T. E. (Thomas Edward) Thorpe.

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salts with oobaltic nitrite and with the chlorides
of platinum, gold, and mercury. Diazonium
perhalides are also known, corresponding with
the perhalides of potassium, rubidium, caesium,
and quaternary ammonium bases (Ber. 1895,
28, 1736, 2754).

The benzenoid diazonium salts with colour-
less anions (nitrates, sulphates, chlorides) are
generally colourless, but the corresponding
bromides, iodides, and thiocyanates are coloured,
and the deeper the colour the more explosive
the salt. When cooled in liquid air, these
coloured salts become less coloured; moreover,
their aqueous solutions are colourless.

The development of colour and increase in
explosibiUty are considered by Hantzsch to
indicate a change in constitution, the coloured
substance beiag regarded as an equilibrium
mixture of diazonium salt and sj/re-diazo-
oompound {v. infra). This equilibrium is dis-
turbed in the sense of forming more colourless
diazonium salt by lowering the temperature or
by dissolving the substance in water (Hantzsch,
Ber. 1897, 33, 2179 ; 1900, 33, 2179 ; Euler, Ber.
1895, 31, 4168). But although in the benzene
series the diazonium chlorides, nitrates, and
sulphates are colourless, yet in the diphenyl and
naphthalene series, many diazonium salts with
these anions are coloured and comparatively
stable. Moreover, this colour (yellow or orange)
is retained either in aqueous solution or at the
temperature of liquid air. Apart from their
colour, these salts have all the properties of the
simpler diazonium salts (neutral solutions,
coupling with phenols, &c.). These facts
indicate that increase in the complexity of the



organic portion of the diazonium cation leads to
the development of colour in normal diazonium
salts.

{Coloured diazonium salts, v. Hantzsch, Ber.
1900, 33, 3183 ; 1901, 3^:, 4168 ; Annalen, 1900,
312, 126 ; Cain, Chem. Soc. Trans. 1905, 87, 5 ;
Morgan and others, ibid. 1907, 91, 1311, 1505 ;
1908, 93, 614 ; 1909, 95, 1319.)

The idea embodied in Blomstrand's diazo-
nium formilla {v. supra) fails to express one
important point, namely, the dependence of the
stability of the diazo- complex on the presence of
an unsaturated group. Yet this is a matter of
fundamental importance, for hitherto no amine
in which the basic nitrogen is attached to a
fully saturated ring or complex has yielded a
diazonium salt.

Cain has suggested an alternative formula,
(2), giving expression to this circumstance
(Chem. Soc. Trans. 1907, 91, 1051), in which the
diazonium salt is represented as having a para-
hemiquinonoid constitution ; and this conception
has been extended by Morgan {ibid. 1908, 93,
617 ; 1910, 97, 2563) so as to include the equally
admissible ortho-hemiquinonoid configurations
(1) and (3):






m



xji
hI.




NCI II"

H H H

(1) (2) (3)

Euler has also advocated a para- hemiquinonoid
structure for diazonium salts (Ber. 1908, 41,
3979).

NON-AEOMATIC DiAZONIFM SALTS..

The foregoing hypotheses of the constitution
of aromatic diazonium salts, which bases their
existence on the unsaturated nature of the
aromatic complex, accord with the fact that
certain non-aromatio primary amines containing
unsaturated organic groups manifest, in some
degree, the property of diazotisability. Among
these bases are aminotriazole (I.) and its deriva-
tives, and aminbantipyrine (II.) :

/NH-N N(CH3)-N(CeF5)-CO

NH,-C'4 II I "I

^N— CH C(CH3) =C-NHa

I. IT.

(Thiele and Manchot, Annalen, 1898, 303, 33 ;
Knorr and Stolz, ibid. 1896, 293, 67 ; c/. Ber.
1900, 33, 1168 ; 1906, 39, 2925 ; Annalen, 1900,
312, 133). In addition to non-aromatic amines
containing an unsaturated cyclic structure, it
has also been shown (K. G. Hoimann, Hock
and Roth, Ber. 1910, 43, 682, 1087) that amino-
guanidine gives rise to diazonium salts, derived,
however, not from the salts of aminoguanidine
itself, but from a more complex molecule con-
taining two guanidine residues, and having a
greater degree of unsaturation. The diazonium
nitrate, for example, is represented by the
formula :

NO,-N,-NH-C(:NH)\ .^l

" \C(]SrH2)-NH— NH-N/'-^ " ?''
containing a diazo- complex associated with an
open chain having three unsaturated linkings.



