Online Encyclopedia

CH3

Online Encyclopedia
Originally appearing in Volume V22, Page 760 of the 1911 Encyclopedia Britannica.
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CH3.CO-CO•CH3 CH3•C-CO-CH E CH3•CO•CO•CH3 HC-CO•C-CH3; whilst P. H. Bayrac (Bull. sac. chim., 1894 (3) 11, p. 1129) obtained anilino-derivatives of the paraquinones by the action of an aqueous solution of potassium chromate on an acetic acid solution of para-aminodimethylaniline and phenol: C6H60H+H2N•C6H4•N (CH3)2->O:C6H4:N.C6H4•N(CH3)2; these compounds yield the quinone when heated with mineral acids. The paraquinones are generally crystalline solids of a yellowish colour, having a characteristic sharp odour and being volatile in steam. They are readily reduced to the corresponding hydroquinones or para-dihydroxy-benzenes, and also combine with hydroxylamine hydrochloride to form nitrosophenols, ON•C6H4.OH, which can further yield quinone dioximes, HON:CsH4:NOH. Paraquinones also combine with ammonia and with amines yielding amino-derivatives and hydroquinones. The orthoquinones more resemble the a-diketones; they are crystalline solids of a red or yellow colour, but differ from the paraquinones in being devoid of smell and not volatile in a current of steam. Benzoquinone (para) or ordinary quinone, C6H402, is formed by the oxidation of aniline with sodium bichromate and sulphuric acid. It sublimes in golden yellow needles. Hot concentrated nitric acid oxidizes it to picric acid and oxalic acid, whilst on treatment with hydrochloric acid and potassium chlorate it yields chloranil (tetrachloroquinone). It combines directly with two and four atoms of bromine. Free hydroxylamine reduces it to hydroquinone. It combines directly with aniline to form dianilidoquinone, dianilidoquinone-anil and dianilidoquinone-dianil or azophenine. Two alternative structural formulae have been given to benzoquinone, namely: ~O O and 0=~>O The former, due to C. Graebe (Zeit. f. Chemie, 1867, 3, p. 39), ascribes to the molecule a peroxide configuration which accounts for its oxidizing powers but not for the fact that each oxygen atom is capable of replacement by one atom of chlorine. The second formula, due to R. Fittig (Ann., 1876, 18o, p. 23) readily explains the formation of the mono- and di-oximes of quinone and also that it readily combines with bromine. Quinone-chiorimide, C1N : C6H4 : 0, is obtained when paraaminophenol is oxidized with bleaching powder. It is a yellow crystalline solid readily volatile in steam. The dichlorimide, CIN : C6H4 : NCI, is formed in a similar manner from paraphenylene diamine. It is a strong oxidizing agent. Quinone-dioxime, HON : C6H4 : NOH, crystallizes in colourless or yellow needles, which decompose when heated to about 240° C. Potassium ferrocyanide in alkaline solution oxidizes it to dinitrosobenzene, whilst cold concentrated nitric acid oxidizes it to para-dinitrobenzene. Quinhydrone, C6H402•C6H4(OH)2, is formed by the direct union of quinone and hydroquinone or by careful oxidation of hydroquinone with ferric chloride solution. On boiling with water it decomposes into quinone and hydroquinone. Benzoquinone (ortho).—C. L. Jackson (Amer. Chem. Jour., 1901, 26, p. to) attempted to prepare this compound by the action of iodine on the lead salt of pyrocatechin suspended in chloroform. A deep red solution was obtained but the free quinone was not isolated since the solution on standing deposits nearly black crystals of dihydroxyphenylhydroxybenzoquinone (HO)2C6H3•C6H2O2.OH. R. Willstatter (Ber., 1904, 37, p. 4744), by dissolving pyrocatechin QUINTAIN in absolute ether containing ignited sodium sulphate and then adding dry silver oxide, obtained the quinone in dark red crystalline plates which decompose between 6o° and 7o° C. For naphthalene quinones see NAPHTHALENE; for anthracene quinone see ANTHRAQUINONE; and for phenanthrene quinone see PHENA NT H RENE. Quinoles.—The quinoles are a series of compounds of the type HoR >(=-- --\–/-O,obtained by the oxidation of para-alkylated phenols with nitric acid, Caro's acid or bromine (Auwers, Ber., 1897–1903; E. Bamberger, ib., 1903, 36, p. 2028; Th. Zincke, ib., 1895, 28, p. 3121); by the action of sulphuric acid on para-substituted phenylhydroxylamines (E. Bamberger), and by the action of the Grignard reagent on quinones (Bamberger). They are crystalline solids which are readily converted into para-alkylated phenols by reducing agents. They possess a weak acid and also an alcoholic character. QUINO%ALINES (Benzopyrazines), in organic chemistry, heterocyclic compounds containing a ring complex made up of a benzene ring and a pyrazine ring (formula I.); they are isomeric with the cinnolenes, phthalazines and quinazolines. They are formed by the condensing ortho-diamines with 1.2 diketones (Hinsberg, Ann., 1887, 237, p. 327), the parent substance of the group (quinoxaline) resulting when glyoxal is so condensed, whilst substitution derivatives arise when a-ketonic acids, a-chlorketones, a-aldehyde alcohols and a-ketone alcohols are used in place of diketones.
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