Artificial organic compounds

The abbreviation QSAR stands for quantitative structure-activity relationships. QSPR means quantitative structure-property relationships. As the properties of an organic compound usually cannot be predicted directly from its molecular structure, an indirect approach Is used to overcome this problem. In the first step numerical descriptors encoding information about the molecular structure are calculated for a set of compounds. Secondly, statistical methods and artificial neural network models are used to predict the property or activity of interest, based on these descriptors or a suitable subset. A typical QSAR/QSPR study comprises the following steps structure entry or start from an existing structure database), descriptor calculation, descriptor selection, model building, model validation. 

Plastics are high-molecular-weight organic compounds of natural or mostly artificial origin. In fabrication, plastics are added with fillers, plasticizers, dyestuffs and other additives, wliich are necessary to lower the price of the material, and give it the desired properties of strength, elasticity, color, point of softening, thermal conductivity, etc. 

Aqueous solubility is selected to demonstrate the E-state application in QSPR studies. Huuskonen et al. modeled the aqueous solubihty of 734 diverse organic compounds with multiple linear regression (MLR) and artificial neural network (ANN) approaches [27]. The set of structural descriptors comprised 31 E-state atomic indices, and three indicator variables for pyridine, ahphatic hydrocarbons and aromatic hydrocarbons, respectively. The dataset of734 chemicals was divided into a training set ( =675), a vahdation set (n=38) and a test set (n=21). A comparison of the MLR results (training, r =0.94, s=0.58 vahdation r =0.84, s=0.67 test, r =0.80, s=0.87) and the ANN results (training, r =0.96, s=0.51 vahdation r =0.85, s=0.62 tesL r =0.84, s=0.75) indicates a smah improvement for the neural network model with five hidden neurons. These QSPR models may be used for a fast and rehable computahon of the aqueous solubihty for diverse orgarhc compounds. 

Hunter, J.V., Origin of organics from artificial contamination, in Organic Compounds in Aquatic Environments, Faust, S.D. and Hunter, J.V., Eds., Marcel Dekker, New York, 1971, pp. 51-94. 

Why are barium- and iodine-based materials selected for contrast media The production of X-ray images depends on the differences between the X-ray absorbing power of various tissues. This difference in absorbing power is called contrast and is directly dependent on tissue density. To artificially enhance the ability of a soft tissue to absorb X-rays, the density of that tissue must be increased. The absorption by targeted soft tissue of aqueous solutions of barium sulfate and iodized organic compounds provides this added density through the heavy metal barium and the heavy nonmetal iodine. 

Most dyes are organic compounds. Before artificial dyes were invented, people prepared natural dyes from roots, berries, leaves, and insects. 

After Dalton, the word synthesis was not usually used yet in chemical parlance. Berzelius (1779-1848), Dumas (1800-1884) and even Wohler (1800-1882) refer to the classical synthesis of urea -achieved in 1828 by Wohler himself-as an artificial production or formation of an organic compound. Only after the publications by Kolbe (1818-1884), Frankland (1825-1899) and Bertholet (1827-1907) was the word synthesis normally used and became familiar to chemists. 

There have been attempts to apply formal methods to the representation of organic compounds [1],[2], some attempts to apply artificial intelligence to organic synthesis [3],[4], and numerous attempts to apply the use of molecular orbital calculations to the verification of the validity of compounds in the synthesis route. This effort was a moderate attempt to examine the representation issues involved in writing production rules for Diels-Alder disconnections. 

Artificial Pollutants Organic compounds (chlorinated pesticides, phosphorus-based pesticides, freons) industriai and municipai wastewaters runoff from urban areas and iandfiii erosion of contaminated soiis and sediments atmospheric deposition Toxic effects inciuding birth defects, reproductive faiiure, cancer, and systemic poisoning. 

Millions of organic compounds have now been synthesised from simpler materials. These substances include many that also occur in nature, such as vitamin C, as well as entirely new compounds. Some, such as cubane, are largely of theoretical Interest and give chemists the opportunity to study special kinds of bonding and reactivity. Others, such as the artificial sweetener saccharin and the drug aspirin have become a part of everyday life. 

Kuster M, Diaz-Cruz S, Rosell M et al (2010) Fate of selected pesticides, estrogens, progestagens and volatile organic compounds during artificial aquifer recharge using surface waters. Chemosphere 79 880-886... 

Production of phenol and acetone is based on liquid-phase oxidation of isopropylbenzene. Synthetic fatty acids and fatty alcohols for producing surfactants, terephthalic, adipic, and acetic acids used in producing synthetic and artificial fibers, a variety of solvents for the petroleum and coatings industries—these and other important products are obtained by liquid-phase oxidation of organic compounds. Oxidation processes comprise many parallel and sequential macroscopic and unit (or very simple) stages. The active centers in oxidative chain reactions are various free radicals, differing in structure and in reactivity, so that the nomenclature of these labile particles is constantly changing as oxidation processes are clarified by the appearance in the reaction zone of products which are also involved in the complex mechanism of these chemical conversions. 

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