- Preparation and catalytic performance of perfluorosulfonic acid-functionalized carbon nanotubes
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Perfluorosulfonic acid-functionalized carbon nanotubes were prepared by liquid deposition of the perfluorosulfonic acid-polytetrafluoroethylene copolymer and characterized by N2 adsorption, scanning electron microscopy, transmission electron mi
- Zhang, Mengxiao,Li, Cuican,Hua, Weiming,Yue, Yinghong,Gao, Zi
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- Sulfonic acid functionalized MCM-41 as solid acid catalyst for tert-butylation of hydroquinone enhanced by microwave heating
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Covalently linked sulfonic acid (SO3H) modified MCM-41 mesoporous catalysts was prepared, characterized and its catalytic activity under microwave irradiation was evaluated. The NH2-MCM-41 was first prepared by anchoring (3-aminoprop
- Ng, Eng-Poh,Mohd Subari, Siti Norbayu,Marie, Olivier,Mukti, Rino R.,Juan, Joon-Ching
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- Candida antarctica lipase B-catalyzed regioselective deacylation of dihydroxybenzenes acylated at both phenolic hydroxy groups
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Candida antarctica lipase B proved to be highly active in the deacylation of substituted hydroquinones and resorcinols acylated at both phenolic hydroxy groups. The deacylation reactions were much faster than the corresponding direct acylations of these dihydroxybenzenes catalyzed by the same lipase. More importantly, they took place generally in a markedly regioselective manner: the acyloxy group remote from the substituent was preferentially cleaved. The main or exclusive products obtained were the regioisomers of those produced through the direct acylation of the dihydroxybenzenes. In the case of alkyl-substituted hydroquinone derivatives, the regioselectivity increased with an increase in the bulk of the substituent. In the case of 4-substituted diacylated resorcinols, the 3-O-monoacyl derivatives were obtained generally as the sole products. Quite interestingly, some secondary alcohols proved to act as better acyl acceptors than the corresponding primary alcohols in these enzymatic deacylations.
- Miyazawa, Toshifumi,Hamada, Manabu,Morimoto, Ryohei
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- Method for synthesizing tert-butylhydroquinone
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The invention discloses a method for synthesizing tert-butylhydroquinone, and relates to tert-butylhydroquinone. The invention provides a synthesis method of tert-butylhydroquinone, and the method hasthe advantages of simple process and lower cost. The method comprises the following steps: 1) sequentially adding a catalyst sulfamic acid, a solvent toluene or xylene, tert-butyl alcohol, hydroquinone and 1, 4-dioxane into a heatable pressure-resistant reactor for reaction at 120-150 DEG C for 4-12 hours; 2) after the reaction is finished, adding ethanol, filtering to remove the catalyst sulfamic acid, and removing the solvent to obtain a crude product; 3) purifying the crude product obtained in the step 2) to obtain the product tert-butylhydroquinone. The defects that catalysts with high corrosivity are needed in the existing synthesis process, the process cost is high, the environmental pollution is serious, and the reaction selectivity is low are overcome.
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Paragraph 0033-0035; 0042-0043
(2021/03/13)
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- Tert-butylhydroquinone preparation method
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The invention relates to the technical field of organic synthesis, and relates to a tert-butylhydroquinone preparation method, which comprises: 1) sequentially adding 2-tert-butylphenol, a transitionmetal copper (I) cooperation compound and a solvent to a high pressure reaction kettle, introducing oxygen to achieve a specified pressure, heating and stirring to a specified temperature, and carrying out a reaction for 0.5-3 h; 2) after the reaction is finished, evaporating out the solvent, washing the residual solid with a solvent, and carrying out steam stripping to obtain 2-tert-butyl p-benzoquinone; 3) sequentially adding the 2-tert-butyl p-benzoquinone obtained in the step 1), a catalyst and a solvent into a high-pressure reaction kettle, introducing hydrogen to a specified pressure after gas exchange is completed, heating and stirring to a specified temperature, and carrying out a reaction for 0.5-3 hours; and 4) after the reaction is finished, evaporating out the solvent, and rectifying to obtain the tert-butylhydroquinone product. According to the invention, the method has the advantages of high product yield, convenient operation, cheap raw materials, economy and reliability, and is suitable for large-scale production.
