- Online ATR-IR investigations and mechanistic understanding of the carbonylation of epoxides - The selective synthesis of lactones or polyesters from epoxides and CO
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In situ ATR-IR spectroscopy is applied as a powerful tool to study the factors that control the reaction of epoxides with carbon monoxide in the presence of [Lewis acid]+ [Co(CO)4]- salts. Based on these investigations, a consistent mechanistic scheme is presented, comprising the main lactone and polyester products and minor components, e.g., acetone and crotonic acid derivatives. β-Alkoxy-acyl-cobalttetracarbonyl species are shown to be key intermediates from which two reaction routes start in dependence of the applied Lewis acid (LA). Labile LA-alkoxy combinations favor a backbiting process of the oxygen function on the Co-acyl bond, primarily producing lactone products. More stable LA-alkoxy entities are unreactive toward PO conversion and afford a polymerization reaction after the addition of a nucleophile. In that case, the Lewis acid remains bonded to the chain end.
- Allmendinger, Markus,Zintl, Manuela,Eberhardt, Robert,Luinstra, Gerrit A.,Molnar, Ferenc,Rieger, Bernhard
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- Selective catalytic oxidation of glycerol to dihydroxyacetone
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High selectivity and high yield characterize the oxidation of glycerol into dihydroxyacetone using catalyst 1, with benzoquinone or air as the oxidant. The mechanism proposed involves reversible palladium-alkoxide formation with the turnover-limiting reoxidation of the palladium complex. Copyright
- Painter, Ron M.,Pearson, David M.,Waymouth, Robert M.
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- Acid-Catalyzed Enolization and Aldol Condensation of Acetaldehyde
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The condensation of acetaldehyde (1) to an equilibrium mixture of aldol (2) and crotonaldehyde (3) is second order in 1.An excess acidity analysis reveals that a water molecule is also involved in the rate-limiting step; the reaction is actually the base-assisted addition of vinyl alcohol to protonated 1, even in concentrated H2SO4.A previous report of a kinetically first-order conversion of 1 to 3 is shown to be due to the presence of a fast-reacting oligomer of 1.The reaction of 1 in D2SO4 leads to partially deuterated 3, a result ascribed to partial conversion of vinyl alcohol to deuterated 1.Hydrogen isotop exchange of 3 was also observed, but at a slower rate.The rates of enolization of 1 were studied by iodination and are consistent with previous results and the proposed mechanism.The interconversion of 2 and 3 is shown to proceed via the enol of 2; in this case the rate-limiting step is water attack on/water loss from protonated 3/2, not proton transfer at carbon.
- Baigrie, Lynn M.,Cox, Robin A.,Slebocka-Tilk, Henryka,Tencer, Michal,Tidwell, Thomas T.
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- Conversion of diols by dehydrogenation and dehydration reactions on silica-supported copper catalysts
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The gas-phase conversion of a 1,3-polyol (1,3-butanediol) containing primary and secondary OH functions was studied on a series of copper-silica catalysts, ZCuSiO2 (Z = 1-25 wt.% Cu), and thoroughly characterized by several techniques such as BET surface area, TPR, XRD, N2O chemisorption, and UV-vis-DRS. The physicochemical properties of the ZCuSiO 2 catalysts depended on whether the metal loading was above or below the copper monolayer surface coverage (Z = 13.5 wt.% Cu). Copper species presenting different degrees of interaction with the silica support were detected. At low Z values Cu0 dispersion was high (D ≈ 40%) due to a predominant contribution of nano-sized Cu species (3 nm) which are difficult to reduce, but for Z > 13.5 wt.%, D abruptly dropped to 3-8% because of formation of larger tridimensional Cu clustered species (30 nm) that reduced at lower temperatures because of a decreased copper-silica interaction. On ZCuSiO2 catalysts, dehydrogenation of the 1,3-butanediol secondary OH function prevailed over that of the primary one and therefore valuable ketones were the main reaction products. Consecutively to dehydrogenation, dehydration and hydrogenation reactions also took place. Products of the tandem reaction were the β-hydroxy ketone (4-hydroxy-2-butanone), the α,β- unsaturated ketone (methyl vinyl ketone) and the saturated ketone (methyl ethyl ketone). A direct 1,3-butanediol dehydration pathway toward methyl ethyl ketone was also found. Reaction pathways were strongly dependent on the Cu loading and therefore on the kind of Cu species (isolated or clustered). When compared at similar conversion levels, selectivity to the dehydrogenation product 4-hydroxy-2-butanone increased with Z suggesting that on large Cu0 particles 4-hydroxy-2-butanone was released to the gas phase before being converted in consecutive steps. On the contrary, on highly dispersed Cu 0 crystals of low Cu loading catalysts, 1,3-butanediol was readily dehydrated giving the saturated ketone. Kinetically relevant reaction steps of 1,3-butanediol conversion by dehydrogenation and dehydration were promoted on Cu0 sites. Dehydration of the intermediate 4-hydroxy-2-butanone also occurred on Cu0 sites. Turnover rates were constant on Cu0 nano particles and slightly higher on clustered species.
- Torresi,Díez,Luggren,Di Cosimo
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- Chemoselective Oxidation of the Primary Alcohol Function of Diols Catalyzed by Zirconocene Complexes
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Zirconocene complexes, Cp2ZrH2 and Cp2Zr2, catalyze the Oppenauer-type oxidation of alcohol functions to the corresponding carbonyl compounds in the presence of an appropriate hydrogen acceptor such as benzophenone.In the oxidation of primary α,ω-diols and of diols containing two secondary alcohol functions, one of the alcohol functions is selectively oxidized to form hydroxy aldehydes and hydroxy ketones, respectively, in substantial yields.The chemoselective oxidation of the primary alcohol function can be achieved in the oxidation of diols containing both the primary and secondary alcohol functions.
