Aroh rocooch3 aroch3 roh c02

Scheme 4.23 Methylation of phenols with mixed organic carbonates (ROCO2CH3). As can be seen, asymmetrical carbonates give high chemoselective methylation reactions, provided that R has at least three carbon atoms (R > n-C3, entries 2-4). Yet, in the case of reactive benzyl or allyl termini, the O-alkylation (forming PhOR) competes significantly with the formation of anisoles (entries 5-6). Most satisfactory results can be obtained with the use of 2-(2-methoxyethoxy) ethyl carbonate...

Batch Methylation Reactions with DMC

Under batch conditions, methylations with DMC must necessarily be run in sealed autoclaves, given its boiling point (90 C) and the reaction temperature (> 160 C). Batch methylations with DMC can be performed on a number of different substrates and, under such conditions, the reaction mechanism can be conveniently investigated in fact, the sampling of the reaction mixture at different conversions, and the identification of possible intermediates (see later) is easier with respect to...

Ccc

There are several means to maximize the yield in the desired monoalkylation product high aromatic alkylation agent ratio, association of a transalkylation unit to the alkylation unit, and use of a shape selective zeolite as catalyst. Figure 12.4 Ethylbenzene synthesis. Commercial processes. AlCl3 + HCl catalyst (1950) AlCl3 corrosivity and problems associated with safe handling and disposal. For one tonne of EB, consumption of 2-4 kg catalyst, 1 kg of HCl, and 5 kg of caustic solution with...

Continuous Flow Plug Flow and CSTR Reactors

Under GL-PTC conditions, a gaseous stream of reagent and DMC flows over a catalytic bed usually composed of a porous inorganic material (usually corundum in the form of a spherical extrudate of 1-3 mm of diameter), which acts as a support for both an inorganic base (an alkaline carbonate) and a phase-transfer (PT) agent such as phosphonium salts,13 crown ethers,14 and polyethylene glycols (PEGs). These latter in particular, although less efficient than other PT agents, are desirable because...

Dielsalder Reactions In Water

In this chapter we will focus our attention first on Diels-Alder reactions in aqueous solutions much to the surprise of many chemists, it has been found that Methods and Reagents for Green Chemistry An Introduction, Edited by Pietro Tundo, Alvise Perosa, and Fulvio Zecchini Copyright 2007 John Wiley & Sons, Inc. Diels-Alder reactions and other types of cycloadditions are often greatly accelerated in water compared to organic solvents. Also the preferred stereochemistry (i.e., endo exo ratio)...

Enantioselective Metal Catalyzed Oxidation Processes

The University of New South Wales, Sydney, Australia One appropriate definition of green chemistry is the design of new synthetic pathways to perform chemical processes in a very controlled way, so as to reduce drastically, or to eliminate completely, all the environmental impact. In terms of synthetic industrial processes, this idea leads to the application of highly efficient catalysts, many of which are based on metal complex or organometallic structures. Some of the most important...

How Do I Prepare Thee Let Me Count The Ways

So, the observations in the preceding section raised the obvious question Just how many ionic liquids are there For each cation series that we consider, a matrix of salts can be generated with the following common anions n Cl2 Al2Cl7 2 BF4 2 PF6 2 CF3SO3 2 CH3CO2 2 RCO2 2 COCl4 22 NiCl4 22 This therefore gives us 81 ionic liquids for each cation type (N.B. we only consider the even chain lengths, as Figure 5.6 shows us that there is no advantage to be gained in using the more expensive odd...

Info

CARBOHYDRATES AS RENEWABLE RAW MATERIALS A MAJOR CHALLENGE OF GREEN CHEMISTRY Institute of Organic Chemistry, Technische Universit t Darmstadt, Darmstadt, Germany A raw material as feedstock should be renewable rather than depleting wherever technically and economically practicable.1 Coal, oil, and natural gas, the fossil resources built up over eons, are not only our main energy suppliers but they are also raw materials for a large variety of man-made products ranging from gasoline and diesel...

