It gives rise to various decomposition products such as pyridine, picoline, &c., when its vapour is passed through a red-hot tube.
By passing the vapour of this compound through a red-hot tube, it yields the isomeric a0- pyridylpyrrol, the potassium salt of which with methyl iodide gives a substance methylated both in the pyridine and pyrrol nuclei.
By distillation over lime, the methyl group is removed from the pyridine ring, and the resulting a- pyridyl-Nmethylpyrrol gives i-nicotine on reduction.
Rhombic sulphur may be obtained artificially by slowly crystallizing a solution of sulphur in carbon bisulphide, or, better, by exposing pyridine saturated with sulphuretted hydrogen to atmospheric oxidation (Ahrens, Ber., 1890, 23, p. 2708).
Thus benzene, (CH) gives thiophene, (CH) S, from which it is difficultly distinguished; pyridine, (CH) N, gives thiazole, (CH) N S, which is a very similar substance; naphthalene gives thionaphthen, C 11 S, with which it shows great analogies, especially in the derivatives.
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.
Six-membered ring systems can be referred back, in a manner similar to the above, to pyrone, penthiophene and pyridine, the substances containing a ring of five carbon atoms, and an oxygen, sulphur and nitrogen atom respectively.
Pyridine gives origin to: pyridazine or ortho-diazine, pyrimidine or metadiazine, pyrazine or para-diazine, osotriazine, unsymmetrical triazine, symmetrical triazine, osotetrazone and tetrazine.
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.
In the aromatic compounds there is no regularity between the increments due to the introduction of methyl groups into the benzene nucleus or side chains; the normal value of 20 0 -21° is exhibited, however, by pyridine and its derivatives.
Normal values of K were given by nitrogen peroxide, N204, sulphur chloride, S 2 C1 21 silicon tetrachloride, SiC1 4, phosphorus chloride, PC1 3, phosphoryl chloride, POC1 31 nickel carbonyl, Ni(CO) 4, carbon disulphide, benzene, pyridine, ether, methyl propyl ketone; association characterized many hydroxylic compounds: for ethyl alcohol the factor of association was 2.74-2.43, for n-propyl alcohol 2.86-2.72, acetic acid 3.62 -2.77, acetone 1 .
Pyrrol is readily converted into pyridine derivatives by acting with bromoform, chloroform, or methylene iodide on its potassium salt, t3-brom-and O-chlorpyridine being obtained with the first two compounds, and pyridine itself with the last.
Other forms are: d- and l-gulose, prepared from the lactones of the corresponding gulonic acids, which are obtained from d- and /-glucose by oxidation and inversion; d- and l-idose, obtained by inverting with pyridine d- and l-gulonic acids, and reducing the resulting idionic acids; d- and l-galactose, the first being obtained by hydrolysing milk sugar with dilute sulphuric acid, and the second by fermenting inactive galactose (from the reduction of the lactone of d, l-galactonic acid) with yeast; and d- and l-talose obtained by inverting the galactonic acids by pyridine into d- and l-talonic acids and reduction.
When l-gulonic acid is heated with pyridine, it is converted into l-idonic acid, and vice versa; and d-gulonic acid may in a similar manner be converted into d-idonic acid, from which it is possible to prepare d-idose.
Lastly, when d-galactonic acid is heated with pyridine, it is converted into talonic acid, which is reducible to talose, an isomeride bearing to galactose the same relation that mannose bears to glucose.
The crude anthracene cake is purified by treatment with the higher pyridine bases, the operation being carried out in large steam-jacketed boilers.
The crystallized anthracene is then removed by a centrifugal separator and the process of solution in the pyridine bases is repeated.
In the first category there are two varieties: - (T) A mixture of ioo litres of spirit and 22 litres of a mixture of 4 parts of wood-naphtha and 1 of pyridine bases; this spirit, the use of which is practically limited to heating and lighting purposes, may be mixed with 50 grs.
of lavender or rosemary, in order to destroy the noxious odour of the pyridine bases.
The "general" mixture consists of Too litres of spirit, and 5 litres of wood spirit or 2 litre of pyridine.
