1455-13-6Relevant articles and documents
Germanium(II) hydride mediated reduction of carbon dioxide to formic acid and methanol with ammonia borane as the hydrogen source
Jana, Anukul,Tavcar, Gasper,Roesky, Herbert W.,John, Michael
, p. 9487 - 9489 (2010)
LGeOC(O)H (3) (L = CH{(CMe)(2,6-iPr2C6H 3N)}2), from the straightforward conversion of LGeH (2) with CO2, reacts with LiH2NBH3 giving 2 and LiOC(O)H (4), while the corresponding reaction of 3 with H3NBH 3 after aqueous workup releases 2 and CH3OH (5). This opens the possibility to use hydride 2 as a mediator in the reduction of carbon dioxide to formic acid and methanol.
Philipson,Burwell
, p. 6125,6127 (1970)
Ion-molecule association of H3O+ and C2H2: Interstellar CH3CHO
Fairley, David A.,Scott, Graham B. I.,Freeman, Colin G.,Maclagan, Robert G. A. R.,McEwan, Murray J.
, p. 1305 - 1309 (1996)
The C2H2 · H3O+ product of the ion-molecule association reaction between H3O+ and C2H2 is found to consist of a ca. 50 : 50 mixture of two isomeric ions. These two isomeric ions are identified in a selected ion flow tube, by their different proton transfer behaviour with the neutral reagents C2H5Br, 4-fluorotoluene, CH3OH and benzene, as protonated vinyl alcohol, CH2CHOH2+ and either protonated acetaldehyde, CH3CHOH+ or the electrostatic complex H3O+ · C2H2. These conclusions are supported by Gaussian G2 level calculations based on ab initio molecular orbital theory, which are applied to calculate the proton affinities of CH3CHO, CH2CHOH, oxirane and acyclic CH2OCH2. Reaction rate coefficients and product ratios are also reported for the reactions of specific C2H5O+ isomers, viz: CH3CHOH+, CH3OCH2+ and CH2OHCH2+ with CH3OH, 4-fluorotoluene and C6H6. The implications of the current results to the interstellar synthesis of CH3CHO are discussed briefly.
The Methyldiazonium Ion in Water: Competition Between Hydrolysis and Proton Exchange
Smith, Richard H.,Koepke, Steven R.,Tondeur, Yves,Denlinger, Cheryl L.,Michejda, Christopher J.
, p. 936 - 937 (1985)
The methyldiazonium ion, generated from four different precursors, was found to undergo proton exchange with deuteriated phosphate buffer solutions.
Formation of HCOH + H2 through the Reaction CH3 + OH. Experimental Evidence for a Hitherto Undetected Product Channel
Humpfer, Robert,Oser, Harry,Grotheer, Horst-Henning
, p. 577 - 596 (1995)
In an extension of our earlier studies at lower temperatures the title reaction was measured directly in a flow reactor at temperatures of 600 and 700 K.The pressure of 0.65 mb was chosen that low in order to reduce the contribution of the stabilization channel.OH was used in an excess over CH3.Both reactants along with the reaction products were monitored by mass spectrometry.CH3 profiles served as the major observable quantity for the extraction of rate data.This had to be done by using computer simulation since it was impossible to work under pseudo-first-order conditions.The obtained total rate coefficients were divided into channel rate coefficients by means of branching ratios as determined by the mass spectrometric measurement of the reaction products.For CH3 + OH, this led to a rate coefficient, k1a into the stabilization channel, and another one, k1e+f referring to the sum of two H2-eliminating channels yielding the biradical HCOH and to a minor extent H2CO.These latter channels have not been measured before.In order to distinguish between them we switched over from OH to OD to get (1'e) CH3 + OD -> HCOD + H2, (1'f) -> H2CO + HD so that the biradical and/or aldehyde channels could be determined by their by-products H2 and HD, respectively.The use of OD makes it also possible to measure the channel (1'd) CH3 + OD -> 1CH2 + HDO through its by-product, HDO.A comparison of the rate coefficients of both systems, i.e., CH3 + OH and CH3 + OD, indicates that within our error limits no significant isotope effect takes place.For the rate coefficient into the HCHO channel, we arrive at a preliminary Arrhenius expression in units of cm, molec, and s: k1e = 9.1*10-11 exp(-1500/T).The H2CO channel could not be detected at our lower temperature rendering us with a rate coefficient at 700 K: k1f(700 K) = 1.7*10-12.Since simulation is needed for the deduction of the total rate coefficients as well as of the branching ratios, an uncertainty factor of 1.5 has to be attributed to these numbers.
