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QUINOLINE (Benzopyridine), C9H7N
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See also:QUINOLINE (Benzopyridine), C9H7N , an organic See also:base first obtained from See also:coal-See also:tar in 1834 by F. Runge (Fogg. See also:Ann., 1834, 31, p. 68), and later by C. See also:Gerhardt by the See also:distillation of cinchonine, See also:quinine and other alkaloids with See also:caustic potash (Ann., 1842, 42, p. 31o; 44, p. 279). It also occurs with See also:pyridine and its homologues in See also:bone-oil. It may be prepared by distilling cinchoninic See also:acid with See also:lime; by the reduction of ortho-aminocinnamic aldehyde (A. See also:Baeyer and V. Drewson, Ber., 1883, 16, p. 2207); by passing the vapour of allyl See also:aniline over heated See also:lead See also:oxide; by the condensation of ortho-aminobenzaldehyde with acetaldehyde in the presence of aqueous caustic soda (P. Friedlander and C. F. Gohring, See also:Bee., 1882, 15, p. 2572; 1883, 16, p. 1833); by the See also:action of orthotoluidine on glyoxal at Iso° C. (V. Kulisch, Monats., 1894, 15, p. 276); by the action of See also:phosphorus pentachloride on hydrocarbostyril (the inner anhydride of ortho-aminohydrocinnamic acid), the chlorinated See also:compound first formed being then reduced by hydriodic acid (A. Baeyer): See also:CH2–CH2 CH=C•Cl CH=CH See also:C6H4\ C6114\\ -->C6H4 \ I i NH–CO N =C.Cl N = CH and by the so-called "Skraup " reaction, which consists in oxidizing a mixture of aniline, See also:glycerin and concentrated sulphuric acid, with See also:nitrobenzene (Z. Skraup, Monats., 188o, 1, p. 316; 1881, 2, p. 141). This reaction is a very violent one, and its mechanism may probably be explained as follows: The glycerin is first converted into acrolein, which combines with the aniline to See also:form acrolein-aniline, and this product is then oxidized by the nitrobenzene: C3HSO3—>C3H4O (±C6H5NH2)--sC6H5N: CH . CH: CH2-*C9H7N. The nitrobenzene may be replaced by See also:arsenic acid, when the reaction proceeds much more quietly and a cleaner product is obtained (C. A. Knueppel, Ber., 1896, 29, p. 703). The Skraup reaction is a perfectly See also:general one for See also:primary amino-compounds; the halogen-, nitro- and oxy-anilines (aminophenols) react similarly, as do also the toluidines, See also:naphthylamines, aminoanthracene, See also:meta- and See also:para-phenylene diamines, and orthoand y-aminoquinoline. Quinoline is a colourless liquid with a See also:smell resembling that of pyridine. It boils at 238° C. and is very hygroscopic. It is a See also:tertiary base and forms well-defined salts. It is almost insoluble in See also:water, but dissolves readily in the See also:common organic solvents. It combines readily with the. alkyl halides. H. See also:Decker (Ber., 1905, 38, p. 1144) has found that many ortho substituted quinolines will not combine with methyl iodide owing to steric hindrance, but the difficulty can be overcome in most cases by using methyl sulphate and See also:heating the reaction components to too° C. for See also:half an See also:hour. Nitric acid and chromic acid have little action on quinoline, but alkaline See also:potassium permanganate oxidizes it to See also:carbon dioxide, See also:ammonia, oxalic, and quinolinic acids (S. Hoogewerff and W. A. v. Dorp, Rec. Pays Bas, 1882, 1, p. 107). See also:Bleaching See also:powder oxidizes it to chlorcarbostyril. a y It is reduced by the action of See also:zinc and ammonia ,/\/Ns to di-and tetra-hydroquinolines. A hexahydro- and a decahydroquinoline have been obtained m\/\N/a by heating tetrahydroquinoline with hydri- o odic acid and phosphorus to high temperatures (E. See also:Bamberger, Ber., 189o, 23, p. 1138). Numerous substitution products of quinoline are known, and the positions in the See also:molecule are generally designated in accordance with the See also:scheme shown in the inset See also:formula: the letters o, m, p, a, See also:standing for ortho-, meta-, para-, and See also:ana-. __ _ The oxvquinolines possess a certain importance owing to their relationship to the alkaloids. Those with the hydroxyl See also:group in the