- MECHANISM OF OXIDATION OF SOME ALIPHATIC KETONES BY N-BROMOSUCCINIMIDE IN ACIDIC MEDIA
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Kinetics of the oxidation of methyl n-propyl ketone and methyl isobutyl ketone by N-bromosuccinimide (NBS) have been studied in perchloric acid media in presence of mercuric acetate.A zero order dependence to N-bromosuccinimide and a first order dependence to both ketones and hydrogen ion concentrations have been observed.Sodium perchlorate, mercuric acetate and succinimide additions have negligible effect while methanol addition has a positive effect on the reaction rate.A solvent isotope effect (k0D2O/K0H2O=2.3-2.7 and 2.4-2.8 for MeCOn.pr and MeCOi-Bu, respectively) has been observed at 35 deg.Kinetic investigations have revealedthat the order of reactivity is methyl n-propyl ketone>methyl isobutyl ketone.Various thermodinamic parameters have been computed and corresponding 1,2-diketones were found to be the products.A suitable mechanism in conformity with the above observations has been proposed.
- Singh, Bharat,Pandey, Lalji,Sharma, J.,Pandey, S. M.
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- Highly efficient and robust Mg0.388Al2.408O4 catalyst for gas-phase decarbonylation of lactic acid to acetaldehyde
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Abstract The process for decarbonylation of lactic acid into acetaldehyde over magnesium aluminum oxides was explored. Magnesium aluminum oxides were prepared with co-precipitation method by varying pH values, Mg/Al molar ratios and calcination temperatures. The as-prepared magnesium aluminum oxides were characterized by nitrogen adsorption-desorption, XRD, FT-IR, NH3-TPD, CO2-TPD and SEM, and were employed to catalyze the gas-phase decarbonylation of lactic acid to produce acetaldehyde. It is found that pH value is a crucial factor for the formation of magnesium aluminum oxides. At pH = 7-8, the obtained magnesium aluminum oxide is indexed to Mg0.388Al2.408O4, while at pH > 8, it is ascribed to MgAl2O4 spinel. At low calcination temperature such as 550°C, Mg0.388Al2.408O4 can be formed, and it enhances crystallinity with an increase of calcination temperature. However, as the calcination temperature exceeded 1200°C, the structure of Mg0.388Al2.408O4 encountered a serious destruction. Comparative study on catalytic performance for Mg0.388Al2.408O4 and MgAl2O4 spinel suggests that the former has more excellent performance than the latter. Besides mixtures including Mg0.388Al2.408O4 and Al2O3, pure MgO and pure Al2O3 were also investigated on their catalytic performance. In the presence of Mg0.388Al2.408O4, the stability experiment was performed at high LA LHSV such as 13.0 h-1. Encouragingly, the decarbonylation reaction of lactic acid proceeded efficiently at around 500 h on stream, and acetaldehyde selectivity remained constant (ca. ～93%).
- Tang, Congming,Zhai, Zhanjie,Li, Xinli,Sun, Liangwei,Bai, Wei
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- An efficient and durable hierarchically porous KLA/TiPO catalyst for vapor phase condensation of lactic acid to 2,3-pentanedione
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Sustainable production of 2,3-pentanedione from bio-lactic acid via a vapor condensation reaction over KLA/TiPO (KLA: potassium lactate) was investigated in this work. A KNO3 precursor supported on the surface of TiPO was in situ converted to basic sites in a KLA/TiPO catalyst. KLA together with Ti4+(Lewis acidic site) make up the acid-base pairs in the KLA/TiPO catalyst, resulting in excellent activity for the condensation of lactic acid to 2,3-pentanedione. The loading amount of KNO3 was shown to have an important influence on the catalytic performance, since the acid-base properties of the catalysts were found to vary with the addition of KNO3. Reaction conditions such as lactic acid feed flow rate and lactic acid concentration were also discussed. Both lactic acid conversion and 2,3-pentanedione selectivity increased with elevated lactic acid feed flow rates, indicating the existence of an external diffusion resistance of the lactic acid reactant during the catalytic reactions. However, the lactic acid feed flow rate increased to 1.0 mL h?1 (corresponding to LA liquid hourly space velocity (LHSV) = 2.6 H?1), and the external diffusion resistance was efficiently eliminated. Enhancing the LA concentration improved the selectivity of 2,3-pentanedione, suggesting that the reaction order of the lactic acid molecule for lactic acid conversion to 2,3-pentanedione is higher than the other side reactions. Encouragingly, in retaining 30-45% of the lactic acid conversion, the condensation reaction with a 2,3-pentanedione selectivity of around 73% proceeded efficiently for at least 116 h on stream. The long-term stability of the present catalyst was found to be related to its hierarchical pores, which ameliorated the mass transfer effect of the reactant and product, except for the appropriate acid-base properties for lactic acid condensation to 2,3-pentanedione.
- Zhang, Ju,Li, Xinli,Pang, Jun,Zou, Weixin,Tang, Congming,Dong, Lin
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- Sustainable production of acrylic acid: Rb+- and Cs+-exchanged Beta zeolite catalysts for catalytic gas-phase dehydration of lactic acid
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Rb+- and Cs+-exchanged Beta zeolites (RbxNa1-xβ and CsxNa1-xβ) of varying exchange degrees (x = 0-1.00) were employed to catalyze the gas-phase dehydration of lactic acid (LA) for sustainable production of acrylic acid (AA) in a flow fixed-bed reactor at 360°C, using an aqueous solution of LA (10 mol% or 35.7%) as the reaction feed at a weight hourly space velocity by LA of 2.1 h-1. An appropriate window of the ion exchange degrees for highly selective AA production (≥60 mol%) was determined for either series of the samples, i.e., x = 0.85-0.98 for the RbxNa1-xβ and x = 0.71-0.90 for the CsxNa1-xβ samples. The best performing catalysts Rb0.95Na0.05β, and Cs0.81-0.90Na0.19-0.10β offered the highest AA selectivity (ca. 70 mol%) and yield (ca. 60-65 mol%) for reaction periods of longer than 10 h. Measurements of the surface acidity and basicity of the catalyst samples by temperature-programmed desorption of NH3 and CO2 showed that the highly selective catalysts in such widows should have both weakly acidic and weakly basic surface sites with suitably balanced acidity and basicity. The acid-catalyzed decarbonylation/decarboxylation and base-catalyzed condensation of LA, which lead respectively to formation of acetaldehyde and 2,3-pentanedione, always occurred as the competing reactions over the investigated catalysts. Observations on the catalyst selectivity changes for these competing reactions clearly demonstrate that the suitably balanced acidity and basicity at the catalyst surface is the key to the high selectivity for the desired dehydration reaction.