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Paragraph 0025-0031
(2020/04/02)
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- Preparation method of high-purity 2-tert-butyl hydroquinone and purification method 2-tert-butyl hydroquinone
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The preparation method 2 - of the high-purity,tert-butyl hydroquinone comprises the following steps: uniformly mixing, heating the hydroquinone, as a reaction solvent, heating temperature rise, to obtain,tert-butyl hydroquinone to obtain the high-purity,tert-butyl hydroquinone . The present invention further provides a preparation method of the high-purity tert-butyl hydroquinone and 2 - hours; of the hydrothermal filtration . The present invention further provides a method for purifying tert-butyl hydroquinone in,tert-butyl hydroquinone after the uniform mixing, of the reaction product 70 °C with water, to obtain the reaction crude product is obtained, 2 - by, heating and heating. the reaction 2 - medium 2 - to the reaction crude product by a heat-filtration temperature of more than two.
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Paragraph 0053-0174
(2020/03/25)
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- Can Donor Ligands Make Pd(OAc)2a Stronger Oxidant? Access to Elusive Palladium(II) Reduction Potentials and Effects of Ancillary Ligands via Palladium(II)/Hydroquinone Redox Equilibria
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Palladium(II)-catalyzed oxidation reactions represent an important class of methods for selective modification and functionalization of organic molecules. This field has benefitted greatly from the discovery of ancillary ligands that expand the scope, reactivity, and selectivity in these reactions; however, ancillary ligands also commonly poison these reactions. The different influences of ligands in these reactions remain poorly understood. For example, over the 60-year history of this field, the PdII/0 redox potentials for catalytically relevant Pd complexes have never been determined. Here, we report the unexpected discovery of (L)PdII(OAc)2-mediated oxidation of hydroquinones, the microscopic reverse of quinone-mediated oxidation of Pd0 commonly employed in PdII-catalyzed oxidation reactions. Analysis of redox equilibria arising from the reaction of (L)Pd(OAc)2 and hydroquinones (L = bathocuproine, 4,5-diazafluoren-9-one), generating reduced (L)Pd species and benzoquinones, provides the basis for determination of (L)PdII(OAc)2 reduction potentials. Experimental results are complemented by density functional theory calculations to show how a series of nitrogen-based ligands modulate the (L)PdII(OAc)2 reduction potential, thereby tuning the ability of PdII to serve as an effective oxidant of organic molecules in catalytic reactions.
- Bruns, David L.,Musaev, Djamaladdin G.,Stahl, Shannon S.
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supporting information
p. 19678 - 19688
(2020/12/18)
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- A PROCESS FOR PREPARATION OF TERTIARY BUTYL HYDROQUINONE
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A PROCESS FOR PREPARATION OF TERTIARY BUTYL HYDROQUINONE The present invention relates to a process for preparation of tertiary butyl hydroquinone. More particularly, it relates to a process for preparation 5 of TBHQ by eradicating the consumption of hazardous solvents like toluene and eliminating hazardous impurities like hydroquinone, tertiary butyl‐p‐benzoquinone and also drastically reducing the presence of heavy metals like lead and arsenic. The present invention includes stages I‐IV in which TBHQ is more purified and precipitated with a high scale purity results. TBHQ has 10 application in food additives, animal feeds, as an antioxidant, emulsifier and in edible oils, effectively as antioxidant.
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Page/Page column 9; 10; 11
(2020/07/15)
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- 1-Methyl-1,4-cyclohexadiene as a Traceless Reducing Agent for the Synthesis of Catechols and Hydroquinones
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Pro-aromatic and volatile 1-methyl-1,4-cyclohexadiene (MeCHD) was used for the first time as a valid H-atom source in an innovative method to reduce ortho or para quinones to obtain the corresponding catechols and hydroquinones in good to excellent yields. Notably, the excess of MeCHD and the toluene formed as the oxidation product can be easily removed by evaporation. In some cases, trifluoroacetic acid as a catalyst was added to obtain the desired products. The reaction proceeds in air and under mild conditions, without metal catalysts and sulfur derivatives, resulting in an excellent and competitive method to reduce quinones. The mechanism is attributed to a radical reaction triggered by a hydrogen atom transfer from MeCHD to quinones, or, in the presence of trifluoroacetic acid, to a hydride transfer process.
