- Conversion of fructose into 5-hydroxymethylfurfural and alkyl levulinates catalyzed by sulfonic acid-functionalized carbon materials
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A series of sulfonic acid-functionalized carbon materials (C-SO 3H), including poly(p-styrenesulfonic acid)-grafted carbon nanotubes (CNT-PSSA), poly(p-styrenesulfonic acid)-grafted carbon nanofibers (CNF-PSSA), benzenesulfonic acid-grafted CMK-5 (CMK-5-BSA), and benzenesulfonic acid-grafted carbon nanotubes (CNT-BSA), have been studied for fructose dehydration to 5-hydroxymethylfurfural (HMF) and fructose alcoholysis to alkyl levulinate. A study for optimizing the reaction conditions such as the catalyst loading, the reaction time, and the temperature has been performed. Under the optimal conditions, high HMF and ethyl levulinate yields of up to 89% and 86%, respectively, are obtained. The catalytic activities of C-SO3H for the conversions of fructose into both HMF and ethyl levulinate follow the order of their acid strength. The relationship between the catalytic activity and acid density of C-SO3H shows a linear correspondence in the fructose dehydration to HMF. The facile separation, ease of recovery, and high thermal stability make the developed C-SO3H efficient and environment-friendly catalytic materials for transforming biomass carbohydrate into fine chemicals.
- Liu, Ruliang,Chen, Jinzhu,Huang, Xing,Chen, Limin,Ma, Longlong,Li, Xinjun
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Read Online
- Alcohol-Activated Vanadium-Containing Polyoxometalate Complexes in Homogeneous Glucose Oxidation Identified with 51V-NMR and EPR Spectroscopy
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Alcoholic solvents, especially methanol, show an activating affect for heteropolyacids in homogenously catalysed glucose transformation reactions. In detail, they manipulate the polyoxometalate-based catalyst in a way that thermodynamically favoured total oxidation to CO2 can be completely supressed. This allows a nearly 100 % carbon efficiency in the transformation reaction of glucose to methyl formate in methanolic solution at mild reaction conditions of 90 °C and 20 bar oxygen pressure. By using powerful spectroscopic tools like 51V-NMR and continuous wave EPR we could unambiguously prove that the vanadate-methanol-complex[VO(OMe)3]n is responsible for the selectivity shift in methanolic solution compared to the aqueous reference system.
- Wesinger, Stefanie,Mendt, Matthias,Albert, Jakob
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p. 3662 - 3670
(2021/06/18)
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- Selective aerobic oxidation of cyclic ethers to lactones over Au/CeO2 without any additives
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Selective oxidation of ethers to lactones with O2 as a benign oxidant using Au/CeO2 as the catalyst has been developed. The oxygen vacancies and Au0 species on the surface of CeO2 contribute to the activation of O2. The excellent selectivity of lactones is due to the adsorption of ethers and activation of the C(sp3)-H bond on Au/CeO2.
- Liu, Shulin,Li, Shaopeng,Shen, Xiaojun,Wang, Yanyan,Du, Juan,Chen, Bingfeng,Han, Buxing,Liu, Huizhen
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supporting information
p. 2638 - 2641
(2020/03/10)
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- Sulfonium Salts as Alkylating Agents for Palladium-Catalyzed Direct Ortho Alkylation of Anilides and Aromatic Ureas
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A novel method for the ortho alkylation of acetanilide and aromatic urea derivatives via C-H activation was developed. Alkyl dibenzothiophenium salts are considered to be new reagents for the palladium-catalyzed C-H activation reaction, which enables the transfer of methyl and other alkyl groups from the sulfonium salt to the aniline derivatives under mild catalytic conditions.