- Yan, Bo,Mahmood, Azhar,Liang, Yu,Xu, Bo-Qing
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- Potassium-Ion-Exchanged Zeolites for Sustainable Production of Acrylic Acid by Gas-Phase Dehydration of Lactic Acid
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Development of high-performance solid acid catalysts for chemicals and materials production from bioresourced feedstock has become an important research topic in heterogeneous catalysis for renewable energy and green chemistry. We provide herein a comprehensive study on the catalytic performance of various K+-exchanged zeolites (KxNa1-xZ-y, x = 0.90-0.98) with similar molar K/Al ratios for acrylic acid (AA) production by gas-phase dehydration of lactic acid (LA) and discuss the effects of zeolite type (Z = ZSM-22, ZSM-35, MCM-22, ZSM-11, ZSM-5, ZSM-5/ZSM-11, and β) and SiO2/Al2O3 ratio (y). ZSM-5 and β are found more efficient than the other zeolites for this LA-to-AA reaction. Variation of y in the zeolite (β and ZSM-5) is shown to significantly affect the catalytic performance: not only higher AA selectivity and yield but also better catalytic stability is achieved by lowering y. A K0.97Na0.03ZSM-5-27 is then identified as the best-performing catalyst, offering very high AA selectivity (80-81 mol%) and yield (74-78 mol%) at 360 °C under high LA space velocity (WHSVLA = 2.1 h-1). This catalyst also shows a remarkable long-term stability, being capable to maintain a high AA selectivity (>70 mol%) and yield (>55 mol%) for longer than 80 h. Furthermore, an in situ calcination of the used catalyst with flowing air at 450 °C is shown to be efficient for complete catalyst regeneration. Correlating the catalyst performance with its surface acid-base property measured by NH3- and CO2-TPD clearly uncovers that balance between the surface acidity and basicity would be a key, besides Z and y of the zeolite, to the catalyst performance.
- Yan, Bo,Tao, Li-Zhi,Mahmood, Azhar,Liang, Yu,Xu, Bo-Qing
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- Efficient Conversion of Bio-Lactic Acid to 2,3-Pentanedione on Cesium-Doped Hydroxyapatite Catalysts with Balanced Acid–Base Sites
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We report the design and synthesis of cesium-doped hydroxyapatite for direct and high-yield conversion of biobased lactic acid to 2,3-pentanedione (72.3 %). Cs species derived from CsNO3 at high temperature of calcination is introduced into the hydroxyapatite structure to regulate its acid–base properties. It is found that a balance of acid–base chemistry favors the condensation of lactic acid to 2,3-pentanedione. As a result, the undesired reactions such as lactic acid dehydration, decarbonylation, and coking are suppressed. Instead, a concerted catalysis between surface basic site and acidic site for lactic acid condensation to 2,3-pentanedione dominates on the cesium-doped hydroxyapatite catalyst, leading to a highly selective process for direct conversion of bio-lactic acid to 2,3-pentanedione.
- Li, Xinli,Sun, Liangwei,Zou, Weixin,Cao, Ping,Chen, Zhi,Tang, Congming,Dong, Lin
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- Selective conversion of lactic acid into acrylic acid over hydroxyapatite catalysts
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Lactic acid conversion into acrylic acid was carried out over Ca-HAP catalysts at 623 K. Stoichiometric Ca-HAP catalyst gave a high acrylic acid yield of about 60 C-%. Furthermore, non-stoichiometric calcium deficient Ca-HAP catalysts containing the specific amounts of sodium ions, which were prepared under hydrothermal conditions, exhibited remarkably high acrylic acid yields of about 80 C-%. In contrast, non-stoichiometric Ca-HAP catalysts with vacancy sites and Ca-HAP catalysts with excess amounts of sodium species showed relatively low acrylic acid yields and high selectivities into acetaldehyde and 2,3-pentanedione.
- Matsuura, Yumiko,Onda, Ayumu,Yanagisawa, Kazumichi
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- Synthesis method of pentanediol and synthesis method for preparing biomass-based linear pentadiene based on lactic acid conversion
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The invention provides a method for synthesizing pentanediol. The method comprises the following steps: carrying out hydrogenation reaction on a mixed solution obtained by mixing pentanedione, a hydrogenation catalyst and an organic solvent in a hydrogen-containing atmosphere to obtain the pentanediol. According to the invention, a large amount of cheap and easily available bio-based chemical lactic acid can be utilized to obtain pentanediol, and linear pentadiene is further obtained; the raw materials are from renewable resources, and linear pentadiene is obtained through the following steps: (1) condensing lactic acid to prepare pentanedione, (2) hydrogenating pentanedione to prepare pentanediol, and (3) dehydrating pentanediol to obtain linear pentadiene; linear pentadiene, especially 1, 3-pentadiene, is prepared from lactic acid through a process route of condensation, hydrogenation and dehydration; and a green and sustainable linear pentadiene synthesis method based on bio-based chemical conversion is provided, and is simple to operate, short in process, free of harsh experimental conditions, easy to prepare raw materials and catalysts, and has a large-scale synthesis prospect.