Oh

Figure 6.22 Selective reduction of haloaromatic ketones in the multiphasic system using Pt C. Figure 6.23 Selective reduction of haloaromatic ketones in the multiphasic system using Pt C. Figure 6.23 Selective reduction of haloaromatic ketones in the multiphasic system using Pt C. known as dioxins). They can be generated by incineration processes, high-temperature transformation of organic compounds, and in some cases they are residues of the agrochemical sector (e.g., insecticides such as DDT,...

PEGStabilized Metal Nanoparticles

Metal nanoparticles, and in particular Pd-nanoparticles (also called Pd-colloids), are stabilized by the presence of, among others, ammonium salts, surfactants, PEGs, ' polysiloxane, and organic thiol mono layers.39 The highly polar ethylene glycol was shown earlier to be a catalyst-philic phase for SAPC. Analogously, polyethylene glycols are an attractive polar and high-boiling class of compounds that can be considered catalyst-philic in a number of instances, and that can be coupled with a...

Problem What Problem

To prevent readers from immediately dashing to their library, let us briefly introduce the concept of green chemistry, prior to examining the role of ionic liquids. To illustrate its importance, and to explain what green chemistry is, and why it is needed, we start by showing you what green chemistry is not. Figure 5.1 is a photograph taken in Central China in 2000, in a beautiful mountainous area frighteningly close to the main panda breeding grounds. Those of you with sharp eyes will spot a...

RNH2 C02 w RNHC02RNH3 RNHC02Me

Scheme 4.21 Carbamation of amines with DMC in the presence of CO2. and aromatic amines to give the corresponding carbamates quantitatively at 90 C. In these conditions high yields of carbamates are obtained in a few minutes (Table 4.7). Since aliphatic amines are harder nucleophiles than aromatic ones, they react faster with the carbonyl of DMC (entries 3-7). No N,N-dimethyl derivates were observed. This pronounced double selectivity has been explained in terms of Pearson's HSAB theory.28...

Supported Liquid Phase

Research in this field started in the wake of the reports of SL-PC. Consisting of a catalyst-containing supported liquid layer for CF reactions in the gas phase, the concept was transferred to batch reactions, using a catalyst dissolved in a supported aqueous phase. This was first referred to as supported aqueous-phase catalysis (SAPC) by Davis in an article published in Nature in 1989.8 Later, the concept was extended, using a variety of names, but the essence has remained the same a supported...

The Multiphasic System

The third liquid catalyst-philic phase was constituted in the majority of cases by Aliquat 336 tricapryl-methylammonium chloride, (C8H17)3N+CH3Cl A336 , a well-known phase-transfer agent that is liquid at room temperature, and that dissolves in toluene and in iso-octane (Figure 6.15a). The peculiarity here is that, when water (even a drop) is added to the A336 isooctane solution, three liquid phases separate out (Figure 6.15b). Figure 6.15 shows the triphasic system at rest in order to...

The Quill Centre

Quill was founded in April 1999 as an industrial consortium, with members from all sectors of the chemical industry.78 It is based on the well-proven industry university cooperative research center (IUCRC) concept developed by the U.S. National Science Foundation and is only the second IUCRC in Europe. There were 17 founding industrial members of the Quill consortium, and the current membership includes (listed alphabetically) bp, Chevron, Cytec, DuPont, Eastman Chemicals, ICI, Invista, Merck,...

Zeolite Catalysts For Cleaner Technologies

University of Poitiers, Poitiers, France The name of zeolites, which originates from the Greek words zeo (to boil) and lithos (stone), was given some 250 years ago to a family of minerals (hydrated aluminosilicates) that exhibited intumescence when heated in a flame.1 However, the history of zeolites really began 60 years ago with the development of synthesis methods. Commercial applications in three main fields ion exchange, adsorption, and catalysis were rapidly developed, the corresponding...