CO2 and CO/H2 Conversion to Methoxide by a Uranium(IV) Hydride
Falcone, Marta,Scopelliti, Rosario,Mazzanti, Marinella
, p. 9570 - 9577 (2019)
Here we show that a scaffold combining siloxide ligands and a bridging oxide allows the synthesis and characterization of the stable dinuclear uranium(IV) hydride complex [K2{[U(OSi(OtBu)3)3]2(μ-O)(μ-H)2}], 2, which displays high reductive reactivity. The dinuclear bis-hydride 2 effects the reductive coupling of acetonitrile by hydride transfer to yield [K2{[U(OSi(OtBu)3)3]2(μ-O)(μ-κ2-NC(CH3)NCH2CH3)}], 3. Under ambient conditions, the reaction of 2 with CO affords the oxomethylene2- reduction product [K2{[U(OSi(OtBu)3)3]2(μ-CH2O)(μ-O)}], 4, that can further add H2 to afford the methoxide hydride complex [K2{[U(OSi(OtBu)3)3]2(μ-OCH3)(μ-O)(μ-H)}], 5, from which methanol is released in water. Complex 2 also effects the direct reduction of CO2 to the methoxide complex 5, which is unprecedented in f element chemistry. From the reaction of 2 with excess CO2, crystals of the bis-formate carbonate complex [K2{[U(OSi(OtBu)3)3]2(μ-CO3)(μ-HCOO)2}], 6, could also be isolated. All the reaction products were characterized by X-ray crystallography and NMR spectroscopy.
Transition state modeling and catalyst design for hydrogen bond-stabilized enolate formation
Zhu, Yimin,Drueckhammer, Dale G.
, p. 7755 - 7760 (2005)
A catalyst for enolate formation was designed that incorporates an amine base along with a thiourea to bind to the oxygen atom of the substrate and enolate through hydrogen bonding. A computational model of the transition state was developed in which the thiourea (modeled initially as a urea) and amine were separate molecules. This model and models incorporating one or two methanol molecules in place of the urea showed an out-of-plane hydrogen bond, apparently to the carbonyl π-bond, in addition to an in-plane hydrogen bond to an unshared electron pair. In contrast, optimized complexes of the ketone and the fully formed enolate showed only in-plane hydrogen bonding. The transition state model with the urea and amine was used to define a database search with the computer program CAVEAT to identify structures suitable for linking the amine and urea/thiourea moieties in the transition state. On the basis of a group of structures identified from this search, a flexible but conformationally biased linker was designed to connect the two catalytic moieties. The molecule having the amine and thiourea moieties connected by this linker was synthesized and was shown to catalyze proton exchange between methanol and deuterated acetone. The catalyst was about 5-fold more efficient than the amine and thiourea as separate molecules and relative to a similar but less conformationally biased catalyst.
Reactions of 1,2-Oxaphospholene 2-Oxides. 6. Free-Radical and Nucleophilic Substitution at C5: Anomalous Proton-Transfer Behavior of Cyclic Ketals
Rardon, Daniel,Macomber, Roger S.
, p. 1493 - 1499 (1990)
The free-radical bromination of 3,5-di-tert-butyl-2-hydroxy-1,2-oxaphosphol-3-ene 2-oxide (1b) with N-bromosuccinimide (NBS) gave the corresponding 5-bromo-3,5-di-tert-butyl-2-hydroxy-1,2-oxaphosphol-3-ene 2-oxide (3) in good yield.Bromide 3 was extremely labile and could not be purified rigorously, but it readily underwent methanolysis to give 3,5-di-tert-butyl-2-hydroxy-5-methoxy-1,2-oxaphosphol-3-ene 2-oxide (7) or hydrolysis to 3,5-di-tert-butyl-2,5-dihydroxy-1,2-oxaphosphol-3-ene 2-oxide (8), both crystalline compounds.Compounds 7 and 8, though somewhat less reactive than 3, were readily interconverted.Treatment of 8 with diazomethane led to dimethyl (Z)-2,2,6,6-tetramethyl-3-oxohept-4-en-5-ylphosphonate (10), indicating that 8 is in equilibrium with its open phosphonic acid isomer.Ketal 7 underwent methoxy exchange at 35.5 deg C with a first-order rate constant of 0.075 m-1, and the rate was only slightly increased by a large excess of trifluoroacetic acid.The conjugate base of 7 did not undergo exchange.By contrast, 3,5-di-tert-butyl-2,5-dimethoxy-1,2-oxaphosphol-3-ene 2-oxide (11), the methyl ester of 7, was totally inert toward methoxy exchange except in the presence of excess HBr at high temperature for extended periods.The contrasting solvolytic behavior of 7 and 11 under acidic conditions has been interpreted as evidence for an intramolecular proton transfer from an oxygen on phosphorus to the nucleofuge.Ketal-ester 11 underwent slow ring opening in base, which was immediately reversed upon neutralization.The methyl ester (1c) of 1b, the 4-bromo derivative (1d) of 1b, and its methyl ester (1e) all undergo similar reactions with NBS.However, 4,5-dibromide 20 was anomalously unreactive toward nucleophilic substitution.