230



DIAZO- COMPOUNDS.



II. Cyclic Diazo- CoMPotrerDS.

In certain instances, the actioii of nitrous
acid on substituted aromatic amines leads to the
formation of compounds having their diazo-
nitrogen in a cyclic complex, this result being
due to the subseq^nent interaction of a sub-
stituent group.

1. InTBENAL DIAZONI0M SALTS.

Salphonated amines oE the benzene and
naphthalene series furnish diazo- derivatives
which are generally misnamed diazo-suPphonic
acids. These compounds, however, do not
contain ionic hydrogen, and are really internal
diazonium salts ; No. 1, the so-calied ' dimo-
henzenesvlphonic acid,' being henzeriRiiazonium-
J)-su.lphonate, whilst No. 2 is naphthahne-1-
diazonium- B-sulphonale

-N. y. x-sr^N,



\/



-SO3



SOs



(1) (2)

These internal diazonium sulphonates are of
great technical importance in the manufacture of
azo- dyes (v. Azo- colourinq mattebs).

Of a similar nature are the cyclic diazo-
derivative.s obtained by diazotising aromatic
aminocarbozylic acids (cf. Biilow and Haas,
Ber, 1911, 44, 601), e.g. ' diazo- anthranilic acid '
or benzenediazoniwm-o-carhoxylate
/N/



I I ,

\/\c^o,

which is employed in the production of methyl

rod (b. ACIDIMETBY AND AlKALIMBTEy).

2. Cyclic Diazo- Compounds dtje to
Internal Condensation.

Aromatic ortho- and peri-diamines do not
yield diazonium salts, inasmuch as their inter-
action with nitrous aoid leads at once to the
formation of cyclic diazoimines {Azimino-
compounds)

NH-N:N



' 1 /
NH



I I



(1) (2)

Phenylene-o-diazoimine (1) (Aziminobenzene)
and naphthylene-l:S-diazoimine (2) (h8-Azimino-
naphthalene) are typical members of this series
of diazo- compounds.

The triazole rings thus set up are remarkably
stable, and in the case of the ortho- derivatives
(No. I) are not opened by mineral acids without
complete rupture of the molecule. The peri-
diazoimines (No. 2) occupy a position inter-
mediate between the ortho-diazoimines (No. 1)
and the para-diazoimines {v. infra).

The 1:2- and 2:3-naphthylenc-diamine3
furnish respectively 1:2- and i:Z-naphthylene-
diaztiimines (1:2- and 2:S-aziminonaphth<denes).
(Constitution of ortho-diazoimines and their
aoyl- derivatives, Griess, Ber. 1882, 15, 2195;



Kekule, l<ehrbuoh, ii. 739 ; Morgan and Goddeu,
Chem. Soc. Trans. 1910, 97, 2557 ; cf. Ber. 1874,
7, 3J0; 1876,9,221; 1887,20,2999; 1894,27
761; Annalen, 1889, 255, 344; Chem. Soe.
Trans. 1906, 89, 4.)

Similar stable cyclic diazo- compounds arc
obtained by diazotising the ortho-aminothio-
phenols, o-phenylenediazosulpbide being a colour-
less crystalline substance with a sweetish odour
and feebly basic properties






(Jacobsen, Annalen, 1893, 277, 209, 218, 232,
2.37).

3. Cyclic Diazo- Compounds due to Combined
Inteknal Condensation and Salt Fokma-
tion.

In this group are found certain diazo-
derivatives of amines containing slightly acidic
substituents in ortho- or para-, but Dot meta-
positions with respect to the aminio nitrogen.