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Paragraph 0204-0206; 0211-0213; 0218-0220; 0225-0227
(2021/05/19)
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- Confined alkali metal ions in two-dimensional aluminum phosphate promoted activity for the condensation of lactic acid to 2,3-pentanedione
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The sustainable production of 2,3-pentanedione from bio-lactic acid was investigated over alkali metal ion-intercalated laminar aluminum phosphate. The confined alkali metal ion through the adjacent layers of aluminum phosphate offered excellent stability for the condensation of lactic acid to 2,3-pentanedione at least 80 h on stream, remaining constant at 55% conversion of lactic acid as well as around 80% of 2,3-pentanedione selectivity. The intercalated alkali metal ions can efficiently stabilize the enol intermediate, promoting the activity of lactic acid condensation. Besides, it can also prevent the occurrence of a layered stack of aluminum phosphate, providing an excellent mass transfer space for molecular diffusion, which is demonstrated by the calculation of the relation between molecular mean free paths for lactic acid and 2,3-pentanedione and the interlamellar spacing of aluminum phosphate. As a result, the alkali metal ion-intercalated laminar aluminum phosphate exhibited excellent performance for the condensation of lactic acid to 2,3-pentanedione at 270 °C, achieving 90% of lactic acid conversion and 80% of selectivity towards 2,3-pentanedione.
- Dai, Yunsheng,Li, Xinli,Tang, Congming,Yang, Chenglong,Zhang, Ju
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supporting information
p. 13806 - 13813
(2021/08/16)
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- PREPARATION METHOD OF ACRYLIC ACID FROM LACTIDE BY USING ION EXCHANGE RESIN
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The present invention provides a method for manufacturing acrylic acid from a dehydration reaction of lactide derived from biomass using two or more strongly acidic cation exchange resins, for example, a strong acid cation exchange resin having a particle
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Paragraph 0050; 0067-0071
(2019/10/11)
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- PREPARATION METHOD OF ACRYLIC ACID FROM LACTIDE BY USING ION EXCHANGE RESIN
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The present invention relates to a method for manufacturing acrylic acid by dehydration of lactide derived from a biomass using a strongly acidic cation exchange resin. An object of the present invention is to provide the method for manufacturing acrylic acid, which is a high moisture absorbent raw material, in an environmentally friendly manner at a high yield and a high selectivity by using the strongly acidic cation exchange resin.COPYRIGHT KIPO 2019
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Paragraph 0051-0054; 0060; 0066; 0072; 0078; 0084
(2019/10/10)
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- Preparation Method for 2,3-pentanedione
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A preparation method for 2,3-pentanedione, including the steps of adding one or both of 3-hydroxy-2-pentanone and 2-hydroxy-3-pentanone into water and conducting mixing, and introducing ozone at the temperature of 3-20° C. for a reaction to obtain 2,3-pentanedione. The synthesis process of the present invention uses ozone for oxidizing a mixture containing 3-hydroxy-2-pentanone and 2-hydroxy-3-pentanone, acetic acid is used as a cocatalyst, reaction conditions are mild, the operation process is simple, the product yield is high, and the cost is low.
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Paragraph 0018-0033
(2019/04/25)
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- Synthetic method of 2,3-pentanedione
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The invention relates to a synthetic method of 2,3-pentanedione. The synthetic method of the 2,3-pentanedione comprises the following steps: mixing a lactic acid solution with a solid alkali catalystM/N and carrying out catalytic reaction for 2-10 hours at the temperature being 100-400 DEG C to obtain 2,3-pentanedione. M is an active load and is any one of K2CO3, KHCO3, KNO3, KPO4 and KF, N is acarrier and is any one of Al2O3, a zeolite molecular sieve and ZrO2, and the mole ratio of the active load to the carrier is 1: (0.1-10); and the mass ratio of the solid alkali catalyst M/N to lacticacid is 1: (5-100). Load type superbase is a catalyst, the 2,3-pentanedione is synthesized by catalyzing the lactic acid, the selectivity and the conversion ratio can be high, and the yield of directly synthesized 2,3-pentanedione reaches 60-80%.
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Paragraph 0021; 0024; 0025; 0033; 0035; 0038; 0040; 0043
(2018/11/03)
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- Efficient synthesis method of 2-ethyl-3-methylpyrazine
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The invention discloses an efficient synthesis method of 2-ethyl-3-methylpyrazine. The method comprises specific steps as follows: 2,3-pentanedione is prepared from lactic acid as a raw material, a porous carrier is prepared from raw materials including diammonium hydrogen phosphate and barium nitrate, caesium supported on the carrier is taken as a catalyst, and the conversion rate of lactic acidis effectively increased; then, prepared 2,3-pentanedione and ethylenediamine are taken as raw materials and are sequentially subjected to dehydration condensation and dehydrogenation reactions, and 2-ethyl-3-methylpyrazine is prepared. The synthesis method is simple, low in cost and high in product yield.
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Paragraph 0024; 0028; 0034; 0040; 0046; 0052
(2018/04/01)
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- Preparation method of 2,3-pentanedione
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The invention discloses a preparation method of 2,3-pentanedione. The preparation method comprises the following steps: one or two of 3-hydroxy-2-pentanone and 2-hydroxy-3-pentanone is/are added to water and uniformly mixed with water, ozone is introduced at the temperature of 3-20 DEG C for a reaction, and 2,3-pentanedione is obtained. According to the synthesis process, ozone is adopted to oxidize the mixture containing 3-hydroxy-2-pentanone and 2-hydroxy-3-pentanone, acetic acid is adopted as a cocatalyst, reaction conditions are mild, and operation process is simple; product yield is high;cost is low; the method has the advantages of being safe and environmentally friendly, and no wastewater is produced.
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Paragraph 0004; 0017; 0020; 0024; 0027; 0031; 0034
(2018/09/08)
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- NOVEL METHOD TO PRODUCE ACRYLIC ACID WITH ACETALDEHYDE AS THE MAIN BY-PRODUCT
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Described herein are solid acid catalysts and the methods for catalytically preparing α,β-unsaturated carboxylic acids and/or esters thereof. In one aspect, a zeolite catalyst may be used. The catalyst may, in certain embodiments, be modified to improve the selectivity and/or conversion of a reaction. For instance, a catalyst may be modified by ion exchange to achieve a desirable acidity profile in order to achieve high level of conversion of reactants and selectivity for desirable products of the catalytic reaction. In another aspect, a variety of feed stocks (e.g., starting compositions) may be used including an α-hydroxycarboxylic acid, an α-hydroxycarboxylic acid ester, a β-hydroxycarboxylic acid, a β-hydroxycarboxylic acid ester, cyclic esters thereof (e.g., lactide), and combinations thereof.
