Manufacture of Colouring Matters of the Rhodamine and Rhodol Groups.
Year: 1896

page_text: COMPLETE SPECIFICATION.
[Communicated from abroad by THE SOCIETY OF CHEMICAL INDUSTRY IN BASLE,
of Basle, Switzerland, Chemical Manufacturers.]
Manufacture of Colouring Matters of the Rhodamine and
Rhodol Groups.
I, OLIVER IMRAY, of No. 28 Southampton Buildings, Chancery Lane, in the
County of London, Chartered Patent Agent, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
The production of colouring matters of the group of the rhodamines by means of
the bases of the series of oxydiphenylamine and of phthalic anhydride forms the subject
of German Letters Patent Nos. 452€3 and 47451 and the transformation of similir
colouring matters soluble in alcohol into colouring matters soluble in water has been
described in the German Patent No. 46807. While, as regards rosaniline, as is well
known, it is only the sulpho phenylised derivatives which offer a technical interest,
it happens that for the sulpho rhodamines it is the orthotolylised derivatives which
are of importance, as compared with the other alphylised derivatives of the sulpho-
rhodamines in consequence of the fine strong tints which they furnish.
In the preparation of such orthotolylised derivatives of the rhodamines, the
difficulty consisted up to the present time not so much in the condensation of the
metaoxy-phenyl-orthotolylamine with the phthalic anhydride in symmetrical or mixed
colouring matters of the series of the rhodamines, as in the insufficient yield of a
sufficiently pure product.
My correspondents have made the discovery, which is very important for practical
purposes, that a phthalic derivative of the meta-oxyphenylorthotolylamine can be
applied admirably to the preparation of a whole series of orthotolylrhodamines.
Every chemist who has already heated the bases of the series of metaoxydiphenyl-
amines with phthalic anhydride according to the German Patents 45263 and 47451,
must have remarked that in heating progressively, the mass, which in the first instance
becomes fluid, thickens 'towards 120° to 130° C. and that a crystalline mass then
separates which again melts after heating to a higher temperature and forms after-
wards the colouring matter. If therefore, metaoxyphenylorthotolylamine is heated
with phthalic anhydride to 120° or 130° C. until the first thickening of the melted
mass takes place, and the latter is then exhausted by means of alcohol or any
other suitable extracting agent, there will be obtained a product of condensation
of phthalic anhydride with netaoxyphenylorthotolyl amine in a chemically pure
condition in the form of microscopic tablets slightly tinted a greenish yellow, while the
impurities will dissolve in the alcohol or other agent employed.
The new substance which is formed of equivalent quantities of metaoxyphenyl-
orthotolylamine and phthalic anhydride, dissolves with great difficulty in the usual
organic solvent, and easily in the alkalies, but it does not dissolve in dilute mineral
acids. It assumes a violet colour when heated to 180° C. and melts above 200° C.
decomposing completely. On heating it with sulphuric acid it assumes a brown
coloration and decomposes into brown products which my correspondents have not
examined. On melting this substance, in the usual manner for the manufacture of
rhodamines with resorcine or the different phenols employed for the manufacture
of rhodamines, the reaction takes place very readily and gives colouring matters

