- ISOTOPE EFFECTS IN AROMATIZATION OF 1,4-DIHYDROBENZENE AND 1,4-DIHYDRONPHTHALENE WITH QUINONES
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Aromatization of 1,4-dihydronaphthalene with 2,3-dichloro-5,6-p-benzoquinone or chloranil is accompanied with kinetic isotope effects of 9.9 and 8.0 respectively.
- Mueller, P.,Joly, D.
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- Evidence for Concerted Transfer of Hydrogen from Tetralin to Coal Based on Kinetic Isotope Effects
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The H/D kinetic isotope effects for the reaction of subbituminous coal with tetralin-d12, tetralin-1,1,4,4-d4, and tetralin-2,2,3,3-d4 are respectively 3.7, 2.0, and 2.0.This pattern is consistent with concerted transfer of a pair of hydrogen atoms from the 1- and 2-positions.It does not result from exchange of hydrogen in unreacted tetralin and is difficult to explain as an anomalous secondary effect.The H/D kinetic isotope effects for 1,2-dihydronaphthalene-d10 and -1,1,3-d3 are 2.7 and 1.1.The latter appears to be a typical secondary effect.The rate determining step is thought to be transfer of a single hydrogen from the 2-position, probably as hydride ion.The activation volume for 1,2-dihydronaphthalene is -23mL mol.This result is consistent with the proposed mechanism or almost any other bimolecular mechanism.
- Brower, K.R.,Pajak, Janusz
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- Efficient H-D exchange of aromatic compounds in near-critical D2O catalysed by a polymer-supported sulphonic acid
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Hydrogen atom exchange of aromatic compounds in neutral near-critical D2O has been improved by using a polymer-supported sulphonic acid catalyst. Phenol, aniline, quinoline, and substituted aromatic hydrocarbons are selectively ring-perdeuterated in high yields with insignificant by-product formation at 325 °C for 24 h in D2O/Deloxan.
- Boix, Carmen,Poliakoff, Martyn
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- Arene-mercury complexes stabilized by gallium chloride: Relative rates of H/D and arene exchange
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We have previously proposed that the Hg(arene)2(GaCl4)2 catalyzed H/D exchange reaction of C6D6 with arenes occurs via an electrophilic aromatic substitution reaction in which the coordinated arene protonates the C6D6. To investigate this mechanism, the kinetics of the Hg(C6H5Me)2(GaCl4)2 catalyzed H/D exchange reaction of C6D6 with naphthalene has been studied. Separate second-order rate constants were determined for the 1- and 2-positions on naphthalene; that is, the initial rate of H/D exchange = k1i[Hg][C-H1] - k2i[Hg][C-H2]. The ratio of k1i/k2 ranges from 11 to 2.5 over the temperature range studied, commensurate with the proposed electrophilic aromatic substitution reaction. Observation of the reactions over an extended time period shows that the rates change with time, until they again reach a new and constant second-order kinetics regime. The overall form of the rate equation is unchanged: final rate = k1f[Hg][C-H1] + k2f[Hg][C-H2]. This change in the H/D exchange is accompanied by ligand exchange between Hg(C6D6)2(GaCl4)2 and naphthalene to give Hg(C10H8)2(GaCl4)2, that has been characterized by 13C CPMAS NMR and UV-visible spectroscopy. The activation parameters for the ligand exchange may be determined and are indicative of a dissociative reaction and are consistent with our previously calculated bond dissociation for Hg(C6H6)2(AlCl4)2. The initial Hg(arene)2(GaCl4)2 catalyzed reaction of naphthalene with C6D6 involves the deuteration of naphthalene by coordinated C6D6; however, as ligand exchange progresses, the pathway for H/D exchange changes to where the protonation of C6D6 by coordinated naphthalene dominates. The site selectivity for the H/D exchange is initially due to the electrophilic aromatic substitution of naphthalene. As ligand exchange occurs, this selectivity is controlled by the activation of the naphthalene C - H bonds by mercury.
- Branch, Catherine S.,Barron, Andrew R.
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- A deuterium perturbation upon electron transfer kinetics
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1H-NMR and X-band EPR were used to study the second-order rate constant for the electron transfer reactions involving naphthalene (C10H8) and perdeuterated naphthalene (C10D8) in the absence of ion association. In hexamethylphosphoramide the second-order rate constant for the intermolecular electron transfer from C10D8·- to C10D8 [(6.4 ± 0.2) × 108 M-1 s-1] is about 20% larger than it is for C10H8·- + C10H8 = C10H8 + C10H8·- (kH-H/ kD-D = 0.80). This is explained in terms of Marcus theory and the known 0.012 A? bond shortening that takes place when H is replaced by D in C10H8 and an estimated 0.02 A? bond shortening when H is replaced by D in C10H8·-. The rate constants for electron transfer from C10D8·- to C10H8 [(9.8 ± 0.1) × 108 M-1 s-1] and from C10H8·- to C10D8 (3.5 ± 0.6) × 108 M-1 s-1] show that the electron transfer rates increase as the donor naphthalene is deuterated and the acceptor is protonated.