- Simkó, Dániel Cs.,Elekes, Péter,Pázmándi, Vivien,Novák, Zoltán
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supporting information
p. 676 - 679
(2018/02/09)
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- Method for preparing formate-type compound
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The invention discloses a method for preparing a formate-type compound. The method comprises the following steps of: adopting an alcohol-type compound and 1,3-dihydroxyacetone as reaction raw materials, and under the existence of a composite catalyst and an oxidant, reacting for 2-48 hours in a reaction medium in a reactor at a reaction temperature of 25-100 DEG C so as to obtain the formate-typecompound. The method disclosed by the invention is simple, and is mild in reaction condition, and by the method, a target product can be obtained by low cost and high yield; the used catalyst has highcatalytic activity, and is easily separated from a reaction system to be repeatedly used; the whole process is environment-friendly, and the reaction raw material (1,3-dihydroxyacetone) is easily converted from a side product (glycerol) of biodiesel, so that the utilization of the glycerol is promoted.
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Paragraph 0039; 0047; 0048
(2018/07/30)
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- Facile aromatisation of Hantzsch 1,4-dihydropyridines by autoxidation in the presence of p-toluenesulfonic acid in acetic acid
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A simple protocol to achieve the aromatisation of Hantzsch dihydropyridines in high yield was established using p-toluenesulfonic acid in acetic acid and yields of 90% were obtained at room temperature. With regards to the Hantzsch 1,4-dihydropyridines derived from alkyl aldehydes bearing one or more á-hydrogens, dealkylation products were obtained through a proposed autoxidation mechanism.
- Zhang, Ding,Sha, Min
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p. 141 - 144
(2018/04/20)
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- Gas-Phase Reaction of Methyl n-Propyl Ether with OH, NO3, and Cl: Kinetics and Mechanism
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Rate constants at room temperature (293 ± 2 K) and atmospheric pressure for the reaction of methyl n-propyl ether (MnPE), CH3OCH2CH2CH3, with OH and NO3 radicals and the Cl atom have been determined in a 100 L FEP-Teflon reaction chamber in conjunction with gas chromatography-flame ionization detector (GC-FID) as the detection technique. The obtained rate constants k (in units of cm3 molecule-1 s-1) are (9.91 ± 2.30) × 10-12, (1.67 ± 0.32) × 10-15, and (2.52 ± 0.14) × 10-10 for reactions with OH, NO3, and Cl, respectively. The products of these reactions were investigated by gas chromatography-mass spectrometry (GC-MS), and formation mechanisms are proposed for the observed reaction products. Atmospheric lifetimes of the studied ether, calculated from rate constants of the different reactions, reveal that the dominant loss process for MnPE is its reaction with OH, while in coastal areas and in the marine boundary layer, MnPE loss by Cl reaction is also important.
- Zhu, Jianqiang,Wang, Shuyan,Tsona, Narcisse T.,Jiang, Xiaotong,Wang, Yifeng,Ge, Maofa,Du, Lin
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p. 6800 - 6809
(2017/09/23)
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- A method for esterification reaction rate prediction of aliphatic monocarboxylic acids with primary alcohols in 1,4-dioxane based on two parametrical taft equation
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Esterification reaction rates of aliphatic monocarboxylic acids with primary alcohols in 1,4-dioxane as inert solvent were investigated. Acids were esterified with 1-propanol and alcohols with acetic acid as model reactants at a constant temperature of 60°C, at a fixed ionic strength and pH in a batch reactor with a constant volume. For evaluation of reaction rates, an exact kinetic equation for the equilibrium reaction was applied. Under these conditions and for low reactants, concentrations reaction rate depends only on the structure of reactants and, therefore, can be predicted by a correlation equation with two Taft coefficients (inductive and steric effects). From these equations, it is possible to estimate the esterification reaction rate constant for other acid-alcohol pairs. This methodology may also be suitable for other kinetic systems measured under comparable experimental conditions.
- Vojtko, Jan,Tomcik, Peter
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p. 189 - 196
(2014/02/14)
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- PIFA-mediated esterification reaction of alkynes with alcohols via oxidative cleavage of carbon triple bonds
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A metal-free esterification of alkynes via C≡C triple bond cleavage has been developed. In the presence of phenyliodine bis(trifluoroacetate), a diverse range of alkyne and alcohol substrates undergoes triple bond cleavage to produce carboxylic ester motifs in moderate to good yields. The transformation is proposed to proceed via hydroxyethanones and ethanediones as intermediates on the basis of mechanistic studies and exhibits a broad substrate scope and good functional group tolerance.