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Page/Page column 41; 53
(2016/12/26)
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- Gas phase dehydration of lactic acid to acrylic acid over alkaline-earth phosphates catalysts
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A series of alkaline-earth phosphates were prepared by co-precipitation method using sodium free or sodium containing precursors and evaluated for gas phase dehydration of lactic acid. The catalysts were characterized by BET measurements, X-ray diffraction, chemical analysis, XPS spectroscopy and both NH3 and CO2-TPD. After checking the stability of catalysts under feed, it was shown that selectivity to acrylic acid strongly depended on reaction temperature but not on contact time. At temperature of 380 C, values ranging from 19 to 49% were measured for the different prepared catalysts. The highest value was reached with Ba3(PO4)2 (55% for C3 products) but selectivities rather close were obtained with different other phosphates suggesting kinetic limitation. Acid-base properties measurements revealed that alkaline-earth phosphates exhibited high proportion of acidic and basic sites with same weak strength. Furthermore, correlation between acrylic selectivity of alkaline earth phosphates and the acid-base balance were clearly established for the first time: selectivity was 50% for balance close to 1 and decreased by factor two increasing this parameter to 2. Finally, FTIR spectra of spent catalysts showed alkaline-earth lactates adsorbed over the catalysts which could be reaction intermediates for dehydration of lactic acid.
- Blanco,Delichere,Millet,Loridant
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p. 185 - 191
(2014/03/21)
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- Nonstoichiometric calcium pyrophosphate: A highly efficient and selective catalyst for dehydration of lactic acid to acrylic acid
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Calcium phosphate catalysts were prepared by co-precipitation method using calcium nitrate and mixtures of ammonium and different sodium phosphates as calcium and phosphate precursors, respectively. Depending on the phosphate precursor, the pH of the synthesis mixture changed during the catalyst precipitation. The catalyst characterisation by XRD and ICP revealed the formation of a calcium pyrophosphate structure with varying Ca/P ratio from 1.02 to 0.76 which could be correlated to the different pH of the synthesis solutions. Vapour phase dehydration of lactic acid to acrylic acid was carried out using these calcium pyrophosphate catalysts. Non-stoichiometric calcium pyrophosphate catalyst with Ca/P ratio 0.76 was found to be the most efficient catalyst among the synthesized series with 100% lactic acid conversion and 78% acrylic acid selectivity at 375 °C. The higher selectivity for acrylic acid has been correlated to the increased acidity and reduced basicity of non-stoichiometric calcium pyrophosphate compared to other stoichiometric pyrophosphates. In situ FTIR studies showed the formation of a higher amount of calcium lactate on non-stoichiometric compared to stoichiometric pyrophosphate leading to higher selectivity for acrylic acid. the Partner Organisations 2014.
- Ghantani, Vidhya C.,Dongare, Mohan K.,Umbarkar, Shubhangi B.
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p. 33319 - 33326
(2014/08/18)
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- Na2HPO4-modified NaY nanocrystallites: Efficient catalyst for acrylic acid production through lactic acid dehydration
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By regulating the H2O/SiO2 molar ratio (n = 13.8, 16.9, 20.1, 26.3), NaY zeolites of different particle sizes (NaY-n, 50-400 nm) were synthesized, and NaY-n was modified with disodium hydrogen phosphate, Na2HPO4
- Zhang, Junfeng,Zhao, Yuling,Feng, Xinzhen,Pan, Min,Zhao, Jing,Ji, Weijie,Au, Chak-Tong
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p. 1376 - 1385
(2014/05/06)
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- Catalytic dehydration of d-xylose to 2-furfuraldehyde in the presence of Zr-(W,Al) mixed oxides. Tracing by-products using two-dimensional gas chromatography-time-of-flight mass spectrometry
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Zirconium-tungsten mixed oxides (ZrW) are effective catalysts in the aqueous-phase dehydration of d-xylose to 2-furfuraldehyde (Fur), at 170 °C. The texture and acid properties of ZrW materials were modified to enhance Fur yields. The catalysts prepared by co-condensation without a templating agent (ZrW(X), X = NO3, Cl; X is related to the type of zirconium precursor) possess relatively low specific surface area and amounts of accessible acid sites, leading to a modest Fur yield of ca. 35% at 99% conversion. The use of a templating agent in the preparation of mesoporous ZrW (ZrW-MP) increased considerably the specific surface area and the amount of accessible acid sites, which resulted in enhanced Fur yields (42%) reached at comparable conversions. Further improvements in Fur yields at high conversions were accomplished by introducing aluminium in the catalyst preparation procedure to give ZrAlW-MP (51% yield at 98% conversion). Fairly good catalytic results were also obtained in the case of the ZrAlW-MP catalyst, using solely water as solvent (46% yield at 93% conversion). A study of the identification of the reaction by-products by two-dimensional gas chromatography (GC × GC) combined with time-of-flight mass spectrometry (ToFMS) was carried out.
- Antunes, Margarida M.,Lima, Sérgio,Fernandes, Auguste,Candeias, Joana,Pillinger, Martyn,Rocha, Sílvia M.,Ribeiro, Maria Filipa,Valente, Anabela A.
