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78-94-4Relevant academic research and scientific papers
Reactivity of Ionic Liquids: Reductive Effect of [C4C1im]BF4 to Form Particles of Red Amorphous Selenium and Bi2Se3 from Oxide Precursors
Knorr, Monika,Schmidt, Peer
, p. 125 - 140 (2020/12/17)
Temperature-induced change in reactivity of the frequently used ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([C4C1im]BF4) is presented as a prerequisite for the rational screening of reaction courses in material synthesis. [C4C1im]BF4 becomes active with oxidic precursor compounds in reduction reaction at ?≥200 °C, even without the addition of an external reducing agent. The reaction mechanism of forming red amorphous selenium from SeO2 is investigated as a model system and can be described similarly to the Riley oxidation. The reactive species but-1-ene, which is formed during the decomposition of [C4C1im]BF4, reacts with SeO2 and form but-3-en-2-one, water, and selenium. Elucidation of the mechanism was achieved by thermoanalytical investigations. The monotropic phase transition of selenium was analyzed by the differential scanning calorimetry. Beyond, the suitability of the single source oxide precursor Bi2Se3O9 for the synthesis of Bi2Se3 particles was confirmed. Identification, characterization of formed solids succeeded by using light microscopy, XRD, SEM, and EDX.
Cassis and Green Tea: Spontaneous Release of Natural Aroma Compounds from β-Alkylthioalkanones
B?ttig, Sarah,Bochet, Christian G.,Egger, Timothy,Flachsmann, Felix,Gey, Olga
, (2021/10/19)
In depth headspace analysis of the slow degradation of β-alkylthioalkanones in ambient air led to the discovery of a novel δ-cleavage pathway, by which β-mercaptoketones are released. Since β-mercaptoketones are potent natural aroma compounds occurring in many fruits, herbs and flowers, the discovery of an enzyme-independent molecular precursor for this class of high-impact molecules is of practical importance. Moreover, the formation of β-diketones and aldehydes by concomitant oxidation at the α-sulfur-position enhances the versatility of this class of aroma precursors. A mechanistic model is proposed which suggests that the oxidative degradation occurs through a novel Pummerer-type rearrangement of initially formed persulfoxides.
Iridium-Catalyzed Hydrochlorination and Hydrobromination of Alkynes by Shuttle Catalysis
Yu, Peng,Bismuto, Alessandro,Morandi, Bill
supporting information, p. 2904 - 2910 (2020/01/25)
Described herein are two different methods for the synthesis of vinyl halides by a shuttle catalysis based iridium-catalyzed transfer hydrohalogenation of unactivated alkynes. The use of 4-chlorobutan-2-one or tert-butyl halide as donors of hydrogen halides allows this transformation in the absence of corrosive reagents, such as hydrogen halides or acid chlorides, thus largely improving the functional-group tolerance and safety profile of these reactions compared to the state-of-the-art. This method has granted access to alkenyl halide compounds containing acid-sensitive groups, such as tertiary alcohols, silyl ethers, and acetals. The synthetic value of those methodologies has been demonstrated by gram-scale synthesis where low catalyst loading was achieved.
Efficient aerial oxidation of different types of alcohols using ZnO nanoparticle–MnCO3-graphene oxide composites
Adil, Syed Farooq,Assal, Mohamed E.,Shaik, Mohammed Rafi,Kuniyil, Mufsir,Hashmi, Azhar,Khan, Mujeeb,Khan, Aslam,Tahir, Muhammad Nawaz,Al-Warthan, Abdulrahman,Siddiqui, Mohammed Rafiq H.