- Nakano, Tatsuya,Terada, Takanobu,Ishii, Yasutaka,Ogawa, Masaya
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- Kinetics and Mechanism of the Oxidation of Diols by Pyridinium Bromochromate
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The kinetics of oxidation of four vicinal diols, four nonvicinal diols, and one of their monoethers by pyridinium bromochromate (PBC) have been studied in dimethyl sulfoxide.The main product of oxidation is the corresponding hydroxyaldehyde.The reaction is first-order with respect to each the diol and PBC.The reaction is acid-catalyzed and the acid dependence has the form: kobs = a + b+>.The oxidation of ethanediol exhibited a primary kinetic isotope effect (kH/kD = 6.70 at 298 K).The reaction has been studied in 19 organic solvents including dimethyl sulfoxide and the solvent effect has been analyzed using multiparametric equations.The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step.A suitable mechanism has been proposed.
- Rao, P. Surya Chandra,Suri, Deepa,Kothari, Seema,Banerji, Kalyan K.
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- Oxidation of Olefins by Palladium(II). 12. Product Distributions and Kinetics of the Oxidation of 3-Buten-2-ol and 2-Buten-1-ol by PdCl42- in Aqueous Solution
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The rate expression for oxidation of both allyl alcohols was determined to be rate = k2->/+>->2, an expression identical in form with that found previously for the oxidation of ethene, allyl alcohol, and other acyclic olefins, indicating similar mechanisms.Contrary to previous reports, the product distribution from 3-buten-2-ol (6) was completely different from that for 2-buten-1-ol (7), indicating that fast isomerization into an equilibrium mixture before oxidation was not occuring.A short study of the rate of isomerization using deuteriated 6 and 7 confirmed that isomerization was slow under the oxidation conditions.The distributions gave considerable information on the effects of steric and electronic factors on the modes of hydroxypalladation.While allyl alcohol gave a 3/1 preference for addition of the Pd(II) to the center carbon due to the directing influence of the hydroxyl group, 6 gave 4/1 preference for addition of Pd(II) to the end carbon.The steric effect of the methyl is thus appreciable.With 7 the double bond is internal so steric factors are not important and the directing influence of the hydroxyl will be the important effect.The ratio of Pd(II) addition next to the carbon containing the hydroxyl group to addition to the other side of the double bond is 34/1, indicating considerable directing influence of the hydroxyl.The preference for secondary over primary hydride shift is 1.25, a value which indicates almost no carbonium ion character and considerable Pd(II)-H character.Using a specifically deuterated 7, the value of the deuterium isotope effect, kH/kD, can be determined by internal competitive hydride transfer by taking into account the positional preferance for secondary hydride shift.This value of 2.2 is close to values previously determined for ethene and allyl alcohol.
- Zaw, Kyaw,Henry, Patrick M.
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- Rate constants for the gas-phase reactions of OH radicals with a series of hydroxyaldehydes at 296 ± 2 K
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Using a relative rate method with in situ generation of the hydroxyaldehydes, rate constants for the reactions of the OH radical with 2-hydroxybutanal [CH3CH2CH(OH)CHO], 3-hydroxybutanal [CH3CH(OH)CH2CHO], 2-hydroxypropanal [CH 3CH(OH)CHO], 2-hydroxy-2-methylpropanal [(CH3) 2C(OH)CHO], and 3-hydroxy-propanal [HOCH2CH 2CHO] have been measured at atmospheric pressure and 296 ± 2 K. The hydroxy-aldehydes were generated in situ from the OH radical-initiated reactions of precursor compounds (1,2- and 1,3-butanediol, 2-methyl-2,4-pentanediol, 2-methyl-3-buten-2-ol, and cis-3-hexen-1-ol) and the rate constants for the reaction of OH radicals with the hydroxyaldehydes were determined relative to those for reaction of OH radicals with the precursor compound. The rate constants obtained (in units of 10-11 cm 3 molecule-1 s-1) were CH3CH 2CH(OH)CHO, 2.37 ± 0.23; CH3CH(OH)CH 2CHO, 2.95 ± 0.24; CH3CH(OH)CHO, 1.70 ± 0.20; (CH3)2C(OH)CHO, 1.40 ± 0.25; and HOCH 2CH2CHO, 1.99 ± 0.29.
- Baker, Jillian,Arey, Janet,Atkinson, Roger
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- Exploring the biocatalytic scope of alditol oxidase from Streptomyces coelicolor
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The substrate scope of the flavoprotein alditol oxidase (AldO) from Streptomyces coelicolor A3(2), recombinantly produced in Escherichia coli, was explored. While it has been established that AldO efficiently oxidizes alditols to D-aldoses, this study revealed that the enzyme is also active with a broad range of aliphatic and aromatic alcohols. Alcohols containing hydroxy groups at the C-1 and C-2 positions like 1,2,4-butanetriol (Km=170 mM, k cat -4.4s-1), 1,2-pentanediol (Km=52 mM, k cat=0.85 s-1) and 1,2-hexanediol (Km=97 mM, kcat=2.0s-1) were readily accepted by AldO. Furthermore, the enzyme was highly enantioselective for the oxidation of 1,2-diols [e.g., for l-phenyl-1,2-ethanediol the (R)-enantiomer was preferred with an Is-value of 74]. For several diols the oxidation products were determined by GC-MS and NMR. Interestingly, for all tested 1,2-diols the products were found to be the a-hydroxy acids instead of the expected α-hydroxy aldehydes. Incubation of (R)-1-phenyl-1,2-ethanediol with 18O-labelled water (H 218O) revealed that a second enzymatic oxidation step occurs via the hydrate product intermediate. The relaxed substrate specificity, excellent enantioselectivity, and independence of coenzymes make AldO an attractive enzyme for the preparation of optically pure 1,2-diols and α-hydroxy acids.