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p. 127 - 135
(2013/01/15)
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- Products and mechanism of the reaction of chlorine atoms with 3-pentanone in 700-950 Torr of N2/O2 diluent at 297-515 K
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The products, kinetics, and mechanism of the reaction Cl + 3-pentanone have been measured by UV irradiation of Cl2/3-pentanone/N2 (O2) mixtures using primarily GC analysis with selected cross checks by FTIR. In the absence of O2, the products are 1- and 2-chloro-3-pentanone with yields of 21 and 78%, respectively. As the temperature is increased, the yield of 1-chloro-3-pentanone increases modestly relative to the 2-chloro-3-pentanone yield. On the basis of this increase, the activation energy for hydrogen abstraction at the 1 position is determined to be 500 (±500) cal mole-1 relative to abstraction at the 2 position. In the presence of 500 ppm of O2 with 900-1000 ppm of Cl2 at 297 K, the yield of 2-chloro- 3-pentanone decreases dramatically from 78 to 2.5%, while the 1-chloro-3-pentanone decreases only modestly from 21 to 17%. The observed oxygenated species are acetaldehyde (59%), 2,3-pentanedione (9%), and propionyl chloride (56%). Increasing the temperature to 420 K (O2 = 500 ppm) suppresses these oxygenated products, and 2-chloro-3-pentanone again becomes the primary product, indicating that the O2 addition reaction to the 2-pentanonyl radical has become reversible. At 500 K and 10 000 ppm O 2, a new product channel opens which forms a small yield (～4%) of ethylvinylketone. Computer modeling of the product yields has been performed to gain an understanding of the overall reaction mechanism in the presence and absence of O2. The reaction of chlorine atoms with 3-pentanone proceeds with a rate constant of 8.1 (±0.8) × 10-11 cm3 molecule-1 s-1 independent of temperature over the range of 297-490 K (Ea = 0 ± 200 cal mole-1). Rate constant ratios of K(C2H 5C(O)CHCH3 + Cl2)/ k(C2H 5C(O)CHCH3 + O2) = 0.0185 ± 0.0037 and k(C2H5C(O)CH2CH + Cl2)/ k(C 2H5CH2C(O)CH2CH2 + O 2) = 2.7 ± 0.4 were determined at 297 K in 800-950 Torr of N2/O2 diluent. In 800-950 Torr of N2/O 2 diluent, the major fate of the alkoxy radical CH 3CH(O)C(O)C2H5 is decomposition to give C 2H5C(O) radicals and CH3CHO. These results show that the chemical mechanisms of the 3-pentanone reactions are very similar to those observed for butanone. In addition, the rate constants of the reactions of chlorine atoms with 1-chloro-3-pentanone [3 (±0.6) x 10-11 over the range of 297-460 K], 2,3-pentanedione [1.4 (±0.3) × 10-11 at 297 K], and ethylvinylketone [1.9 (±0.4) × 10-10 over the range of 297-400 K, decreasing rapidly above 400 K] were measured at ambient pressure.
- Kaiser,Wallington,Hurley
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experimental part
p. 343 - 354
(2010/06/15)
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- Process for the preparation of 2,3-pentanedione
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The present invention relates to a novel process for the preparation of 2,3-pentanedione starting with hydroxyacetone and paraldehyde.
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- Method for producing dicarbonyl compounds
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The invention relates to a method for producing α-dicarbonyl compounds of formula (I), wherein R1 and R2, independently of each other, mean C1-6-alkyl. Said method is characterised in that an α,β-unsaturated ketone of formula (II), wherein R1 and R2 have the meaning above and R3 and R4, independently of each other, mean hydrogen, C1-6-alkyl or di-C1-6-alkylamino, is reacted with ozone and the resulting ozonide is treated reductively.
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- Regiospecific synthesis of α-diones, α,α-dialkoxyketones and α-alkoxy-α-sulfenylated ketones
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A convenient synthesis of α-diones and their monoprotected acetals, i.e. α-ketoacetals, was developed by mercury induced solvolysis of regiospecifically formed α-chloro-α-(alkylthio)ketones. Analogously, α-alkoxy-α-sulfenylated ketones were formed when reacting α-chloro-α-sulfenylated ketones with an alkaline alcoholic medium, α-Alkoxy-α-sulfenylated ketones themselves could be transformed into α-diones or ?-ketoacetals, which in turn were hydrolyzed under anhydrous conditions into the corresponding α-diones. (C) 2000 Elsevier Science Ltd.
- Tehrani,Boeykens,Tyvorskii,Kulinkovich,De Kimpe
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p. 6541 - 6548
(2007/10/03)
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- Condensed phase preparation of 2,3-pentanedione
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A condensed phase process for the preparation of purified 2,3-pentanedione from lactic acid and an alkali metal lactate is described. The process uses elevated temperatures between about 200° to 360° C. for heating a reaction mixture of lactic acid and an alkali metal lactate to produce the 2,3-pentanedione in a reaction vessel. The 2,3-pentanedione produced is vaporized from the reaction vessel and condensed with water.
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- Structure-reactivity dependence in the rearrangements of a family of alkylacetoxycarbenes
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Absolute rate constants and activation parameters are presented for the 1,2-H and 1,2-acetyl migrations of a family of alkylacetoxycarbenes.
- Moss, Robert A.,Merrer, Dina C.
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p. 8067 - 8070
(2007/10/03)
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- Lactic acid conversion to 2,3-pentanedione and acrylic acid over silica-supported sodium nitrate: Reaction optimization and identification of sodium lactate as the active catalyst
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Lactic acid is converted to 2,3-pentanedione, acrylic acid, and other products in vapor-phase reactions over silica-supported sodium lactate formed from sodium nitrate. Multiparameter optimization of reaction conditions using a Box-Benkhen experimental design shows that the highest yield and selectivity to 2,3-pentanedione are achieved at low temperature, elevated pressure, and long contact time, while yield and selectivity to acrylic acid are most favorable at high temperature, low pressure, and short contact time. Post-reaction Fourier transform infrared spectroscopic analyses of the catalyst indicate that sodium nitrate as the initial catalyst material is transformed to sodium lactate at the onset of reaction via proton transfer from lactic acid to nitrate. The resultant nitric acid vaporizes as it is formed, leaving sodium lactate as the sole sodium-bearing species on the catalyst during reaction.
- Wadley, Douglas C.,Tam, Man S.,Kokitkar, Prashant B.,Jackson, James E.,Miller, Dennis J.
