Rudolph August Witthaus.

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hydes, and such a decolorized magenta solution is used as a reagent
for the detection of aldehydes (Schiff's reagent).

By the action of methyl iodid upon fuchsin a number of methyl-
ated derivatives are obtained, which are violet dyes, such as crystal
violet, Hofmann's violet, dahlia, etc. By further methylation of
the violets, green dyes are formed, as the iodin greens, and aldehyde
green. By substitution of phenyl in place of methyl, a number of
blue dyes, as Lyons blue, soluble blue and alkali blue are ob-
tained. Pyoktanin -blue, dahlia, is penta- and hexa-methyl para-
rosanilin hydrochlorid, produced from dimethyl anilin. It is a violet
powder, soluble in water and .very diffusible, non- poisonous and
used internally as an antiseptic. Pyoktanin-yellow, used medici-
nally for the same purposes as the blue, is the hydrochlorid of imido-

tetramethyl-diamido-diphenyl methane, HH:0^3;(^J.. Tri-

phenyl - pararosanilin, HO.C ; ( C 6 EU.NH. Cells h, is the base of a
number of blue dyes, among which is methyl - blue, the sodium salt
of its trisulfonic acid, which has been used locally in diphtheria.
It is poisonous, and has caused death by its administration in mis-
take for methylene-blue (p. 459).




452 MANUAL OF CHEMISTRY



HETEROCYCLIC COMPOUNDS.

These compounds differ from the carbocyclic in that they contain
elements other than carbon as constituents of the nuclei. They
form series parallel to the carbocyclic, from which, indeed, they may
be considered as being derived by substitution in the rings. Thus
thiophene corresponds to pentole, pyridin to benzene, and quinolin
to naphthalene:

H H H

C C C

/ \ S \ / \

HC CH HC CH HC C CH

II I I II I

HC CH HC C CH

vJV \ / \ /

C C C

H H H

Benzene. Naphthalene.

H H H

C C C

/ \ s \ / \

HC CH HC CH HC C CH

II II II I I II I

HC CH HC CH HC C CH

\ / \ ^ \,/ \ S

S N C N

H
Thiophene. Pyridin. Quinolin.

The elements which can be thus introduced into a cyclic nucleus
are few ; oxygen, sulfur, selenium, phosphorus and nitrogen being
the only ones now known to enter into such formation, and of these
the nitrogen -containing compounds are far the most numerous and
the most important. The facility with which the N atom takes the
place of the methine group, CH=, in the benzene ring is to be
anticipated from their equivalence. Pyridin also resembles benzene
in its general characters, and, on the other hand, the five membered
compounds, furfurane, thiophene and pyrrole, have general charac-
ters similar to those of benzene, from which they may be considered
as being derived by substitution of the bivalents O, S, and NH for
one of the three acetylenes, CH:CH , of benzene. The number
of hetero- atoms which may be contained in the nucleus is not
limited to one, and five and six membered rings containing as many
as four nitrogen atoms, the tetrazoles and tetrazins, are known.

A classification of the heterocyclic compounds requires many
subdivisions, because of the great number and variety of these sub-
stances, due to the presence of one or more atoms of one or more



HETEEOCYCLIC COMPOUNDS 453

of the elements above mentioned, in three, four, five or six mem-
bered rings, contained in mono-, di-, tri-, or tetra- nucleate mole-
cules, in which, also, differences in the ring -valence are caused by
differences in internal linkage. A broad classification may, however,
be here followed, somewhat similar to that for the aromatic sub-
stances (p. 384).

A. Mono -nucleate compounds: containing a single nucleus. These
may be subdivided into: (a) Substances containing three - membered

H 2 C



rings; such as ethylene oxid, I /O, sulfid, I /S, and imid,



H 2 C



H 2 C H 2 C



\



NH.



(b) Four-membered compounds, such as trimethylene oxid,
H 2 C O H 2 C O H 2 C CH 2

I I , thetin, I I , and trimethylene imid, I I .
H 2 C CH 2 H 2 C S HoC NH



L X

HC=CH'
HC=CH>



(c) Five-membered substances, such as furfurane, _l _ /0,thi-



ophene, I /S, and pyrrole, I /NH.
/ /



V
/
HC=CH/ HC=CH

HC-CH=CH
(d) Six- membered compounds, such as pyridin, II I , pi-

HC CH=N

H 2 C CH 2 CH 2 N=N CH

peridin, I I , and sym. tetrazin, I II .

