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PYRIMIDINES, METADIAZINES

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Originally appearing in Volume V22, Page 692 of the 1911 Encyclopedia Britannica.
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PYRIMIDINES, METADIAZINES Or MIAZINES, in organir See also:chemistry, a See also:series of heterocyclic compounds containing a rin1 complex, composed of four See also:carbon atoms and two See also:nitrogen atoms the nitrogen atoms being in the See also:meta-position. The oxyderiva tives of the tetrahydro- and hexahydro-pyrimidines are the uracils and the ureides of malonic See also:acid (see See also:PURIN). The purins themselves may be considered as a See also:combination of the pyrimidine and glyoxaline See also:ring systems. For formulae see below; the See also:numbers about the first ring explain the See also:orientation of pyrimidine derivatives. The pyrimidines may be obtained by condensing 1.3-di- See also:ketones with the See also:amidines (A. Pinner, Ber., 1893, 26, p. 2125). N CHs See also:CH2•CO(See also:CH3) + N HN C6H6_> CHsCH C(CH3)Clv,CsHb. The 0-ketonic See also:esters under like treatment yield oxypyrimidines, whilst if cyanacetic ester be employed then amino-oxypyrimidines are obtained. By using See also:urea, See also:guanidine, thiourea and related compounds instead of amidines, one obtains the uracils. The cyanalkines (aminopyrimidines) were first obtained, although their constitution was not definitely known, by E. See also:Frankland and H.

See also:

Kolbe (See also:Ann. 1848, 65, p. 269) by See also:heating the nitriles of acids with metallic See also:sodium or with sodium ethylate between 13o° C. and 18o° C. 3CH3CN =C4HN2(CH3)2•See also:NH2[2.4.6]. Pyrimidine, C4H4N2, itself is a See also:water-soluble See also:base which melts at 21° C. and possesses a narcotic See also:smell. Its methyl derivatives yield the corresponding carboxylic acids when oxidized by See also:potassium permanganate. The amino derivatives are See also:stable bases which readily yield substitution derivatives when acted upon by the halogen elements. Cyanmethine, C6H9N2 (dimethyl-aminopyrimidine—2.4.6), melts at 18o—181°C. The See also:simple oxypyrimidines are obtained by the See also:action of nitrous acid on the amino derivatives, or by heating these latter with concentrated hydrochloric acid to 18o° C. They show both basic and phenolic properties and are indifferent to the action of reducing agents. Acid oxidizing agents, however, completely destroy them. By the action of See also:phosphorus pentachloride, the hydroxyl See also:group is replaced by See also:chlorine.

Hydropyrimidines.--The dihydro derivatives are most probably those compounds which are formed in the condensation of acidyl derivatives of See also:

acetone, with urea, guanidine, &c. Tetrahydropyrimidines are obtained by the action of amidines on trimethylene bromide: Br(CH2)3Br+C6H6C(:NH) •NH2 =2HBr+C4H7N2(C6Hs)[2]. The 2.6-diketo-tetrahydropyrimidines or uracils may be considered as the ureides of ,B-aldehydo, and 0-ketonic acids. Uracil and its homologues may be obtained in many cases from the hydrouracils by the action of See also:bromine, and subsequent elimination of the elements of hydrobromic acid; or by the condensation of aceto-acetic ester and related substances with urea, thiourea, guanidine, &c. Uracil, C4H402N2, crystallizes in colourless needles, is soluble in hot water and melts with decomposition at 335° C. Hydrouracil, C4H602N2, is obtained by the action of bromine and See also:caustic alkalis on succinamide (H. Weidel and E. Roithner, Monats. , 1896, 17, p. 172) ; by the See also:fusion of 0-aminopropionic acid with urea; by the electrolytic reduction of barbituric acid (J. Tafel, Ber., 1900, 33, p. 3385), and by the condensation of acrylic acid with urea at 210—220° C.

Phoenix-squares

(E. See also:

Fischer, Ber., 1901, 34, p. 3759). It crystallizes in needles and is soluble in water. It melts at 275° C. 4-Methyluracil, C5He02N2, has See also:long been known, having first been synthesized by R. Behrend (see PURIN). It crystallizes in needles which melt at 3200 C. and is soluble in caustic alkalis. On oxidation with potassium permanganate it is converted into acetyl urea, together with other products. 5-Methyluracil (Thymin) is obtained from the corresponding methyl bromhydrouracil (E. Fischer) ; or from 2.4.6-trichlor-5-methylpyrimidine by the action of sodium methylate. This yields a 2.4-dimethoxy-5-methyl-6-chlorpyrimidine, which on reduction and subsequent treatment with hydrochloric acid is converted into thymin (O.

Gerngross, See also:

Bee., 1905, 38, p. 3394). For methods of preparation and properties of numerous other pyrimidine compounds see T. B. See also:Johnson, Journ. Biol. Chem., 1906, &c. ; Amer. Chem. Journ., 1906, &c.; W. Traube, Ber., 1900, &c.; O. Isay, ibid., 1906, 39, P.

251.

End of Article: PYRIMIDINES, METADIAZINES

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