- Jiang, Qing,Zhao, An,Xu, Bin,Jia, Jing,Liu, Xin,Guo, Cancheng
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supporting information
p. 2709 - 2715
(2014/04/17)
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- MONOMER, POLYMER, RESIST COMPOSITION, AND PATTERNING PROCESS
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A polymer comprising recurring units derived from a (meth)acrylate monomer of tertiary ester type having branched alkyl on alicycle is used to form a resist composition. When subjected to exposure, PEB and organic solvent development, the resist composition is improved in dissolution contrast.
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- Nickel-catalyzed hydrosilylation of CO2 in the Presence of Et3B for the synthesis of formic acid and related formates
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The reaction of CO2 with Et3SiH catalyzed by the nickel complex [(dippe)Ni(μ-H)]2 (1) afforded the reduction products Et3SiOCH2OSiEt3 (12%), Et 3SiOCH3 (3%), and CO, which were characterized by standard spectroscopic methods. Part of the generated CO was found as the complex [(dippe)Ni(CO)]2 (2), which was characterized by single-crystal X-ray diffraction. When the same reaction was carried out in the presence of a Lewis acid, such as Et3B, the hydrosilylation of CO2 efficiently proceeded to give the silyl formate (Et3SiOC(O)H) in high yields (85-89%), at 80 C for 1 h. Further reactivity of the silyl formate to yield formic acid, formamides, and alkyl formates was also investigated.
- Gonzalez-Sebastian, Lucero,Flores-Alamo, Marcos,Garcia, Juventino J.
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p. 7186 - 7194
(2014/01/06)
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- Room-temperature selective aliphatic carbon-carbon bond activation and functionalization of ethers by rhodium(II) porphyrin
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Selective aliphatic carbon(α)-carbon(β) bond activation of ethers by (5,10,15,20-tetramesitylporphyrinato)rhodium(II) (Rh(tmp) (1)) was achieved at room temperature to yield corresponding rhodium porphyrin alkyls and the functionalized esters. Rh(tmp)OH was the proposed intermediate responsible for cleaving the C(α)-C(β) bond. The reaction is general for both straight- and branch-chain ethers.
- Lee, Siu Yin,Lai, Tsz Ho,Choi, Kwong Shing,Chan, Kin Shing
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scheme or table
p. 3691 - 3693
(2011/09/20)
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- Hypervalent λ3-bromane strategy for Baeyer-Villiger oxidation: Selective transformation of primary aliphatic and aromatic aldehydes to formates, which is missing in the classical Baeyer-Villiger oxidation
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A conceptually distinct, modern strategy for Baeyer-Villiger oxidation (BVO) was developed. Our novel method involves initial hydration of water to carbonyl compounds, followed by ligand exchange of hypervalent aryl-λ3-bromane on bromane(III) with the resulting hydrate, yielding a new type of activated Criegee intermediate. The intermediate undergoes BV rearrangement and produces an ester via facile reductive elimination of an aryl-λ3-bromanyl group, because of the hypernucleofugality. The novel strategy makes it possible to induce selectively the BV rearrangement of straight chain primary aliphatic as well as aromatic aldehydes, which is missing in the classical BVO: for instance, octanal and benzaldehyde afforded rearranged formate esters with high selectivity (>95%) under our conditions, while the attempted classical BVO produced only carboxylic acids. This firmly establishes the powerful nature of new methodology for BVO.