- Van Hellemond, Erik W.,Vermote, Linda,Koolen, Wilma,Sonke, Theo,Zandvoort, Ellen,Heuts, Dominic P. H. M.,Janssen, Dick B.,Fraaije, Marco W.
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- Fructose 1,6-Diphosphate Aldolase Catalyzed Stereoselective Synthesis of C-Alkyl and N-Containing Sugars: Thermodynamically Controlled C-C Bond Formations.
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Fructose 1,6-diphosphate aldolase catalyzed aldol condensations have been used in syntheses of several new N-containing and C-alkyl sugars on 4-20 mmol scales.The enzyme is highly specific for dihydroxyacetone phosphate as donor but accepts a number of achiral and chiral aldehydes (both D and L isomers) as acceptors.Due to the reversible nature of the aldol reaction, a thermodynamically controlled approach was employed for the syntheses in which racemic aldehydes were used as substrates and thermodynamically more stable products were preferentially produced.
- Durrwachter, John R.,Wong, Chi-Huey
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- IR spectral evidence of aldol condensation: Acetaldehyde adsorption over TiO2 surface
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The adsorption of acetaldehyde on particulate TiO2 surfaces has been studied at 233 K by FT-IR spectroscopy using a specially designed IR cell. It has been found that acetaldehyde initially adsorbs onto the surface through hydrogen bonding and Lewis acid sites. As the temperature is raised to 251 K, the spectroscopic evidence of formation of 3-hydroxybutanal surface intermediate is observed during aldol condensation reaction. The presence of this transient species has been characterized by the infrared features at 3185 cm-1-ν(OH), 1334 cm-1-δ(CH), 1273 cm-1-δ(COH), and 1105 cm-1-ν(C{single bond}C) and δ(COH). The assignments of all surface species are confirmed by adsorbing pure 3-hydroxybutanal and 2-butenal on TiO2 surface. A reaction mechanism consistent with the detectable surface intermediates is proposed.
- Singh, Manishwar,Zhou, Nanjia,Paul, Dilip K.,Klabunde, Kenneth J.
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- Kinetic Study of Oxidation of Diols by Sodium N-Bromobenzenesulphonamide
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The kinetics of the oxidation of five vicinal diols, four other diols, and one of their monoethers by sodium N-bromobenzenesulphonamide have been studied.The vicinal diols yielded products arising out of glycol bond fission while other diols yielded hydroxycarbonyl compounds.The reaction is first order with respect to the diol and the oxidant.The oxidation of vicinal diols follows two mechanistic pathways, one acid-independent and the another acid-dependent.The oxidation of the other diols shows a first-order dependence on hydrogen ion.The oxidation of ethanediol showed the absence of a primary kinetic isotope effect.The values of solvent isotope effect, k(H2O)/k(D2O), at 303 K for the oxidation of ethanediol, propane-1,3-diol, and 3-methoxybutan-1-ol are 2,24, 0.42. and 0.42, respectively.An acyclic mechanism involving glycol bond fission has been proposed for the vicinal diols.The other diols are oxidized by a hydride-transfer mechanism as are monohydric alcohols.
- Mathur, Abha,Banerji, Kalyan K.
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- Metalloenzyme-inspired catalysis: Selective oxidation of primary alcohols with an iridium-aminyl-radical complex
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(Chemical Equation Presented) A little goes a long way: An iridium-nitrogen-radical complex is a highly active and selective catalyst for the dehydrogenation (oxidation) of primary alcohols to aldehydes in the presence of the oxidant benzoquinone (see simplified scheme). With only 0.01 mol% of the complex, turnover frequencies of up to 150 000 s-1 are reached.
- Koenigsmann, Martin,Donati, Nicola,Stein, Daniel,Schoenberg, Hartmut,Harmer, Jeffrey,Sreekanth, Anandaram,Gruetzmacher, Hansjoerg
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- Preparation method of 1,3-butanediol
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The invention provides a preparation method of 1,3-butanediol, which comprises the following steps: acetaldehyde condensation, hydrogenation and separation. In the hydrogenation step, the purity of the prepared 1,3-butanediol is greater than 99.5% by adopting methods of staged hydrogenation, addition of a modifier into a hydrogenation catalyst and the like, the content of 1,3-dioxane impurity canbe reduced to 0.01 wt% or below, and the product is odorless. The method has the advantages of simple process, low energy consumption, simple operation, high yield and selectivity of 1,3-butanediol, high purity of 1,3-butanediol and the like, and odorless 1,3-butanediol can be obtained.
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Paragraph 0074; 0075; 0076
(2020/03/05)
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- Method for improving selectivity of aldol condensation reaction
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The invention provides a method for improving selectivity of aldol condensation reaction. The method comprises the following steps: introducing C1-C5 aldehyde participating in the reaction and an aqueous solution of an alkaline compound into a coiled tube type reactor in a parallel flow manner, forming a continuous phase under a turbulence condition by the aqueous solution of the alkaline compound, and dispersing the C1-C5 aldehyde in the continuous phase in a droplet form. The C1-C5 aldehyde is selected from one or two of formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde and isovaleraldehyde; the alkaline compound is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate,ammonia water, trimethylamine, triethylamine and diisopropylamine. The invention also provides preparation of 1, 3-butanediol by condensation of acetaldehyde and an inorganic alkali compound and preparation of hydroxypivalaldehyde by condensation of formaldehyde, isobutyraldehyde and a trimethylamine aqueous solution. With application of the coiled tube type reactor, the reaction temperature, thematerial ratio and the retention time can be accurately controlled, side reactions are effectively reduced, and the reaction efficiency, the reaction stability and the product selectivity are improvedby adopting the reaction process.