Green Chemistry Catalysis And Waste Minimization

Delft University of Technology, Delft, The Netherlands A growing environmental awareness and increasingly stringent environmental legislation have focused the attention of chemical manufacturers on what has become known as sustainable development or green chemistry. A working definition of green chemistry is Technologies that efficiently utilize energy and (preferably renewable) raw materials and reduce, or preferably, eliminate, the generation of waste and avoid the use of toxic and or...

The Fourcomponent Reaction And Other Multicomponent Reactions Of The Isocyanides

Institute of Organic Chemistry and Biochemistry, Technische Universit t M nchen, Germany The usual syntheses of products from three or more educts require several preparative processes, and its intermediate or final product must be isolated and purified after each reaction. As the number of steps increase, the amounts of solvents and the preparative work grows, while the yields of products decrease and more and more solvents and by-products must be removed. In such reactions, scarcely all...

Adv Carbohyd Chem 1956 Publisher Beelik

Green Chemistry Theory and Practice, Oxford Univ. Press, Oxford, 1998, pp. 30-48. 2. Okkerse, C. van Bekkum, H. From fossil to green, Green Chem., 1999, 107-114. 3. National Research Council, USA, Priorities for Research and Commercialization of Biobased Industrial Products, Natl. Acad. Sci. Press, Washington, DC, 2000. 4. U.S. Department of Energy (DOE) (a) Vision for Bioenergy & Biobased Products in The United States, October 2002 Web.pdf. (b) Roadmap for...

Nonfood Valorization of Sucrose

Sucrose, affectionately called the royal carbohydrate,29 is a nonreducing dis-accharide, because its component sugars, d-glucose and d-fructose, are glycosidi-cally linked through their anomeric carbon atoms. Hence, it constitutes a b-d-fructofuranosyl a-d-glucopyranoside (Figure 2.7). It is widely distributed throughout the plant kingdom, is the main carbohydrate reserve and energy source, and an indispensable dietary material for humans. For centuries, sucrose has been the world's most...

Rationale And Definitions Why Use Ionic Liquids

Ionic liquids are, quite simply, liquids that are composed entirely of ions.17-22 Thus, molten sodium chloride is an ionic liquid a solution of sodium chloride in water (a molecular solvent) is an ionic solution. The term ionic liquids was selected with care, as it is our belief that the more commonly used phrase molten salts (or simply melts) is referential, and invokes a flawed image of these solvents as being high-temperature, corrosive, viscous media (cf. molten cryolite). The reality is...

Ionic Liquid Applications

Reactor Solvent

There now is a proven extensive organic chemistry in ionic liquids, of which a few key reactions are listed below 21,26,28 Oxidation (with air and or dioxygen) N-Alkylation and O-alkylation It is clear that there are few restrictions to the possible reactions that can be studied. Of particular interest is an article demonstrating that the nature of the ionic liquid can dramatically influence the outcome of a reaction.69 In a study of the reactions between toluene and nitric acid, three...

Isobutane 2butene

Very strong Strong Medium-weak C5-C7 TMPs DHMs C C9 Figure 13.5 The influence of acid strength on the nature of the reaction products during the isobutane 2-butene alkylation. TABLE 13.2 Isobutane Alkylation Catalyzed by Beta Zeolite and Sulfated Zirconia at Different Reaction Temperatures A clear example of the possible use of acid and or superacid solids as catalysts is the alkylation of isobutane with butenes. Isobutane alkylation with low-molecular-weight olefins is one of the most...

Biocatalysis For Industrial Green Chemistry

Zhi Li, Martin Held, Sven Panke, Andrew Schmid, Renata Mathys, and Bernard Witholt Eidgen ssische Technische Hochschule Z rich, Switzerland Biocatalysis can make an important contribution to green chemistry due to several distinctive features, such as mild reaction conditions, nontoxicity, high chemo-, regio-, and stereoselectivity, and high turnover frequency. The potential of biocatalysis for the synthesis of chemicals is evident1-3 and examples of several industrial processes that are...