, (2020/06/08)
Graphene–metal nanocomposites have been found to remarkably enhance the catalytic performance of metal nanoparticle-based catalysts. In continuation of our previous report, in which highly reduced graphene oxide (HRG)-based nanocomposites were synthesized and evaluated, we present nanocomposites of graphene oxide (GRO) and ZnO nanoparticle-doped MnCO3 ([ZnO–MnCO3/(1%)GRO]) synthesized via a facile, straightforward co-precipitation technique. Interestingly, it was noticed that the incorporation of GRO in the catalytic system could noticeably improve the catalytic efficiency compared to a catalyst (ZnO–MnCO3) without GRO, for aerial oxidation of benzyl alcohol (BzOH) employing O2 as a nature-friendly oxidant under base-free conditions. The impacts of various reaction factors were thoroughly explored to optimize reaction conditions using oxidation of BzOH to benzaldehyde (BzH) as a model substrate. The catalysts were characterized using X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, Energy dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), and Raman spectroscopy. The (1%)ZnO–MnCO3/(1%)GRO exhibited significant specific activity (67 mmol.g?1.hr?1) with full convversion of BzOH and >99% BzH selectivity within just 6 min. The catalytic efficiency of the (1%)ZnO–MnCO3/(1%)GRO nanocomposite was significantly better than the (1%)ZnO–MnCO3/(1%)HRG and (1%)ZnO–MnCO3 catalysts, presumably due to the existence of oxygen-possessing groups on the GRO surface and as well as a very high surface area that could have been instrumental in uniformly dispersing the active sites of the catalyst, i.e., ZnO–MnCO3. Under optimum circumstances, various kinds of alcohols were selectively transformed to respective carbonyls with full convertibility over the (1%)ZnO–MnCO3/(1%)GRO catalyst. Furthermore, the highly effective (1%)ZnO–MnCO3/(1%)GRO catalyst could be successfully reused and recycled over five consecutive runs with a marginal reduction in its performance and selectivity.
TBN-Catalyzed Dehydrative N-Alkylation of Anilines with 4-Hydroxybutan-2-one
Cheng, Wenchen,Deng, Shue,Jiang, Liya,Ren, Lanhui,Wang, Zicheng,Zhang, Jian,Song, Weiguo
, p. 7372 - 7377 (2019/11/28)
Until now, the substitution of alcohols by N-nucleophiles via TBN-catalyzed dehydrogenation was not known. Herein, we reported a TBN catalyzed dehydrative N-alkylation of anilines with 4-hydroxybutan-2-one in the presence of TEMPO, which was different from the TEMPO/TBN catalyzed oxidation reactions. A range of anilines reacted successfully with 4-hydroxybutan-2-one to generate the N-monoalkylation products in good yields. Mechanistic studies revealed that this reaction most possibly proceeded through aza-Michael addition. Water was the only by-product, making it more environmentally friendly. The gram-scale reactions verified the synthetic practicality of this protocol.
Vapor-phase catalytic dehydration of butanediols to unsaturated alcohols over yttria-stabilized zirconia catalysts
Ohtsuka, Shota,Nemoto, Takuma,Yotsumoto, Rikako,Yamada, Yasuhiro,Sato, Fumiya,Takahashi, Ryoji,Sato, Satoshi
, p. 48 - 57 (2019/02/19)
Vapor-phase catalytic dehydration of butanediols (BDOs) such as 1,3-, 1,4-, and 2,3-butanediol was investigated over yttria-stabilized tetragonal zirconia (YSZ) catalysts as well as monoclinic zirconia (MZ). BDOs were converted to unsaturated alcohols with some by-products over YSZ and MZ. YSZ is superior to MZ for these reactions in a view point of selective formation of unsaturated alcohols. Calcination temperature of YSZ significantly affected the products selectivity as well as the conversion of BDOs: high selectivity to unsaturated alcohols was obtained over the YSZ calcined at high temperatures over 800 °C. In the conversion of 1,4-butanediol at 325 °C, the highest 3-buten-1-ol selectivity of 75.3% was obtained over the YSZ calcined at 1050 °C, whereas 2,3-butanediol was less reactive than the other BDOs. In the dehydration of 1,3-butanediol at 325 °C, in particular, it was found that a YSZ catalyst with a Y2O3 content of 3.2 wt.% exhibited an excellent stable catalytic activity: the highest selectivity to unsaturated alcohols such as 2-buten-1-ol and 3-buten-2-ol over 98% was obtained at a conversion of 66%. Structures of active sites for the dehydration of 1,3-butanediol were discussed using a crystal model of tetragonal ZrO2 and a probable model structure of active site was proposed. The well-crystalized YSZ inevitably has oxygen defect sites on the most stable surface of tetragonal ZrO2 (101). The defect site, which exposes three cations such as Zr4+ and Y3+, is surrounded by six O2? anions. The selective dehydration of 1,3-butanediol to produce 3-buten-2-ol over the YSZ could be explained by tridentate interactions followed by sequential dehydration: the position-2 hydrogen is firstly abstracted by a basic O2? anion and then the position-1 hydroxyl group is subsequently or simultaneously abstracted by an acidic Y3+ cation. Another OH group at position 3 plays an important role of anchoring 1,3-butanediol to the catalyst surface. Thus, the selective dehydration of 1,3-butanediol could proceed via the speculative base-acid-concerted mechanism.
