidin-3-ol or 4-dimethylaminopyridine and a photoredox catalyst to generate carbon radicals from either boronic acids or esters. This system enabled a wide range of alkyl boronic esters and aryl or alkyl boronic acids to react with electron-deficient olefins via radical addition to efficiently form C?C coupled products in a redox-neutral fashion. The Lewis base catalyst was shown to form a redox-active complex with either the boronic esters or the trimeric form of the boronic acids (boroxines) in solution.
- Lima, Fabio,Sharma, Upendra K.,Grunenberg, Lars,Saha, Debasmita,Johannsen, Sandra,Sedelmeier, Joerg,Van der Eycken, Erik V.,Ley, Steven V.
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p. 15136 - 15140
(2017/11/20)
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- β-Selective Reductive Coupling of Alkenylpyridines with Aldehydes and Imines via Synergistic Lewis Acid/Photoredox Catalysis
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Umpolung (polarity reversal) strategies of aldehydes and imines have dramatically expanded the scope of carbonyl and iminyl chemistry by facilitating reactions with non-nucleophilic reagents. Herein, we report the first visible light photoredox-catalyzed β-selective reductive coupling of alkenylpyridines with carbonyl or iminyl derivatives with the aid of a Lewis acid co-catalyst. Our process tolerates complex molecular scaffolds (e.g., sugar, natural product, and peptide derivatives) and is applicable to the preparation of compounds containing a broad range of heterocyclic moieties. Mechanistic investigations indicate that the key step involves single-electron-transfer reduction of aldehydes or imines followed by the addition of resulting ketyl or α-aminoalkyl radicals to Lewis acid-activated alkenylpyridines.
- Lee, Katarzyna N.,Lei, Zhen,Ngai, Ming-Yu
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p. 5003 - 5006
(2017/05/04)
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- Palladium-Catalyzed Divergent Arylation with Triazolopyridines: One-Pot Synthesis of 6-Aryl-2-α-styrylpyridines
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We have developed a new strategy for palladium-catalyzed arylation reactions with triazolopyridines, wherein two different chemical transformations (C-3 vs. C-7) are observed by differentiating the substrates using different bases. The reactive palladium carbenoids were directly generated from triazolopyridines and underwent denitrogenative arylations with aryl bromides. Intriguingly, when potassium carbonate was replaced with potassium tert-butoxide, direct C-H arylation occurred at the most acidic position (C-7). Moreover, two different catalytic arylation events were successfully performed in a one-pot sequence, providing a convenient access to 6-aryl-2-α-styrylpyridines.
- Moon, Youngtaek,Kwon, Soonhyung,Kang, Dahye,Im, Honggu,Hong, Sungwoo
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p. 958 - 964
(2016/04/05)
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- Manganese-Catalyzed Direct Nucleophilic C(sp2)-H Addition to Aldehydes and Nitriles
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Herein, a manganese-catalyzed nucleophilic addition of inert C(sp2)-H bonds to aldehydes and nitriles is disclosed by virtue of a dual activation strategy. The reactions feature mild reaction conditions, excellent regio- and stereoselectivity, and a wide substrate scope, which includes both aromatic and olefinic C-H bonds, as well as a large variety of aldehydes and nitriles. Moreover, mechanistic studies shed light on possible catalytic cycles.
- Zhou, Bingwei,Hu, Yuanyuan,Wang, Congyang
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p. 13659 - 13663
(2015/11/16)
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- Copper-catalyzed α-methylenation of benzylpyridines using dimethylacetamide as one-carbon source
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The direct α-methylenation of benzylpyridines was achieved using N,N-dimethylacetamide (DMA) as a one-carbon source under copper catalysis. An intermediary species was detected at an early stage, and a possible mechanism was proposed. Additionally, α-oxygenation and dimerization of benzylpyridines could also be performed efficiently.
- Itoh, Masaki,Hirano, Koji,Satoh, Tetsuya,Miura, Masahiro
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supporting information
p. 2050 - 2053
(2014/05/06)
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- Copper-catalysed oxidative Csp3-H methylenation to terminal olefins using DMF
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A copper-catalysed direct oxidative Csp3-H methylenation to terminal olefins using DMF as one carbon source was developed. In this reaction, various functional groups were well tolerated, thus providing a simple way to construct arylvinylketones and arylvinylpyridines. The preliminary mechanistic investigations revealed that CH2 was from DMF (N-CH3).