- Ochiai, Masahito,Yoshimura, Akira,Miyamoto, Kazunori,Hayashi, Satoko,Nakanishi, Waro
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supporting information; experimental part
p. 9236 - 9239
(2010/11/02)
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- Promotional effect of potassium salt in low-temperature formate and methanol synthesis from CO/CO2/H2 on copper catalyst
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Alkyl formates can be formed from CO2-containing syngas with C1-C4 alkyl alcohol solvents in the presence of potassium carbonate, which changed to potassium formate as catalyst. The formates can be in situ hydrogenolysized further to produce methanol effectively over manganese oxide or magnesia-supported copper catalysts. These homogeneous and heterogeneous catalysts constitute a novel system for methanol synthesis from CO/CO2/H2 even at 443 K. Copyright
- Zhao, Tian-Sheng,Yoneyama, Yoshiharu,Fujimoto, Kaoru,Yamane, Nodyuki,Fujimoto, Kenichiro,Tsubaki, Noritatsu
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p. 734 - 735
(2008/02/09)
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- The application of N,N′dibromo-N,N′-1,2-ethanediyl bis(P-toluenesulfonamide) as a powerful reagent for conversion of carboxylic acids into esters and amides with triphenylphosphine
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In the presence of equivalent amounts of triphenylphenylphosphine and N,N′-dibromo-N,N′-1,2-ethanediylbis(p-toluenesulphonamide) ester and amide compounds can be generated in high yields from the corresponding carboxylic acid and alcohols or amines.
- Khazaei, Ardeshir,Mallakpour, Shadpour,Zolfigol, Mohammad Ali,Ghorbani-Vaghei, Ramin,Kolvari, Eskandar
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p. 1715 - 1721
(2007/10/03)
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- METHOD FOR CATALYTIC OXYGENATION OF CYCLIC ETHERS WITH HOMO AND HETERO METALLIC MO/RU COMPLEXES AND MOLECULAR OXYGEN
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A process has been invented for the oxygenation of cyclic ethers. General problems in the process are the use of expensive and toxic oxidants, low TONs (turnover numbers), low selectivity and working at elevated temperatures (energy costs). These problems were solved by employing appropriate organometallic catalyst precursors. Using lnd(CO)3Mo-Ru(CO)2Cp, Cp(CO)3Mo-Ru(CO)2Cp and Cp(CO)2Ru-Ru(CO)2Cp or other ruthenium compounds, the aerobic oxidation of tetrahydrofurane (THF) proceeds at room temperature and produces selectively γ-butyrolactone. Use of the catalysts yields replacement of stoichiometric, toxic co-oxidants by cheap air oxygen, working at room temperature, high selectivity, high TONs and overall formulation of green chemistry which is applicable to cyclic ethers: formula (I) The invented process satisfies the urge for green chemistry by using cheap air oxygen in a catalytic process with unlimited catalyst lifetime and plain water as the side product. Functionalised lactones will be available from corresponding ethers.
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- Ruthenium-catalyzed hydrogenation of carbon dioxide to formic acid in alcohols
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Catalytic hydrogenation of CO2 to formic acid with the (solvento)metal hydride complex, TpRu(PPh3)(CH3CN)H [Tp = hydrotris(pyrazolyl)borate], in various alcohols was studied. High-pressure NMR monitoring of the catalytic reaction in non-acidic methanol shows that the observable intermediate is a formate complex resulting from CO2 insertion into the Ru-H bond and is stabilized by the hydrogen-bonding interaction between the formato ligand and a methanol molecule. However, in the case of the acidic alcohol, CF3CH2OH, the observable intermediates are [TpRu(PPh3)(CH3CN)2] +CF3CH2O- and the alkyl carbonate complex, TpRu(PPh3)(η2O2COCH 2CF3), which are formed by the reaction of CO2 with the alkoxide species, TpRu(PPh3)(CH3CN)(OCH 2CF3), generated by a very facile reaction between TpRu(PPh3)(CH3CN)H and CF3CH2OH. We propose that the productive catalytic cycles of the reactions conducted in a variety of alcohols are similar to the one we formulated for the catalytic hydrogenation of CO2 in hydrous THF. The formic acid is produced by the transfer of a hydride and a proton from the transient alcohol hydride intermediate, TpRu(PPh3)(ROH)H, to an approaching CO2 molecule. The activity of TpRu(PPh3)(CH3CN)H is higher in CF3CH2OH than in methanol and other non-acidic alcohols and it is probably due to the enhanced electrophilicity of the carbon atom of CO2, which results from the strong interaction between the proton of the highly acidic alcohol in TpRu(PPh3)(CF3CH 2OH)H and an oxygen atom of CO2. The electrophilic carbon atom of CO2 could in turn abstract the hydride from Ru-H in a more facile manner. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Ng, Siu Man,Yin, Chuanqi,Yeung, Chi Hung,Chan, Tak Chung,Lau, Chak Po
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p. 1788 - 1793
(2007/10/03)
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- PROCESS FOR PREPARATION OF FORMATE ESTERS OR METHANOL AND CATALYST THEREFOR
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A production process and a catalyst are provided, which can be less decreased in activity of the catalyst even when CO2, water and the like are present in the starting material and/or the reaction system, and which can produce a formic ester or a methanol at a low temperature and a low pressure. The present invention relates to a process for producing methanol, comprising reacting carbon monoxide with an alcohol in the presence of an alkali metal-type catalyst, and/or an alkaline earth metal-type catalyst to produce a formic ester, wherein a hydrogenolysis catalyst of formic ester and hydrogen are allowed to be present together in the reaction system to hydrogenate the produced formic ester and thereby obtain a methanol.