Konigs, expressed the opinion that the alkaloids were derivatives of pyridine or quinoline.
This view has been fairly well supported by later discoveries; but, in addition to pyridine and quinoline nuclei, alkaloids derived from isoquinoline are known.
(1) Pyridine group. Piperine; conine; trigonelline; arecaidine; guvacine; pilocarpine; cytisine; nicotine; sparteine.
It can also be used for the synthesis of pyridine derivatives, since A.
Hantzsch has shown that aldehydes condense with aceto-acetic ester and ammonia to produce the homologues of pyridine, thus: R R [[Rooc Ch 2 Cho Ch 2 Coor Rooc C - Ch - C Coor]] + + 1 = Ii II +3H20.
The 1 5 diketones of this type, when heated with aqueous ammonia, form pyridine derivatives.
Those in which the keto groups are in combination with phenyl residues give pyridine derivatives on treatment with hydroxylamine, thus benzamarone, C 6 H 5 CH[CH(C 6 H 5) CO.
In practice, the crude anthracene is purified by solution in the higher pyridine bases, after which treatment it is frequently sublimed.
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.
When heated with pyridine to 140° C., it is converted into allomucic acid.
Moissan, contains only a trifling amount of morphia, and the effect produced by it is apparently due, not to that alkaloid, but to such decomposition products as pyrrol, acetone and pyridine and hydropyridine bases.
Formulae have been proposed by Pschorr and Knorr explaining this and other decompositions (in Pschorr's formula the morphine ring system is a fusion of a phenanthrene and pyridine nucleus); another formula, containing a fusion of a phenanthrene with a pyrrol ring, was proposed by Bucherer in'1907.
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.
To celebrate his seventieth birthday his scientific papers were collected and published in two volumes (Gesammelte Werke, Brunswick, 1905), and the names of the headings under which they are grouped give some idea of the range and extent of his chemical work: (1) organic arsenic compounds, (2) uric acid group, (3) indigo, (4) papers arising from indigo researches, (5) pyrrol and pyridine bases, (6) experiments on the elimination of water and on condensation, (7) the phthaleins, (8) the hydro-aromatic compounds, (9) the terpenes, (io) nitroso compounds, (11) furfurol, (12) acetylene compounds and "strain" (Spannungs) theory, (13) peroxides, (14) basic properties of oxygen, (15) dibenzalacetone and triphenylamine, (16) various researches on the aromatic and (17) the aliphatic series.
PYRIDINE, C 5 H 5 N, an organic base, discovered by T.
The amount of pyridine produced in most of these processes is very small, and the best source for its preparation is the "light-oil" fraction of the coal-tar distillate.
Pyridine is a colourless liquid of a distinctly unpleasant, penetrating odour.
On the constitution of the pyridine nucleus, see K6rner, Gior.
As regards the isomerism of the pyridine substitution products, three mono-derivatives are known, the different positions being indicated by the Greek, letters a, s and y, as shown in the inset formula.
The oxypyridines may be prepared by distilling the corresponding oxypyridine carboxylic acids with lime, or by fusing the pyridine carboxylic acids with caustic potash.
Pechmann, Ber., 1895, 28, p. 1624), thus corresponding to the formulae The homologues of pyridine may be synthesized in various ways.
Hantzsch (Ann., 1882, 215, p. I; Ber., 1882, 15, p. 2914) which consists in the condensation of two molecules of aceto-acetic ester with one of an aldehyde and one of ammonia: RO 2 C CH 2 R' CHO CH 2 CO 2 R RO 2 C C CHR' C C02R CH 3 CO + NH 3 + CO CH 3 -' CH3 C-NH-C CH3 The resulting dihydro-compound is then oxidized with nitrous acid, the ester hydrolysed and the resulting acid heated with lime; carbon dioxide is eliminated and a trisubstituted pyridine of the type CH C(CH3) is obtained.
Of the other methods for preparing pyridine homologues mention may be made of the discovery by A.
5 diketones of the type inset, when heated with ammonia, also yield pyridine derivatives.
The subjoined table shows the chief homologues of pyridine: Pyridine carboxylic acids are usually prepared by oxidizing the homologues of the base; they also result as decomposition products of various alkaloids.
