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Home >> Chemistry Dictionary >> Chromyl Compound Claisen Condensation
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Chromium steel. Any of a group of stainless steel might contain 18% of chromium 8% of nickel, and 0.5% of carbon, chromium steels have been highly resistant to corrosion and have been used for cutlery chemical plant, ball bearings etc.
Chromous compounds. Compounds having chromium in its lower (f2) oxidation state e.g. chromous chloride in chromium (II) chloride (CrCl2).
Chromyl chloride. CrO2Cl2. See chromyl compounds.
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Chromyl compounds. Derivatives containing the CrO2 unit Chromyl chloride (Nacl plus K2Cr2O7 plus H2SO4) is the best known derivative. Dark and liquid m.p. -96°C, b.p. 117°C. violently hydrolysed by water. Powerful oxidizing agent for e.g., P and S, used in Elard’s reaction (oxidation of alkyl aromatic to a ketone or aldehyde).
Cinchonine (C19H22ON). A whiter optically solid m.p. 537 k. Its structure is similar to that of quinine except that the methoxy group is absent.
Cinchonine. C19H22N2O. Colourless needles; m.p. 225°C. One of the cinchona alkaloids.
1,8-Cineole, eucalyptol.
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C10H18O. A very widely distributed constituent of essential of oil; often considered as the active constituent of medicinal eucalyptus oils.
Also present in worm seed oil, cajuput oil and in various eucalyptus oils. It is a colourless, viscous oil of characteristic camphor-like small m.p. -1°C, b.p. 174.4°C.
Cinnabar. A bright red mineral form of mercury (II) sulphide, HgS, crystallizing in the hexagonal system; the principal ore of mercury. It is deposited in veins and impregnations near recent volcanic rocks and hot springs. The chief sources include Spain, Italy and Yugoslavia.
Cinnamic Acid, 3-Phenylpropenoic acid. C9H8O2, PhCH=CHCO2H.
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Colourless crystals. Decarboxytates on prolonged heating. Oxidized by nitric acid to benzonic acid. Ordinary Cinnamic acid is the trans-isomer, m.p. 135-136°C; on irradiation with u.v. light it can be isomerized to the less stable cis-isomer, m.p. 42°C.
Prepared by heating benzaldehyde with sodium ethanoate and ethanoic anhydride (Pekin reaction) or with ethyl ethanoate and sodium ethoxide. Occurs in storax, or liquidamber, as the ester cinnamyl cinnamate made from cinnamyl alcohol, PhCH=CH.CH2OH. Cinnamic acid and its derivatives are used in flavours, perfumery, cosmetics and pharmaceuticals.
Cis. A geometrical arrangement in like groups are adjacent to each other.
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Citral. C10H16O. A terpene aldehyde. A volatile oil of pleasant odour forming the main constituent of lemon- grass oil from cymbopogon flexuosus, and also found in other essential oils. Lemon-grass oil is on important article of commerce. The citral found in natural products is a mixture of isomers.
With dilute sulphuric acid citral forms p-cymene. Citral can be condensed with propanone to form a ketone, pesudotonone, C13H20O, which is technically important, as it is readily convertible into α and β-ionone.
Citrate. A salt or ester of citric acid.
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Cl. Chlorine
Claisen condensation. Condensation of an ester with another ester, a ketone or a nitrile in the presence of sodium ethoxide, sodium or sodamide, with the eliminator of an alcohol. The result is the formation of a β-ketonic ester, ketone, or nitrile respectively, e.g.,
CH3COOC2H5 + HCH2COOC2H5 CH3COCH2COOC2H5 + C2H5OH.
The reaction is of general application and of great importance, and a large number of syntheses have been effected by its use.
Claisen reaction. Condensation of an aldehyde with another aldehyde or a ketone in the presence of sodium hydroxide with the elimination of water. Thus benzaldehyde and methanal give Cinnamic aldehyde, phCH : CH.CHO.
Clarification. The removal from a liquid of small amounts of suspended matter with the object of obtaining a clear product. Clarification may be achieved by filtration centrifugation, or by the use of a clarifier.
Clarification. The removal from a liquid of small amounts of suspended matter with the object of obtaining a clear product. Clarification may be achieved by filtration centrifugation, or by the use of a clarifier.
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