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C6H5CHO

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Originally appearing in Volume V01, Page 532 of the 1911 Encyclopedia Britannica.
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C6H5CHO . The See also:

aldehydes are characterized`by their See also:great chemical re-activity. They See also:act as reducing agents, See also:silver nitrate in the presence of See also:ammonia being rapidly reduced to the See also:condition of metallic silver. They are easily oxidized to the corresponding fatty See also:acid, in many cases simply by exposure to See also:air. Nascent See also:hydrogen reduces them to See also:primary See also:alcohols, and See also:phosphorus pentachloride replaces the carbonyl See also:oxygen by See also:chlorine. They See also:form many addition compounds, combining with ammonia to form aldehyde ammonia s of the type R•CH(OH)•NH,. . These are colourless crystalline compounds, which are most readily prepared by passing ammonia See also:gas into an ethereal See also:solution of the aldehyde. With See also:sodium bisulphite they form the so-called bisulphite compounds R•CH(OH)•SO3Na, which are readily resolved into their components by See also:distillation with dilute acids, and are frequently used for the preparation of the pure aldehyde. With hydrocyanic acid aldehydes form the cyanhydrins R•CH(OH)•CN. They react with See also:hydroxylamine and phenylhydrazine, with the formation of aldoximes and See also:hydra-zones. (For the See also:isomerism of the aldoximes see See also:OXIMES). The hydrazones are crystalline substances which are of value in the characterization of the aldehydes.

Both oximes and hydrazones, on boiling with dilute acid, regenerate the See also:

parent aldehyde. The hydrazones are best prepared by mixing the aldehyde with phenylhydrazine in dilute acetic acid solution, in the See also:absence of any See also:free See also:mineral acid. Semioxainazid, NH2•CO•CO•NH•NH2, has also been employed for the See also:identification of aldehydes (W. Kerp and K. Unger, Berichte, 1897, 30. p. 585)• Aldehydes are converted into resins by the See also:action of See also:caustic alkalies. On See also:heating with alcohols to loo° C. they form acetals, and they also form condensation products with See also:para-amido-di-methyl-See also:aniline (A. Cahn, Berichte, 1884, 17, p. 2939). They react with the See also:zinc alkyls to form addition products, which are decomposed by See also:water with formation of secondary alcohols (K. Thurnlach, Ainalen, 1882, 213, p. 369) thus: Zn(See also:C2H3)z See also:H2O CH3•CHO CH3•CHCO2ZnC2H6 See also:CH3-CH<OH 3--ZnO+See also:C2H6.

The reaction is a See also:

general one for all aldehydes with zinc methyl and zinc See also:ethyl, but not with the higher zinc alkyls. V. Grignard (Comptes Rendus, 1900 et seq.) showed that aldehydes combine with See also:magnesium alkyl iodides (in See also:absolute See also:ether solution) to form addition products, which are decomposed by water with the OC<RI+Cl • See also:CH2. COOC2H5- 0 formation of secondary alcohols, thus from acetaldehyde and magnesium methyl iodide, isopropyl See also:alcohol is obtained.

End of Article: C6H5CHO

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