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Paragraph 0024-0027; 0031-0036
(2020/09/16)
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- Preparation method of 1, 3-butylene glycol
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The invention provides a preparation method of 1, 3-butylene glycol. The preparation method comprises following steps: A, acetaldehyde is introduced into a fixed bed reactor, under the effect of a supported type solid basic catalyst, aldol condensation reaction is carried out so as to obtain 3-hydroxybutyraldehyde; and B, 3-hydroxybutyraldehyde is subjected to continuous hydrogenation reaction inthe fixed bed reactor so as to obtain 1, 3-butylene glycol. According to the preparation method, the fixed bed reactor is adopted, at the same time, the supported type solid basic catalyst is adoptedto replace a conventional liquid alkali (such as sodium hydroxide) catalysts, and in the step of hydrogenation reduction, a supported nickel hydrogenation catalyst is adopted. The preparation method is capable of solving problems in the prior art product quality is poor, product yield is low, technology process is complex, and a large amount of waste water and waste residue is generated; aldol condensation quenching step is avoided; side reactions are reduced; relatively high reaction conversion rate and yield are achieved; no neutralizing or desalting process is needed in reaction process; and great improvement of traditional 1, 3-butylene glycol preparation technology is realized.
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Paragraph 0033-0037; 0044-0049; 0055-0060; 0066-0069
(2019/03/26)
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- Engineering a Promiscuous Tautomerase into a More Efficient Aldolase for Self-Condensations of Linear Aliphatic Aldehydes
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The enzyme 4-oxalocrotonate tautomerase (4-OT) from Pseudomonas putida mt-2 takes part in a catabolic pathway for aromatic hydrocarbons, where it catalyzes the conversion of 2hydroxyhexa-2,4-dienedioate into 2-oxohexa-3-enedioate. This tautomerase can also promiscuously catalyze carbon–carbon bond-forming reactions, including various types of aldol reactions, by using its amino-terminal proline as a key catalytic residue. Here, we used systematic mutagenesis to identify two hotspots in 4-OT (Met45 and Phe50) at which single mutations give marked improvements in aldolase activity for the self-condensation of propanal. Activity screening of a focused library in which these two hotspots were varied led to the discovery of a 4-OT variant (M45Y/F50V) with strongly enhanced aldolase activity in the self-condensation of linear aliphatic aldehydes, such as acetaldehyde, propanal, and butanal, to yield α,β-unsaturated aldehydes. With both propanal and benzaldehyde, this double mutant, unlike the previously constructed single mutant F50A, mainly catalyzes the self-condensation of propanal rather than the cross-condensation of propanal and benzaldehyde, thus indicating that it indeed has altered substrate specificity. This variant could serve as a template to create new biocatalysts that lack dehydration activity and possess further enhanced aldolase activity, thus enabling the efficient enzymatic self-coupling of aliphatic aldehydes.
- Rahimi, Mehran,van der Meer, Jan-Ytzen,Geertsema, Edzard M.,Poelarends, Gerrit J.
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p. 1435 - 1441
(2017/07/25)
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- METHODS AND HOST CELLS FOR ENHANCING PRODUCTION OF 1, 3-BUTANEDIOL
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This application describes non-naturally occurring host cells for enhanced 1,3-butanediol (1,3-BDO) production, methods for producing 1,3-BDO using such non-naturally occurring host cells, and 1,3-BDO products produced by such non-naturally occurring host cells and methods.
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Paragraph 0138-0141
(2017/01/31)
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- Synthesis of C4 and C8 Chemicals from Ethanol on MgO-Incorporated Faujasite Catalysts with Balanced Confinement Effects and Basicity
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A new type of catalyst has been designed to adjust the basicity and level of molecular confinement of KNaX faujasites by controlled incorporation of Mg through ion exchange and precipitation of extraframework MgO clusters at varying loadings. The catalytic performance of these catalysts was compared in the conversion of C2 and C4 aldehydes to value-added products. The product distribution depends on both the level of acetaldehyde conversion and the fraction of magnesium as extraframework species. These species form rather uniform and highly dispersed nanostructures that resemble nanopetals. Specifically, the sample containing Mg only in the form of exchangeable Mg2+ ions has much lower activity than those in which a significant fraction of Mg exists as extraframework MgO. Both the (C6+C8)/C4 and C8/C6 ratios increase with additional extraframework Mg at high acetaldehyde conversion levels. These differences in product distribution can be attributed to 1) higher basicity density on the samples with extraframework species, and 2) enhanced confinement inside the zeolite cages in the presence of these species. Additionally, the formation of linear or aromatic C8 aldehyde compounds depends on the position on the crotonaldehyde molecule from which abstraction of a proton occurs. In addition, catalysts with different confinement effects result in different C8 products.
- Zhang, Lu,Pham, Tu N.,Faria, Jimmy,Santhanaraj, Daniel,Sooknoi, Tawan,Tan, Qiaohua,Zhao, Zheng,Resasco, Daniel E.
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p. 736 - 748
(2016/05/09)
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- An improved production process of butenal
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The invention relates to an improvement of a crotonaldehyde production technique, which comprises the following steps: steam condensate is added into a condensation tower, an acetaldehyde condensation tower, a 3-hydroxybutyraldehyde dehydration tower and a primary distillation tower are in a water distillation state, tetramethyl ammonium hydroxide is used as a catalyst, the catalyst:acetaldehyde:acetic acid mole ratio is 1:1000:5, the catalyst solution, acetaldehyde and acetic acid are respectively added into the 10th, 11th and 6th tower trays of a bubbling hood condensation tower to generate 3-hydroxybutyraldehyde at the condensation temperature of 42-49 DEG C under the pressure of 0.05 MPa, the tower top condensate completely flows back, the tower bottom 3-hydroxybutyraldehyde enters the dehydration tower and is dehydrated under acidic conditions to generate crude crotonaldehyde, 0.34 part of the tower top distillation product condensate flows back, the rest tower top distillation product condensate and uncondensed gas enter the primary distillation tower to be concentrated, the tower top acetaldehyde gas condensate returns to the condensation tower for cyclic utilization, the crotonaldehyde is recovered from the middle part of the condensation tower, and the supernatant 89% crude crotonaldehyde is refined into 99.3% crotonaldehyde; and the wastewater is introduced into an incinerator to be incinerated, thereby implementing the zero discharge of wastewater and the production green technique.