(i.) Internal diazo- oxides are produced from
ortho- and para- aminophenols and tfaeii
derivatives. In some cases, an intermediate
diazonium salt is formed which condenses to the
diazo-oxide on treatment with silver oxide or
an alkali (Schmitt, Ber. 1868, 1, 67 ; Hautzsch
and Davidson, ibid. 1896, 29, 1522; Cameron,
Amer. Chem. J. 1898, 20, 229). The first diazo-
compound prepared by Griess (Annalen, 1858,
106, 123), namely, dinitrobenzenediazo-oxide.

(NOjJaC.HuC I belongs to this class; it is

produced by diazotising picramic acid, and has
been utilised in the production of azo- colours
(D. E. P. 151332). The 1:2-, 2:1-, 2:3-, apd
1 : 8-aminonaphthols and their sulphonic acids
similarly give rise to intexnal diazo-oxides which
are so stable that they can be nitrated. These
internal diazo-oxides are readily transformed
into diazonium salts by mineral acids, and are
therefore available in the production of azo-
dyes (Eng. Pat. 28107, of 1897 ; 10235, 15025,
of 1904 ; Fr. Pat. 353786 of 1905 ; D. B. PP.
155083, 164665, 171024, 172446, 175593, 176618,
176619, 176620).

Internal diazo-oxides can also be produced
by leaving the diazonium salts of h^hly sub-
stituted amines (e.g. 2:4:6-trichloroaniline) in
aqueous solutions containing no free mineral
acid (Orton, Proc. Roy. Soe. 1903, 71, 153;
Chem. Soe. Trans. 1903, S3, 796).

These diazo- derivatives have been formu-
lated either as cyclic diazo-oxides (I.) or as
quiuonediazides (II.) :

OjC^N, 0:C,H<^

I. II.

(cf. Wolff, Annalen, 1900, 312, 126; Morgan
and Micklethwait, Chem. Soe. Trans. 1908, 93,
607).

(ii.) FaTa-diazoimines and diazoimides.

The simplest example of the |)ara-diazo-
imines is obtained by the action of alkalis on the
diazonium salts of . p-aminodiphenvlamine
(Annalen, 1888, 243, 282 ; Ber. 1902, 35, 895).
The following alternative formulae (III. and IV.)
have been given to this product : —



DIAZO- COMPOUNDS.



231



CA-N-CeHvN, c.H,N:C3H<J



III. IV.

corresponding respectively with the foregoing
formulea (I. and II.) for the internal diazo-ozides.
Successive nitration of the phenyl group
gbadually ' increases the stability of these ■p-
diazoimiues (Chem. Soc. Trans. 1908, 93, 604).

The para- diazoimidea are produced from the
aoyl- and aryl-sulphonyl- derivatives of the
para-diamines, and similar products are obtained
from the arylsulphonyl-1 : 8-naphthylenedi-
amines. The production' of these diazoimides
takes place in two stages, the diazonium salt
first produced being decomposed by sodium
acetate or mild alkali, yielding the internal
condensation product :

NaAc
R-SOj-NH-OsHj-Na-Cl ^ B-SOa-N-CaHi Na

HCl I 1

V. VI.

These para-diazoimides (VI.) are yellow
sparingly soluble substances readily reconverted
by strong acids into the correspoudug diazonium
salts. They combine additively with phenols,
naphthols, naphthylamines, and their sulphonio
acids, yielding azo- colouring matters (Morgan
and MicMethwait, J. Soc. Dyers and Colourists,
1909, 25, 107 ; c/. Chem. Soc. Trans. 1905, 87,
74, 921, 1302 ; 1906, 89, 1162 ; 1907, 91, 1509 ;
1908, 93, 615 ; Badische Anilin- und Soda-Fabrik.
D. R. P. 205037).