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p. 162 - 171
(2007/10/03)
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- On the Role of 2,3-Dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one in the Maillard Reaction
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To investigate the thermal degradation pathways of 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (1) in the Maillard reaction, the 13C-labeled and unlabeled 1 were synthesized and heated in model systems of food processing. The extent and position of the labeling of the reaction products were interpreted by the mass spectroscopy data. The volatiles identified were, among others, 2,4-dihydroxy-2,5-dimethyl-3(2H)-furanone (2), 2,5-dimethyl-4-hydroxy-3(2H)-furanone, cyclotene, maltol, 5-hydroxymaltol, and some acyclic carbonyls. Under roasting conditions, 2 was formed as a major product. It was concluded that 1 might be transferred to highly reactive open-chain intermediates like the enolic forms of 1-deoxyosone. The further reaction pathways varied with the reaction conditions. Possible degradation pathways of 1 that resulted from the labeling experiments as well as the formation of the described products are discussed.
- Kim, Myong-Ock,Baltes, Werner
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p. 282 - 289
(2007/10/03)
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- Ruthenium(VIII) mediated oxidation of some aliphatic and alicyclic ketones by periodate-ruthenium(III) system in aqueous HClO4 medium
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The kinetics of Ruthenium(III) chloride mediated oxidation of acetone, 2-butanone, 4-methyl-2-pentanone, 2-pentanone, 2-pentanone, cyclopentanone, and cyclohexanone by sodium periodate in aqueous HClO4 media was zero-order in [IO4-] and first-order dependence on [H+] for all the ketones independent of added [Ru(III)] and showed first-order dependence on [H+] for all the ketones studied, except acetone. In the case of acetone at [H+] +], the order in [Ru(III)] being unity; but at [H+] > 0.05 M the reaction showed unit dependence on [H+] and the order in [Ru(III)] was zero. Ruthenium(VIII) generated in situ is postulated as the hydride abstracting species. A mechanism involving enolization as the rate determining step is proposed. Acetone at lower acidity of the medium is shown to react directly with Ru(VIII). In the absence of ruthenium(III) chloride, the kinetics were first-order in [IO4-], [ketone], and [H+]. Structure-reactivity relationship is discussed and thermodynamic parameters are reported.
- Panda,Pati
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p. 453 - 460
(2007/10/03)
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- Electrolytic Oxidation of Ketones in Ammoniacal Methanol in the Presence of Catalytic Amounts of KI
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The indirect electrooxidation of ketones in ammoniacal methanol using iodide ion as a mediator afforded 2,2-dialkyl-2,5-dihydro-1H-imidazoles 3 via an oxidative cyclocoupling of ketimine intermediates formed from ketones and ammonia.The treatment of 3 with dilute HCl gave α-amino ketone hydrochlorides 4 and the parent ketones in good yields.A similar electrooxidation of 3 resulted in the formation of the corresponding 2H-imidazoles 6, which were hydrolyzed to α-diketones and the parent ketones.The same products 6 could also conveniently be obtained by chemical oxidation of 3 with aqueous NaOCl.
- Chiba, Toshiro,Sakagami, Hirotoshi,Murata, Miki,Okimoto, Mitsuhiro
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p. 6764 - 6770
(2007/10/03)
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- Formation of 2,3-Pentanedione from Lactic Acid over Supported Phosphate Catalysis
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Lactic acid is converted to 2,3-pentanedione, acrylic acid, and acetaldehyde in vapour-phase reactions at 0.5 MPa over phosphate salts.Highest selectivities to 2,3-pentanedione are achieved at 280-300 deg C and Long (2-4 sec) residence times, while selectivity to acrylic acid is best at 350 deg C and short residence times (0.4 sec). 2,3-Pentanedione is proposed to form by a second-order condensation in the presence of phosphate, while acrylic acid is proposed to result from elimination of water via a cyclic lactic acid phosphate transition state.
- Gunter, Garry C.,Miller, Dennis J.,Jackson, James E.
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p. 252 - 260
(2007/10/02)
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- Cobalt(II)-Catalyzed Reaction of Aldehydes with Acetic Anhydride under an Oxygen Atmosphere: Scope and Mechanism
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The reaction of aldehydes with acetic anhydride in the presence of catalytic cobalt(II) chloride under an oxygen atmosphere at ambient temperature is dependent upon the reaction medium.Aliphatic aldehydes react in acetonitrile to give 1,2-diones whereas the aromatic aldehydes are acylated to yield the corresponding acylals.On the other hand, carboxylic acids are obtained from aliphatic and aromatic aldehydes by conducting the reaction in dichloroethane or benzene.Cobalt(II) chloride in acetonitrile catalyzes the conversion of aliphatic aldehydes to the correspondinganhydrides in the absence of acetic anhydride whereas aromatic aldehydes remain largely unaffected under these conditions.A preliminary mechanistic study in three different solvents (i.e. acetonitrile, dichloroethane, and DMF) has revealed that in acetonitrile and in the presence of acetic anhydride, aliphatic aldehydes behave differently than aromatic aldehydes.Some trapping experiments using methyl acrylate and stilbene have been conducted to demonstrate the occurence of an acyl cobalt and peroxyacyl cobalt intermediate during these reactions.
- Bhatia, Beena,Punniyamurthy, T.,Iqbal, Javed
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p. 5518 - 5523
(2007/10/02)
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- DICHLORODIISOPROPOXYTITANIUM - A CONVENIENT REAGENT FOR THE SELECTIVE TRANSFORMATIONS OF α,β-EPOXYCARBONYL COMPOUNDS
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Depending on the structure and the reaction conditions, α,β-epoxycarbonyl compounds isomerize selectively in the presence of dichlorodiisopropoxytitanium to α-diketones or undergo nucleophilic cleavage with the formation of the corresponding hydroxychloro ketones.
- Sosnovskii, G. M.,Astapovich, I. V.
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- DEPROTECTION OF CARBONYL GROUPS BY ANODIC OXIDATION OF DITHIOACETALS: A KEY STEP IN THE SYNTHESIS OF α-DIONES, α-KETOLS AND CHIRAL SYNTHONS.