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Paragraph 0011-0013
(2018/02/04)
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- MICROORGANISMS FOR PRODUCING 4C-5C COMPOUNDS WITH UNSATURATION AND METHODS RELATED THERETO
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The invention provides a non-naturally occurring microbial organism having a butadiene, crotyl alcohol, 2,4-pentadienoate, 3-buten-2-ol, or 3-buten-1-ol, pathway. The microbial organism contains at least one exogenous nucleic acid encoding an enzyme in a pathway. The invention additionally provides a method for producing butadiene, crotyl alcohol, 2,4-pentadienoate, 3-buten-2-ol, or 3-buten-1-ol,. The method can include culturing a butadiene, crotyl alcohol, 2,4-pentadienoate, 3-buten-2-ol, or 3-buten-1-ol-producing microbial organism, where the microbial organism expresses at least one exogenous nucleic acid encoding a pathway enzyme in a sufficient amount, and under conditions and for a sufficient period of time to produce butadiene, crotyl alcohol, 2,4-pentadienoate, 3-buten-2-ol, or 3-buten-1-ol.
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Paragraph 0014; 00100
(2016/01/25)
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- Improving the selectivity to C4 products in the aldol condensation of acetaldehyde in ethanol over faujasite zeolites
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The selective conversion of acetaldehyde to C4 products, minimizing the production of secondary (C6, C8) condensation products, could be a potential path in the production of butadiene from ethanol, a process of commercial interest. Therefore, we have investigated the selective aldol condensation of acetaldehyde in liquid phase over faujasite zeolites, NaX and NaY. Specifically, we have examined the influence of the number and location of the exchangeable cations, type of cations, and post-synthesis treatments on product selectivity. At 230 °C, NaY results in higher C4/(C6 + C8) product ratio than NaX, which can be explained in terms of the strength, density, and accessibility of basic sites, which are less favorable in NaX than NaY. In fact, the CO2 TPD measurements indicate the presence of three types of basic sites of varying strength, of which those with weak and medium strength are most important for the selective condensation. A confinement effect is observed when adding K to the NaY zeolite. The observed selectivity changes suggest that when larger cations partially occupy the supercages, the production of C8 products decreases, while C6 products increase. Also, post-synthesis washing treatments show significant variations in selectivity, which demonstrate the effects of partial occupation of the zeolite pores in the reaction. It is also shown that at a given conversion, the C4/(C6 + C8) ratio can be adjusted by modifying the micro/mesoporosity balance in the zeolite.
- Zhang, Lu,Pham, Tu N.,Faria, Jimmy,Resasco, Daniel E.
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p. 119 - 129
(2015/03/18)
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- Method for synthesising heterogeneous solid chiral catalysts and their use in stereoselective reactions
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This invention describes the method to produce solid heterogeneous chiral organocatalysts which can be used in condensation reactions. The catalysts can be recovered in a simple manner by means of filtration and also be reused.
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Page/Page column
(2014/06/11)
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- Novel urushiols with human immunodeficiency virus type 1 reverse transcriptase inhibitory activity from the leaves of Rhus verniciflua
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Two novel urushiols, 1 and 2, and two known urushiols, 3 and 4, were isolated from the leaves of Rhus verniciflua and were examined for their human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) inhibitory activity. The novel urushiols were found to be 1,2-dihydroxyphenyl-3-[7(E),9(Z),11(Z)-pentadecatrienyl]-14-ol (1) and 1,2-dihydroxyphenyl-3-[8(Z),10(E),12(E)-pentadecatrienyl]-14-ol (2) by spectroscopic analyses. The absolute configuration at C-14 in 1 and 2 was determined to be a racemic mixture of (R) and (S) isomers by ozonolysis. Compound 2 (IC50: 12.6 μM) showed the highest HIV-1 RT inhibitory activity among the four urushiols, being 2.5-fold more potent than the positive control, adriamycin (IC50: 31.9 μM). Although the known urushiols were isolated from the sap and leaves of R. verniciflua, 1 was exclusively present in the leaves, and higher amounts of 2 were found in the leaves than in the sap. Present findings indicate that the leaves of R. verniciflua represent a new biological resource from which novel and known urushiols may be prepared, and the possible use of novel urushiols as bioactive products.
- Kadokura, Kazunari,Suruga, Kohei,Tomita, Tsuyoshi,Hiruma, Wataru,Yamada, Motoyuki,Kobayashi, Akio,Takatsuki, Akira,Nishio, Toshiyuki,Oku, Tadatake,Sekino, Yoshihiro
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p. 148 - 153
(2015/02/19)
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- Kinetics and mechanism of the oxidation of diols by butyltriphenylphosphonium dichromate
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The oxidation of four vicinal, four non-vicinal diols and one of their monoethers by butyltriphenylphosphonium dichromate (BTPPD), in dimethylsulfoxide (DMSO), resulted in the formation of corresponding hydroxyaldehyde as a main product of the oxidation. The reactions are of first order with respect to BTPPD, however, second order dependence is obtained with respect to each the diol and hydrogen ion. The oxidation of [1,1,2,2-2H 4]ethanediol exhibited primary kinetic isotope effect (k H/kD = 6.61 at 298 K). The temperature dependence of the kinetic isotope effect suggested the symmetrical transition state in the rate-determining step. The rate constants of oxidation of four vicinal diols show excellent correlation with Taft's ∑ σ* values with negative reaction constant, ρz.ast;. The rate of oxidation of ethanediol has been determined in nineteen different solvents. An analysis of the solvent effect indicates the importance of the cation-solvating power of the solvents. A suitable mechanism has been postulated involving the formation of chromate ester in a pre-equilibrium.