III. DlAZOAMIlIES.

The diazoamines or diazoamino- compounds
have the general formula XNjj-NHY, and may
be either aromatic, mized aromatic-aliphatic, or
aliphatic in character, according as to whether
X and Y are aromatic or aliphatic hydrocarbon
radicles.

1. Aeomatio Diazoamtnes.

The aromatic diazoamines are produced
(1) by the action of nitrous acid (1 molecule) on
two molecular proportions of a primary benze-
noid amino; (2) by coupling a diazonium salt
with a primary or secondary benzenoid amine.

Diazoaminohenzene08H5-N2-l<fH-C„H5,yellow
crystals, m.p. 98°, is produced in quantitative
yield by dissolving 10 parts of aniline in
two parts of water containing 12 parts of
hydrogen chloride, diazotisiug with 8 parts of
sodium nitrite, and adding the diazo- solution to
a solution of 10 parts of aniline in the calculated
amoaat of hydrochloric acid. The diazoamine
is precipitated on the addition of sodium
acetate.

When warmed with aniline containing
aniline hydrochloride, diazoaminobenzene is
transformed into p-aminoazobenzene (n. Azo-
COLOITBING MATTEEs), the velocity of transforma-
tion obeying the law of unimolecular reactions.

Diazoamino -p-toluene CvH^-Na-NH-C,!!,- is
prepared in a similar manner, and undergoes
transformation into an ortho-azo- compound,
but the velocity of this change is only about
one-ninth of that of the -preceding transfor-
mation to para-azo- derivative.

The coupling of diazonium salts with meta-
phenylenediamine, diphenylamine, the naphthyl-
amines and their alkyl derivatives, leads directly



to the production of azo- derivatives ; in these
cases, intermediate diazoamines have not been
isolated, except when the reactive ortho- or
para- positions are already substituted (Morgan,
Chem. Soc. Trans. 1902, 81, 91 ; 1907, 91, 370).

When an aromatic base, XNHa, is coupled
with a diazonium salt YNjCl, the resulting
diazoamine is identical with that produced from
XNjCl and YNH^, and is generally regarded as
being an equilibrium mixture of the two iso-
merides XNH-NjY and XN^-NHY. This ex-
planation assumes the migration of the diazo-
group which has been observed to occur in
several instances (Ber. 1882, 15, 2190; 1896,
29, 287 ; 1897, 30, 1412).

(For the constitution of the unsymmetrical
aromatic diazoamines, XNH-NjY, v. Meldola
and StreatfeUd, Chem. Soc. Trans. 1886, 49,
624 ; 1887, 57, 102, 434 ; 1886, 53, 664 ; 1889,
55,412; 1890,57,786; c/. Forster and Garland,
ibid. 1909, 95, 2051.)

2. Aliphatic-abomatic Diazoamines.

The diazoamines containing one aUphatic
and one aromatic group can be produced by
(1) coupling a diazonium salt with an aliphatic
amine (Ber. 1888, 21, 1016, 1112 ; 1889, 22, 938,
1302) ; (2) by treating an azide with Grignard
reagent :

/N

R-N, II +R'-MgBr=R-N(MgBr)-N:NR'

\N

HjO -^ R-NH-N:NR'+MgBr-OH

(Dimroth, Ber. 1903, 36, 909; 1905, 38, 670,

2328; 1907, 40, 2390). Diazoamines present

the possibility of stereoisomerism, but their

relative stability and the fact that they couple

only slowly with 3-naphthol, confirm the view

that they are generally aMti-diazo- compounds.

(For stereoisomeric diazoamines, v. 3. Russ.
Phys. Chem. Soc. 1906, 38, 587; Zeitsoh.
angew. Chem. 1900, 13, 762 ; 1902, 15, 1209.)

Aromalio hisdiazoamino- compounds, e.g.
(C8H5-!N2)2N-CjH5, have been obtained by the
action of 2 molecular proportions of a diazonium
salt on one of an aromatic amine (Ber. 189i, 27,
1863, 2597 ; 1895, 28, 170).