- Baschieri, Andrea,Amorati, Riccardo,Valgimigli, Luca,Sambri, Letizia
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p. 13655 - 13664
(2019/10/28)
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- Direct Synthesis of Hydroquinones from Quinones through Sequential and Continuous-Flow Hydrogenation-Derivatization Using Heterogeneous Au–Pt Nanoparticles as Catalysts
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Pt–Au bimetallic nanoparticle catalysts immobilized on dimethyl polysilane (Pt–Au/(DMPSi-Al2O3)) have been developed for selective hydrogenation of quinones to hydroquinones. High reactivity, selectivity, and robustness of the catalysts were confirmed under continuous-flow conditions. Various direct derivatizations of quinones, such as methylation, acetylation, trifluoromethanesulfonylation, methacrylation, and benzoylation were successfully performed under sequential and continuous-flow conditions to afford the desired products in good to excellent yields. Especially, air-sensitive hydroquinones, such as anthrahydroquinones and naphthohydroquinones, could be successfully generated and derivatized under closed sequential and continuous-flow conditions without decomposition.
- Miyamura, Hiroyuki,Tobita, Fumiya,Suzuki, Aya,Kobayashi, Shū
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supporting information
p. 9220 - 9224
(2019/06/13)
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- From simple phenols to potent chain-breaking antioxidants by transposition of benzo[1,4]oxathiines to benzo[b]thiophenes
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Simple phenols, including food stock recycled derivatives, were used for the synthesis of 1,4-benzooxathiine intermediates, with limited or no antioxidant activity. Depending upon their substitution pattern, these compounds, through an acid promoted transposition, can be converted into o-hydroxydihydrobenzo[b]thiophenes or o-hydroxy-benzo[b]thiophenes as a new class of potent chain-breaking antioxidants, showing, in the reaction with alkyl peroxyl radicals, kinetic rate constants (kinh) comparable to that of α?tocopherol, the more potent natural lipophilic phenolic antioxidant.
- Viglianisi, Caterina,Pietro, Leonardo Di,Meoni, Valentina,Amorati, Riccardo,Menichetti, Stefano
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supporting information
p. 65 - 85
(2019/12/23)
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- Heterogeneous Nitrogen-doped Graphene Catalysed HOO? Generation via a Non-radical Mechanism for Base-free Dakin Reaction
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A heterogeneous nitrogen-doped graphene catalytic pathway for H2O2 activation to generate alkaline hydrogen peroxide (HOO?) through a non-radical mechanism was reported. Remarkably, the heterogeneous catalytic procedure has been used for the evergreen and environmentally Dakin reaction without using any transition metals, homogeneous bases, ligands, additives or promoters, completely. The study of catalyst structure and catalytic activities indicate that the most active sites are created by the graphitic N atoms at zig-zag edges of the sheets. In addition, N as dopant element changes the reactivity of the neighbour C atoms, and leads to the formation of carbon-hydroperoxide (C?(HOOH)) and C?O* (C?O?) transition state species on the graphene surface in catalytic the reaction. (Figure presented.).
- Sun, Wei,Gao, Lingfeng,Sun, Xu,Yang, Hua,Zheng, Gengxiu
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supporting information
p. 5210 - 5216
(2019/11/03)
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- Reactivity of iPrPCPIrH4 with para-benzoquinones
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In the interest of investigating new hydrogen acceptors for pincer–iridium catalyzed dehydrogenations with the ability to be catalytically recycled, a series of para-benzoquinones have been reacted with iPrPCPIrH4 in various solvents and conditions. Preliminary results indicate that a wide range of quinones are capable of dehydrogenating iPrPCPIrH4, and that several turn-overs in alcohol dehydrogenation by iPrPCPIr are possible at room temperature using benzoquinone acceptors. However, strong acceptor–catalyst interactions are inhibitory toward catalysis when the acceptor is used in excess. A new class of (bis)-η2 pi-adducts, formed between iPrPCPIr and benzoquinones, nicknamed “barber-chairs”, has been identified and 3 examples have been characterized.
- Wilklow-Marnell, Miles,Brennessel, William W.,Jones, William D.
