Page:EB1911 - Volume 22.djvu/707
| Name. | Formula. | Position of Sub- stituent. |
Remarks. |
| Picolinic acid. |
C5H4(CO2H)N | α | M.p. 137°. Easily soluble in water. Yellow coloration with FeSO4. Position of carboxyl group determined by synthesis from α-naphthylamine (Z. Skraup and A. Cobenzl, Monats., 1883, 4. p. 436).
|
| Nicotinic acid. |
C5H4(CO2H)N | β | M.p. 228–229°. An oxidation product of nicotine, hydrastine and berberine. Constitution determined by synthesis from β-naphthylamine (Skraup).
|
| Quinolinic acid. |
C5H3(CO2H)2N | αβ | M.p. 192–195° with decomposition into nicotinic acid. Formed by oxidation of quinoline.
|
| Cinchomeronic acid. |
C5H3(CO2H)2N | βγ | M.p. 258–259°. Formed by oxidation of quinoine, cinchonine, and isoquinoline.
|
| α-Carbochinco- meronic acid. |
C5H2(CO2H)3N | αβγ | M.p. 249–250°. Crystallizes with 1+1/2H2O. An oxidation product of cinchonine, quinine and papaverine. |
| Berberonic acid. |
C5H2(CO2H), | βγ | M.p. 243°. An oxidation product of berberine. Gives a red coloration with FeSO4. Boiling with glacial acetic acid gives cinchomeronic acid.
|
Trigonelline, C7H7NO2, the methyl betaine of nicotinic acid, was discovered in 1885 by E. Jahns (Ber., 1885, 18, p. 2518), and is found in the seeds of Trigonella and Strophanthus hispidus. It is very soluble in water. With baryta it yields methylamine, and when heated with concentrated hydrochloric acid, to 260° C. it yields methyl chloride and nicotinic acid. It was synthesized by A. Hantzsch (Ber., 1886, 19, p. 631) by condensing methyl iodide and potassium nicotinate at 150° C. the resulting iodide being then decomposed by moist silver oxide. A. Pictet (Ber., 1897, 30, p. 2117) obtained it by oxidizing nicotine methyl hydroxide with potassium permanganate. Apophyllenic acid, C8H7NO4-HZO, the methyl betaine of cinchomeronic acid, was synthesized by W. Roser (Ann., 1886, 234, p. 118).
Piperidine or hexa-hydro pyridine, C5H11N, was first obtained in 1848 by distilling piperine with lime. It is formed in the hydrolysis of piperine by alcoholic potash, by the reduction of trimethylene cyanide (A. Ladenburg) and by the action of alkalis on ε-chloramylamine, Cl(CH2)5-NH2 (S. Gabriel, Ber., 1892, 25, p. 421). It is also produced in the electrolytic oxidation of N-nitroso piperidine in sulphuric acid solution (F. B. Ahrens, Ber., 1898, 31, p. 2275). It is a liquid which boils at 105-106° C., and possesses an ammonia cal smell. It is readily soluble in water, alcohol and ether, and is a very powerful base. 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. The piperidine ring is easily split. When heated with fuming hydriodic acid to 300° C. it yields normal pentane and ammonia, and hydrogen peroxide oxidizes it to glutarimide and to a piperidinium oxide or oxime (R. Wolffenstein, Ber., 1904, 37, p. 3228). A. W. Hofmann (Ber. 1881, 14, p. 660), by a process of exhaustive methylation and distillation, obtained the unsaturated hydrocarbon piperylene, CH2:CH·CH2·CH:CH2 from piperidine (see also A. Ladenburg, Ann., 1894, 279, p. 344)
- C5H11N(+CH3I)⟶C5H10N(CH3)2I(+AgOH)⟶ C5H10N(CH3)2·OH
- (distil)↓
- C5H9N(CH3)3·OH⟵('+AgOH)C5H9N(CH3)3I⟵(+CH3l)C5H9N(CH3)2
- (distil)↓
- C5+N(CH3)3+H2O
J. v. Braun (Ber., 1904; 37, p. 2915) showed that benzoyl pieridine, when heated with phosphorus pentachloride to 200° in sealed tubes, yields benzonitrile, and pentamethylene dichloride, thus leading to a simple method of preparing pentamethylene compounds. At 125-130° C. the compound C6H5C-Cl:N(CH¢)5-Cl is obtained; this with water yields benzoylamidochloramylamine C5H5CONH(CH2)5Cl, which when heated with hydrochloric acid tc 170-180° C. furnishes e-chloramylamine, NH¢(CH2)5Cl. a-Propy1piperidine is the alkaloid conine (q.v.).