Comparison of ΔG°Acid (gas phase) and kinetic acidities measured in methanolic sodium methoxide
Koch, Heinz F.,Biffinger, Justin C.,Mishima, Masaaki,Mustanir,Lodder, Gerrit
, p. 614 - 617 (1998)
Hydron exchange rates, kexc (M-1s-1), using methanolic sodium methoxide were compared with ΔG°Acid, (kcal mol-1) (gas phase) for 9-phenylfluorene, C6H5CH(CF3)2, m-CF3C6H4CH(CF3)2, p-CF3C6H4CHClCF3, m-CF3C6H4CHClCF3, 3,5-(CF3)2C6H3CHClCF3, fluorene and C6F5H. There is a good linear correlation for p-CF3C6H2CHClCF3, m-CF3C6H4CHClCF3 and 3,5-(CF3)2C6H3CHClCF3, with the others falling off the line. The fluorinated benzyl compounds and pentafluorobenzene have near-unity isotope effects and therefore differ from the fluorenyl compounds. Although the acidity and the exchange rates for three of the compounds [9-phenylfluorene, C6H5CH(CF3)2 and p-CF3C6H4CHClCF3] are similar, the important proton-transfer step to form a hydrogen-bonded carbanion intermediate and the subsequent breaking of that weak bond to form a free carbanion in methanol differ significantly for the fluoernyl compound compared with the two fluorinated benzylic compounds.
Cobalt catalysed reduction of CO2via hydroboration
Tamang, Sem Raj,Findlater, Michael
, p. 8199 - 8203 (2018/07/10)
We report an operationally convenient reduction of CO2 to methanol via cobalt catalysed hydroboration which occurs under mild reaction conditions. Addition of NaHBEt3 to Co(acac)3 generates an active hydroboration catalyst, which is proposed to be a “Co-H” species on the basis of infrared spectroscopy. The reduction of CO2 in the presence of various boranes showed that BH3·SMe2 afforded near quantitative conversion (98% NMR yield) to methanol upon hydrolysis.
Aqueous phase hydrodeoxygenation of polyols over Pd/WO3-ZrO2: Role of Pd-WO3 interaction and hydrodeoxygenation pathway
Liu, Changjun,Sun, Junming,Brown, Heather M.,Marin-Flores, Oscar G.,Bays, J. Timothy,Karim, Ayman M.,Wang, Yong
, p. 103 - 109 (2016/05/11)
Aqueous phase processing of biomass derived sugar alcohols is one of the promising routes to convert biomass into fuels and chemicals. Bifunctional catalysts are critical in the aqueous phase hydrodeoxygenation of sugar alcohol. Understanding the interaction between metal and acidic metal oxides as well as the hydrodeoxygenation pathways will help develop more efficient bifunctional catalysts. Here, tungstated zirconia supported palladium catalysts were prepared and further characterized using nitrogen sorption, X-ray diffraction, FT-IR analysis of adsorbed pyridine, CO chemisorption and diffuse reflectance UV-vis. Strong interaction between palladium and WO3 in addition to a synergetic effect of the acidic and metallic sites were found to promote the aqueous phase hydrodeoxygenation of ethylene glycol. H-D exchange experiments using 13C{1H} NMR spectroscopy confirmed that the aqueous phase hydrodeoxygenation follows a dehydration-hydrogenation pathway. The hydrogenation of the dehydration products shifts the dehydration-hydration equilibrium toward the dehydration pathway and leads to highly selective C-O cleavage.