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p. 209 - 214
(2017/11/24)
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- Pd0-PyPPh2@porous organic polymer: Efficient heterogeneous nanoparticle catalyst for dehydrogenation of 3-methyl-2-cyclohexen-1-one without extra oxidants and hydrogen acceptors
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In this contribution, we have developed an efficient and recyclable porous organic polymer (POP) supported Pd nanoparticle catalyst (Pd°-PyPPh2@POP) for dehydrogenation of 3-methyl-2-cyclohexen-1-one. This heterogeneous catalytic system represents a totally clean process without using any extra oxidant and hydrogen acceptors. The SEM-EDS mapping images of the Pd°-PyPPh2@POP catalyst reveal the highly uniformly dispersed character of C, Pd, P and N elements. The coordination bonds between Pd nanoparticle and exposed P atom as well as N atom on the surface of PyPPh2@POP polymer are confirmed by means of solid-state 31P NMR and XPS. Importantly, both P atom and pyridyl ring on the PyPPh2@POP polymer are themselves used as solid base over the Pd°-PyPPh2@POP catalyst, leading to a catalytic conversion of 88.2% even without the employment of inorganic base additives (K2CO3). Our results have provided a strategy for designing highly active bifunctional POP supported nanoparticle catalysts.
- Chen, Xingkun,Wang, Wenlong,Zhu, Hejun,Yang, Wenshao,Ding, Yunjie
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- METHOD FOR THE PURIFICATION OF TERTIARY BUTYL HYDROQUINONE
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A method for the purification of a composition comprising at least tertiary butyl hydroquinone, 2, 5-ditertiary butyl hydroquinone, and a non-polar solvent. Said method notably comprises addition of a polar solvent and distillation of the mixture.
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Page/Page column 12-15
(2018/12/13)
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- Preparation method for tert-butyl hydroquinone
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The invention provides a preparation method for tert-butyl hydroquinone. The preparation method is performed through the following steps: 1, preparation of a catalyst; 2, preparation of a mixed solution; and 3, preparation of the tert-butyl hydroquinone. In the preparation process of the tert-butyl hydroquinone through the method provided by the invention, a polysulfonic acid based ionic liquid isused as a catalyst, and after a reaction is completed, the ionic liquid can be separated for repeated use; thus, the method provided by the invention only uses a few amount of an organic solvent, mainly uses water as a solvent, is friendly to the environment, has low reaction temperature which minimally reaches 20 DEG C, and can save energy consumption.
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Paragraph 0009; 0011; 0014; 0017
(2019/01/04)
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- Catalytic Electrophilic Alkylation of p-Quinones through a Redox Chain Reaction
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Allylation and benzylation of p-quinones was achieved through an unusual redox chain reaction. Mechanistic studies suggest that the existence of trace hydroquinone initiates a redox chain reaction that consists of a Lewis acid catalyzed Friedel–Crafts alkylation and a subsequent redox equilibrium that regenerates hydroquinone. The electrophiles could be various allylic and benzylic esters. The addition of Hantzsch ester as an initiator improves the efficiency of the reaction.
- Xu, Xiao-Long,Li, Zhi
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supporting information
p. 8196 - 8200
(2017/06/30)
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- A process for preparation of TBHQ
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The invention discloses a technology for preparing tert-butylhydroquinone (TBHQ) quality goods. The technology comprises the following steps: 1) pouring 2-4 parts by weight of phosphoric acids and 0.1-0.4 part by weight of water into a mixing cylinder, and then adding 5-7 parts by weight of hydroquinone to the mixing cylinder to agitate; 2) putting a mixed solution into a reaction kettle to heat to 55-65 DEG C after agitating, and then feeding 7-9 parts by weight of tertiary butanol to the reaction kettle; 3) heating to 75-85 DEG C, and then preserving heat for 2-3 hours to react; 4) centrifugally separating, washing and dewatering a reaction product to obtain a TBHQ crude product; 5) heating 1-3 parts by weight of acids and 93-96 parts by weight of water after mixing, adding 4.5-6.5 parts by weight of TBHQ crude product when heating to 82-88 DEG C, heating while agitating, and heating to 92-95 DEG C; and 6) carrying out the first centrifugal separation on the solution obtained in the step 5), separating out DTBHQ (ditert-butylhydroquinone) which is not dissolved into water in TBHQ, and then cooling the solution, carrying out the second centrifugal separation when cooling to below 45 DEG C, washing, dewatering and baking the obtained TBHQ crystal, so as to obtain the TBHQ quality goods.