- Stevenson, Cheryl D.,Rice, Charles V.
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- Heterolytic Oxidative Addition of sp2and sp3C-H Bonds by Metal-Ligand Cooperation with an Electron-Deficient Cyclopentadienone Iridium Complex
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Oxidative addition reactions of C-H bonds that generate metal-carbon-bond-containing reactive intermediates have played essential roles in the field of organometallic chemistry. Herein, we prepared a cyclopentadienone iridium(I) complex 1 designed for oxidative C-H bond additions. The complex cleaves the various sp2 and sp3 C-H bonds including those in hexane and methane as inferred from their H/D exchange reactions. The hydroxycyclopentadienyl(nitromethyl)iridium(III) complex 2 was formed when the complex was treated with nitromethane, which highlights this elementary metal-ligand cooperative C-H bond oxidative addition reaction. Mechanistic investigations suggested the C-H bond cleavage is mediated by polar functional groups in substrates or another iridium complex. We found that ligands that are more electron-deficient lead to more favorable reactions, in sharp contrast to classical metal-centered oxidative additions. This trend is in good agreement with the proposed mechanism, in which C-H bond cleavage is accompanied by two-electron transfer from the metal center to the cyclopentadienone ligand. The complex was further applied to catalytic transfer-dehydrogenation of tetrahydrofuran (THF).
- Higashi, Takuya,Kusumoto, Shuhei,Nozaki, Kyoko
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supporting information
p. 12999 - 13004
(2021/08/16)
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- METHOD FOR PREPARING DEUTERATED ORGARNIC COMPOUNDS AND DEUTERATED ORGARNIC COMPOUNDS PRODUCED BY THE SAME
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The present invention relates to a manufacturing method of a deuterated organic compound and a deuterated organic compound manufactured thereby. According to the manufacturing method of a deuterated organic compound, it is possible to provide a deuterated organic compound having an excellent deuterium conversion ratio. In addition, by using an aliphatic hydrocarbon solvent having 7 or more carbon atoms, it is possible to increase solubility of an organic compound, thereby increasing the deuterium conversion ratio.COPYRIGHT KIPO 2019
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Paragraph 0202-0205
(2019/08/21)
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- Iridium Hydride Complexes with Cyclohexyl-Based Pincer Ligands: Fluxionality and Deuterium Exchange
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Two hydride compounds with aliphatic pincer ligands, (PCyP)IrH2 (PCyP = {cis-1,3-bis[(di-tert-butylphosphino)methyl]cyclohexane}- (1) and (PCyP)IrH4 (2), have been studied, with emphasis on features where such systems differ from arene-based analogues. Both compounds reveal relatively rapid exchange between α-C-H and Ir-H, which can occur via formation of carbene or through demetalation, with nearly equal barriers. This observation is confirmed by deuterium incorporation into the α-C-H position. Complex 1 can reversibly add an N2 molecule, which competes with the α-agostic bond for a coordination site at iridium. The hydrogen binding mode in tetrahydride 2 is discussed on the basis of NMR and IR spectra, as well as DFT calculations. While the interpretation of the data is somewhat ambiguous, the best model seems to be a tetrahydride with minor contribution from a dihydrido-dihydrogen complex. In addition, the catalytic activity of 1 in deuterium exchange using benzene-d6 as a deuterium source is presented.
- Polukeev, Alexey V.,Marcos, Rocío,Ahlquist, M?rten S. G.,Wendt, Ola F.
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p. 2600 - 2608
(2016/09/04)
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- Equatorial preference in the C-H activation of cycloalkanes: GaCl 3-catalyzed aromatic alkylation reaction
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GaCl3 catalyzes the aromatic alkylation of naphthalene or phenanthrene using cycloalkanes. The C-C bond formation predominantly takes place at the least hindered positions of the substrates, and equatorial isomers regarding the cycloalkane moiety are generally obtained. The reaction of bicyclo[4.4.0]decane and naphthalene occurs at the 2-position of naphthalene and at the 2- or 3-carbons of the cycloalkane, and the products possess a trans configuration at the junctures and an equatorial configuration at the naphthyl groups. Notably, cis-bicyclo[4.4.0]decane turns out to be much more reactive than the trans isomer, and a turnover number "TON" up to 20 based on GaCl3 is attained. 1,2-Dimethylcyclohexane reacts similarly, and the cis isomer is more reactive than the trans isomer. Monoalkylcycloalkanes react at the secondary carbons provided that the alkyl group is smaller than tert-butyl. Adamantanes react at the tertiary 1-position. The alkylation reaction is considered to involve the C-H activation of cycloalkanes with GaCl3 at the tertiary center followed by the migration of carbocations and electrophilic aromatic substitution yielding thermodynamically stable products. The stereochemistry of the reaction reveals that GaCl 3 activates the equatorial tertiary C-H bond rather than the axial tertiary C-H bond.