- Liu, Jianming,Yi, Hong,Zhang, Xin,Liu, Chao,Liu, Ren,Zhang, Guoting,Lei, Aiwen
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supporting information
p. 7636 - 7638
(2014/07/08)
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- Ring-closing metathesis reactions on azinium salts: Straightforward access to quinolizinium cations and their dihydro derivatives
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(Chemical Equation Presented) The ring-closing metathesis reaction of 1-butenyl-2-vinylpyridinium salts and 2-butenyl-1-vinylpyridinium salts using Grubbs second generation and Hoveyda-Grubbs catalysts proved to be an efficient approach to 3,4-dihydro- and 1,2-dihydroquinolizinium salts and the corresponding quinolizinium derivatives by an improved thermal oxidation in the presence of Pd/C without solvent. A comparative study showed that the quinolizinium system was obtained in better yields through the 3,4-dihydroquinolizinium route, thus allowing the synthesis of quinolizinium derivatives or improvements in the yields of some examples reported previously.
- Nunez, Ana,Abarca, Beatriz,Cuadro, Ana M.,Alvarez-Builla, Julio,Vaquero, Juan J.
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supporting information; experimental part
p. 4166 - 4176
(2009/09/08)
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- A strategy for C-H activation of pyridines: Direct C-2 selective alkenylation of pyridines by Nickel/Lewis acid catalysis
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The C-2 selective alkenylation of pyridine derivatives is achieved with a catalyst consisting of nickel and Lewis acid. Use of diorganozinc compounds as the Lewis acid catalyst gives C-2 monoalkenylation products, whereas AlMe3 changes the reaction course to afford C-2 dienylated products, which are derived from double insertion of alkynes into the C(2)-H bond. The reaction demonstrates a broad substrate scope and proceeds with high chemo-, regio-, and stereoselectivities under mild conditions compared with previous examples of direct C-H functionalization of pyridines. Copyright
- Nakao, Yoshiaki,Kanyiva, Kyalo Stephen,Hiyama, Tamejiro
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p. 2448 - 2449
(2008/09/20)
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- Synthesis and activity studies of analogues of the rat selective toxicant norbormide
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Norbormide [5-(α-hydroxy-α-2-pyridylbenzyl)-7-(α-2-pyridylbenzylidene)-5-norbornene-2,3-dicarboximide] (NRB, 1), an existing but infrequently used rodenticide, is known to be uniquely toxic to rats but relatively harmless to other rodents and mammals. A series of NRB-related analogues were prepared to investigate the structural features responsible for, and the in vitro biological markers indicative of, in vivo lethality of the parent molecule in rats. Their synthesis and biological evaluation (vasoconstriction, vasodilation, mitochondrial dysfunction, cardiotoxicity and lethality) is described.
- Rennison, David,Bova, Sergio,Cavalli, Maurizio,Ricchelli, Fernanda,Zulian, Alessandra,Hopkins, Brian,Brimble, Margaret A.
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p. 2963 - 2974
(2008/02/01)
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- Oxime-Derived Palladium Complexes as Very Efficient Catalysts for the Heck-Mizoroki Reaction
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Oxime-derived, chloro-bridged palladacycles 16 are efficient complexes for the Heck vinylation of aryl halides. The isolated catalysts are thermally stable, not sensitive to air or moisture and easily accessible from inexpensive starting materials. The reaction can be performed under aerobic conditions, with aryl iodides, bromides and chlorides with acrylic esters and olefins displaying turnover numbers (TON) of up to 1010 for phenyl iodide and turnover frequencies (TOF) of 1.4 × 108 h-1. Deactivated aryl bromides undergo the Heck reaction with styrene with TON and TOF values up to 97,000 and 6063 h-1, respectively. Even aryl chlorides undergo the coupling reaction with olefins with TON up to 920. Complexes 16 catalyze the synthesis of 2,3-disubstituted indenones and indoles in good yields via annulation reaction of internal alkynes with o-bromoor o-chlorobenzaldehyde and o-iodoaniline, respectively.
- Alonso, Diego A.,Najera, Carmen,Pacheco, Ma. Carmen
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p. 172 - 183
(2007/10/03)
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- α-oxygen-atom induced methylenation of ketones by CH2(ZnI)2
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Ketones bearing a hetero-atom at α-position were methylenated selectively by CH2(ZnI)2 to give allylic alcohols; a nucleophilic attack of the zinc species was accelerated with a coordination of a hetero-atom at α-position.
- Ukai,Arioka,Yoshino,Fushimi,Oshima,Utimoto,Matsubara
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p. 513 - 514
(2007/10/03)
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- Highly asymmetric dihydroxylation of 1-aryl-1'-pyridyl alkenes
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The asymmetric dihydroxylation of 1-aryl-1'-pyridyl alkenes afforded the diols in high yield and excellent enantioselectivity. (C) 2000 Published by Elsevier Science Ltd.
- Wang, Xin,Zak, Mark,Maddess, Mathew,O'Shea, Paul,Tillyer, Richard,Grabowski,Reider, Paul J.