Mixed aliphatic-aromatic hisdiazoamino- de-
rivatives {v. Ber. 1888, 21, 1016 ; 1889, 22, 933 ;
1907, 40, 2390).

Diazo-t^-semicarhazines' (v. Forster, Chem.
Soc. Trans. 1906, 89, 223).

3. Aliphatic Diazoamines.

Dimroth's general method may be applied
to the production of purely aliphatic diazo-
amino- compounds. In this way, the simplest
member of the series, dlazoaminomethane
(dimethyltriazene) CHaNiN-NH-CHa, has been
prepared from methyl azide and magnesium
methyl iodide. This substance, which is
isolated by distilling its copper derivative with
diazoaminobenzene under reduced pressure, is a
colourless liquid, solidifying at —12° and boiling
at 92° (Dimroth, Ber. 1905, 38, 1575 ; 1906, 39,
3905).

IV. Diazo- Oxides.

When a diazonium salt couples with a phenol
the product is generally an ortho- or a para-
hydroxyazo- compound (the C-azo- derivative),



232



DIAZO- COMPOUNDS.



but in all probability, the 0-azo- derivative is
first produced, for in a few instances, when the
velocity of transformation has been lessened by
substitution, the intermediate 0-azo- compound
or diazo-oxide has been isolated. p-Bromo-
benzenediazonium chloride and p-nitrophenol
give p-iromdbenzenediazoA-oxynitrdbenzene

CeHjBr-NiN-O-CsHi-NOa,
which, at 80°, becomes transformed into its
iaom.eiide,p-l>romobenzene-2-azo-i-nitrophenol

CeH4BrN:N-C,H4(N02)0H
(Ber. 1908, 41, 4027, 4304).

Occasionally traces of these intermediate
diazoamines and diazo-oxides can be detected in
the commercial azo- colouring matters (Vaubel,
ZeitBch. Farben. Textil. Ind. 1902, 1, 3).

V. Metaiuo Demvatives of Diazo-

COMPOTJNDS.

In 1894 Schraube and Schmidt (Ber. 27,
514) found that on adding a 10 p.c. solution of
p-nitrobenzenediazonium chloride to 18 p.c,
aqueous sodium hydroxide at 50°-60°, a sodium
diazo- derivative separated in golden - yellow
leaflets, to which they gave the formula

NOa-CjHt-NNa-NO.HaO,
regarding the compound as the sodium deriva-
tive of p-nitrophenylmtrosamine. This view of
the constitution of the product was confirmed
by the action on the compound of methyl iodide
when jj-nitrophenylmethylnitrosamine
NOj-CcHi-N(CHa)-NO

was obtained.

This sodium salt, which was regarded by
Hantzsoh as having the constitution of an anti-
diazo- compound, sodium ji-nitrobenzenediazo-
oxide {v. infra), has been manufactured for use
in the production of ' nitrosamine red ' (Badische
Anilin- und Soda-Fabrik X). E. PP. 78874, 80263,
81134, 81202). The addition of excess of
mineral acid to this metallic diazo- derivative,
determines the regeneration of the original
diazonium salt, but treatment with dilute acetic
acid leads to the formation of a yellow product,
■p-nitrophenylnitrosamine NOj-CsHj-NH-NO, a
substance showing little tendency to couple with
;8-naphthol.

The sUver derivative obtained from the
foregoing sodium salt yields on methylation
an oxygen ether N02'C|,H4'N:N-0-CHj, a re-
action suggesting the possibility of tautomeric
change. In many instances, two isomeric
modifications of these metallic diazo- deri-
vatives have been isolated.

Benzenediazonium chloride and cold concen-
trated potassium hydroxide yield the normal
Ubih form of potassium ienzenediazo-oxide (I.),
which readily couples with /3-naphthol. The
stable modification of potassium benzenediazo-
oxide (II.) is produced by heating the strongly
alkaline solution of the noi'mal or labile salt at
130°-140° ; this isomeride couples only very
slowly with /3-naphthol.

According to Hantzsoh, these isomerides have
respectively the following formula) :—

C'eH^-N CeH,-N



KO-N
I. Syn- (labile form).