H 2 C CH 2 NH HC=N-N

The five- and six -membered compounds are much more numerous
and important than the three- and four -membered.

B. Condensed compounds, containing two or more rings, usually
five- or six -membered, of which at least one is heterocyclic, fused
together, and having two carbon atoms in common. These com-
pounds, which correspond to the condensed benzenic compounds
(p. 438), include the indole, quinolin, anthraquinolin, quinoquinolin,
and diphenylene derivatives.

C. Compounds containing two (or more) nuclei, one at least hete-
rocyclic, united directly without fusion, corresponding to the di-
phenyls, and including phenyl-pyridyl, dipyridyl, pyridyl- pyrrole,
and pyridyl -piperidyl derivatives.

D. Compounds containing two (or more) nuclei, one at least
heterocyclic, united by aliphatic groups, corresponding to the
diphenyl- paraffins, and including the " ester -alkaloids" such as
atropin, cocain, etc.

In a more detailed classification the members of the several classes
are subdivided into the groups of mono-, di-, tri-, and tetrahetero-
atomic compounds, according as they contain one, two, three or four
atoms other than carbon, of like or different kinds, in the ring.



454 MANUAL OF CHEMISTRY

A.-MONONUCLEATE HETEROCYCLIC COMPOUNDS.

FIVE MEMBERED RINGS.

The parent substances of these compounds are furfurane, thio-
pheiie, and pyrrole* (see p. 453).

The heterocyclic rings differ from the carbocyclic in that the
several carbon atoms are not equal in value, and therefore two dif-

ferent monosubstituted deriva-

C tives exist for the five membered

/t\ rings containing a single hetero-

^ /H ||~ ~IJ H/} ^H J^ atom ' such as furfurane > and

HC CH HC CH three such compounds in six

^ o / a/Ny N membered rings, such as pyri-

Furfurane. Pyridin. din, according to the position

of substitution with reference

to the hetero-atom. These positions are distinguished by the first
three letters of the Greek alphabet, as shown in the margin, or,
sometimes by numbers. The positions a and <*', and p and $' are
of equal value.



v

Furfurane I /O exists in the product of distillation of
HC=CH/

pine and fir wood, and is also formed by distillation of barium pyro-

HC-CH 2x

mucate (below), and from dihydrofurfurane, II /O, a product

HC CH2

of reduction of erythrol (p. 254). It is a liquid; b. p. 32 (89.6
F.) ; having a peculiar odor. Its vapor colors a pine shaving moist-
ened with HC1 green (pp. 390, 455).

HC=C CHO
a-Furfuraldehyde Furfurole Furole I *^^ is produced

HC=CH O

by the dry distillation of sugar or of wood; by the distillation of
these substances, or of bran, carbohydrates or glucosids with dilute
H2SO4; by the action of the concentrated acid upon sugar; and by
distilling pentoses (p. 265), or glucuronic acid (p. 299) with HC1.
It is a colorless liquid; agreeable in odor; b. p. 162 (323.6 F.);
soluble in water and in alcohol. Being an aldehyde, it undergoes the
reactions common to those substances. In concentrated solution,
with urea and a trace of acid, it is colored yellow, changing to blue,
to violet and to purple, and finally fading, with formation of a black
precipitate (Schiff's reaction). It produces a red color with anilin,.a
very sensitive reaction for its presence. Paper moistened with anilin

*The usual spelling Is pyrrol, furfurol, indol. The terminal e is used because these gubstanceg
are neither alcohols nor phenols, for whose names the termination ol is reserved.



FIVE MEMBERED HETEROCYCLIC RINGS 455

acetate solution is used. Adamkiewicz' and Liebermann's reactions
for the proteins, and Pettenkofer's reaction for the biliary salts, etc.,
depend upon the formation of furfurole.

HC=C COOH
a-Furfurane Carboxylic Acid Pyromucic acid I ^^

HC=CH O

the acid corresponding to furfurole, is produced from that substance
by oxidation, also by distillation of mucic and isosaccharic acids
(p. 297). It is a solid; f. p. 134 (273.2 F.).