Accessing Frustrated Lewis Pair Chemistry through Robust Gold@N-Doped Carbon for Selective Hydrogenation of Alkynes
Fiorio, Jhonatan Luiz,Gon?alves, Renato Vitalino,Teixeira-Neto, Erico,Ortu?o, Manuel A.,López, Núria,Rossi, Liane Marcia
, p. 3516 - 3524 (2018/04/14)
Pyrolysis of Au(OAc)3 in the presence of 1,10-phenanthroline over TiO2 furnishes a highly active and selective Au nanoparticle (NP) catalyst embedded in a nitrogen-doped carbon support, Au@N-doped carbon/TiO2 catalyst. Parameters such as pyrolysis temperature, type of support, and nitrogen ligands as well as Au/ligand molar ratios were systematically investigated. Highly selective hydrogenation of numerous structurally diverse alkynes proceeded in moderate to excellent yield under mild conditions. The high selectivity toward the industrially important alkene substrates, functional group tolerance, and the high recyclability makes the catalytic system unique. Both high activity and selectivity are correlated with a frustrated Lewis pairs interface formed by the combination of gold and nitrogen atoms of N-doped carbon that, according to density functional theory calculations, can serve as a basic site to promote the heterolytic activation of H2 under very mild conditions. This "fully heterogeneous" and recyclable gold catalyst makes the selective hydrogenation process environmentally and economically attractive.
Synthesis, Characterization, and Relative Study on the Catalytic Activity of Zinc Oxide Nanoparticles Doped MnCO3, -MnO2, and -Mn2O3 Nanocomposites for Aerial Oxidation of Alcohols
Assal, Mohamed E.,Kuniyil, Mufsir,Shaik, Mohammed Rafi,Khan, Mujeeb,Al-Warthan, Abdulrahman,Siddiqui, Mohammed Rafiq H.,Adil, Syed Farooq
, (2017/08/04)
Zinc oxide nanoparticles doped manganese carbonate catalysts [X% ZnOx-MnCO3] (where X = 0-7) were prepared via a facile and straightforward coprecipitation procedure, which upon different calcination treatments yields different manganese oxides, that is, [X% ZnOx-MnO2] and [X% ZnOx-Mn2O3]. A comparative catalytic study was conducted to evaluate the catalytic efficiency between carbonates and oxides for the selective oxidation of secondary alcohols to corresponding ketones using molecular oxygen as a green oxidizing agent without using any additives or bases. The prepared catalysts were characterized by different techniques such as SEM, EDX, XRD, TEM, TGA, BET, and FTIR spectroscopy. The 1% ZnOx-MnCO3 calcined at 300°C exhibited the best catalytic performance and possessed highest surface area, suggesting that the calcination temperature and surface area play a significant role in the alcohol oxidation. The 1% ZnOx-MnCO3 catalyst exhibited superior catalytic performance and selectivity in the aerial oxidation of 1-phenylethanol, where 100% alcohol conversion and more than 99% product selectivity were obtained in only 5 min with superior specific activity (48 mmol·g-1·h-1) and 390.6 turnover frequency (TOF). The specific activity obtained is the highest so far (to the best of our knowledge) compared to the catalysts already reported in the literatures used for the oxidation of 1-phenylethanol. It was found that ZnOx nanoparticles play an essential role in enhancing the catalytic efficiency for the selective oxidation of alcohols. The scope of the oxidation process is extended to different types of alcohols. A variety of primary, benzylic, aliphatic, allylic, and heteroaromatic alcohols were selectively oxidized into their corresponding carbonyls with 100% convertibility without overoxidation to the carboxylic acids under base-free conditions.
