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Encyclopedia Britannica

CH8

This article appears in Volume V22, Page 691 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: CAU-CHA

CH8 .CO + NH3 + COCH3 CH3C-NH-G.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

PYRIDINE

of the type
CH C(CHI) is obtained. The reaction is apparently a
RC' \N general one for all aldehydes. On the course
\CH :C(CH3)/ of the reaction see also C. Beyer, Ber., 1891,
24, p. 1662, and E. Knoevenagel, Ber., 1898, 31, p. 738. In this reaction the proportions of aldehyde and acetoacetic ester may be interchanged and ay disubstituted pyridines are then obtained. Of the other methods for preparing

pyridine

PYRIDINE

homologues mention may be made of the discovery by A. Ladenburg that the pyridinium alkyl iodides rearrange themselves when strongly heated and yield a and y alkyl pyridines (Ber., 1883, 16, p. 1410 seq. ; Ann., 1888, 247, p. I). S. Ruhemann prepared 7-substituted dioxypyridines by condensing alkyl-dicarboxy-glutaconic esters with ammonia.
R'02C)2C:CRCH(CO2R')2-,R'02Co.c CRHNCCOHCO2R'-HHOC:CRNC. On Of C OH
M. Scholtz (Ber., 1895, 28, p. 1726) prepared aa- methylphenylpyridine by distilling cinnamenylidene acetoxime,
CSHSCH:CHCH:CHC(:NOH).CH3= H CCHc H2O CeHscN :CCHs--
The 1.5 diketones of the type inset, when heated with ammonia, also yield pyridine derivatives. Alkyl pyridines
-CO\ /CO- are also obtained by

heating

HEATING

aldehyde
>C:CHCH< ammonias alone or with aldehydes and
-CO CO- ketones (A. v. Baeyer, Ann., 187o, 155,
pp. 281, 294; J. Pldchl, Ber., 1S87, 20, p.
subjoined table shows the

chief

CHIEF (from Fr. chef, head, Lat. caput)

homologues of pyridine:
Name.

Formula

. Position Remarks.
of Sub-
stituent.
Picolines C5H4(CHa)N a Liqquid, b.p. 129. Oxi-
Lutidines CSH4(C2H5)N y dizes to picolinic acid.
a, /3, y, Condenses readily
with aldehydes.
Liquid, b.p. 143. Oxi-
dizes to nicotinic acid.
Does not condense
with aldehydes.
Liquid, b.p. 144-145.
Three isomers. All
liquids. The /3 com-
pound is a decompo-
sition product of
cinchonine, quinine,
strychnine and bru-
cine.
CSH3(CHa)2N aa', ay, a,B' Five isomers. All
/3l3', /37. liquids.
Collidines C5H4(CaH1)N a, P. Liquids. The a com-
C5H3(CH3)(C2H5)N a, y. pound is a decomposi-
CSH2(CHa)3N a'a, y(3, tionproductof conine.
ay, a/3' Both contain the nor-
aya' mal propyl group.
ay/3' Containing the isopro-
Lis.rou p.
qu1id
Liquid, b. . 171-172.
Prepared by the
Hantzsch

synthesis

SYNTHESIS (Gr. a6vOeacs, from avvrcBivac, to put together)

.
Found in coal-tar.
Pyridine carboxylic acids are usually prepared by oxidizing the homologues of the base; they also result as decomposition products of various alkaloids. The more important are shown in the table.
Name.

Formula

. Position Remarks.
of Sub-
stituent.
Picolinic C5H4(CO2H)N a M.p. 137. Easily solu-
acid. ble in water. Yellow
coloration with
FeSO4. Position of
carboxyl group deter-

mined

MINED

synthesis

SYNTHESIS (Gr. a6vOeacs, from avvrcBivac, to put together)

from a-naphthyl-
amine (Z. Skraup and
A. Cobenzl, Monals.,
Nicotinic C5H4(CO2H)N p 1883, 4, p. X36).
acid. M.p. 228229 . An oxi-
dation product of
nicotine, hydrastine
Quinolinic C6H3(CO2H)2N a$ and berberine. Con-
acid. C5H3(CO2H)2N py stitution determined
Cincho- C6H2(CO2H)2N apy by synthesis from
meronic C6H2(CO2H)3N ayf3' p-naphthylamine
acid. (Skraup).
a-Carbo- M.p. 192195 with de-
cincho- composition into nico-
meronic tinic acid. Formed
acid. by oxidation of
Berbero-

quinoline

QUINOLINE (Benzopyridine), C9H7N

.
nic M.p. 2582590. Formed
acid. by oxidation of quin-
ine, cinchonine, and
of isoquinoline.
M.p. 249-250. Crystal-
hies with IIH2O. An
oxidation product of
cinchonine, quinine
and papaverine.
M.p. 243. An oxida-
tion product of ber-
berine. 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 26o C. it yields methyl chloride and nicotinic acid. It was synthesized by A. Hantzsch (Ber., 1886, 19, p. 31) by condensing methyl iodide and potassium nicotinate at 150 C. the resulting iodide being then decomposed by moist silver

oxide

OXIDE

. A. Pictet (Ber., 1897, 30, p. 2117) obtained it by oxidizing nicotine methyl hydroxide with potassium permanganate. Apophyllenic acid, C8H7NO4H20, the methyl betaine of cinchomeronic acid, was synthesized by W. Roser (Ann., 1886, 234, p. 118).
Piperidine or hexa-hydropyridine, C6H21N, 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 e-chloramylamine, Cl(CH2)sNH2 (S. Gabriel, Ber., 1892, 25, p. 42I). It is also produced in the electrolytic oxidation of N-nitroso piperidine in sulphuric acid solution (F. B.

Ahrens

AHRENS, FRANZ HEINRICH LUDOLF (1809–1881)

, Ber., 1898, 31, p. 2275). It is a liquid which boils at 105106 C., and possesses an ammoniacal smell. It is readily soluble in water, alcohol and ether, and is a very powerful base. It is oxidized to pyridine by

heating

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

OXIDE

or oxime (R. Wolffenstein, Ber., 1904, 37, p. 3228). A. W. Hofmann (Ber.. 1881, 14, p. 66o), by a process of exhaustive methylation and

distillation

DISTILLATION (from the Lat. distillare, more correctly destillare, to drop or trickle down)

, obtained the unsaturated hydrocarbon piperylene, C H2: C H C H2 CH : CH2, from piperidine (see also A. Ladenburg, Ann., 1894, 279, P. 344)-
C6HnN(+CH3I) C5HI0N(CH3)2I (+AgOH) j C6H,6N(CH3)2.OH
(distil) 1 CiH9N(CH3)3.OHE--(+AgOH)C5H9N(CH3)3I<(-}CHsI)C6H9N(CHs)2
(distil)
C1H2+N(CH3)3+H20
J. v. Braun (Bee., 1904, 37, p. 2915) showed that benzoyl piperidine, when heated with phosphorus pentachloride to 20o C. in sealed tubes, yields benzonitrile, and pentamethylene dichloride, thus leading to a simple method of preparing pentamethylene
compounds. At 125130 C. the compound C6H2CCl:N(C112)sG is obtained; this with water yields benzoylamidochloramylamine C6H5CONH(CH2)5Cl, which when heated with hydrochloric acid tc 17o18o C. furnishes e-chloramylamine, NH2(CH2)SCI. a-Propyl, piperidine is the alkaloid conine (q.v.).

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