NOK

II. AtUi- (stable, form)



Dobbie and Tinkler (Chem. Soc. Trans. 1906,
87, 273) have found, however, that these iso-
meric potassium salts have totally different
ultra-violet absorption spectra. But as stereo-
isomerides, like the benzaldoximes, have iden-
tical absorption spectra, it seems probable that
the above isomeric salts are structurally dis-
similar. Confirmation of the stereochemical
theory would be obtained by isolating the anti-
diazohydroxide from the stable (anti-) potassium
salt, but on treating this with an acid, the nitro-
samine separates. Moreover, the product sup-
posed by Hantzsch and Pohl to be an anti-
diazohydroxide (Ber. 1902, 36, 2964) was shown
by Orton to be a mixture of quinonediazide and
a hydroxyazo- compound (Proc. Roy. Soc. 1903,
71, 153 ; Chem. Soc. Trans. 1903, 83, 796).

The existence of the syn- diazohydroxides is
doubtful, and diazonium hydroxides {v. supra)
are only known in solution.

Diazo- anhydrides E-N:N-ON:NB, . or
E-!N-0-N:NR are very unstable explosive com-

N
pounds produced by the action of acetic acid
on the metallic syn- diazo-oxides. The anti-
diazo-oxides, when thus treated, give nitro-
samines.

VI. Diazo- Cyanides.

The addition of the calculated amount of
potassium cyanide to a cold acid solution of a
diazonium salt determines the formation of a
sparingly soluble diazo- cyanide. In many
instances, two modifications of the diazo-
cyanides can be distinguished, and these varieties
are regarded by Hantzsch as being stereoiso-
meric forms. jj-Chlorobenzenediazoninm chlor-
ide, from y-chloraniline, yields first the yellow
labUe £^7i-p-chIorobenzenediazocyanide (I.),
which readily evolves nitrogen, yields
CeHiCl-N CeH^Cl-N

II II

CN-N N-CN

I. Sj/B-diazooyanide. II. Anti-iia,zots^saide.

p-ohlorobenzonitrile on treatment with copper
powder, and passes into the stable anti-p-ebloio-
benzenediazoeyanide (II.). The latter sub-
stance, which is not affected by copper powder,
may be distiUed in steam without decomposition.

Confirmation of this stereochemical theory
of the constitution of the diazo-cyanides has
been obtained by a study of the cyanides de-
rived from p-methoxybenzenediazonium chlor-
ide. This salt with potassium cyanide in
alcoholic solution yields the «^ra-diazocyanide
(III.), an orange-red insoluble substance (m.p.
51°), which couples with /3-naphthol and slowly,
changes into the non-coupling anti - diazo-
cyanide (IV.), a brownish-red compound,
meltmg at 121°.

OHa-O-CeH^-N CHa-O -CuHj-N

II II

CN-N N-CN

III. IV.

The existence of a third isomeric cyanide is
indicated by evaporating at the ordinary tem-
perature in the presence of excess of hydro-
cyanic acid, an aqueous solution of jj-methoxy-
benzenediazonium hydroxide. The colourless
crystalUne product has the composition :
CH30-CeH4-Nj-CN,HCN,2Hj0,



DIAZO- COMPOUNDS.



233



and possesses all the properties of a true metaUio
salt; it is very soluble, and its solution is an
electrolyte. Moreover, this double salt couples
with j3-naphthol, and is converted by alkalis into
the yellow syn-dietzo- cyanide. These properties
correspond with those of the normal diazonium
salts, and the foregoing soluble cyanide is re-
garded as having the following constitution :
CHs-O-CsHi-N-CN
N
(Hantzsch, Ber. 1900, 33, 2161 ; 1904, 34, 4166).

The two pairs of diazo- cyanides from p-
chloraniliue and y-anisidine were examined
speotroacopioaUy by Dobbie and Tinkler, who
found that each pair gave almost identical
ultra-violet absorption spectra, whereas the above
soluble diazonium cyanide gave an entirely
different spectrum. These results are in accord-
ance with Hautzsch's view of the configuration
of the diazo- and diazonium cyanides (Ohem.
Soo. Trans. 1905, 87, 273).