See also:benzene See also:nucleus are prepared from the aminophenols by the Skraup reaction. Only two are known containing the hydroxyl group in the pyridine nucleus, namely, carbostyril (a-oxyquinoline), which is formed by the reduction of ortho-aminocinnamic acid with ammonium sulphide (L. Chiozza, Ann., 1852, 83, p. m8) or with ferrous sulphate and baryta, and kynurine (y-oxyquinoline), which is obtained by the action of nitrous acid on y-aminoquinoline (A. Claus and H. Howitz, Jour. prak. Chem., 1894, 158, p. 232). It is also formed by the condensation of anthranilic acid with acetaldehyde (S. Niemeritowski, Ber., 1895, 28, p. 2811). They are both crystalline solids, the former melting when anhydrous at 199-200°, and the latter at 52° C. Of the homologues of quinoline, the most important are quinaldine, lepidine, -y-phenylquinoline, and flavoline. Quinaldine (a-methylquinoline) is See also:present in coal-tar; it may be prepared by condensing aniline with See also:paraldehyde and concentrated hydrochloric acid (O. Doebner and W. v. See also:Miller, See also:Bet., 1881, 14, pp. 2812 et seq.). The reaction is a perfectly general one, for the aniline may be replaced by other aromatic See also:amines and the aldehyde by other See also:aldehydes, and so a large number of quinoline homologues may be prepared in this way. Quinaldine may also be obtained by condensing ortho-aminobenzaldehyde with See also:acetone in presence of caustic soda (P. Friedlander, loc. cit.). It is a colourless liquid which boils at -247° C. The -See also:CH3 group is very reactive, condensing readily with aldehydes and with See also:phthalic anhydride. Potassium permanganate oxidizes it to acetylanthranilic acid, HOOC(l)•CeH4.(2)NH•COCH3, while chromic acid oxidizes it to quinaldic acid (quinoline-a-carboxylic acid). Lepidine(y-methylquinoline) was first obtained by distilling cinchonine with caustic potash. It may be prepared synthetically by condensing ortho-aminoacetophenone with paraldehyde and caustic soda (L. Knorr, Ann., 1886, 236, p. 69) or from aniline, acetone, formaldehyde and hydrochloric acid (C. Beyer, Jour. prak. Chem., 1885, 140, p. 125). It may also be prepared by condensing ay-dimethylquinoline and formaldehyde, the resulting a-ethanollepidine, C9H5•CH3N(CH2•CH2.OH), breaks See also:clown on. heating and forms lepidine (W. Konigs and A. Mengel, Ber., 1904, 37, p. 1322). It is a colourless liquid which boils at 255° C. Chromic acid oxidizes it to cinchoninic acid (see below), whilst potassium permanganate oxidizes it to lepidinic acid (y-methylquinolinic acid) and cinchomeronic acid (see PYRIDINE). y-Phenylquinoline, which is probably the See also:parent substanceof the See also:cinchona alkaloids, is prepared by heating y-phe.lt lquinaldic acid, the oxidation product of the -y-phenylquinaldine, which results from the action of alcoholic potash on a mixture of orthoaminobenzophenone and acetone (W. Konigs and R. Geigy, Ber., 1885, 18, p. 2400), or by the action of sulphuric acid on Lenzoylacetone anilide (C. Beyer, Ber., 1887, 20, p. 1767). It crystallizes in needles which melt at 61 ° C. Faavoline (a-phenyl-y-methylquinoline) is formed on heating flavenol (see below) with excess of zinc dust, or by heating molecular proportions of ortho-aminoacetophenone and See also:acetophenone, in dilute alcoholic See also:solution, with a small quantity of Io% caustic soda solution (O. See also:Fischer, Ber., 1886, 19, p. 1037). Closely related to flavoline is flavaniline or (a)-para-aminophenyl-y-methylquinoline, which is formed when acetanilide and anhydrous zinc chloride are heated together for many See also:hours at 250-270° C. (O. Fischer and C. See also:Rudolph, Ber., 1882, 15, p. 1500), or by heating ortho- and para-aminoacetophenone with zinc chloride to 9o° C. (O. Fischer, Ber., 1886, 19, p. IC38). It crystallizes from benzene in prisms; which melt at 97° C. See also:Sodium nitrite in the presence of excess of acid converts it into the corresponding hydroxylic compound flavenol. The oxy derivatives of the quinoline homologues are best obtained from the aniline derivatives of 0-ketonic acids. At 110° C. aniline and acetoacetic ester condense to form anilido-acetoacetic