- Panday, Dinesh,Kothari, Seema
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experimental part
p. 918 - 925
(2011/09/19)
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- Oxidation of some vicinal and non-vicinal diols by morpholinium chlorochromate: A kinetic and mechanistic study
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The kinetics of oxidation of four vicinal, four non-vicinal diols and two of their monoethers by morpholinium chlorochromate (MCC) have been studied in dimethylsulphoxide (DMSO). The main product of oxidation is the corresponding hydroxycarbonyl compound. The reaction is first order in MCC and the diols. The reaction is catalysed by hydrogen ions. The hydrogen ion dependence is taking the form : kobs = a + b [H+]. The oxidation of [1,1,2,2-2H4]ethanediol exhibits a substantial primary kinetic isotope effect (kH/kD = 5.82 at 298 K). The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using Taft's and Swain's multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step. A suitable mechanism has been proposed.
- Barthora,Baghmar,Agarwal,Sharma, Vinita
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experimental part
p. 677 - 683
(2012/04/10)
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- Oxidation of butane-1,3-, butane-1,4-, 2-methyl pentane-2,4- and 3-methyl pentane-2,4-diols by cerium(IV) in aqueous acidic medium catalyzed by rhodium(III)
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The oxidation kinetics of butane-1,3-diol, butane-1,4-diol, 2-methyl pentane-2,4-diol and 3-methyl pentane-2,4-diol with cerium(IV) catalyzed by rhodium(III) in aqueous sulfuric acid showed a peculiar nature with respect to the variation in oxidant concentration, such that the reaction follows first-order kinetics in [Ce(IV)] at low [Ce(IV)] and then reaches a maximum with increasing [Ce(IV)], beyond which further increase in the oxidant concentration retards the rate. The rate shows direct proportionality with respect to [diol] at low concentrations, becoming independent of [diol] at higher concentrations. The rate is first order in catalyst. Retarding effects are observed when [H +] and [Ce(III)] are increased, while [Cl-] and hence ionic strength have a positive effect on the rate. Spectroscopic studies confirmed that the primary hydroxyl groups in butane-1,3-diol and butane-1,4-diol resulted in the formation of 3-hydroxy butanal and 4-hydroxy butanal, respectively. In the case of oxidation of the secondary hydroxyl groups in 2-methyl pentane-2,4-diol and 3-methyl pentane-2,4-diol, the products of oxidation were 4-hydroxy-4-methyl pentan-2-one and 4-hydroxy-3-methyl pentan-2-one, respectively.
- Tandon, Praveen K.,Khanam, Shaista Z.,Yadav, Suresh C.,Shukla, Ritesh C.
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scheme or table
p. 739 - 746
(2012/07/01)
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- Thieme chemistry journal awardees - Where are they now? aldol synthesis by anti-markovnikov hydration of propargyloxy substrates: Feasibility, stereospecifity, and reiterative alkynylation-hydration
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Aldol derivatives have been synthesized by redox-neutral catalytic anti-Markovnikov hydration of propargyloxy sub-strates. A reiterative sequence of aldehyde alkynylation and alkyne hydration leads to 1,3-polyol derivatives. Georg Thieme Verlag Stuttgart.
- Hintermann, Lukas,Kribber, Thomas,Labonne, Aurélie,Paciok, Eva
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scheme or table
p. 2412 - 2416
(2009/12/08)
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- Selective photooxidation of diols with silica bound W10 O324 -
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The decatungstate anion W10 O324 - has been heterogenized on silica previously functionalized with different ammonium cations covalently bound to the surface of the solid support. These materials are investigated as photocatalysts for the oxygen-assisted oxidation of 1,3-butanediol and 1,4-pentanediol. Product distribution and adsorption experiments indicate that the polarity of the environment surrounding the photoactive anion plays a crucial role in controlling the adsorption of diols on the surface and, consequently, their reaction with the photoexcited decatungstate. Proper reaction conditions are found for obtaining more than 90% of 4-hydroxy-2-butanone from 1,3-butanediol and for stopping the oxidation of 1,4-pentanediol to 4-hydroxypentanal with good yield. The employed photocatalysts present a very good stability in repeated experiments.
- Maldotti,Molinari,Bigi
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p. 312 - 317
(2008/09/16)
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- Methods for preparing 1,3 butylene glycol
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1,3 butylene glycol, prepared through an intermediate aldol condensation reaction of acetaldehyde, is produced at increased yield efficiencies. The efficiencies are achieved by utilizing an acetaldehyde having low carboxylic concentrations. The aldol condensation takes place in the presence of an alkali agent at a concentration of about 2 ppm to about 10 ppm to produce a 3-hydroxybutanal intermediate product that is hydrogenated in the presence of a Raney nickel catalyst to yield 1,3 butylene glycol at efficiency yields of greater than about 75%.
