الرئيسية » Simplified Chemistry (صفحه 4)

Simplified Chemistry

Anthracene

Anthracene (C₁₄H₁₀), molar mass 178.23 g·mol−1 , density 1.28 g/cm3 , melting point 215.76 °C . A white crystalline solid used extensively in the manufacture of dyes. Anthracene is found in the heavy- and green-oil fractions of crude oil and is obtained by fractional crystallization. Its structure is benzene-like, having three six-membered rings fused together. The reactions are …

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Annealing

A type of heat treatment applied to metals to change their physical properties. The metal is heated to, and held at, an appropriate temperature before being cooled at a suitable rate to produce the desired grain structure. Annealing is most commonly used to remove the stresses that have arisen during …

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alkylbenzene

A type of organic hydrocarbon containing one or more alkyl groups substituted onto a benzene ring. Methylbenzene (C₆H₅CH₃) and 1,3-dimethylbenzene are simple examples. Alkylbenzenes can be made by a Friedel- Crafts reaction or by the Fittig reaction. Industrially, large quantities of methylbenzene are made by the hydroforming of crude oil. …

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alkali metals (group 1 elements)

alkali metals (group 1 elements) A group of soft reactive metals, each represent in the start of a new period in the periodic table and having an electronic configuration consisting of a rare-gas structure plus one outer electron. The alkali metals are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), …

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Aldol reaction

A reaction in which two molecules of aldehyde combine to give an aldol – i.e. a compound containing both aldehyde and alcohol functional groups. The reaction is base-catalyzed; the reaction of ethanal refluxed with sodium hydroxide gives: 2CH3CHO → CH3CH(OH)CH2CHO The mechanism is similar to that of the Claisen condensation: …

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Acidic Salt

Salt in which there is only partial replacement of the acidic hydrogen of an acid by metal or other cations. For polybasic acids the formulae are of the type NaHSO₄ (sodium hydrogensulfate) and Na₃H(CO₃)₂.2H₂O (sodium sesquicarbonate). For monobasic acids such as HF the acid salts are of the form KHF2 …

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Agate

A hard microcrystalline form of the mineral chalcedony (a variety of quartz). Typically it has greenish or brownish bands of coloration, and is used for making ornaments. Moss agate is not banded, but has moss like patterns resulting from the presence of iron and manganese oxides. Agate is used in …

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Abscisic Acid

A plant hormone (C15H20O4) and weak acid that generally acts to inhibit growth, induces dormancy, and helps the plant tolerate stressful conditions by closing stomata. Abscisic acid was named based on a belief that the hormone caused the abscission (shedding) of leaves from deciduous trees during the fall. At times …

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