HC=CH V
Thiophene I /S and its superior homologues, methyl-

HC=CH

thiophenes, etc., occur in gas -tar, and accompany the various prod-
ucts, benzene, etc., obtained from it. It is a colorless liquid; b. p.
84 (111.2 F.); which is so nearly that of benzene, 80.5, that the
two substances cannot be separated by distillation. With sulfuric
acid and isatin it gives a fine blue color, due to formation of indo-
phenin. Sulfuric acid alone is colored brown by thiophene, which it
absorbs; and thiophene may be recovered from the solution by neu-
tralization and distillation.
HC=CH>



Pyrrole _J[ n /NH exists in coal-tar and accompanies the



L \i

HC=CH'

pyridin bases (p. 459) in oil of Dippel. It is formed in a great variety
of reactions, as by the action of baryta at 150 (303 F.) upon
albumens, by the dry distillation of gelatin or of ammonium saccha-
rate, etc. It is a colorless, oily liquid, having the odor of chloro-
form; b. p. 131 (267.8 F.). Being a secondary amin, it has basic
properties, and its imid hydrogen is readily replaced by other atoms
or groups. A pine shaving moistened with HC1 is colored flame -red
by pyrrole (the pine-shaving reaction; see also, Phenol, p. 390). It
also yields an indigo -blue color with H2S04 and isatin. Heated with
dilute acids it gives off ammonia, and a red powder (pyrrole red) is
deposited.

The homologous pyrroles, methyl -pyrroles, etc., have reactions
similar to those of pyrrole.

Pyrrole and its homologues form series of substitution products:
haloid, nitro-, azo-, carboxylic, etc. Among these is tetriodopyrrole,
or iodol, C^NH, formed as a brown powder by acting upon pyrrole
with an ethereal solution of iodin, and used in surgery as a sub-
stitute for iodoform, over which it has the advantage of being
odorless.

Hydropyrrole Derivatives Nascent hydrogen combines with

CH :CH V

pyrrole to form, first dihydropyrrole, or pyrrolin, I yNH, an

CH2.CH2

alkaline liquid, soluble in water; b. p. 91; and, finally, tetrahydro-



456



MANUAL OF CHEMISTRY



CH 2 .CH 2 y

pyrrole, or pyrrolidin, or tetramethylene-imin, I yNH, which

CH2.CH 2

bears the same relation to pyrrole that piperidin does to pyridin
(p. 461). Pyrrolidin resembles piperidin in its reactions, and also
forms an addition product with methyl iodid. It is formed by heating
tetramethylene-diamin hydrochlorid (p. 333) : H 2 N. (CH 2 )4.NH 2 .HC1 =
NH4CI+ (01X2)4: NH, and constitutes the nucleus of the hygrins
(p. 472) and one of those of nicotin (p. 474). It is a strongly alka-
line liquid; b. p. 87. Among the derivatives of pyrrolidin is pyrroli-

CH 2 .CH V
done, or butyrolactam, I /NH, a simple cyclic imid derived from

7-amidobutyric acid (p. 362).



AZOLES AND THEIR DERIVATIVES.

The azoles are derivable from furfurane, thiophene and pyrrole
by substitution of one or more nitrogen atoms for inethine groups.
They are distinguished, according to their parent substances, and the
number of nitrogen atoms introduced, as furo-monazoles, thio-diazoles,
pyrro-triazoles, etc. There are nine of each of these classes of sub-
stances known either as the parent substance or in some of its
derivatives. They are distinguished by the lettering indicating the
position or positions of the non-imid nitrogen. Thus we have the
following pyrazoles:



HC-



HC

\ /

N

H

Pyrrole.



CH



N



N

II
CH



HC
\ /

N

H

/3-/3'-Diazole.



HC CH

II II
HC N

V

H

a-Monazole.

HC N

II II

N CH

V

H

a'-/3-Diazole.



N



CH



HC-
II
HC

N

H

/3-Monazole.



HC

II

N
\



HC CH

ii H


HC N

ii H


II II

N N


II II
HC N


\ /


\ /


N


N


H


H


a-a'-Diazole.


a-/3-Diazole.



N
II
N



N
II
CH



\



N

II

N

\



a / -a-/3-Triazole. a-jS-jS'-Triazole. Tetrazole.



Corresponding to each of these are derivatives, formed by substi-
tution and by modification of the internal linkages. Those derived
from pyrro-a-monazole are the most important, and may serve as
types. The n-phenyl derivatives (those in which CeHs is substituted
for H in NH) are the best known, and the most readily obtainable.
Pyrro-a-monazole, or pyrazole, is reduced by sodium to dihydropyr-



FIVE MEMBERED HETEROCYCLIC RINGS 457

azole, or pyrazolin (formula below) ; The phenyl derivative of a
tetrahydropyrazole, phenyl-pyrazolidin, is also known.