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Paragraph 0095-0104
(2017/06/24)
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- TBHQ crude product synthesis process
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The present invention discloses a TBHQ crude product synthesis process, which comprises: 1) pouring 2-5 parts by weight of phosphoric acid and 0.2-0.5 part by weight of water into a stirring jar, adding 4-6 parts by weight of hydroquinone to the stirring jar, and stirring; 2) after the stirring, placing the mixed solution into a reaction kettle, heating to a temperature of 50-69 DEG C, and pouring 7-10 parts by weight of tert-butanol to the reaction kettle; 3) heating to a temperature of 73-83 DEG C, carrying out thermal insulation for 2-3 h, and carrying out a reaction; and 4) carrying out centrifugation separation on the reaction product, carrying out water washing, and dewatering to obtain the TBHQ crude product. According to the TBHQ crude product preparation process of the present invention, the water is adopted as the solvent while the use of the toluene as the solvent is abandoned, such that the pollution is low, the raw material utilization rate is high, and the TBHQ purity in the obtained TBHQ crude product is high.
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Paragraph 0011
(2016/12/01)
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- Preparation process of tert-butylhydroquinone
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The invention relates to the technical field of antioxidant preparation methods, and particularly relates to a preparation process of tert-butylhydroquinone (TBHQ). The preparation process comprises the following steps of (1) simultaneously adding excessive dilute sulphuric acid, equimolar hydroquinone and tertiary butyl acetate to a reaction still, wherein the weight ratio of the dilute sulphuric acid to the tertiary butyl acetate is 1:(3 to 6); (2) stirring and heating to 85 to 95 DEG C, and reacting for 1 to 8 hours; (3) stopping stirring, cooling to 65 to 75 DEG C, and then performing centrifugal filtration, wherein filtrate of sulphuric acid is recycled, and obtained filter residues are washed with 1 to 3 times warm water, so as to obtain a crude product of the TBHQ. Compared with the prior art, the preparation process has the advantages that the hydroquinone and the tertiary butyl acetate are used as raw materials, and the dilute sulphuric acid is used as a catalyst and a reaction solvent, so as to promote a reaction; tertiary butyl is supplied by the tertiary butyl acetate, so that side reactions are reduced; the crude product contains 70% to 75% of TBHQ, the content of DTBHQ (Di-Tert-Butylhydroquinone) as a by-product is low, the yield can reach 65 to 70% after purification, the yield is greatly increased, and great economic benefits are obtained.
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Paragraph 0027; 0028
(2016/10/07)
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- Enhanced activity over alkyl/aryl functionalized porous pillared-zirconium phosphates in liquid-phase reaction
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A series of porous pillared-zirconium phosphates functionalized with methyl, ethyl, propyl and phenyl groups were prepared and characterized by SEM, 29Si MAS NMR, TG and N2 adsorption. Their total surface acidity and accessible one were measured by potentiometric titration of n-butylamine and liquid phase 2,6-di-tert-butyl-pyridine adsorption, respectively. The catalytic behaviors of these hybrid materials for alkylation of hydroquinone and esterification of lauric acid were compared. Not the total acid sites but the accessible ones play a crucial role in both reactions of alkylation and esterification. The accession for acid sites can be enhanced by the introduction of alkyl/aryl groups, due to the improved hydrophobicity of the surface.
- Liu, Ke,Wang, Xueyan,Ding, Shengda,Li, Ying,Hua, Weiming,Yue, Yinghong,Gao, Zi
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- LIGNIN OXIDATION AND PRODUCTS THEREOF
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Provided herein is a method of oxidizing lignin. Further disclosed herein are aromatic and non-aromatic compounds obtained from oxidized lignin.
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- PROCESS FOR CONVERSION OF PHENOL TO HYDROQUINONE AND QUINONES
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The present invention relates to a process for the conversion of phenol to hydroquinone and quinones. More particularly this invention relates to a process for the oxidation of phenol to a mixture of 1,4-benzoquinone and hydroquinone using an oxidant in the presence of titanium superoxide as a reusable catalyst in a liquid phase condition.
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Page/Page column 7
(2008/06/13)
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- Preparation of hydroxy compounds
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A new process for preparing a compound of the general formula ArOH (I) in which Ar represents an aryl or heteroaryl group substituted by at least one electron-donating group.
