Reagent

About: Reagent is a research topic. Over the lifetime, 60091 publications have been published within this topic receiving 1234928 citations. The topic is also known as: reagens.

Efficient Production of the Liquid Fuel 2,5-Dimethylfuran from Fructose Using Formic Acid as a Reagent†

Abstract: Biofuels that are obtainable from renewable sources have attracted recent interest. The ultimate goal of current research is the conversion of our most abundant renewable hydrocarbons, lignocellulose, into liquid fuels for motor vehicles. Such carbon-neutral resources, in addition to being more geographically disperse than petroleum reserves, promise to minimize the emission of greenhouse gases. The majority of lignocellulose is cellulose, a polymer derived from glucose. The main approaches to the utilization of cellulose involves acid-catalyzed hydrolysis followed by either chemical or biological conversions of glucose. Glucose readily isomerizes into fructose, from which one can envision a number of promising liquid fuels such as 2,5-dimethylfuran (DMF), g-valerolactone (VL), and ethyl levulinate (EL) (Scheme 1). DMF is particularly attractive because of its nearly ideal boiling point (92–94 8C), its high energy density (30 kJ cm ), and its high research octane number (RON = 119). Furthermore it is immiscible with water and is easier to blend with gasoline than ethanol. 5-(Hydroxymethyl)furfural (HMF) is a compound of interest since it is an intermediate in biofuel conversions as well as a valued fine chemical. HMF can either undergo hydrogenation/hydrogenolysis to form DMF or acid-catalyzed conversion into levulinic acid (LA), a precursor to VL. In considering alternative conversions 11] of fructose that ultimately lead to DMF, we conceived of a process whereby several steps could be conducted in one pot. Key to our strategy is the use of formic acid (FA), which has the potential to serve as an acid catalyst, a source of hydrogen (H2), and a deoxygenation agent. FA has attracted much recent interest in the area of green chemistry because of its potential as a hydrogen carrier and as a means of utilizing carbon dioxide. FA is currently produced industrially by the hydration of carbon monoxide as well as the hydrogenation of carbon dioxide. FA is also generated as a by-product from biomass degradation processes. Initial experiments were aimed at evaluating the usefulness of formic acid for conversions of HMF. As expected, HMF can be readily hydrogenated into bis(hydroxymethyl)furan (BHMF) using formic acid (4 equiv) in the presence of Pd/C. The conversion is essentially quantitative in refluxing tetrahydrofuran (THF). No additional reactions occurred even after prolonged reaction times. Featuring two benzyliclike alcohol groups, BHMF is well suited for hydrogenolysis to deliver DMF. Indeed, the gas-phase conversion of BHMF into DMF has been conducted at 220 8C with 6.8 bar H2 over a copper/ruthenium catalyst. Formic acid provides a milder pathway for this conversion. Specifically, we found that the diformate ester of BHMF (BFMF) is quantitatively converted into DMF in refluxing THF upon the addition of Pd/C [Eq. (1)]. Given the lability of BFMF, we turned our attention to conditions for the formation of BFMF from BHMF. We found that a THF solution of BHMF and formic acid (10 equiv) converted into BFMF at 120 8C upon the addition of small amounts (0.13 equiv) of H2SO4. The intermediate monoester was observed spectroscopically. Scheme 1. Conversions of glucose into liquid fuels.

Ionic-Liquid-Supported Synthesis: A Novel Liquid-Phase Strategy for Organic Synthesis

Abstract: Soluble ionic liquids have recently been used as supports for catalyst/reagent immobilization and synthesis in homogeneous solution phase. The wide range of ionic liquid supports available makes their use as supports compatible with most common chemistries. The solubility properties of these ionic liquid supports can be tuned by the variation of cations and anions to make them phase separate from less polar organic solvents and aqueous media. The ionic-liquid-supported species can therefore be purified from the reaction mixture by simple washings. Ionic-liquid-supported catalysts and reagents have been prepared and used, and they are easily recovered and reused. Parallel and combinatorial libraries of small molecules have been synthesized. Ionic-liquid-supported synthesis (ILSS) has been applied to the preparation of oligopeptides and oligosaccharides. The comparison of ILSS with solid-phase synthesis, soluble-polymer-supported synthesis, and fluorous phase synthesis has been highlighted where applicable.

Oxidation of chlorobenzene with fenton's reagent

Abstract: The degradation of chlorobenzene and its oxidation products by hydroxyl radicals generated with Fenton's reagent was studied. In the absence of oxygen, chlorophenols, dichlorobiphenyls (DCBs), and phenolic polymers were the predominant initial products. In the presence of oxygen, DCB yields decreased markedly and chlorobenzoquinone was also formed. Chlorophenol isomers were further oxidized by OH's to form chlorinated and nonchlorinated diols. DCBs and the phenolic polymers were also oxidized. The highest yield of product formed per mole of H{sub 2}O{sub 2} consumed was observed in the pH range of 2-3. The pH dependence and product distributions suggest that complexes of aromatic intermediate compounds with iron and oxygen may play a role in regulating reaction pathways. At pH 3.0, approximately 5 mol of H{sub 2}O{sub 2}/mol of chlorobenzene were required to remove all of the aromatic intermediate compounds from solution.