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The anodic oxidation of α-keto and α-hydroxythioacetals provides an efficient way for the regeneration of α-diones and α-ketols, specially in the cases where chemical reactions are unsuccessful.
- Martre, Anne-Marie,Mousset, Guy,Rhlid, Rachid Bel,Veschambre, Henri
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p. 2599 - 2602
(2007/10/02)
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- Synthesis of Dialkyl- and Alkylacylrhenium Complexes by Alkylation of Anionic Rhenium Complexes at the Metal Center. Mechanism of a Double Carbonylation Reaction That Proceeds via the Formation of Free Methyl Radicals in Solution
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The site of alkylation of salts of acylrhenates such as Li(1+)(1-) (1) can be controlled by adjusting the hardness of the alkylating agent.Thus, treatment of 1 with the hard alkylating agent (CH3)3OPF6 gives predominantly the clssical Fischer carbene complex Cp(CO)2Re=C(OCH3)(CH3) (2), whereas reaction with the softer electrophile CH3I leads almost exclusively to the new metal-alkylated complex Cp(CO)2Re(CH3)(COCH3) (3).The structure of 3 has been determined by X-ray diffraction.The availability of this material, a relatively rare example of astable alkylacylmetal complex, has provided an opportunity to study the products and mechanisms of its carbon-carbon bond-forming decomposition reactions.Thermally, the alkyl acyl complex undergoes simple reductive elimination, leading (in the presence of a metal-scavenging ligand L) to a quantitative yield of acetone and CpRe(CO)2(L).Photochemically, a more complicated reaction takes place, especially under 20 atm of CO, where CpRe(CO)3 and 2,3-butanedione are formed.Strikingly, irradiation of Cp(CO)2Re(CH3)2 (9) under 20 atm of CO gives products identical with those formed from 3.Labeling experiments using (13)CO and mixtures of acetyl- and propionylrhenium complexes are inconsistent with a mechanism involving simple migratory CO insertion followed by reductive elimination.They are, however, consistent with metal-carbon bond homolysis leading to methyl and acetyl radicals, followed by carbonylation of the methyl radicals to give a second source of acetyl radicals; these reactive intermediates then dimerize to give 2,3-butanedione.Confirmation of this mechanism was obtained by trapping all the initially formed radicals withhalogen donors.BrCCl3, proved to be much more efficient than CCl4 for this purpose: irradiation of alkyl acyl complex 3 in the presence of BrCCl3 diverted the reaction completely from 2,3-butanedione production, giving instead CH3Br, CH3COBr, Cp(CO)2Re(CH3)Br, and Cp(CO)2Re(CH3CO)Br.
- Goldberg, Karen I.,Bergman, Robert G.
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p. 1285 - 1299
(2007/10/02)
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- Simple Gas Chromatographic Identification of Monosaccharides Using a Curie-Point Type Pyrolyzer
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Simple and rapid identification of monosaccharides by gas chromatography was achieved by the application of Curie-point pyrolysis.Almost all monosaccharides were distinguishable under pyrolysis conditions of 358 deg C for 3 s.Each sugar group, e.g. aldohexoses, aldopentoses, deoxysugars, uronic acids, sugar alcohols, and aminosugars, showed a characteristic pyrogram.Keywords - carbohydrate; Curie-point pyrolysis; monosaccharide; identification; gas chromatography; GC-MS; pyrolysis gas chromatography; pyrogram
- Mitsuo, Naoki,Nakayama, Nobuko,Matsumoto, Hitoshi,Satoh, Toshio
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p. 1624 - 1626
(2007/10/02)
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- Kinetics and Mechanism of Oxidation of Aliphatic Ketones by Bromamine-B in Alkaline Buffer Medium
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The title reaction in buffer medium (pH 9-11) at 303.15 K shows first order dependence in 0 but variable dependence (one to zero) in 0.The rate increases with increase in pH.The reaction product, benzenesulphonamide retards the rate.Variation of ionic strength of medium or the addition of halide ions has no effect on the rate.Kinetic and thermodynamic parameters have been calculated and the isokinetic temperature, 350 K is much above the temperature employed (303.15 K).The rate increases in the order: pentan-3-one A suitable mechanism is proposed.
- Mohan, K.,Mahadevappa, D. S.
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p. 702 - 705
(2007/10/02)
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- Kinetics of Oxidaton of Aliphatic Ketones with Bromamine-T in Acid Medium
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The kinetics of oxidation of 2-propanone, 2-butanone, 2-pentanone, 3-pentanone, and 4-methyl-2-pentanone by sodium salt of N-bromo-p-toluenesulfonamide or bromamine-T (BAT) in presence of HClO4 was studied at 30 degC.The rate law is: .Variation of ionic strength of medium or addition of reaction product p-toluenesulfonamide have no effect on the rate.The dielectric effect is positive.The acid-catalyzed enolization of ketone is assumed to be the rate-limiting step and enolization rate coefficients have been calculated.Proton inventory studies made in H2O-D2O mixtures have been employed to calculate the isotropic fractionation factors.Isokinetic temperature is 320 K indicating enthalpy as a controlling factor.
- Mahadevappa, Dandinasivara S.,Swamy, Putta
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p. 543 - 548
(2007/10/02)
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- Substituted pyridine derivatives
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It is disclosed that aryl-substituted 2,6-bis[N,N-di(carboxyalkyl)aminoalkyl] pyridines in which the aryl groups are substituted with one or more electron-releasing groups are an advantageous ligand for forming fluorescent chelates with rare earth metals. The pyridine moieties can be linked to target molecules, especially biologically active target molecules to provide fluorescent tagging for use in fluoroassay techniques. The pyridine moieties are disclosed as tetraacids, as salts and as esters. Preparation processes and precursors including the corresponding aryl-substituted 2,6-dicarboxypyridines as acids, salts and esters, are disclosed as well.
