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Applied Chemistry and Physics
Published in Robert A. Burke, Applied Chemistry and Physics, 2020
The structural formula illustrates the way the bonding takes place between the atoms of elements in a compound. The molecular formula shows the numbers of each atom in the compound. Responders may encounter the molecular formula along with the name; however, it is unlikely that they will see a structural formula in the field. As can be seen with the structural formula of carbon disulfide, there are two bonds between the sulfur and the carbon. This configuration of bonding is referred to as double bonding. Double bonds are very unstable; which is why carbon disulfide is so very flammable. Most compounds that have this carbon to carbon double bond are unstable. Triple bonds are even more unstable so these compounds are not usually shipped in transportation except for welding bottles of acetylene. Acetylene is the only commercially valuable triple-bonded material you are likely to encounter.
Indoor Air Pollution
Published in William J. Rea, Kalpana D. Patel, Reversibility of Chronic Disease and Hypersensitivity, Volume 4, 2017
William J. Rea, Kalpana D. Patel
The classifications for hydrocarbons, defined by the IUPAC nomenclature of organic chemistry, are as follows: methane, ethane, propane, butane, pentane, hexane, heptanes, octane, etc. Saturated hydrocarbons are the basis of petroleum fuels and are found as either linear or branched species. Natural gas (methane) is the number 1 inducer and propagator of chemical sensitivity, along with pesticides. Saturated hydrocarbons (alkanes are the simplest of the hydrocarbon species and are composed entirely of single bonds and are saturated with hydrogen. The general formula for saturated hydrocarbons is CnH2n+2 [assuming noncyclic structures]).34 Hydrocarbons with the same molecular formula but different structural formulae are called structural isomers.35 As given in the example of 3-methylhexane and its higher homologs, branched hydrocarbons can be chiral.36 Chiral saturated hydrocarbons constitute the side chains of biomolecules such as chlorophyll and tocopherol.37Unsaturated hydrocarbons have one or more double or triple bonds between carbon atoms. Those with double bond are called alkenes. Those with one double bond have the formula CnH2n (assuming noncyclic structures).38 Those containing triple bonds are called alkynes, with general formula CnH2n−2 (Table 3.2).39
Mechanical and microscopic properties of alkali-activated fly-ash-stabilised construction and demolition waste
Published in European Journal of Environmental and Civil Engineering, 2023
Lihua Li, Haoqi Zhang, Henglin Xiao, Yaoyao Pei, Jinzhong Wang
The diffraction pattern of FA appears broad and wide ‘drum peak’ within the range of 15°–35° (2θ), signifying the existence of a typical amorphous phase. The ‘drum peak’ of the diffraction pattern of the mixture reduces after the alkaline activation occurs, probably caused by two reasons. The first reason could be the dilution of the construction waste soil, whereas the second reason could be the occurrence of alkaline activation reaction, which consumes the amorphous phase. The activation reaction also causes the peaks of these ridges to shift to the right, roughly between 20° and 40° (2θ), which represents the formation of hydrated calcium aluminosilicate (C-A-S-H) and hydrated sodium aluminosilicate (N-A-S-H) in the amorphous phase (Kamilla et al., 2010). At the same time, the XRD analysis detected the presence of orthorhombic calcium zeolite (Gismondine; chemical formula is CaAl2Si2O8H2O; structural formula is CaOAl2O32SiO24H2O). However, hydrated aluminosilicate was not detected; the reason may be that its amount was too small to be detected. It is mentioned in the literature (Hui et al., 2005; Wang et al., 2008; Williams & Roberts, 2009) that the zeolite phase is converted from the C, N-A-S-H gel of the amorphous phase.
The electronic and optical properties of Cs2 Ti1-xBxI6(B=Sn, Te, Se) with first principle method
Published in Molecular Physics, 2022
Similar with chemical structural formula for ABBX, CsTiBI (B=Sn, Te, Se) is a typical Fm−3m space configuration. The vertex of a stable octahedral structure is constituted by iodine, and titanium element (including B) locates in the centre of the octahedron. Cesium is surrounded by four octahedron structures of BI. The optimised geometric structures of CsTiBI (B=Sn, Te, Se) are displayed in Figure 1, view along the (1 0 0) axis (green: Cs; purple: I; blue: area of TiI; brown: area of BI). x is the concentration of B-cation which means the substituted ratio of Ti. Considering influences of different lattice distributions with the same doping concentration, all band structures and optical spectrums are calculated, and the results are the same, which demonstrated that materials with the same doping concentration have the same structural properties.
Studying some networks using topological descriptors and multi-criterion decision making
Published in Molecular Physics, 2023
Guoping Zhang, Arfa Mushtaq, Adnan Aslam, Saima Parveen, Salma Kanwal
Chemical graph theory is a branch of mathematics that combines chemistry and graph theory. It is used to mathematically model molecules in order to obtain awareness about the physical properties of the chemical compound. Chemical structure is a depiction of the structural formula of a chemical compound in terms of graph postulations. Silicate and oxide networks have much importance in chemistry. The fundamental block of all the silicate mineral structures is the silicon-oxygen tetrahedron , where is at the centre and is at each vertex. Each is shared between two such tetrahedron and forms the formula . Thus, in has a network structure that is very difficult to dissociate due to the higher number of bonds. In addition to this, connection is one of the strongest inorganic connections due to similarity in atomic sizes and back bonding. All these contribute to a very stable network that demands a lot of energy to melt, making the melting point very high. Such networks include oxide, dominating oxide, triangular silicate and dominating silicate networks, etc. Topological indices are numerical number associated with a molecular structure and may be helpful to predict their physical. In the past two decades, many topological invariants have been proposed and used in theoretical chemistry, toxicology and pharmacology for correlation analysis.