It has, however, been suggested by several
workers in this field that the isomerism of the
diazo- cyanides is structural, the syn- compounds
being iso-cyanides R-N:N-NC and their arUi-
isomerides, cyanides E-N:N-CN (Ber. 1895, 28,
861 ; Chem. Soc. Trans. 1903, 83, 805).

VII. Diazo- Sui-phonatbs.

Although the stereochemical theory of the
constitution of diazo- cyanides is supported by
physical as well as chemical evidence, yet it is
significant that the only other series of salts in
which this isomerism has been detected is one
derived from sulphurous acid, a substance
resembling hydrocyanic acid in giving rise to
organic isomeric derivatives which are structur-
ally dissimilar.

The diazo- sulphonates, prepared by adding
potassium sulphite to aqueous solutions of
benzenoid diazonium chlorides, frequently exist
in two differently coloured modifications, but in
most cases the syn- isomeride is too unstable to
be isolated in a pure state.

Potassium syn-2:4-diiodol)enzenediazosuIpho-
nate (I.) is an orange substance, whilst the anti-
salt (11.) is yellow:

CsHal.-N CeHjI.-N

II II

KSOj-N N-SOsK

I. II.

The diazotised naphthylamines behave ex-
ceptionally, yielding only si/»-diazosulphonates,
which, on warming pass, not into their anii-
isomerides, but into the corresponding azo-
naphthalenes (Ber. 1897, 30, 71).

The syn- and anti- modifications of potassium
benzenedlazosulphonate CeHj-NiN-SOjK, were
found by Dobbie and Tinkler (I.e.) to have
identical ultra-violet absorption spectra. This
fact supports the stereochemical theory of their
structures {cf. Ber. 1894, 27, 1726, 2099, 2586,
2930, 3527; 1895, 28, 242, 447, 834, 861 ; J. pr.
Chem. 1894, [ii.] 60, 239; Meyer and Jacobson,
Lehrbuch der Org. Chem. ii. 303).

VIII. ALrPHATio Diazo- Compounds.
The amines of the aliphatic seriea, when
treated with nitrous acid, generally lose their
basic nitrogen, the amino- group becoming re-



placed by hydroxyl. In some cases, however,
the nitrogen is retained and an aliphatic diazo-
compound is produced, having the general

/N
formula RH-0:; || with the azo- group attached

\N
entirely to the same carbon atom.

Although glycine is converted by nitrous
acid or al^l nitrites into glycollic acid, yet its
ethyl ester gives rise to ethyl diazoacetate
N\
II jCH-COjj'CsH., a yellow liquid freezing at

n/

24° and boiling at I43''-144772 mm. (Curtius,
Ber. 1883, 16, 2230).

One kilogram of ethyl aminoacetate hydro-
chloride and 750 grams of sodium nitrite are
added successively to 2 litres of water containing
5 grams of sodium acetate. The mixture is
shaken until the temperature falls to 0° ; 6 c.c.
of 10 p.c. sulphuric acid and 500 c.c. of ether are
added and the liquids thoroughly agitated. The
ethereal layer separated and the treatment with
dilute acid and ether repeated until red fumes
are evolved. The ethereal extracts are washed
with dilute aqueous sodium carbonate tiU
alkaline, dried with calcium chloride, and the
solvent removed on the water-bath._ The yield
of ethyl diazoacetate is 94-7 p.c. of the calculated
quantity (Silberrad, Chem. Soc. Trans. 1902, 81,
600).

With iodine, ethyl diazoacetate yields
diiodoacetic acid, and with aldehydes it con-
denses to form ketonic esters :
R-CHO-fNaiOH-COa-CjH.
-> ]

One of the most remarkable reactions of this



Online LibraryT. E. (Thomas Edward) ThorpeA dictionary of applied chemistry → online text (page 55 of 183)