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- Structural Effects Affecting Hydration of 1,2-Diones Studied by Linear-Sweep Voltammetry
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Linear-sweep voltammetry was used for determination of values KdCO = and KdCO = +R'>+)R'> for some aliphatic and alicyclic 1,2-diketones.Values obtained were compared with data obtained from UV and NMR spectra.Dc polarographic data were used to choose the most reliable value.In all cases, the protonated form predominating in solutions of sulfuric acid is less strongly hydrated than the unprotonated form.The effect of ring size on the hydration in polycyclic species is discussed.Steric hindrance of the hydration due to the 7- and possibly the 1-methyl group in 2,3-camphorquinone has been confirmed.
- Segretario, James P.,Sleszynski, Neal,Partch, Richard E.,Zuman, Petr,Horak, Vaclav
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p. 5393 - 5396
(2007/10/02)
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- OXIDATION OF ALIPHATIC KETONES BY BROMAMINE-B: A KINETIC STUDY
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The kinetics of oxidation of propan-2-one, butan-2-one, pentan-2-one, pentan-3-one and 4-methyl pentan-2-one by sodium N-bromobenzenesulphonamide or bromamine-B (BAB) in perchloric acid medium was studied at 30 deg C.The rate shows a first order dependence each on and +> and is independent of .Variation of ionic strength of medium and addition of the reaction product benzenesulphonamide have no effect on the rate and the dielectric effect is positive.The proposed mechanism involves acid catalysed enolisation of ketone in the rate limiting step followed by a fast interaction with the oxidant.This is supported by the magnitude of inverse solvent isotope effect of 1.62 +/- 0.01 observed in D2O medium.Activation parameters Ea, ΔH*, ΔS*, ΔG* and log A have been calculated by studying the reaction at different temperatures (293-309 K).
- Mahadevappa, D.S.,Mohan, K.,Ananda, S.
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p. 4857 - 4866
(2007/10/02)
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- Note on the Autoxidation of 3-Alkyl-2,4-pentanediones
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Acetic acid (2) and 2,3-diketones (3) as well as 3-hydroxy-2-ketones (4) are formed as main products from 3-methyl- and 3-ethyl-2,4-pentanediones 1 under the influence of air.
- Weiss, Willy,Musso, Hans
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p. 1271 - 1272
(2007/10/02)
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- KINETICS AND MECHANISM OF THE OXIDATION OF SOME ALIPHATIC KETONES BY N-BROMOACETAMIDE IN ACIDIC MEDIA
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Kinetics of the oxidation of methyl ethyl ketone (MEK) and diethyl ketone (DEK) by N-bromoacetamide (NBA) have been studied in perchloric acid media in the presence of mercuric acetate.A zero order dependence to NBA and a first-order dependence to both ketones and H(1+) have been observed.Acetamide, mercuric acetate and sodium perchlorate additions have negligible effect while addition of acetic acid has a positive effect on the reaction rate.A solvent isotope effect (K0D2O/k0H2O=2.1-2.4 and 2.2-2.5 for MEK and DEK, respectively) has been obsvered at 40 deg C.Kinetic investigations have revealed that the order of reactivity is MEK > DEK.The rates were determined at four different temperatures and the activation parameters were evaluated.The main product of the oxidation is the corresponding 1,2-diketone.A suitable mechanizm consistent with the above observations has been proposed.
- Singh, Bharat,Saxena, B. B. L.,Samant, A. K.
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p. 3321 - 3324
(2007/10/02)
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- The Mechanism of Ozone-Alkene Reactions in the Gas Phase. A Mass Spectrometric Study of the Reactions of Eight Linear and Branched-Chain Alkenes
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The stable products of the low-pressure (4 - 8 torr (1 torr = 133.33 Pa)) gas-phase reactions of ozone with ethene, propene, 2-methylpropene, cis-2-butene, trans-2-butene, trans-2-pentene, 2,3-dimethyl-2-butene, and 2-ethyl-1-butene have been identified by using a photoionization mass spectrometer coupled to a stirred-flow reactor.The products observed are characteristic of (i) a primary Criegee split to an oxoalkane (aldehyde or ketone) and a Criegee intermediate, (ii) reactions of the Criegee intermediates such as unimolecular decomposition, secondary ozonide formation, etc., and (iii) secondary alkene chemistry involving OH and other free-radical products formed by the unimolecular decomposition of the Criegee intermediates.The secondary OH - alkene - O2 reactions account for a significant fraction of the alkene (CnH2n) consumed and lead to characteristic products such as Cn dioxoalkanes nH2n + 30)>, Cn acyloins nH2n + 32)>, and Cn alkanediols nH2n + 34)>.Cn oxoalkanes and Cn epoxyalkanes observed at m/e (CnH2n + 16) are probably formed primarily via epoxidation of the alkene by O3.A general mechanism has been proposed to account for the observations.
- Martinez, Richard I.,Herron, John T.,Huie, Robert E.
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p. 3807 - 3820
(2007/10/02)
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- Ru-Catalyzed Oxidation of Acetylenes to α-Diketones with Iodosylbenzene
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Disubstituted acetylenes are oxidized with PhIO in presence of Ru-catalysts to afford α-diketones in 65-68percent yield.Under the same conditions terminal acetylenes are cleaved to carboxylic acids.
- Mueller, Paul,Godoy, Jose
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p. 2531 - 2533
(2007/10/02)
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- The Reversible Hydration of Carbonyl Compounds in Aqueous Solution. Part I, The Keto/Gem-diol Equilibrium
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The equilibrium constants of hydration (given in parenthesis) have been determined for the aliphatic aldehydes acetaldehyde (1.2), propionaldehyde (1.24), butyraldehyde (0.58), pentanal (0.34), and hexanal (0.41), for the halogenated acetones chloraceton (0.091), fluoroacetone (0.167), and 1,1,1-trifluoroacetone (35), and for the 1,2-dicarbonyl compounds 2,3-butanedione (2.1) and 2,3-pentanedione (1.7).Comparing the constants shows, that the equilibrium of hydration of carbonyl compounds is determined mainly by the inductive effects of the substituents.
- Buschmann, Hans-Juergen,Fueldner, Hans-Hagen,Knoche, Wilhelm
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