Structure/activity relationships applied to the hydrogenation of α,β-unsaturated carbonyls: The hydrogenation of 3-butyne-2-one over alumina-supported palladium catalysts
Morisse, Clément G.A.,McInroy, Alastair R.,Anderson, Craig,Mitchell, Christopher J.,Parker, Stewart F.,Lennon, David
, p. 110 - 118 (2017/01/05)
The gas phase hydrogenation of 3-butyne-2-one, an alkynic ketone, over two alumina-supported palladium catalysts is investigated using infrared spectroscopy in a batch reactor at 373?K. The mean particle size of the palladium crystallites of the two catalysts are comparable (2.4?±?0.1?nm). One catalyst (Pd(NO3)2/Al2O3) is prepared from a palladium(II) nitrate precursor, whereas the other catalyst (PdCl2/Al2O3) is prepared using palladium(II) chloride as the Pd precursor compound. A three-stage sequential process is observed with the Pd(NO3)2/Al2O3catalyst facilitating complete reduction all the way through to 2-butanol. However, hydrogenation stops at 2-butanone with the PdCl2/Al2O3catalyst. The inability of the PdCl2/Al2O3catalyst to reduce 2-butanone is attributed to the inaccessibility of edge sites on this catalyst, which are blocked by chlorine retention originating from the catalyst's preparative process. The reaction profiles observed for the hydrogenation of this alkynic ketone are consistent with the site-selective chemistry recently reported for the hydrogenation of crotonaldehyde, an alkenic aldehyde, over the same two catalysts. Thus, it is suggested that a previously postulated structure/activity relationship may be generic for the hydrogenation of α,β-unsaturated carbonyl compounds over supported Pd catalysts.
Isoprene Heterogeneous Uptake and Reactivity on TiO2: A Kinetic and Product Study
Romanias, Manolis N.,Zeineddine, Mohamad N.,Riffault, Veronique,Thevenet, Frederic
, p. 773 - 788 (2017/10/07)
The heterogeneous interaction of isoprene with TiO2 surfaces was studied under dark and UV light irradiation conditions. The experiments were conducted at room temperature, using zero air as bath gas, in a flow reactor coupled with a SIFT-MS (selected-ion flow-tube mass spectrometer) and a FTIR spectrometer for the gas-phase monitoring of reactants and products. The steady-state uptake coefficient and the yields of the products formed were measured as a function of TiO2 mass (9–120 mg), light intensity (37–112 W m?2), isoprene concentration (36–12000 ppb), and relative humidity (0.01–90% of RH). Under dark and dry conditions, isoprene was efficiently and reversibly adsorbed on TiO2. In contrast, under humid conditions, isoprene uptake was diminished, pointing to competitive adsorption with water molecules. In the presence of UV light irradiation, isoprene reacted on the surface of TiO2. The reactive steady-state uptake coefficient, γss, was independent of RH under most ambient relative humidity conditions (>50%). However, γss was strongly dependent on isoprene initial concentration according to the empirical expression: γss = (2.0 × 10?4) × [isoprene]0?n with n = 0.35 and 0.28 for 37 and 112 W m?2 irradiation conditions, respectively. In addition to the kinetics, a detailed product study was performed. The gas-phase oxidation products were mostly CO2 (ca. 90% of the carbon mass balance) and a large variety of carbonyl compounds (methyl vinyl ketone, acetone, methacrolein, formaldehyde, acetaldehyde, propanal, traces of butanal, and pentanal), the distribution of which was investigated as a function of mineral oxide mass, isoprene concentration, and RH. Furthermore, the surface-adsorbed products were determined employing off-line HPLC chromatography; their concentrations were inversely dependent on RH and decreased to background levels at RH greater than 30%. Finally, the reaction mechanism and possible implications of isoprene reaction on TiO2 are briefly discussed.