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p. 4865 - 4869
(2007/10/03)
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- Electrophilic activation of acetyl-substituted heteroaromatic compounds
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The chemistry of acetyl-substituted pyridines, thiazoles, quinoline, isoquinolines, and pyrazine (1-9 and 28) has been studied. These heteroarenes (1-8) condense with benzene in good yields (74-96%) in the Bronsted superacid, CF3SO3H (triflic acid). In these acid-catalyzed hydroxyalkylation reactions, compounds 1-8 are significantly more reactive than acetophenone. It is proposed that compounds 1-8 readily form dicationic electrophiles in triflic acid.
- Klumpp,Garza,Sanchez Jr.,Lau,De Leon
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p. 8997 - 9000
(2007/10/03)
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- On the stille vinylation reactions with α-styryltrimethyltin
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Stille vinylation reactions involving α-styryltrimethyltin 3b and a series of chloro- or bromo-pyridine derivatives are described. In contrast to the rare cine selectivity observed with iodobenzene 10a or 3-iodotoluene 10b, reactions between vinyltin 3b and a series of 2-halopyridine derivatives 15(a-d) yield 1,1-disubstituted ipso-coupled olefins 16(a-d) as the predominant products.
- Chen, Shu-Hui
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p. 4741 - 4744
(2007/10/03)
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- Flash Vacuum Pyrolysis of Substituted Pyridine N-Oxides and Its Application to Syntheses of Heterocyclic Compounds
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Flash vacuum pyrolysis of 2-picoline N-oxide gave 2-picoline, pyridine, 2-ethylpyridine, 2-vinylpyridine, 2-pyridylmethanol, bis(2-pyridyl)methane, 1,2-bis(2-pyridyl)ethane, and 1,2-bis(2-pyridyl)ethylene.These reactions are explained by intermediary participation of the 2-picolyl radical.Flash vacuum pyrolysis of methyl-substituted 2-benzylpyridine N-oxides led to methyl-substituted pyridoindoles or to benzoquinoline in moderate yields.
- Ohsawa, Akio,Kawaguchi, Takayuki,Igeta, Hiroshi
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p. 3497 - 3503
(2007/10/02)
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- FLASH VACUUM PYROLYSIS OF 2-BENZYLPYRIDINE N-OXIDES. SYNTHESIS OF METHYLPYRIDOINDOLES
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Flash vacuum pyrolysis of 2-benzylpyridine N-oxides afforded pyridoindole and its various methyl-substituted derivatives in moderate yields.Benzoquinoline in the pyrolyses of 2-(o-methylbenzyl)pyridine N-oxide and 2-benzyl-3-methylpyridine N-oxide, and 2-(β-styryl)pyridine in the reaction of 2-(β-phenethyl)pyridine N-oxide were major products as exceptional cases.
- Ohsawa, Akio,Kawaguchi, Takayuki,Igeta, Hiroshi
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p. 1737 - 1738
(2007/10/02)
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- Kinetic Energy Release and Position of Transition State during Intramolecular Aromatic Substitution in Ionized 1-Phenyl-1-(2-pyridyl)ethylenes
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The loss of substituents (X = H, CH3, Cl, Br, I) from the molecular ions of ortho-substituted 1-phenyl-1-(2-pyridyl)ethylenes 1a-f and of the isomeric 1-phenyl-1-(3-pyridyl)- and 1-phenyl-1-(4-pyridyl)ethylenes 2 and 3 has been investigated.Cyclic fragment ions a are formed from the ortho-substituted 1-phenyl-1-(2-pyridyl)ethylene molecular ions by an intramolecular aromatic substitution reaction.The energetic requirements of this reaction have been studied in dependence from the dissociation energy of the C-X bond by measurements of the ionization energies, appearance energies, and kinetic energies released during the reaction.The activation energy εh of the process varies only slightly with the dissociation energy of the C-X bond cleaved during the reaction, whereas the entalpy of reaction changes from positive (endothermic) to very negative (exothermic) values in the reaction series 1a-f.Consequently the reverse activation energy εr ranges from small to very large values in this series.This trend in εr is not followed by the kinetic-energy release.A large kinetic-energy release and energy partitioning quotient q = 0.7 - 1.0 is only observed for endothermic or thermoneutral processes, while a small kinetic-energy release and q ca. 0.2 is associated with exothermic reactions in spite of a large εr.This behavior has been correlated to the position Xo* of the transition state on the reaction coordinate according to Miller's quantification of the Hammond postulate.The release of εr as kinetic energy is only observed for reactions with "symmetrical" or "late" transition states (Xo* > 0.4) while most of εr remains as internal energy in the products of reactions with "early" transition states (Xo* 0.4).
- Schubert, Ralf,Gruetzmacher, Hans-Friedrich
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p. 5323 - 5328
(2007/10/02)
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