- Yonehara, Fumi,Kido, Yoshiyuki,Sugimoto, Hiraku,Morita, Satoshi,Yamaguchi, Masahiko
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p. 6752 - 6759
(2007/10/03)
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- Chemically-induced discotic liquid crystals. Structural, studies with NMR spectroscopy
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The use of nuclear magnetic resonance (NMR) spectrometry for the structural studies of chemically-induced discotic liquid crystals was discussed. The synthesis of the phase inductor with two deutrons in the phenyl ring was accomplished in a single step using the catalytic exchange procedure. The reaction was quenched by the addition of 5 ml D2O, the organic layer was left to evaporate and 0.38 g of the product was obtained. The degree of deuteriation was found by proton NMR to be approximately 70%.
- Hughes,Luckhurst,Praefcke,Singer,Tearle
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p. 187 - 225
(2007/10/03)
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- Electron transfer catalyzed [2 + 2] cycloreversion of benzene dimers
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The catalysis of the [2 + 2] cycloreversion of the anti-o,o'-benzene dimer 1 and the syn-o,o'naphthalene-benzene dimer 2 through thermal and photoinduced electron transfer is studied using experimental and computational methods. The reaction of the radical cations formed by electron transfer is at least 105 times faster than the thermal background reaction. It is demonstrated that the photoinduced electron transfer catalyzed reaction proceeds via an electron transfer sensitized pathway and that the observed inverse secondary deuterium isotope effect of 0.91 ± 0.02 on the reaction is due to the equilibrium isotope effect on the electron transfer step. The relevance of these findings on the mechanism of the electron transfer catalyzed [2 + 2] cycloreversion of the biologically important cis,syn- cyclobutane-thymine dimer is also discussed.
- Reddy, Devi,Wiest, Olaf,Hudlicky, Tomas,Schapiro, Valeria,Gonzalez, David
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p. 2860 - 2863
(2007/10/03)
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- An N.M.R. Study of Electron Donor-Electron Acceptor Interaction Between Aromatic Hydrocarbons and Diazines
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Equilibrium constants have been measured by n.m.r. spectroscopy for the electron donor-electron acceptor interaction between a number of aromatic hydrocarbons and diazines.The values obtained have shown that the interaction is weak, and that the aromatic hydrocarbon acts as the electron donor and the diazine as the electron acceptor in the systems studied.Chemical-shift data have provided evidence for the relative positioning of the donor and acceptor components within the various complexes.The effect of temperature on the equilibrium constant for complex formation between (2H6)benzene and pyrazine has shown that the enthalpy of format ion is close to zero.
- Hurst, Derek T.,Thakrar, Usha B.,Wells, Clifford H. J.,Wyer, John
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p. 1313 - 1319
(2007/10/02)
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- Kinetic Isotope Effects and Pressure Effects in Several Hydrogen-Transfer Reactions of Tetralin and Related Compounds
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The H/D kinetic isotope effects and activation volumes have been measured for several hydrogen-transfer reactions using tetralin, dihydronaphthalenes, cyclohexa-1,4-diene, and cyclohexanol as donors.The isotope effects were found to exhibit different patterns for reactions of different mechanisms.They indicate whether hydrogen is in transit in the activated complex and show the number of atoms in transit (one or two).The KIE for the reaction of tetralin with quinones is consistent with concerted transfer of two hydrogens whereas the other reactions were found to be stepwise.The activation volumes lie within the range -23 to -33 mL/mol and do not seem to differetiate among bimolecular mechanisms.The relevance to previous studies of the KIE and ΔV(excit.) for coal hydrogenation reactions is discussed.
- Pajak, Janusz,Brower, K. R.
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p. 2210 - 2216
(2007/10/02)
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- Hydrogen-deuterium exchange and rearrangement of polycyclic aromatic hydrocarbons in dilute acid medium at elevated temperatures
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The high temperature-dilute acid (HTDA) method has been applied to the preparation of perdeuterated polycyclic aromatic hydrocarbons.Naphthalene (1), 1-methylnaphthalene(2), 2-methylnaphthalene (3), anthracene (4), phenanthrene (5), chrysene (6), pyrene (7), benzanthracene (8), benzopyrene (9), 1,1'-binaphthyl (10), 1,2'-binaphthyl (11), and 2,2'-binaphthyl (12) have been perdeuterated in high yield in dilute DCl-D2O solutions at elevated temperatures (240-280 deg C). 2, 3, 10, 11, and 12 also rearrange.
- Werstiuk, Nick Henry,Timmins, George
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p. 3218 - 3220
(2007/10/02)
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