The pyrazolons are ketonic derivatives of the pyrazolins,in which
O takes the place of Ek in the a- position. Thus:

HC CH HC CH H->C CH H 2 C CH

II II II II I II I II

HCf CH HC N H 2 C N OC N

\ / \ / \ / \/

N N N N

H H H H

Pyrrole. Pyrazole. Pyrazolin. Pyrazolon.

The pyrazolons are obtained from the hydrazones (p. 429) of the
esters of the /? ketone acids (p. 298) by elimination of alcohol, or by
the action of phenylhydrazin upon these esters themselves. Thus
1, 3-phenylmethyl-pyrazolon is formed either from phenylhydrazone-
acetoacetic ester:

COO(C 2 H 5 ) H 2 C C.CH 3

CH 2

C:N.NH.C 6 H 5 = OC N +

I \ /

CH 3 N

CH 5

or from aceto- acetic ester and phenylhydrazin:

COO(C 2 H 5 ) H 2 C C.CH 3

CH 2



f

CH 3



H 2 N.NH.C 6 H 5 = OC N -f C 2 H 5 .OH+H 2 O.

\ /

N
C 6 H 5



Antipyrin 1, 2, 3 (or n-a-/2) Phenyldimethyl Pyrazolon
C e H 5 N.CO.CH

I II is formed, as its hydroiodid, by heating 1, 3-phenyl-
CH 3 N C . CH 3

methyl pyrazolon, formed by the second reaction given above, with
methyl iodid and methylic alcohol to 100 (212 F.) in sealed vessels.
It forms colorless, odorless scales, somewhat bitter in taste; f . p.
110.5 (230.9 F.). A mixture of equal parts of antipyrin and
antifebrin (f. p. 112.5) fuses at 45 (113 F.). Antipyrin is readily
soluble in water, alcohol and chloroform, less soluble in ether. With
nitrous acid or the nitrites (sp. a3th. nitr.), in the presence of free
acid, it forms a green, crystalline, sparingly soluble nitro- derivative,
which is poisonous. Its solution is colored deep red-brown by Fe2Cle,
the color being discharged by EbSO-t. Nitrous acid colors its solutions



458 MANUAL OF CHEMISTRY

bright green, and on heating the mixture, after addition of a drop
of fuming nitric acid, the color changes to light -red, then to blood-
red, and finally a purple oil is deposited. Addition of a drop of
fuming nitric acid to cold, concentrated solution of antipyrin causes
precipitation of small, green crystals. Antipyrin is strongly basic,
and some of its salts are used in medicine: Salipyrin is antipyrin
salicylate. It is formed by the action of the acid and the base upon
each other at 100 (212 F.). It is a white, crystalline powder,
almost insoluble in water.

Tolypyrin 1-toluyl, 2, 3 -dimethyl pyrazolon is obtained in
the same manner as antipyrin, using p-toluyl-hydrazin in place of
phenyl-hydrazin, and contains toluyl, CeHt.CHs in place of phenyl.
It forms colorless crystals; f. p. 136 (276.8 F.) ; and has a physio-
logical action similar to that of antipyrin. Its salicylate is preferred
to that of antipyrin medicinally.



SIX MEMBERED RINGS.

Six membered heterocyclic compounds are known, containing
oxygen, sulfur and nitrogen in the nucleus:

H H 2 H H 2

C C C C N

S \ / \ X\ / \ / \

HC CH HC C.CH 3 HC CH H 2 C CH 2 HC CH

I II II II II I II II I

OC CH HC CH HC CH H 2 C CH 2 HC CH

\ / \ / vx \ / \ s

OS N N N

H
o-pyrone. /3-Methylpenthiophene. Pyridin. Piperidin. Pyrazin.

The oxygen and sulfur compounds are neither numerous nor im-
portant. Some of the former are products of condensation of ali-
phatic compounds, 8-lactones and 8-anhydrids (p. 320).

Pyrone (y) Pyrocomane O^ CH Z CH /CO is an oxidized deriva-
tive of 7 furane, produced from comenic acid by the action of heat
and constituting the nucleus of comenic, chelidonic, and meconic
acids.

Comenic acid CsHaCMCOOH) is produced by the action of
hot H2O, of dilute acids, or of bromin water upon meconic acid. It
crystallizes in yellowish prisms, rather soluble in H2O. It is mono-
basic. It is decomposed by heat into CC>2 and pyrone.

Chelidonic acid CsH2O2 ( OH ) COOH exists in chelidonium ,
in combination with the alkaloids sanguinarin and chelidonin. It
is a crystalline solid, and a dibasic acid. Heat converts it into
comenic acid, which in turn yields pyrone.