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Page/Page column 2
(2008/06/13)
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- Continuous chemoselective methylation of functionalized amines and diols with supercritical methanol over solid acid and acid-base bifunctional catalysts
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The selective N-methylation of bifunctionalized amines with supercritical methanol (scCH3OH) promoted by the conventional solid acids (H-mordenite, β-zeolite, amorphous silica-alumina) and acid-base bifunctional catalysts (Cs-P-Si mixed oxide and γ-alumina) was investigated in a continuous-flow, fixed-bed reactor. The use of scCH 3OH in the reaction of 2-aminoethanol with methanol (amine/CH 3OH = 1/10.8) over the solid catalysts led to a significant improvement in the chemoselectivity of the N-methylation. Among the catalysts examined, the Cs-P-Si mixed oxide provided the most efficient catalyst performance in terms of selectivity and reactivity at 300 °C and 8.2 MPa; the N-methylation selectivity in the products reaching up to 94% at 86% conversion. The present selective methylation was successfully applied to the synthesis of N-methylated amino alcohols and diamines as well as O-methylated ethylene glycol. Noticeably, ethoxyethylamine was less reactive, suggesting that the hydroxy group of the amino alcohols is a crucial structural factor in determining high reactivity and selectivity, possibly because of the tethering effect of another terminus, a hydroxo group, to the catalyst surface. The magic-angle-spinning NMR spectroscopy and X-ray diffraction analysis of the Cs-P-Si mixed oxide catalyst revealed that the acidic and basic sites originate from P2O5/SiO2 and Cs/SiO2, respectively, and the weak acid-base paired sites are attributed to three kinds of cesium phosphates on SiO2. The weak acid-base sites on the catalyst surface might be responsible for the selective dehydrative methylation.
- Oku, Tomoharu,Arita, Yoshitaka,Tsuneki, Hideaki,Ikariya, Takao
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p. 7368 - 7377
(2007/10/03)
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- Kinetics and mechanism of oxidation of some diols by benzyltrimethylammonium chlorobromate
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Kinetics of oxidation of five vicinal, four non-vicinal diols, and one of their monoethers by benzyltrimethylammonium chlorobromate (BTMACB) have been studied. The vicinal diols yield the products arising out of the glycol-bond fission while the other diols afford the hydroxycarbonyl compounds. The reaction is first order with respect to diols and the BTMACB. The reaction failed to induce the polymerization of acrylonitrile. There is no effect of benzyltrimethylammonium chloride or potassium bromide on the reaction rate. The proposed reactive oxidizing species is chlorobromate ion. The effect of solvent composition indicated that the rate increases with an increase in the polarity of the solvent. The oxidation of [1,1,2,2-2H4]ethanediol show an absence of primary kinetic isotope effect. The value of solvent isotope effect, k(H2O)/k(D2O), at 288 K for the oxidation of ethanediol, propane-1,3-diol and 3-methoxybutan-1-ol are 3.32, 1.04 and 1.01 respectively. A cyclic mechanism involving a glycol-bond fission has been proposed for the oxidation of the vicinal diols. The other diols are oxidised by a hydride-transfer mechanism, as are monohydric alcohols.
- Bhatt, Monica,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 826 - 831
(2007/10/03)
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- Method of producing β-hydroxyaldehydes
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β-Hydroxyaldehydes are produced by a method in which 1,2-oxiranes are reacted with carbon monoxide and hydrogen in the presence of transitional metal compounds which are modified with phosphorus-oxygen ligands or nitrogen-oxygen ligands and which act as a catalyst.
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- Kinetics and mechanism of oxidation of diols by quinolinium fluorochromate
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The kinetics of oxidation of four vicinal diols, four non-vicinal diols and two of their monoethers by quinolinium fluorochromate (QFC) have been studied in dimethylsulphoxide. The main product of oxidation is the corresponding hydroxycarbonyl compound. The reaction is first order in QFC. Michaelis-Menten type kinetics have been observed with respect to the diols. The oxidation of [1,1,2,22H4] ethanediol exhibits a substantial primary kinetic isotope effect (k(H)/k(D) = 6.35 at 303 K). The reaction has been in nineteen different organic solvents and the solvent effect has been analysed using Taft's and Swain's multiparametric equation. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step. A suitable mechanism has been proposed.
- Choudhary, Kirti,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 325 - 330
(2007/10/03)
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- Kinetics and Mechanism of Oxidation of Diols by Hexamethylenetetramine-bromine
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Kinetics of oxidation of five vicinal, four non-vicinal diols, and one of their monoethers by hexamethylenetetramine-bromine (HABR) have been studied. The vicinal diols yielded the products arising out of the glycol bond fission while the other diols yielded the hydroxycarbonyl compounds. The reaction is first order with respect to HABR. Michaelis-Menten type kinetics were observed with respect to the diol. Addition of hexamethylenetetramine resulted in an increase in the rate of reaction. The oxidation of 2H4>ethanediol showed an absence of primary kinetic isotope effect. A mechanism involving a glycol bond fission has been proposed for the oxidation of the vicinal diols. The other diols are oxidised by a hydride-transfer mechanism as are monohydric alcohols.
- Gangwani, Hemlata,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 854 - 871
(2007/10/03)
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- Kinetics and Mechanism of the Oxidation of Diols by 2.2'-Bipyridinium Chlorochromate
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The kinetics of oxidation of four vicinal diols. four non-vicinal diols and two of their monoethers by 2.2'-bipyridinium chlorochromate (BPCC) have been studied in dimethyl sulfoxide.The main product of oxidation is the corresponding hydroxycarbonyl compound.The reaction is first order with respect to both BPCC and the diol.The oxidation of ethanediol exhibits a substantial primary kinetic isotope effect (kN/kD = 6.35 at 303 K).The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using Taft's and Swain's multiparametric equations.The temperature dependence of the kinetic isotope effect indicates the presence of a symetrical transition state in the rate-determining step.A suitable mechanism has been proposed.
- Loonker, Kavita,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 1663 - 1680
(2007/10/03)
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- MECHANISM OF THE ALDOL CONDENSATION OF ALDEHYDES, CATALYZED BY THE SALTS OF METALS AND HIGHER ORGANIC ACIDS
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The salts of transition metals are the most active catalysts for the aldol condensation of aliphatic aldehydes.By IR spectroscopy it was found that an intermediate complex between the aldehyde and the catalyst is formed at the initial stage of the reaction.A chelate mechanism of catalysis is proposed for the aldol condensation and satisfactorily explains the order of formation of the intermediate and final products.
- Katsnel'son, M. G.,Kagna, S. Sh.,Nikitina, L. I.,Oranskaya, O. M.,Semenskaya, I. V.
