noun
definition
Any of a class of aromatic heterocyclic compounds containing a ring of five carbon atoms and an nitrogen atom; especially the simplest one, C5H5N.
Examples of pyridine in a Sentence
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.
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.
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.
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.
The 1 5 diketones of this type, when heated with aqueous ammonia, form pyridine derivatives.
In practice, the crude anthracene is purified by solution in the higher pyridine bases, after which treatment it is frequently sublimed.
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.
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.
Hofmann had shown that conine on distillation with zinc dust gave a-propyl pyridine (conyrine).
It also occurs with pyridine and its homologues in bone-oil.
Quinoline is a colourless liquid with a smell resembling that of pyridine.
Alkaline potassium permanganate oxidizes it to pyridine tricarboxylic acid (236).
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.
The aldehydes condense readily with acetoacetic ester in the presence of ammonia, to pyridines (see Pyridine), whilst 0.
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.
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).