SIX MEMBERED HETEEOCYCLIC RINGS 459

Meconic acid CsHCMOH) (COOH) 2 is peculiar to opium, in
which it exists in combination with a part, at least, of the alkaloids.
It crystallizes in small prismatic needles ; acid and astringent in
taste; loses its Aq at 120 (248F.); quite soluble in water, soluble
in alcohol, sparingly soluble in ether.

With ferric chlorid it forms a blood -red color, which is not dis-
charged by dilute acids or by mercuric chlorid; but is discharged
by stannous chlorid and by the alkaline hypochlorites.

Among the six-membered heterocyclic derivatives containing both
N and O, or N and S in the nucleus are a number of important
dyes: rosorufin, naphthol blue, Nile blue, Lauth's violet, toluylene
red, safranins, indulines, and

Methylene blue (CHshrN^Ha.NS.CeHsrN i (CH 3 ) 2 C1 which
is formed by oxidation of dimethyl -p-phenylene diamin in EbS solu-
tion. A blue powder, sparingly soluble in water. It is used as a
dye, as a bacterial stain, and is administered as a antipyretic and
antiperiodic.

SIX-MEMBERED, NITROGEN -CONTAINING RINGS PYRIDIN AND
ITS DERIVATIVES.

The pyridin bases, closely related to the vegetable alkaloids (p.
470) as well as to some of the basic substances formed during putre-
faction, were first obtained from oil of Dippel, or bone-oil (oleum
animale), an oil produced during the dry distillation of bones, horns,
etc., and as a by-product in the manufacture of ammoniacal com-
pounds from those sources. They also occur in coal-tar, naphtha,
commercial ammonia, methylic spirit and fusel oil. They are formed
synthetically : ( 1 ) By heating the aldehyde -ammonias (p. 360)
alone, or with aldehydes or ketones: ( 2 ) From pyrrole by the
action of K or Na in presence of methylene iodid, etc. (3) By
oxidation of hexahydropyridins, piperidins; also by other methods.

The pyridin bases are colorless liquids of peculiar, penetrating
odor. The superior homologues are metameric with the anilins.
They are strong triacid bases, and behave like tertiary monamins.
Oxidizing agents do not attack pyridin, nor the nucleus of its supe-
rior homologues, but the lateral chains of the picolins, etc., are
readily oxidized, with formation of carbopyridic acids. Reducing
agents convert them into piperidins (p. 461). They react with sev-
eral of the general reagents for the alkaloids (p. 472). The two
most nearly characteristic properties of the pyridin bases are: (1)
the formation of chloroplatinates such as (CsH^N.HClhPtCU, which
on boiling with water, lose two molecules of HC1 to form "modified
salts" such as (CsHsNhPtCU (Anderson's reaction), and, (2) the



460 MANUAL OF CHEMISTRY

formation of crystalline addition products, alkyl-pyridinium iodids,
such as CsHsN^i^ on contact of their alcoholic solutions with
alkyl iodids.



/CH 'CH\
Pyridin HGQ CH ' CH ^N is obtained from oil of Dippel, or

from piperidin. It boils at 115 (239 F.), mixes with water in all
proportions, is strongly alkaline in reaction. Its hydrochlorid is
crystalline, but deliquescent. Its chloroplatinate fuses at 240 (464
F.). When reduced by sodium and alcohol, it forms piperidin, or
hexahydropyridin ; and when reduced by hydriodic acid, normal
pentane, CH 3 .CH2.CH2.CH 2 .CH 3 .

Pyridin Homologues Alkyl Pyridins are substitution prod-
ucts containing alkyl groups for H. Owing to the inequality in
value of the several C atoms of pyridin (p. 454), the number of
substituted derivatives is greater than with benzene. There are three
monosubstituted derivatives, six each of the bi- and tri- substituted,
three tetra-, and one penta- substituted.

Methyl-pyridins Picolins C5H 4 N(CH 3 ) The three picolins,
a, /3 and 7, exist in oil of Dippel, and have been formed synthetically.
Their b. p.'s are 130, 143, and 144.

Lutidins Three ethyl pyridins, CsEUN^Hs), are known, a ?
b.p. 148; 0, b.p. 166; and 7, b.p. 165. Of the six possible
dimethyl - pyridins, CsHaNCCHsh, four are known, three of which
exist in bone oil.