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- SLIME REMOVER AND SLIME PREVENTING/REMOVING AGENT
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A drainage slime remover capable of spreading a solution of a solid over slime generated wall surface portions, comprising a solid containing a microorganism growth retarding substance and a container which has a shape for permitting the installation thereof at the inlet or upper portion of a drain outlet and stores the solid characterized in that the container has drain flow-in holes having an opening capable of controlling a drain flow-in amount and provided in the upper surface or the upper side portion of the container and solution flow-out holes having an opening capable of controlling a flow-out amount of a solid solution and provided in the bottom or the lower side portion of the container or additionally in the side surface thereof, and a slime preventing/removing agent which can remove slime from portions such as kitchen sinks and bathroom drain outlets where slime is grown by metabolites such as miscellaneous germs and mildews and which can prevent the occurrence of slime safely and for an extended period of time.
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- Reaction of aromatic radical cations with RuCl3·3H2O
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Interactions of RuCl3·3H2O with radical cations of aromatic ethers, 1,4-di-tert-butyl-2,5-dimethoxybenzene, 3,5-di-tert-butyl-1,2-dimethoxybenzene and 2-tert-butyl-1,4-dimethoxybenzene, and with aromatic amines, 2,4,6-tri-tert-butylaniline and N,N,N′,N′-tetramethyl-1,4-phenylenediamine, were observed by voltammetry. ESR and UV spectroscopies were used for the study of the the first two ethers. The effect of RuCl3·3H2O was also examined by controlled potential electrolysis.
- Michman, Michael,Oron, Miriam,Schaefer, Hans J.
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p. 924 - 940
(2007/10/03)
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- Comparative pulse radiolysis studies of alkyl- and methoxy-substituted semiquinones formed from quinones and hydroquinones
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Absorption spectra and rate constants for the disproportionate of 12 alkyl- and methoxy-substituted semiquinone anion free radicals (Q?-) produced by the one-electron reduction (using CO2?- as a reductant) of 1,4-benzoquinones and 1,4-naphthoquinone (Q) as well the oxidation (using N3? as an oxidant) of the corresponding hydroquinones (QH2) were determined by pulse radiolysis in 50 mM sodium phosphate buffer, pH 7.40 at room temperature. Both spectral and kinetic characteristics of Q?- only moderately depended on whether Q?- was produced from Q or QH2. Spectra of benzosemiquinones display two peaks with maximum at 310-320 nm and ca. 430 nm with the ratio of about 2-2.5. Molar absorption coefficients were determined. Rate constants for Q?- disproportionation (2k1) were correlated with the nature of substituents. While 2k1 was scarcely affected by methyl substitution, Q?- containing isopropyl, tert-butyl and methoxy substituents were visibly more stable than non-substituted and methyl-substituted Q?-.
- Roginsky, Vitaly A.,Pisarenko, Leonid M.,Bors, Wolf,Michel, Christa,Saran, Manfred
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p. 1835 - 1840
(2007/10/03)
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- p-di-t-butoxybenzene
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p-Di-t-butoxybenzene (1) [p-di-tert-butoxybenzene; benzene, 1,4-di-tert-butoxy-; 1,4-bis(1,1-dimethylethoxy)benzene; 1,4-benzenediol (or benzene-1,4-diol) di-tert-butyl ether; Chem. Abstr. number 15360-01-7] does not have the physical properties ascribed to it in the Dictionary of Organic Compounds, where it has been mistaken for 2,5-di-t-butylhydroquinone (4).
- Carman, Raymond M.,Kanizaj, Nicholas,Taylor, Richard J.K.
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p. 515 - 516
(2007/10/03)
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- Model studies of topaquinone-dependent amine oxidases. 1. Oxidation of benzylamine by topaquinone analogs
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The aerobic oxidation of benzylamine by model compounds of topaquinone, the active site organic cofactor in copper-containing amine oxidases, was studied in order to elucidate the chemical function of the cofactor in substrate oxidation. In this study, topaquinone hydantoin (1(ox)) and a series of 2-hydroxy-5-alkyl-1,4-benzoquinones which differ in the bulk of their alkyl substituent (5, 6, 7, and 8) were employed as model compounds of the cofactor. The p-quinones (9, 10, 11, and 12) and the o-quinone (13 and 14) were prepared in order to compare them to the topaquinone analogs. Benzylamine was oxidized by the topaquinone analogs (1(ox), 5, 6, 7, and 8) to yield N-benzylidenebenzylamine (PhCH = NCH2Ph) as a sole product in acetonitrile at room temperature. The quinones bearing a bulky substituent (1(ox), 5, and 6) were found to be more efficient catalysts than those bearing a small primary alkyl group (7 and 8). In the latter case, the dimers (16 and 17) of the substrate Schiff base intermediates (15, R = methyl, ethyl) were isolated. The p-quinones (9, 10, 11, and 12) were catalytically inactive. The o-quinones (13 and 14) had detectable catalytic activity at room temperature. In anaerobic reactions of the o-quinones (13 and 14) with benzylamine, quantitative formation of the product (PhCH = NCH2Ph) was observed. For both o-quinones, products and intermediates which support a transamination mechanism were identified by 1H NMR spectroscopy. The order of reactivity of quinones (5 > 14 > 13) reflects their redox potentials, such that regeneration of quinone may be rate-determining with o-quinones. These results demonstrate a substantial role of the 2-hydroxyl group of the topaquinone in preventing the formation of Michael adducts with substrate amine and in facilitating the reoxidation of aminoresorcinol intermediates.
