Rr-base

Common terms used to describe ligands that can interact with a metal center in a ir-fashion are u-acid and it-base. The definitions of ir-acid and ir-base are similar to those used for Lewis acidity. A n-acid is a ligand that can accept electrons using ir-type orbitals, and a rr-base donates electrons using ir-type orbitals. On the basis of these definitions, describe the following ligands as either ir-acids, 7r-bases, or neither (a) CN- ... 

Dufner G, Schworer R, Muller B, Schmidt RR. Base- and sugar-modified cytidine monophosphate iV-acetylneuraminic acid (CMP-Neu5Ac) analogues - synthesis and smdies with (2-6)-sialyltransferase from rat Uver. Eur. J. Org. Chem. 2000 1467—... 

The indole unit, which is a -rr-base, is believed to have an attractive interaction with the dienophile, which is a rr-acid. When the dienophile has associated to the Lewis acidic boron, the enal may adopt either the s-cis (8.03) or s-trans (8.04) conformation, as illustrated in Figure 8.1. Complex (8.04) (s-trans) undergoes an unfavourable interaction between the bromine atom and indole ring as the diene approaches, and the bromine atom is forced downwards. The reaction prefers to proceed through the s-cis conformation (8.03) and the model accounts for the very high selectivity that is observed. ... 

Both forms must be sent to the MTAC if the item requested is not currently used by the hospital or if it does not conform to previously adopted hospital standards. The MTAC has the authority to recommend either acceptance or rejection of any RR, based on a consensus of its members. A task force consisting of potential equipment users will determine the must have equipment functions, review the impact of the various equipment configurations, and plan technical and clinical evaluations. 

Electrophilic attack is favored when the metal is a weak a acid but a strong rr base, for example, if the complex has a net anionic charge, a low oxidation state, and ligands L that are good donors. The electron density of one of the ligands is enhanced by back donation so that it now becomes susceptible to attack by electrophiles, (H, Mel, etc.). 

Uses of RR-based a. (the following is only focusing on these) are limited, with some exceptions, to less demanding and traditional but still large-volume applications ... 

The global adhesive market (1998) is estimated to be in the range of 54.8 x 10 mt. This figure covers all kinds of a. from low-price starch to expensive specialties. There are no figiures available about the volume of RR-based a. 

The trends show a preference to environmentally oriented products (biodegradable, no solvent). This may at least stabilize the market share of RR-based products. 

A. are now available in more than pilot-plant volume. Production plants with a capacity up to 80000 mt/a exist worldwide. The excellent environmental and consumer-friendly properties of these first totally RR-based nonionic surfactants will allow a bright outlook for the future. 

L-Phenylalanine and L-aspartic acid are of increasing importance because 1-aspartyl-L-pheny-lalanine methyl ester is a powerful, modem, RR-based sweetener (r.s. 200). 

G. Keramik F. c6ramique The production of c. needs auxiliaries. Depending on the various technologies used in this industry, there are applications of RR-based products as plasticizers and lubricants (- stearic acid and their - metallic soaps, - oleic acid and - glycerol), deflocculants (mainly -+oleic acid, but also - stearic acid, - tartaric acid), - surfactants and foam depressants (steara-tes,-4metallic soaps,- fatty alcohols). 

Syn. Cleansers Cleaning Agents G. Reiniger F produits i nettoyer There are numerous household, institutional and industrial c. available, which have multipurpose or specific functions. The products are formulated from many ingredients, but the most important are - surfactants and sequestering agents. The use of RR-based products is rather limited. 

The only RR-based preservative is phenyl-mercury oleate. 

Fatty acid amine salts and monoatnides as well as tannin derivatives are RR-based products used. 

Modem inorganic constmction materials require some RR-based products as auxiliaries and additives ... 

The oldest organic construction material was and still is ->wood. Modem reconstituted wood materials are plywood and various kinds of chip boards. Sometimes, RR-based products are used as binders for their production. 

All these RR-based materials, whether used as such or in composites, have the advantage of biodegradability and mostly good physical properties. However, they swell more or less in water and are sensitive to attacks of microorganisms, insects and small mammals. Flammability is an other property that can simultaneously be of advantage or disadvantage. 

D. contain the following RR-based ingredients Vegetable - fats and oils, liquid or solid - fatty acids,- fatty alcohols, - glycerol, waxy products, - fatty acid amides and sulfonamides. 

Builders impart the function of complexing and sequestering, mainly Ca-ions in the water used (hardness), from soil and from the fiber surface. The only RR-based sequestering agents are - citric acid and citrates, but they are of increasing importance. 

Fragrances are used to mask unpleasant odors and to give a fresh odor to d., to the wash liquor and to the laundry itself. RR-based perfuming agents are in use together with synthetic substances. 

This method of purification, widely used in the chemical industry, is also applied to RR-based products, especially in oleochemistry. 

Explosive emulsions are a more modem form of aqueous e. and may contain RR-based emulsifiers (e.g., - soibitan ester). 

The most common feedstocks (culture medium) are carbohydrates, such as sugar, molasses, starch and many other RR-based materials. 

R agents d extinction des incendies, extincteurs There are not many techniques and materials in which RR-based products are used for f. 

Only a few RR-based products are able to avoid or at least delay the spoilage of food by microorganisms. - Sorbic acid (and sorbates) act against molds that form carcinogenic aflatoxins. 

Sequestrants form complexes with metal ions, which accelerate oxidative degradation, and show synergistic effects with the a.m. antioxidants. - Phytic acid, calcium gluconate (- gluconic acid), - lactic acid and lactates, - tartaric acid and tartrates, - citric acid and citrates and - lecithin are such RR-based products. 

The majority (85%) is based on mineral oil, but 15% are synthetic products, some of them RR-based and used in special applications, e.g., the diesters of -+sebacic acid and - azelaic acid with branched alcohols or the esters of trimethylolpro-pane and pentaerythritol with saturated and unsaturated - fatty acids. 

Automatic transmission fluids may consist of up to 15 components to meet the complex specifications. Not many RR-based products are involved. 

H. is the reaction of an olefin (in case of RR-based products, unsaturated fatty acid, e.g., ->oleic acid) with synthesis gas under pressure ... 

Fiber(felt)-tip pens, The only RR-based products used in i. are surfactants to improve flow-behavior ... 

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