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Page column 7
(2008/06/13)
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- Laboratory studies of the OH-initiated photooxidation of di-n-propyl ether
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The OH-initiated photooxidation of di-n-propyl ether was investigated in this study. Di-n-propyl ether was mixed with nitric oxide and a hydroxyl radical precursor and irradiated using UV black lamps in a glass environmental chamber. Mass spectrometry was used as the primary analytical technique to monitor the reactants and products. FTIR spectroscopy was used to monitor formaldehyde. The products observed were propyl formate, acetaldehyde, propionaldehyde, and propyl propionate, with molar yields relative to di-n-propyl ether concentration loss of 0.61±0.044, 0.60±0.057, 0.15±0.062, and 0.043±0.015, respectively. Errors represent ±2σ. Nitrates could not be quantified because of a lack of commercially available standards. However, evidence exists for nitrate formation from the photooxidation of di-n-propyl ether. Formaldehyde concentrations were negligible. Mechanism predictions were performed on the di-n-propyl ether/OH system using the Carter kinetic software. Propyl formate and acetaldehyde yields were reasonably predicted (under 11.7% error). However, propionaldehyde and propyl propionate yields were vastly underpredicted, and examination of the experimental data suggested secondary production of both propionaldehyde and propyl propionate. Reactions were proposed for the photolysis and OH-initiated photooxidation of a primary nitrate product (1-propoxy propyl nitrate) that resulted in the formation of propionaldehyde and propyl propionate. Basic semiempirical computational chemistry calculations at the UHF/PM3 level of theory were performed using Hyperchem to investigate pathways for the secondary formation of propionaldehyde in particular.
- Sempeles, John,Andino, Jean M.
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p. 703 - 711
(2007/10/03)
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- Hydroxyl radical reaction rate constant and atmospheric transformation products of 2-propoxyethanol
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The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of 2-propoxyethanol (2PEOH, CH3CH2CH2OCH2CH2(OH)). 2PEOH reacts with OH with a bimolecular rate constant of (21.4±6.0)×10-12 cm3 molecule-1 s-1 at 297±3 K and 1 atm total pressure, which is a little larger than previously reported. Assuming an average OH concentration of 1×106 molecules cm-3, an atmospheric lifetime of 13 h is calculated for 2PEOH. In order to more clearly define this hydroxy ether's atmospheric reaction mechanism, an investigation into the OH+2PEOH reaction products was also conducted. The OH+2PEOH reaction products and yields observed were: propyl formate (PF, 47±2%, CH3CH2CH2OC(double bond O)H), 2 propoxyethanal (CH3CH2CH2OCH2C(double bond O)H 15±1%), and 2-ethyl-1,3-dioxolane (5.4±0.4%). The 2PEOH reaction mechanism is discussed in light of current understanding of oxygenated hydrocarbon atmospheric chemistry. The findings reported here can be related to other structurally similar alcohols and may impact regulatory tools such as ground-level ozone-forming potential calculations (incremental reactivity).
