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 with alkalis yields a dimethoxyisoquinoline, whilst hydrohydrastinine, hydrocotarnine and the salts of cotarnine may be considered as derivatives of reduced isoquinolines (see ).

QUINONES, in organic chemistry, a group of compounds in which two hydrogen atoms of a benzene nucleus are replaced by two oxygen atoms. This replacement may take place either in the ortho or para positions, giving rise to orthoquinones or to paraquinones; metaquinones do not appear to have been isolated. The para or true quinones are obtained by the oxidation of hydrocarbons with chromic acid or of various para di-derivatives of benzene with chromic acid mixture, such, for example, as para-aminophenol, para-phenylene diamine, para-aminoazobenzene, &c. H. v. Pechmann (Ber., 1888, 21, p. 1417) has shown that -diketones are converted into paraquinones by the action of warm solutions of the caustic alkalis, diacetyl yielding para-xyloquinone: whilst P. H. Bayrac (Bull. soc. chim., 1894 (3) II, 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: C6H5OH+H2N·C6H4·N (CH3)2→O:C→6H4: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:C6H4:NOH. Paraquinones also combine with ammonia and with amines yielding amino-derivatives and hydroquinones. The orthoquinones more resemble the -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, C6H4O2, 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:



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, 180, p. 23) readily explains the formation of the mono- and di-oximes of quinone and also that it readily combines with bromine.

Quinone-chlorimide, ClN:C6H4:O, is obtained when para-aminophenol is oxidized with bleaching powder. It is a yellow crystalline solid readily volatile in steam. The dichlorimide, ClN: C6H4: NCl, 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, C6H4O2⋅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. 10) 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 stand ling deposits nearly black crystals of dihydroxyphenylhydroxybenzoquinone (HO)2C6H3⋅C6H2O2⋅OH. R. Willstätter (Ben, 1904, 37, p. 4744), by dissolving pyrocatechin in absolute ether containing ignited sodium sulphate and then adding dry silver oxide, obtained the quinone in dark red crystalline plates which decompose between 60° and 70° C. For naphthalene quinones see ; for anthracene quinone see ; and for phenanthrene quinone see .

Quinoles.—The quinoles are a series of compounds of the type == __ 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.

QUINOXALINES (Benzopyrazines), in organic chemistry, hetero cyclic 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 -ketonic acids, -chlorketones, -aldehyde alcohols and -ketone alcohols are used in place of diketones. In a similar manner, diamino derivatives are formed when cyanogen is condensed with ortho-diamines, and these amino compounds readily pass into the corresponding dioxy derivatives when acted upon with dilute hydrochloric acid. The quinoxalines are weak bases, and are stable towards oxidizing agents but are readily reduced to hydro derivatives. The tetrahydroquinoxalines are formed by condensing ortho-diamines with ortho-dihydroxy benzenes, and the keto-dihydro derivatives arise similarly by condensing mono-alkyl diamines with ketonic acids (Kehrmann and Messinger, Ber., 1892, 25, pp. 1628 et seq.). The azonium bases (formula II.) of this series are produced when the dihydroquinoxalines (obtained by similar condensations from the mono-alkyl-ortho-diamines) are oxidized with ferric chloride.

QUINSY, a common term for acute suppurative (q.v.). The English word (formerly “squinzey”) is a corruption of Fr. esquinancie, from Gr.  (, dog, and  , to choke), and is derived from the suffocating tendency of the ailment.

QUINTAIN (O. Fr. quintaine, from Lat. quintana, a street between the fifth and sixth maniples of a camp, where warlike exercises took place), an instrument used in the age of chivalry in practising for the tournament. Originally perhaps the mere trunk of a tree upon which the knight practised his sword strokes, as may be seen in an ancient illustration reproduced in Strutt’s Sports and Pastimes, the quintain developed into various forms of posts at which the soldier tilted with his lance, not only on horseback but on foot and even in boats. An early form consisted of the wooden figure of a Saracen armed with shield and sword; the object being to strike the figure on the forehead directly between the eyes. This, according to Strutt, was called by the Italians “running at the armed man” or “at the Saracen.” The “pel,” or post-quintain, was generally about 6 ft. high.

As late as the 18th century running at the quintain survived in English rural districts. In one variation of the pastime the quintain was a tun filled with water, which, if the blow was a poor one, was emptied over the striker. A later form was a post with a cross-piece, from which was suspended a ring, which the horseman endeavoured to pierce with his lance while at full speed. This sport, called “tilting at the ring,” was very popular in England and on the continent of Europe in the 17th century, and is still practised as a feature of military and equestrian sport.