Marckwald (Ann., 93, 74, 331; 1894, 79, 14) has supported this formula from considerations based on the syntheses of the quinoline ring.
Bamberger's observations on reduced quinoline derivatives point to the same conclusion, that condensed nuclei are not benzenoid, but possess an individual character, which breaks down, however, when the molecule is reduced.
Similarly a CH group may be replaced by a nitrogen atom with the production of compounds of similar stability; thus benzene gives pyridine, naphthalene gives quinoline and isoquinoline; anthracene gives acridine and a and 3 anthrapyridines.
A-pyrone condenses with the benzene ring to form coumarin and isocoumarin; benzo-'y-pyrone constitutes the nucleus of several vegetable colouring matters (chrysin, fisetin, quercetin, &c., which are derivatives of flavone or phenyl benzo-y-pyrone); dibenzo--ypyrone is known as xanthone; related to this substance are fluorane (and fluorescein), fluorone, fluorime, pyronine, &c. The pyridine ring condenses with the benzene ring to form quinoline and isoquinoline; acridine and phenanthridine are dibenzo-pyridines; naphthalene gives rise to a-and /3-naphthoquinolines and the anthrapyridines; anthracene gives anthraquinoline; while two pyridine nuclei connected by an intermediate benzene nucleus give the phenanthrolines.
Naphthyridines and naphthinolines result from the condensation of two pryridine and two quinoline nuclei respectively; and quino-quinolines are unsymmetrical naphthyridine nuclei condensed with a benzene nucleus.
On oxidation with potassium permanganate it yields acridinic acid (quinoline -a-(-dicarboxylic acid) C 9 H 5 N(COOH) 2.
The identity of the formulae and osazones of d-mannose and d-glucose showed that the stereochemical differences were situated at the carbon atom adjacent to the aldehyde group. Fischer applied a method indicated by Pasteur in converting dextro into laevo-tartaric acid; he found that both d-mannonic and d-gluconic acids (the latter is yielded by glucose on oxidation) were mutually convertible by heating with quinoline under pressure at 140°.
Instances of its application are found in the separation of orthoand para-nitrophenol, the o-compound distilling and the p- remaining behind; in the separation of aniline from the mixture obtained by reducing nitrobenzene; of the naphthols from the melts produced by fusing the naphthalene monosulphonic acids with potash; and of quinoline from the reaction between aniline, nitrobenzene, glycerin, and sulphuric acid (the product being first steam distilled to remove any aniline, nitrobenzene, or glycerin, then treated with alkali, and again steam distilled when quinoline comes over).
His perception of the analogy between it and ammonia led to his famous work on the amines and ammonium bases and the allied organic phosphorus compounds, while his researches on rosaniline, which he first prepared in 1858, formed the first of a series of investigations on colouring matters which only ended with quinoline red in 1887.
Reduction of orthonitrocinnamic acid gives orthoaminocinnamic acid, C 6 H 4 (NH 2)CH:CH 000H, which is of theoretical importance, as it readily gives a quinoline derivative.
This view has been fairly well supported by later discoveries; but, in addition to pyridine and quinoline nuclei, alkaloids derived from isoquinoline are known.
(3) Quinoline group. The alkaloids of the quina-barks: quinine, &c.; the strychnos bases: strychnine, brucine; and the veratrum alkaloids: veratrine, cevadine, &c.
This compound condenses in alkaline solution with compounds containing the grouping - CH 2 - CO - to form quinoline or its derivatives; thus, with acetaldehyde it forms quinoline, and with acetone, a-methyl quinoline.
It occasionally acts as an oxidizing agent, as in the preparation of quinoline and fuchsine.
They are strong bases characterized by a quinoline-like smell.
The aldo-ketenes are colourless compounds which are not capable of autoxidation, are polymerized by pyridine or quinoline, and are inert towards compounds containing the groupings C :N and C :O.
The ketoketenes are coloured compounds, which undergo autoxidation readily, form ketene bases on the addition of pyridine and quinoline, and yield addition compounds with substances containing the C:N and C:0 groupings.
Distilled with zinc dust morphine yields phenanthrene, pyridine and quinoline; dehydration gives, under certain conditions, apomorphine, C17H17N02, a white amorphous substance, readily soluble in alcohol, either and chloroform.
Cinchonine yields on oxidation cinchoninic acid (y - quinoline carboxylic acid).
The subject has been especially studied by Skraup, Konigs, and von Miller; Kiinigs and von Miller have proposed formulae consisting of a piperidine ring substituted with a vinyl group; in the former that is a bridge of CH 2 C(OH) from the nitrogen atom to the -y-carbon atom, connexion with the quinoline residue being made at the hydroxylic carbon atom through a CH2 group: whilst in the latter the piperidine ring is substituted by a methyl group in addition to the vinyl group and the bridge is simply C(OH), with which connexion is made as before.
QUINOLINE (Benzopyridine), C 9 H 7 N, an organic base first obtained from coal-tar in 1834 by F.
Quinoline is a colourless liquid with a smell resembling that of pyridine.
Nitric acid and chromic acid have little action on quinoline, but alkaline potassium permanganate oxidizes it to carbon dioxide, ammonia, oxalic, and quinolinic acids (S.
Numerous substitution products of quinoline are known, and the positions in the molecule are generally designated in accordance with the scheme shown in the inset formula: the letters o, m, p, a, standing for ortho-, meta-, Para-, and ana-.
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.
The reaction is a perfectly general one, for the aniline may be replaced by other aromatic amines and the aldehyde by other aldehydes, and so a large number of quinoline homologues may be prepared in this way.
Potassium permanganate oxidizes it to acetylanthranilic acid, [[Hooc(') C 6 H 4 (2)Nh Coch]] 31 while chromic acid oxidizes it to quinaldic acid (quinoline-a-carboxylic acid).
The oxy derivatives of the quinoline homologues are best obtained from the aniline derivatives of (3-ketonic acids.
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.
Cinchoninic acid (quinoline-y-carboxylic acid) is formed when cinchonine is oxidized by nitric acid, or by the oxidation of lepidine.
Acridinic acid (quinoline-a0dicarboxylic acid) is formed when acridine is oxidized by potassium permanganate (C. Gracbe and H.
It crystallizes in needles, which are easily soluble in alcohol, and 'v hen heated above 130° C. lose carbon dioxide and leave a residue of quinoline-fl-carboxylic acid.
Isoquinoline, isomeric with quinoline, was first discovered in coal-tar in 1885 by S.
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.
Riiber (Ber., 1902, 35, p. 2411; 1904, 37, P. 22 74), by oxidizing diphenyl-2.4-cyclo-butane-bismethylene malonic acid (fron cinnamic aldehyde and malonic acid in the presence of quinoline) with potassium permanganate.
Cyclo-heptatriene (tropilidine), C 7 H 81 is formed on distilling tropine with baryta; and from cyclo-heptadiene by forming its addition product with bromine and heating this with quinoline to 150-160° C. (R.