- Markgraf, Stewart J.,Semples, John,Wells
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p. 315 - 322
(2007/10/03)
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- Alkylation Reactions by Means of Alkanols and Carbon Monoxide: An Efficient Synthesis of Thioethers and of Caffeine from Theophylline
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The reaction of sodium or potassium thiolates with alkanols and carbon monoxide provides a versatile route to produce thioethers in excellent yields.By analogy, the potassium salt of theophylline suffers a nearly quantitative conversion to caffeine when heated with methanol under CO pressure.The mechanism of these alkylation reactions is discussed. - Key Words: Nucleophilic alkylation / Thioethers / Caffeine / Carbon monoxide / Alkanols
- Bott, Kaspar
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p. 1955 - 1956
(2007/10/02)
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- General base catalysis of ester hydrolysis
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The hydrolysis of alkyl formates with leaving groups in the range pKa = 12-16 is catalyzed by substituted acetate anions. There is an increase in the Br?nsted β value for general base catalysis with decreasing pKa of the leaving alcohol and a complementary increase in -β1g with decreasing pKa of the catalyzing base, both of which are consistent with a value of pxy = ?β/-pK1g = ?β1g/-?pKBH ? 0.11. This result supports a class n mechanism of general base catalysis, in which a proton is abstracted from the nucleophilic water molecule by the base catalyst in the transition state; it is not consistent with the kinetically equivalent class e mechanism of electrophilic catalysis by general acids of a reaction with hydroxide ion, by proton donation to the leaving alcohol. Solvent deuterium isotope effects in the range kH2O/kD2O = 3.6-5.3 for the buffer-independent reaction and 2.5-2.8 for catalysis by CHaCOO- support concerted proton transfer and O-C bond formation. The secondary isotope effect for catalysis of the hydrolysis of LCOOMe by acetate ion is kD/kH = 1.05. Both nucleophilic and general base mechanisms of catalysis by acetate anions are observed for the hydrolysis of substituted phenyl formates with leaving groups of pKa = 7.1-10.1. A small value of β = 0.12 for general base catalysis of the hydrolysis of phenyl formate and p-methylphenyl formate represents catalysis of the addition of water by hydrogen bonding of water to the base catalyst. On the other hand, a larger value of β = 0.35 and a decrease in kH2O/kD2O to 1.2 were observed for general base catalysis of the hydrolysis of p-nitrophenyl formate. It is suggested that the increase in β with decreasing pK1g (an apparent "anti-Hammond effect") may be accounted for by a change in mechanism, from catalysis of a stepwise reaction of phenyl and p-methylphenyl formates to concerted general base catalysis of formyl transfer to water for the reaction of p-nitrophenyl formate.
- Stefanidis, Dimitrios,Jencks, William P.
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p. 6045 - 6050
(2007/10/02)
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- Determination of Organic Acid Structure Effect on the Equilibrium Constant of Esterification
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Equilibrium constants of esterification were measured using both static and dynamic methods.Simultaneously, the measured rate constants of the organic acids esterifications with propanol and the rate constants of propylesters hydrolysis were correlated by the Taft's-equation.It was found, that the equilibrium constant of this reaction does not depend on the structure of the organic acid, and has for T = 60 deg C the value 3.96 +/- 0.08.
- Vojtko, J.
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p. 1227 - 1235
(2007/10/02)
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- Evidence for C-O bond formation, aldehyde decarbonylation, and dimerization by reaction of formaldehyde and acetaldehyde with trans-ROIr(CO)(PPh3)2
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The reaction of formaldehyde and acetaldehyde with trans-ROIr(CO)(PPh3)2 (R = Me, i-Pr, n-Pr, t-Bu) leads to formation of esters ROC(O)R′ (R′ = H or Me) by formation of a carbon-oxygen bond between the alkoxide and the acyl from the aldehyde and to catalytic production of the ester R′CH2C(O)OR′ in a Tischenko reaction.
- Bernard, Karen A.,Atwood, Jim D.