PYRIMIDINES, Metadiazines or Miazines, in organic chemistry, a series of hetero cyclic compounds containing a rig complex, composed of four carbon atoms and two nitrogen atoms the nitrogen atoms being in the meta-position. The oxyderivatives of the tetrahydro- and hexahydro-pyrimidines are the uracils and the ureides of malonic acid (see Purin). The purins themselves may be considered as a combination of the pyrimidine and glyoxaline ring systems; For formulae see below; the numbers about the first ring explain the orientation of pyrimidine derivatives.
The pyrimidines may be obtained by condensing 1·3-diketones with the amidines (A. Pinner, Ber., 1893, 26, p. 2125).
| CH3·CO | + | NH2C·C6H5 | ⟶ | CH3·C:N——— ———C·C6H5. |
| CH2·CO(CH3) | HN | CH:C(CH3)·N |
The β-ketonic esters under like treatment yield oxypyrimidines, whilst if cyanacetic ester be employed then amino-oxypyrimidines are obtained. By using urea, 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. Frankland and H. Kolbe (Ann. 1848, 65, p. 269) by heating the nitriles of acids with metallic sodium or with sodium ethylate between 130° C. and 180° C.
3CH3CN＝C4HN2(CH3)2·NH2[2·4·6].
Pyrimidine, C4H4N2, itself is a water-soluble base which melts at 21° C. and possesses a narcotic smell. Its methyl derivatives yield the corresponding carboxylic acids when oxidized by potassium permanganate. The amino derivatives are stable bases which readily yield substitution derivatives when acted upon by the halogen elements. Cyanmethine, C6H9N3 (dimethyl-amino pyrimidine-2·4·6), melts at 180–181°C. The simple oxypyrimidines are obtained by the action of nitrous acid on the amino derivatives, or by heating these latter with concentrated hydrochloric acid to 180° 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 phosphorus pentachloride, the hydroxyl group is replaced by chlorine.
Hydropyrimidines.—The dihydro derivatives are most probably those compounds which are formed in the condensation of acidyl derivatives of acetone, with urea, guanidine, &c. Tetrahydropyrimidines are obtained by the action of amidines on trimethylene bromide:
Br(CH2)3Br+C6H5C(:NH)·NH2＝2HBr+C4H7N2(C6H5)[2].
The 2·6-diketo-tetra hydro pyrimidines or uracils may be considered as the ureides of β-aldehydo, and β-ketonic acids. Uracil and its homologues may be obtained in many cases from the hydrouracils by the action of 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, C4H4O2N2, crystallizes in colourless needles, is soluble in hot water and melts with decomposition at 335° C. Hydrouracil, C4H6O2N2, is obtained by the action of bromine and caustic alkalis on succinamide (H. Weidel and E. Roithner, Monats., 1896, 17, p. 172); by the fusion of β-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. (E. Fischer, Ber., 1901, 34, p. 3759). It crystallizes in needles and is soluble in water. It melts at 275° C. 4-Methyluracil, C5H6O2N2, has long been known, having first been synthesized by R. Behrend (see Purin). It crystallizes in needles which melt at 320° 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-methyl pyrimidine 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, Ber., 1905, 38, p. 3394). For methods of preparation and properties of numerous other. pyrimidine compounds see T. B. Johnson, Journ. Biol. Chem., 1906, &c.; Amer. Chem. Journ., 1906, &c.; W. Traube, Ber., 1900, &c.; O. Isay, ibid., 1906, 39, p. 251.
| 123 | ||
| N:CH·N | N:C(CHa)·N | NH·CO·NH |
| ĊH:CH·ĊH | NH2C:ĊH·C..·CH3 | ĊH:CH·ĊO |
| 654 | ||
| Pyrimidine | Cyanmethine | Uracil |