- Mure, Minae,Klinman, Judith P.
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p. 8698 - 8706
(2007/10/02)
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- Equilibria and Rates of Redox Reactions Involving the 2-tert-Butyl-1,4-benzosemiquinone Radical in Aqueous Solution: An Investigation by Potentiometry, ESR, and Pulse Radiolysis
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Midpoint potentials, Em, for two-electron reduction of 2-tert-butyl-1,4-benzoquinone (TBQ) were measured in aqueous solution as a function of pH at 22 deg C and given ionic strength I.From Em(pH), the practical pK values, pK'(I), of the corresponding hydroquinone (TBQH2) were obtained at given values of I.By use of an empirical Debye-Hueckel (D-H) type approximation, the values of pK' were extrapolated to I = 0 for estimating the thermodynamical pKa values for acid dissociation of TBQH2 (pKa,1 = 10.7 +/- 0.1; pKa,2 ca. 13.6 +/- 0.2).Optical absorption spectra and molar extinction coefficients of the transient semiquinone radical (TBQH. and TBQ.-) were obtained by pulse-radiolytic one-electron reduction of TBQ in aqueous solution.The pKa of TBQH. is 4.3 +/- 0.1 at 22 deg C in the presence of 2-propanol (2 M) and acetone (0.1 M).Oxidation of TBQH2 by OH. to eventually give TBQ.- has been studied (k15 = 8 x 1E9 M-1 s-1 for formation of the intermediate . in aqueous soluiton at 22 deg C).The equilibrium for formation of TBQ.- from TBQ and TBQH2 was investigated by ESR (aqueous solution, pH 6.8-9.4, I = 0.12 M).Hyperfine couplings and the g value of TBQ.- are given.The apparent semiquinone formation constant at pH i, K'f,i(I), was determined as a function of pH (log K'f,7 = -8.8 +/- 0.1, pH 7) at I = 0.12 M.The pH-independent thermodynamical formation constants, at I = 0, of TBQH. from TBQ and TBQH2 (log K17 = -14.4 +/- 0.3) and of TBQ.- from TBQ and TBQ2- (log K18 = 1.3 +/- 0.4) were determined by use of the above pKa values and D-H type approximations.Various other one-electron-transfer reactions involving TBQH. or TBQ.- have been investigated in detail.The standard potentials, Eo (at I = 0), for one-electron reduction of TBQ and of TBQH. (or TBQ.-) have been obtained by combining the two-electron reduction potentials of TBQ and the semiquinone formation constants.Pulse-radiolytic equilibration studies of TBQ with O2.- and of TBQ2- with DMAP. (DMAP. = 4-(dimethylamino)phenoxyl) afforded the redetermination of the thermodynamical standard potential for one-electron reduction of O2 (Eo = -0.140 +/- 0.012 V vs NHE for 1 M O2 in aqueous solution at 22 deg C and I = 0) and of the midpoint potential of the couple DMAP./DMAP-, respectively, at pH 13.5 (Em,13.5 = 0.10 +/- 0.02 V vs NHE at 22 deg C and I = 0.5 M).The respective rate and equilibrium constants are given.All these results are discussed in terms of substituent and solvent effects as well as in view of the Marcus theory of electron transfer.Another objective of the present study is to contribute to a better understanding of the properties of the synthetic, antioxidant 2- or 3-tert-butyl-4-hydroxyanisole (BHA).