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p. 235 - 236
(2008/10/08)
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- Process for the production of formates
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An alkyl ester of formic acid is prepared by reacting carbon monoxide with an alcohol in the presence, as catalyst, of (a) a guanidine or (b) an amidine and an epoxide. The amidine or guanidine structure can by cyclic. The process can be operated in the liquid phase at pressures from 20 to 120 bars and temperatures from 40° to 150° C. with excess carbon monoxide over that required for conversion of the alcohol to the formate ester.
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- Vacuum-ultraviolet photlysis (185) nm of liquid 1,3-dioxan
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1,3-Dioxan photolytic destruction at 185 nm occurs with a quantum yield of about 0.3 in the liquid phase.Of the 22 products determined, the major ones are n-propylformate (φ = 0.10), formaldehyde (0.075), 1,3-diox-4-en (0.06), hydrogen (0.05), ethylene (0.04), and 3-methoxypropionaldehyde (0.04).A number of the minor products are of the general type B, some of which bear a hydroxyl function at the end of the side chain.N2O interacts with excited 1,3-dioxan, leading to the production of N2.Some experiments have been carried out in the vapour phase, the results of which indicate that considerable fragmentation of hot primary intermediates and products into low-molecular-weight products occurs.The nature of these products cannot be linked directly to the primary photolytic process inferred from the liquid-phase studies.Certain contrasts in the photolytic behaviour of 1,3-dioxan and 1,4-dioxan are discussed.
- Schuchmann, Heinz-Peter,Clemens, Sonntag von
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p. 1833 - 1839
(2007/10/02)
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- TRANSFORMATIONS OF CYCLIC ORTHO MONO- AND DIESTERS BY THE ACTION OF FREE RADICALS IN THE LIQUID PHASE
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The homolytic liquid-phase reactions of 2-propoxy-1,3-dioxane, 1,2-di(1,3-dioxolan-2-yloxy)ethane, and 1,3-di(1,3-dioxan-2-yloxy)propane, initiated by tert-butoxyl radicals, were investigated.A mechanism is proposed for the formation of dipropylcarbonate, 1,3-dioxan-2-one, propylformate, propionaldehyde, and propane from 2-propoxy-1,3-dioxane.The kinetic parameters characterizing the rate and direction of the transformations were determined.It was found that the corresponding linear and cyclic carbonates are mainly formed from the ortho diesters.
- Kostyukevich, L. L.,Pastuschenko, E. V.,Zlot-skii S. S.,Rakhmankulov, D. L.
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p. 127 - 132
(2007/10/02)
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- KINETIC ISOTOPE EFFECT IN THE OXIDATION OF CYCLIC AND LINEAR ACETALS WITH OZONE AND MOLECULAR OXYGEN
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Substitution of hydrogen atoms at the acetal carbon by deuterium in 1,3-dioxolane, 1,3-dioxane, and dipropoxymethane leads to a decrease in the rate constant of ozonization and oxidation.The magnitude of the kinetic isotope effect lies in the range of 2-3 and is somewhat lower than the known values (4-6) for alcohols, ethers, and carboxylic acids.This is evidently due to the smaller extension of the C-H bond in the transition state of the reaction of acetals with ozone molecules and peroxide radicals.
- Kuramshin, E. M.,Sadaeva, R. Kh.,Gumerova, V. K.,Zlot-skii, S. S.,Rakhmankulov, D. L.
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p. 136 - 139
(2007/10/02)
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- Rational Mechanism for Homogeneous Hydrogenation of Carbon Monoxide to Alcohols, Polyols, and Esters
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The products derived from synthesis gas conversion by homogeneous catalysis are concluded to be formed via the key intermediate formaldehyde.The intermediacy of formaldehyde is supported by reaction rate studies, comparison reactions of formaldehyde with synthesis gas, and the trapping of formaldehyde and glycolaldehyde intermediates during a reaction as their ethylene glycol acetals.Although the formation of formaldehyde from synthesis gas is themodynamically unfavorable, it is argued that the concentration of formaldehyde permitted by thermodynamics is more than sufficient for a transient intermediate.The overall mechanism incorporates only step that are already well established in the science of homogeneous catalysis.
