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Atmospheric Pollution and Pollutants
Published in Wayne T. Davis, Joshua S. Fu, Thad Godish, Air Quality, 2021
Wayne T. Davis, Joshua S. Fu, Thad Godish
Carbon atoms can share one to three electron pairs. A double bond is formed when two pairs of electrons are shared. HCs that contain one or more double bonds are called alkenes or olefins; the simplest is ethylene (C2H4). The olefins also include a number of longer-chained compounds (e.g. propylene and butylene). Because double bonds are somewhat unstable, olefinic compounds are very reactive. Olefins and other compounds with double bonds serve as primary reactants in the photochemical processes that produce haze and smog. Their atmospheric lifetimes are on the order of several hours.
Introduction of Carbon Nanotubes
Published in Abhay Kumar Singh, Tien-Chien Jen, Chalcogenide, 2021
Abhay Kumar Singh, Tien-Chien Jen
The second possible hybridization schematic is represented in Fig. 3.1(c), according to this, such an atomic orbital can consist by mixing three and four orbitals electrons. The mixing of one 2s orbital and two 2p orbitals can lead to the formation of three sp2 hybrid orbitals, in which each orbital is filled from only one electron. Moreover, the three sp2 hybrid orbitals can rearrange themselves to make them far apart, as a consequence, they can form a trigonal planar geometry in which the angle between the individual orbital is around 120°. The other p-type orbitals usually do not mix and are perpendicular to the corresponding plane. Under such a configuration three sp2 hybrid orbitals may form σ bonds with the three nearest neighbors as well as side-by-side overlap of the unmixed pure p orbitals which allows to form π bonds between the carbon atoms, this attributes for the carbon–carbon double bond. Typical examples include ethylene ( C2H4 ) and benzene ( C6H6 ) aromatic molecules sp2 hybridization.
Alkenes and Alkynes: Structure, Nomenclature, and Reactions
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
Each carbon of ethene is sp2-hybridized. Each is trigonal planar, attached to three other atoms and possesses a p-orbital (as part of the π-bond). This sp2-hybridization is characteristic of the carbon–carbon double bonds of all alkenes. What is the shape of an sp2-hybrid orbital?
Decarboxylation of oleic acid using iridium catalysis to form products of increased aromatic content compared to ruthenium systems
Published in International Journal of Sustainable Engineering, 2021
Kenneth M. Doll, Bryan R. Moser, Gerhard Knothe
One of the most promising recent developments in this area is a reaction based on ruthenium catalysis (Murray, Doll, and Liu 2018; Murray, Walter, and Doll 2014). This process, building on ruthenium carbonyl carboxylates described earlier (Crooks et al. 1969; Salvini, Frediani, and Piacenti 2000), is most effective on mono-unsaturated carboxylic acid substrates. The mechanism involves isomerisation of the double bond and then a decarboxylation reaction to yield carbon dioxide and an alkene that is has one fewer carbon atom than the original carboxylic acid. The isomerisation aspect of the invention improved the chemical and physical properties of a lubricant additive (Doll et al. 2016), but the decarboxylation aspect is considered most useful for the synthesis of polymer additives and fuels.
Cotton pulp for bone tissue engineering
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Sandhya Singh, Dharm Dutt, Narayan Chand Mishra
During gelatin modification of CC-scaffold, electrostatic interactions took place between the carboxyl group of CC-scaffold and amino group of gelatin. Gelatin is a protein made up of a group of amino acids and each amino acid is joined by peptide bonds between the carbonyl and amino groups of adjacent amino acid residue forming a linear chain. In each amino acid groups, due to electron-withdrawing nature of carbonyl group, the lone pair of electron on the nitrogen atom is delocalized by resonance and forming a partial double bond with the carbonyl carbon. Furthermore putting a negative charge on the oxygen and positive charge on the nitrogen atom and this partial positive site in the nitrogen atom due to resonance effect could be act as the site of interaction with anionic CC-scaffold. This is the reason that gelatin molecules were speedily absorbed onto the surface of CC-scaffold fibers. Gelatin improves the mechanical, bio-adhesive and stability properties of materials [29].
Chalconoid metal chelates: spectral, biological and catalytic applications
Published in Journal of Coordination Chemistry, 2019
Metal–chalcone bonding upon chelation serves both to influence the steric environment of the metal coordination sphere and to adapt the electronic properties of the metal. These strong interactions provide some control over the molecular geometry and reactivity of chalconoid metal chelates. Understanding of the chalcone influence on structure and reactivity when they are bound to the metal ions leads to new materials in the field of medicine. In addition, such an understanding allows chemists to understand reactive complexes of relevance, and to expose new modes of bonding between metal centers and chalcone scaffolds. The α,β-unsaturated ketone (enone) moiety is responsible for the biological performances and also is significant in defining the geometry of coordination complexes. The enone consists of two key functionalities, a carbon–oxygen double bond (carbonyl group) and carbon–carbon double bond adjacent to the carbonyl group. The heterodiene molecular functionalities form stable complexes with transition as well as non-transition elements, so we can expect more than one type of coordination when chalcones interact with the metal center.