- Dohrmann, Juergen K.,Bergmann, Barbara
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p. 1218 - 1227
(2007/10/02)
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- Clathrate composition including essential oils and method of using same
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A composition for killing harmful organisms, which contains a clathrate compound composed of one or more natural essential oils and/or derivatives thereof selected from the group consisting of the following substances (1) to (22) and a polymolecular host compound capable of including the natural essential oils and/or derivatives thereof: (1) hinoki oil; (2) 1,8-cineole; (3) l-α-terpineole; l-carbone; (5) l-menthone; (6) d-pulegone; (7) citronellal; (8) linelool oxide; (9) d,l-citronellol; (10) 3,3,5-trimethylcyclohexanol; (11) l-perillaldehyde; (12) l-carveol; (13) myrtenal; (14) peppermint oil; (15) eucalyptus oil; (16) cinnamic aldehyde; (17) α-bromo-cinnamic aldehyde; (18) salicylaldehyde; (19) benzaldehyde; (20) paraphenyl-propionaldehyde; (21) paratolualdehyde; and (22) l-menthol.
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- Desmutagenic Effects of Sulfhydryl Compounds on a Mutagen Formed from Butylated Hydroxyanisole Reacted with Sodium Nitrite
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The desmutagenic activities of some vegetable and fruit juices to the mutagenicity of 2-tert-butyl-p-quinone (t-BQ) were assayed by the Ames test using Salmonella typhimurium TA 100. t-BQ is a strong mutagen and is produced from butylated hydroxyanisole when treated with nitrite under acidic conditions.The juices of sweet pepper, lemon, tomato, orange, strawberry, melon, and kiwi fruit reduced the mutagenicity of t-BQ, the desmutagenic activities being proportionally related to the content of the sulfhydryl group contained in these juices.The authentic sulfhydryl compounds, glutathione, pantetheine and dithiothreitol, were then tested for their desmutagenicity against t-BQ by the induced-mutation frequency method, and they were proved responsible for the desmutagenicity.Glutathione reduced half of the t-BQ to 2-tert-butyl-hydroquinone during the desmutagenic reaction, the other half being suggested to have been a conjugated compound between glutathione and t-BQ.
- Mizuno, Masashi,Toda, Masaya,Danno, Gen-ichi,Kanazawa, Kazuki,Natake, Masato
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p. 2843 - 2850
(2007/10/02)
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- Long-acting pyrethrum/pyrethroid based pesticides with silicone stabilizers
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Pesticidal compositions based on nontoxic, naturally unstable insecticides (pyrethrum, synthetic pyrethroids and mixtures thereof) include a liquid alkyl aryl silicone polymer which stabilizes the insecticide to provide an extended effective killing life. The compositions additionally include a synergist to provide an immediate killing action and an antioxidant to protect the insecticide against destruction by oxygen. Ultraviolet protectants and insect repellents may also be included. Applications include control of insect pests to animals and plants and general purpose insect control. Exemplary formulations are given for compositions to be applied as sprays, dips, powdered or dusts, foggers and shampoos.
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- Process for treating 2-ethylhexyl p-methoxycinnamate in the presence of a phenol
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A process for treating 2-ethylhexyl p-methoxycinnamic acid ester is described. The process comprises heating, preferably distilling, the ester in the presence of a phenol to insure that the ester is considered Ames negative.
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- Vat dye and sulfur dye compositions
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Specific vatting accelerators according to claims 1 and 2 are described. These can be added to a vat dye or sulfur dye composition, or to a dye bath or printing paste containing a vat dye or sulfur dye, by virtue of which an improvement of dye yield, particularly on cellulose materials, is obtained.
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- Silica Gel as an Effective Catalyst for the Alkylation of Phenols and Some Heterocyclic Compounds
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In the presence of silica gel, the reaction of phenol with t-BuBr was examined under a variety of conditions and it was found that silica gel is an effective catalyst for the alkylation.As a result of this work 2-tert-butyl-, 2,6-di-tert-butyl-, and 2,4,6-tri-tert-butylphenols, all of which are hard to obtain directly by the Friedel-Crafts process, could be prepared easily by this one-step reaction.Several other alkyl halides were also used in this reaction.The alkylations of some heterocyclic aromatic compounds which cannot be alkylated by the conventional Friedel-Crafts method were also succesfully performed by this reaction.
- Kamitori, Yasuhiro,Hojo, Masaru,Masuda, Ryoichi,Izumi, Tatsuo,Tsukamoto, Shuichi
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p. 4161 - 4165
(2007/10/02)
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