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p. 1437 - 1441
(2007/10/02)
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- SIDE REACTIONS LEADING TO ETHERS AND ACETALS.
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Condensation of formaldehyde with acetaldehyde results in formation of dipentaerythritol and a number of similar byproducts whose molecules include five-carbon units with central carbon atoms, linked by ether or acetal bonds. A reaction mechanism is proposed for the condensation of formaldehyde with acetaldehyde with formation of byproducts. The proposed mechanism is verified experimentally. The results of photometric measurements at 280 nm during the course of the process provide direct experimental confirmation of the rapid reversibility of the main and side reactions, ensuring the observed interrelationships of the reaction system. The experimental observations demonstrate that the reversible reactions of the process are interrelated, as is indicated by the proposed mechanism. It is concluded that proposed mechanism with side reactions of formation of dipentaerythritol and similar products from pentaerythritol and unsaturated intermediate aldehydes is correct.
- Belkin
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p. 365 - 368
(2007/10/02)
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- The retroaldol reaction of 3-methyl-2-butenal
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In aqueous sodium hydroxide solutions at 25 deg C, 3-methyl-2-butenal, 1c, undergoes retroaldol cleavage to acetone and acetaldehyde.The kinetics of the retroaldol reaction were followed spectrophotometrically at 242 nm and showed simple first order behavior.When 3-methyl-3-hydroxybutanal, 2c, was added to aqueous sodium hydroxide solutions at 25 deg C, there was an initial increase in absorbance at 242 nm, attributed to formation of 1c, followed by a 20-fold slower decrease; the rate of the slow decrease matches the rate of disappearance of 1c under the same conditions.Analysis of the kinetics allows determination of the three rate constants needed to describe the system: khyd=0.00342; kdehyd=0.00832; kretro=0.0564; all M-1s-1.The equilibrium constant for enone hydration is 0.41.Rate constants for the analogous reactions for acrolein and crotonaldehyde could be obtained from the literature.There is a reasonable rate-equilibrium correlation for the retroaldol step.For the enone hydration step, rate and equilibrium constants respond differently to replacement of hydrogen by methyl.It is proposed that this results from release of strain after the rate-determining step by rotation about a single bond; this decrease in strain is reflected in the equilibrium constant but not in the rate constant.
- Guthrie, J. Peter,Dawson, Brian A.
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p. 171 - 178
(2007/10/02)
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- SIDE REACTION IN THE ALDOL CONDENSATION OF ACETALDEHYDE
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It was established that the main side products in the condensation of acetaldehyde in the presence of cobalt naphthenate are 3-hydroxybutanal, 2,4- and 2,5-hexadienal, the monoacetate of 1,3-butanediol, and dihydrotoluylaldehyde.From the proposed scheme of side reactions it follows that the majority of the side products are formed in the reaction of 3-hydroxybutanal with acetaldehyde.Realization of the process at an increased temperature with a low initial concentration of acetaldehyde and for short contact times makes it possible to reduce the yield of the side products.
- Nikitina, L. I.,Katsnel'son, M. G.,Kagna, S. Sh.,Skop, S. L.,Rabinovich, A. S.,Sysoeva, G. A.
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p. 2003 - 2006
(2007/10/02)
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- Kinetics and Mechanism of Oxidation of Diols by Pyridinium Chlorochromate in Dimethyl Sulphoxide
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The kinetics of oxidation of several diols and two of their mono ethers by pyridinium chlorochromate (PCC) have been studied in DMSO.The principal product of the oxidation is the corresponding hydroxyaldehyde.The reaction is first order each in and .The oxidation of ethanediol-1,1,2,2-d4 exhibits a primary kinetic isotope effect, kH/kD = 6.75 at 298 K.The activation energies and entropies of the oxidation of the diols and their monoethers are linearly related.The reaction involves transfer of a hydride ion in the rate-determining step.The temperature dependence of the kinetic isotope effect points to a planar pericyclic transition state.
- Banerji, Kalyan, K.
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p. 650 - 652
(2007/10/02)
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- Kinetics and Mechanism of Oxidation of Diols by Chloramine-B in Acid Solution
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The kinetics of the oxidation of four vicinal diols, three other diols, and 3-methoxybutan-1-ol by sodium N-chlorobenzenesulphonamide (CAB) have been studied in acid solution.The products of oxidation of vicinal diols result from the fission of the glycol bond while other diols yield corresponding hydroxyaldehydes.The reaction is first order in oxidant, diol and acidity.The oxidation of ethanediol-1,1,2,2-d4 indicates absence of a primary kinetic isotope effect.The values of solvent isotope effect, k(H2O)/k(D2O), for the oxidation of ethanediol and propane-1,3-diol are 7.61 and 0.39 respectively.PhSO2NHCl has been postulated as the reactive species.A mechanism involving a rate-determining cleavage of the C-C bond has been proposed for the vicinal diols.Other diols like the monohydric alcohols are oxidised by a hydride transfer mechanism.
- Shah, Bindu,Jain, Anandi L.,Banerji, Kalyan K.
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p. 720 - 722
(2007/10/02)
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- STUDY OF THE TRANSFORMATIONS OF DIOLS AND CYCLIC ETHERS, XLVII TRANSFORMATION OF 1,3-BUTANEDIOL ON SOME SUPPORTED METAL CATALYSTS (NEW DATA ON THE MECHANISM OF DEHYDRATION)
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The dehydration of 1,3-butanediol was studied on supported Ag, Co and Cu catalysts.The differences between the effects of these catalysts were interpreted.Intermediates of the transformations were detected, which provide new support for the reaction mechanism proposed earlier.Correlations were established between the selectivities of the reactions, the mass velocity and the temperature.
- Molnar, A.,Sirokman, G.,Bartok, M.
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p. 189 - 196
(2007/10/02)
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