Collidins CgHuN There are twenty -two possible collidins, of
which twelve are known. Of these several are products of decom-
position of vegetable alkaloids, or exist in oil of Dippel, or are pro-
duced during putrefaction. Conyrin, a basic substance produced by
boiling conim (p. 472) with ZnCl2, is a-propyl-pyridin. /s-propyl-
pyridin is produced from nicotin by passing its vapor through a
red-hot tube. Aldehydin is 1, 4-methyl-ethyl-pyridin, formed by
heating aldehyde -ammonia in alcoholic solution to 120 (248 F.),
and from other aldehyde compounds; and exists also in the products
of rectification of alcohol. An oily ptomain produced during putre-
faction of gelatin in presence of pancreas is a collidin of undetermined
constitution.

Parvolins CgHiaN. Theory indicates the existence of 57 par-
volins, of which five are known. One of these is a ptomain, produced
during putrefaction of mackerel and of horse-flesh. It is an oily
substance, slightly soluble in water, having, when fresh, the odor of
hawthorn -blossoms, but becoming brown and resinous on exposure
to air.

Coridins CioHi 5 N. One of the coridins has been obtained as
a product of putrefaction of fibrin and of jellyfish during several



SIX MEMBERED HETEROCYCLIC RINGS 461

months. It is an alkaline oil, which has a poisonous action similar
to that of curari. The pyridin bases in general exert a paralyzing
action upon the central, and to a less degree upon the peripheral
nervous system. They are the antagonists of strychnin.

Besides the alkyl-pyridins a number of phenyl-pyridins (p. 469)
and pyridins containing unsaturated lateral chains, such as vinyl-
pyridin, CsH^N^Hs), are known.

Pyridin Carboxylic Acids. These acids, which bear the same
relation to pyridin that the benzoic, phthalic, etc., acids bear to
benzene, are formed by oxidation of the alkyl-pyridins. As most of
the alkaloids contain pyridin nuclei with lateral chains, they yield
pyridin -carboxylic acids upon sufficient oxidation. Thus pyridin-
/3-monocarboxylic acid, or /3-picolinic acid, C 5 H4N(COOH)( 2 ), is nico-
tinic acid, formed by oxidation of nicotin, of pilocarpin, as well as
of /3-picolin. The acid is formed by oxidation of -picolin. The
7 acid, isonicotinic acid, is formed by oxidation of 3-picolin, and of
many of its derivatives. Pyridin- 1, 2-dicarboxylic acid, CoH 3 N-
(COOH) 3{ i, 2) , is quinolinic acid, formed by oxidation of quinolin,
and pyridin -2, 3-dicarboxylic acid is cinchomeronic acid, formed
by oxidation of cinchonin, cinchonidin and quinin.

Hydropyridins Piperidins are compounds produced from the
pyridins by the action of nascent hydrogen. Dihydropyridins and
tetrahydropyridins are known, the latter known as piperideins, but
by far the most important of the group is

Piperidin Hexahydropyridin H 2 C xcH^CHs/ NH ~ which is
produced by saponification of piperin (p. 474) by heating with alco-
holic KHO, and is also formed by reduction of pyridin, or by heating
pentamethylene-diamin hydrochlorid. It is a colorless liquid; b. p.
106 (222.8 F.); having an odor like that of pepper; readily
soluble in water and in alcohol. Oxidizing agents rupture the
piperidin ring, with formation of aliphatic compounds. When heated
with methyl iodid is converted into methylpiperidin hydroiodid,



\CH 3

Piperidin and methyl -piperidin are particularly of interest as
being the nuclei of a number of vegetable alkaloids. Thus coniin is
apropyl-piperidin, and tropin and ecgonin, the basic nuclei of the
atropic and cocain alkaloids, are derivatives of methyl -piperidin
(see pp. 475, 477).

Di-, tri-, and tetrazins are substances containing two, three,
and four N atoms in the benzene ring. There are three diazins,
three triazins, and three tetrazins, o-, m-, and p-, as the nitrogen
atoms are placed in adjacent, symmetrical or unsymmetrical positions.
Each of these forms a series of substituted derivatives.



462 MANUAL OF CHEMISTRY

N.CH:CH
Ortho-diazin Pyridazin II I , Meta-diazin Pyrimidin

N.CH:CH
N.CH:CH CH.N.CH

I , and Para-diazin Pyrazin II I II are known. The
CH.N:CH CH.N.CH

last-named is formed by oxidation of amido-acetaldehyde by distillation

CH.N.CH

with mercuric chlorid solution : 2CHO.CH 2 .NH 2 +O= II I II + 3H 2 O.

CH.N.CH



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