- Fahey, Darryl R.
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p. 136 - 141
(2007/10/02)
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- Products and mechanism of the reaction of ozone with acetals
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As a result of the ozonized oxidation of acetals at -20-60 deg C esters and alcohols (or glykol monoesters), hydroperoxides, and water accumulate in parallel in the initial period of the reaction.The formation of esters and alcohols is explained by molecular paths, and the formation of hydroperoxides and water is explained by radical paths; the yields of hydroperoxides and water can be reduced by reducing the ozonization temperature.The reactivity of acetals increases with increase in the size of the alkoxyl group.
- Brudnik, B. M.,Kuramshin, E. M.,Imashev, U. B.,Zlotskii, S. S.,Rakhmankulov, D. L.
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p. 608 - 614
(2007/10/02)
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- Thermolyse en solution de t-butylperoxy-2 oxacyclanes
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The thermal decomposition of 2-tert-butylperoxytetrahydrofuran (1a), 2-tert-butylperoxytetrahydropyran (1b) and 2-tert-butylperoxyoxepan (1c) was studied in dibutyl phtalate.A free radical mechanism was suggested to explain the formation of the thermolysis products. The first step of this mechanism is the homolysis of the peroxidic bond.Two kinds of radicals are obtained: tert-butoxy (2) and oxacyclan-2-oxy (3a, b or c) radicals. When they have escaped out of the solvent cage, tert-butoxy radicals lead to the formation of tert-butanol (4), by transfer reactions to the solvent, and of acetone (5), by β-scission reactions. In the solvent cage, part of the oxacyclan-2-oxy radicals (3) give open alkyl radicals (3'): formyloxy-3-propyl (3'a), formyloxy-4-butyl (3'b) or formyloxy-5-pentyl (3'c) radicals, by β-scission reactions.About half of the radicals (3') diffuse out of the solvent cage, leading, after transfer to the solvent,the corresponding n-alkyl formates (6): n-propyl formate (6a), n-butyl formate (6b) or n-pentyl formate (6c). By coupling in the solvent cage of tert-butoxy and the remaining radicals (3'), 3-tert-butoxypropyl formate (6'a), 4-tert-butoxybutyl formate (6'b) or 5-tert-butoxypentyl formate (6'c) are obtained.Morover in the solvent cage, disproportionation reactions between tert-butoxy (2) and oxacyclan-2-oxy radicals (3) give the corresponding lactones (7): 4-butanolide (7a), 5-pentanolide (7b) or 6-hexanolide (7c). The balance of the products resulting from the behaviour of the oxacyclan-2-oxy (3) or the related formyloxy-n-alcyl (3') radical shows that about 50 percent of these radicals reacted before they had escaped out of the solvent cage.Thus, since the radicals issued from the thermolysis of 2-tert-butylperoxyoxacyclanes (1) undergo few interactions with the solvent in wich the decomposition take place, it appears that these cyclic peroxyketals act as rather poor free radical initiators.
- Maillard, Bernard,Manigand, Claude,Pavlovna Tarassova, Natalia,Villenave, Jean-Jacques,Filliatre, Claude
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p. 255 - 260
(2007/10/02)
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- JOINT HOMOLYTIC LIQUID-PHASE TRANSFORMATIONS OF ALKYL ORTHOFORMATES AND ACETALS
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The reaction kinetics and the reactivity of ethyl orthoformate were studied in joint transformations with 1,3-dioxane, 1,1-dialkoxyalkanes, and hexyl orthoformate, initiated by tert-butyl peroxide.It was established that the corresponding dialkyl carbonates and esters are formed as a result of specific radical-chain transformations.From the ratio of the products in the range 120-150 deg C it was determined that alkyl orthoformates are more reactive than linear and cyclic acetals.
- Kostyukevich, L. L.,Kalashnikov, S. M.,Pastushenko, E. V.,Zlot-skii, S. S.,Rakhmankulov, D. L.
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p. 1664 - 1666
(2007/10/02)
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