ester, See also:CH3CO•CH2•CO.NH•See also:C6H5, which is converted by concentrated ' acids into a-oxy-y-methylquinoline (L. Knorr, Ann., 1886, 236, p. 73). On the other See also:hand, at about 240° C., the amine and ester react to form 13-anilidocrotonic ester, CH3•C(NHC6H5) : CH•COOC2H5, which yields -y-oxy-a-methylquinoline (M. See also:Conrad and L. Limpach, Ber., 1887, 20, p. 947). Numerous carboxylic acids of quinoline are known,' the most important of which are quinaldic, cinchoninic and acridinic acids. Quinaldic acid (quinoline-a-carboxylic acid) is produced when quinaldine is oxidized by chromic acid. It crystallizes in needles, which contain two molecules of water of See also:crystallization, and melt at 156° C. When heated above the melting-point it loses carbon dioxide and yields quinoline. Alkaline potassium pernanganate oxidizes it to pyridine tricarboxylic acid (2.3.6). Cinchoninic acid (quinoline-y-carboxylic acid) is formed when cinchonine is oxidized by nitric acid, or by the oxidation of lepidine. It crystallizes from water in needles or prisms and in the anhydrous See also:state melts at 253-254° C. Potassium permanganate oxidizes it to pyridine tricarboxylic acid (2.3.4). Acridinic acid (quinoline-a$-dicarboxylic acid) is formed when See also:acridine is oxidized by potassium permanganate (C. Graebe and H. See also:Caro, Ber., 188o, 13, p. 100). It crystallizes in needles, which are easily soluble in See also:alcohol, and when heated above 13o° C. lose carbon dioxide and leave a See also:residue of quinoline-0-carboxylic acid. Isoquinoline, isomeric with quinoline, was first discovered in coal-tar in 1885 by S. Hoogewerff and W. A. v. Dorp (Rec. Pays Bas, 1885, 4, 125) ; its formula is shown in the inset. It may be separated from the quinoline which accompanies it by means of the difference in the solubility of the sulphates of the two compounds, isoquinoline sulphate being much less soluble than quinoline sulphate. It may be prepared by passing Isoquinoline. the vapour of benzylidene ethylamine through a red-hot See also:tube (A. Pictet and S. Popovici, Ber., 1892, 25, p. 733); by the action of concentrated sulphuric acid on benzyl amino-acetaldehyde, CIHS•CH2•NH•CH2•CHO (E. Fischer), or on benzylidene aminoacetal, C6H5CH : N • CH2 . CH(OC2H6)2 (C. Pomeranz, Monats., 1892, 14, p. 116) ; by heating cinnamenyl aldoxime with phosphorus pentoxide to 7o° C. (E. Bamberger, Ber., 1894, 27, p. 1955), C6H5CH : CH.CH : NOH. --s[C6H5CH • CH•NH•See also:COH]-sC9H7N; by the action of hydriodic acid on the oxydichlorisoquinoline formed when phosphorus pentachloride reacts with hippuric acid; by the distillation of homophthalimide over zinc dust (M. Le See also:Blanc, Ber., 1888, 21, p. 2299), or by treatment with phosphorus oxychloride followed by the reduction of the resulting dichloriso- quinoline wiIthorhydgH4 I Criodic acid (S. See also:Gabriel, Bet., 1886, 19, pp. 1655, 2355): CHz-CO CH = C(OH) CfiH4CH=C•CI CHCH Ce5H4 \CO- NH \C(OH): N C CI=NI > C6H41 \CH= It is also formed from isobenzalphthalide by the action of ammonia, followed by phosphorus oxychlorid-*eCanH ,d, reduction of the chlorinated product (S. Gabriel), CH= C•C5H5 /CH= C•C6H5 C6He < \CO - CO-NH CH= GC6H5 CH= C C,H6 • >See also:c6H.,I - sC,H9 I \CCI=N CH=Nl and from isocoumarin carboxylic acid by See also:conversion into isocarbostyril on heating, and subsequent reduction by distillation with zinc dust (E. Bamberger, Bet., 1892, 25, p. 1138). It melts at 22-23° C. and boils at 240° C., and behaves in most respects similarly to quinoline. By oxidation with alkaline potassium permanganate it yields phthalic acid and cinchomeronic acid. Reduction by means of See also:tin and hydrochloric acid gives a tetrahydro derivative. Numerous derivatives of isoquinoline are obtained in the de-See also:composition of various See also:vegetable alkaloids. Papaverine on See also:fusion with alkalis yields a dimethoxyisoquinoline, whilst hydrohydrastinine, hydrocotarnine and the salts of cotarnine may be considered as derivatives of reduced isoquinoliaes (see OP1uM). Additional information and CommentsThere are no comments yet for this article.
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