Focusing on Carbon

Li C. J. Organic Reactions in Aqueous Media - With a Focus on Carbon-Carbon Bond Formation Chem. Rev. (Washington, D. C.) 1993 93 2023-2035 Keywords Diels-Alder reactions... 

Abstract This chapter focuses on carbon monoxide as a reagent in M-NHC catalysed reactions. The most important and popular of these reactions is hydro-formylation. Unfortunately, uncertainty exists as to the identity of the active catalyst and whether the NHC is bound to the catalyst in a number of the reported reactions. Mixed bidentate NHC complexes and cobalt-based complexes provide for better stability of the catalyst. Catalysts used for hydroaminomethylation and carbonyla-tion reactions show promise to rival traditional phosphine-based catalysts. Reports of decarbonylation are scarce, but the potential strength of the M-NHC bond is conducive to the harsh conditions required. This report will highlight, where appropriate, the potential benefits of exchanging traditional phosphorous ligands with iV-heterocyclic carbenes as well as cases where the role of the NHC might need re-evaluation. A review by the author on this topic has recently appeared [1]. 

Li, C.J. (2005) Organic reactions in aqueous media with a focus on carbon-carbon bond formations. A decade update. Chem. Rev. 105, 3095-3165. 

Numerous reports published in recent years have focused on carbon-centered radicals derived from compounds with selected substitution patterns such as alkanes [40,43,47], halogenated alkanes [43,48,49,51-57], alkenes [19], benzene derivatives [43,47], ethers [51,58], aldehydes [48], amines [10,59], amino acids [23,60-67] etc. Particularly significant advances have been made in the theoretical treatment of radicals occurring in polymer chemistry and biological chemistry. The stabilization of radicals in all of these compounds is due to the interaction of the molecular orbital carrying the unpaired electron with energetically and spatially adjacent molecular orbitals, and four typical scenarios appear to cover all known cases [20]. 

The development of new transducing materials for DNA analysis is a key issue in the current research efforts in electrochemical-based DNA analytical devices. The use of platinum, gold, indiiun-tin oxide, copper solid amalgam, mercury and other continuous conducting metal substrates has been reported [6]. However, this chapter is focused on carbon-based materials and their properties for immobihzing DNA by simple adsorption procedures. 

The simple addition reaction in Scheme 19 illustrates how the notation is used. Ester (1) can be dissected into synthons (2), (3) and (4). Synthons for radical precursors (pro-radicals) possess radical sites ( ) A reagent that is an appropriate radical precursor for the cyclohexyl radical, such as cyclohexyl iodide, is the actual equivalent of synthon (2). By nature, alkene acceptors have one site that reacts with a radical ( ) and one adjacent radical site ( ) that is created upon addition of a radical. Ethyl acrylate is a reagent that is equivalent to synthon (3). Atom or group donors are represented as sites that react with radicals ( ) Tributyltin hydride is a reagent equivalent of (4). In practice, such analysis will usually focus on carbon-carbon bond forming reactions and the atom transfer step may be omitted in the notation for simplicity. 

These ESR observations focus on carbon radicals, unpaired electrons in the carbonaceous matrix of the macerals associated with incomplete carbon bonds. In the macerals surveyed here, these radical densities span a substantial range of values from 4 x 1018 radical spins/g-carbon for some subbituminous... 

Chapter 6 focuses on carbon-carbon bond formations via reactions of enolate anions. 

The depth and breadth of our knowledge of terran chemistry tempts us to focus on carbon because terran life is based on carbon, and organic chemistry as we know it emerged from 19th-century natural-product chemistry... 

The aim of this chapter is to provide an understanding of how carbon black particle size and shape translate into dispersion quality and other performance attributes in plastics applications. While this chapter focuses on carbon black s effectiveness as a pigment, some attention will also be paid to some of the other plastics performance properties it influences, such as stability against UV radiation, effects on mechanical properties, and electrical conductivity. At its conclusion, this chapter will help the reader select an appropriate carbon black grade for specific plastics applications. 

Chizawa, H. et ah. Study of accelerated test protocol for PEFC focusing on carbon corrosion, ECS Trans., 3, 645, 2006. 

This study focused on carbon deposits on alununa- and zeolite-supported cobalt catalysts and their effects on CO hydrogenadon. A thermogravimetiic flow system and Auger electron spectrometer were employed to characterize the carbon deposits. 

Carbon formation may lead to blockage of the reactor tubes resulting in the development of hot spots or it may cause catalyst breakdown [7]. It is therefore important to avoid carbon formation by choosing suitable operating conditions. Carbon formation may also be reduced by proper formulation of the catalyst itself. The present work focuses on carbon formation from CH4 and CH4 mixed with HjO or Hj on a Ni/a-AljOj catalyst and on the same catalyst promoted by Ca and Mg. 

In the nineteenth century chemists focused on the remarkable diversity of molecules produced by living organisms, which have in common the presence of tetravalent carbon atoms. As a result the unique versatility of carbon for the design and synthesis of new molecules was discovered, and the subdiscipline of organic chemistry (the science of carbon-containing molecules) has become the dominant part of the discipline. Clearly, the results from a focus on carbon-based chemistry have been immensely useful to science and to society. 

Organic chemistry focuses on carbon and following movement of the electrons in carbon chains and rings, and also how electrons are shared with other carbon atoms and heteroatoms. Organic chemistry is primarily concerned with the properties of covalent bonds and non-metallic elements, though ions and metals do play critical roles in some reactions. 

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