It is oxidized to pyridine by heating with concentrated sulphuric acid to 300° C., or with nitrobenzene to 250° C., or with silver acetate to 180° C. Being an imide it readily yields a nitroso derivative, and N-alkyl and acidyl derivatives.
Hofmann had shown that conine on distillation with zinc dust gave a-propyl pyridine (conyrine).
This substance when heated with hydriodic acid to 300° C. is converted into a-propyl piperidine, which can also be obtained by the reduction of a-allyl pyridine (formed from a-methyl pyridine and paraldehyde).
a tetrahydro propyl pyridine.
It also occurs with pyridine and its homologues in bone-oil.
Quinoline is a colourless liquid with a smell resembling that of pyridine.
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.
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).
Alkaline potassium permanganate oxidizes it to pyridine tricarboxylic acid (236).
It crystallizes from water in needles or prisms and in the anhydrous state melts at 253-254° C. Potassium permanganate oxidizes it to pyridine tricarboxylic acid (234).
The transformation of piperidine into pyridine by W.
When reduced in alcoholic solution by means of sodium amalgam it yields methyl granatoline, 08H130H NCH3; this substance, on oxidation with cold potassium permanganate, is converted into granatoline, C 8 H, 5 NO, which on distillation over zinc dust yields pyridine.
The hydrochloride of the latter base when distilled over zinc dust yields a-propyl pyridine.
carboxylate oxygen or the pyridine nitrogen.
pyridine nucleotide metabolism.
pyridine amplificant is invariant.
pyridine nucleotide transhydrogenase catalyzes the reduction of NADP + to NADPH with the concomitant oxidation of NADH to NAD + .
pyridine derivatives (Kadlec & Hanslian 1965 ).
In the aromatic compounds there is no regularity between the increments due to the introduction of methyl groups into the benzene nucleus or side chains; the normal value of 20 0 -21Ã‚° is exhibited, however, by pyridine and its derivatives.
The aldehydes condense readily with acetoacetic ester in the presence of ammonia, to pyridines (see Pyridine), whilst 0.
It is a reddish amorphous mass, insoluble in alcohol, and when distilled yields picoline (methyl pyridine) (A.
The amount of eugenol in oil of cloves can be estimated by acetylation, in presence of pyridine (A.
The metal was first obtained electrolytically in 1910 by electrolysing the fused hydroxide in a nickel vessel, with an iron wire cathode and iron cylinder anode; the product on cooling being opened under pyridine cooled by a freezing mixture (G.
When heated with pyridine to 140Ã‚° C., it is converted into allomucic acid.
It is oxidized to pyridine by heating with concentrated sulphuric acid to 300Ã‚° C., or with nitrobenzene to 250Ã‚° C., or with silver acetate to 180Ã‚° C. Being an imide it readily yields a nitroso derivative, and N-alkyl and acidyl derivatives.
Chem., 3, p. 601) obtained it by electrolysing the chloride in pyridine solution, a carbon anode and an iron or platinum cathode being used.
This substance when heated with hydriodic acid to 300Ã‚° C. is converted into a-propyl piperidine, which can also be obtained by the reduction of a-allyl pyridine (formed from a-methyl pyridine and paraldehyde).
It is a colourless liquid which boils at 255Ã‚° 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).
It crystallizes from water in needles or prisms and in the anhydrous state melts at 253-254Ã‚° C. Potassium permanganate oxidizes it to pyridine tricarboxylic acid (234).
Hofmann (see Pyridine).
Thus, axon protection is likely to be mediated by altered ubiquitination or pyridine nucleotide metabolism.
The attachment locant " 4 " in each pyridine amplificant is invariant.
First, look at the hydroxyl group on the pyridine ring.
Ladenburg (1883, 1887) demonstrated that the molecule contained a reduced pyridine nucleus.
Contact dermatitis from castor oil and vitamin B was attributed to pyridine derivatives (Kadlec & Hanslian 1965).
The word usage examples above have been gathered from various sources to reflect current and historial usage. They do not represent the opinions of YourDictionary.com.