page_text: of orthotolylrhodol and orthololylrhodamine. All these colouring matters are dis-
tinguished by the extraordinary readiness with which they can be transformed into
sulphoconjugated derivatives. Their sulphoconjugation being effected without an
energetic sulphonating agent by heating them in a water bath, for example even
with sulphuric acid at 80 p.c. The rhodamines soluble in water thus obtained dye
wool and silk in acid bath in fine tints from violet-red to red-violet which resist
the action of air and light and are very uniform on the fibre.
The preparation of the new colouring matters of the rho.lol and rhodamine groups"
will be readily understood by the following examples:
17.5 parts of the condensation products of phthalic anhydride with metaoxyphenyl-
orthotolylamine 5-5 parts of resorcine and 15 parts of bi-sulphate of potash are
'mixed intimately and heated together in a suitable vessel to a temperature of from
170° to 175° C. taking care to stir continuously. The mixture commences to melt
already below 170° C., takes at this temperature a metallic lustre and is completely
fluid between 173° and 175° C. The temperature is maintained during about one hour
between the indicated limits. At the end of this time the melted mass will have become
so viscous that it can hardly be stirred any longer, which indicates that the reaction
has terminated. After cooling there is obtained a hard brittle glassy mass, and with
metallic lustre which is finely pulverized and which is boiled repeatedly with water
for extracting the sulphate of potash and the bi-sulphate which has not been decom-
posed. The product is then dried at 100° C. and it is exhausted by means of toluene
for separating the small amount of resinous impurities which it contains. The dried
residue is pulverised and constitutes a brown powder with metallic lustre, insoluble in
water. If as was proposed in the German Patent No. 54684, one designates by
"rhodol" the simplest form of rhodamine in which an amido group has been replaced
by a hydroxyle group the colouring matter obtained will be sulphate of orthotolyl-
rhodol. Its properties are indicated in one of the tables at the end of this specification.
17-5 parts of the product of condensation of phthalic anhydride with metaoxy-
phenylorthotolylamine, 6-2 parts of orthoamidoparacresol (CH, NH, OH = 1:2:4)
and 15 parts of bi-sulphate of potash are heated together at a temperature of 190° C.
at which the mass melts. When the whole of the mass is melted, the temperature is
allowed to drop to 180° or 183° C. and the mass is maintained at this temperature as
long as it can be stirred, that is to say during about one hour.
After cooling, the melted mass with metallic lustre is pulverised and treated as
described in the previous example, the sulphate of orthotolylhomorholamine constitutes
a brilliant dark brown powder.
If in example (1) the quantity of resorcine indicated be replaced by the phenols
for rhodamine as indicated in the English Patent No. 15374 of 1887, for example
by 7 parts of dimethylmetaamidophenol, 83 parts of diethylmetaamidophenol, 7 parts of
monoethylmetaamidophenol, 10 parts of orthotolylmetaamidophenol, 7 parts mono-
methylorthoamidoparacresol, or equivalent quantities of methylethylmetaainidophenol,
of monomethylmetaamidophenol of monoethylorthoamidoparacresol or other alphylised
(phenylised, tolylised or benzilised) or monoalkylalphylised derivatives of metaamido-
phenol, or the alphylised derivatives of orthoamidoparacresol (the preparation of
which can be effected according to the process described in the German Patent 46869
in condensing orthoamidoparacresol with the primary aromatic amines) there will be
obtained in operating as above described corresponding orthotolylrhodamines which
can be transformed with the same facility into derivatives soluble in water, as will
be shown from the following examples.

page_text: Also, in Example 1 the product of condensation of phthalic anhydride with meta-
oxyphenylorthotolylamine can be replaced by those resulting from the condensation
of the latter with the substitution products of phthalic anhydride obtained by
substitution of the hydrogen of the nucleus of phthalic anhydride, as for instance, the
chlorophthalic anhydride, bromophthalic anhydride &c.

page_text: Ethyl ortho tolyl bromo- Red-yellow color-
rhodamine-sulphonate of
sodium or methyl-ortho
tolyl bromo-rhodamine
sulphonate of sodium.
ation, yellow-
green fluor-
escence.
Formation of a The colou
red flocculent
precipitate.
solution
again to
Ortho tolyl bromo-rhod- Red coloration,
amine sulphonate of weak
Formation of a
cloudy
slight finely di-
. sodium.
yellow
fluor-
vided precipi-
escence.
tate.

page_text: By diluting with water the solutions mentioned in the fourth column of the above.
able, they again assume their original colour.
Having now particularly described and ascertained the nature of this inven-
ion and in what manner the same is to be performed I declare that what I
laim is :-
1. The separation of the intermediate product resulting from the combination of
molecule of phthalic anhydride with one molecule of meta-oxy phenyl ortho tolyl
mine, and which is formed by the fusion together of these substances, substantially
s described.
2. The herein described process for the preparation of colouring matters of the
eries of ortho tolyl rhodamine and of ortho tolyl rhodol, soluble in alcohol, which
process consists in condensing a molecule of the intermediate product referred to in
he first claim with one molecule of resorcine, metaanidophenol, ortho amido para
resol, or of the alkylised, alphylised or alkylalphylised derivatives of the metamido-
phenol and of the ortho amido paracresol above mentioned.
3. The transformation of the colouring matters soluble in alcohol obtained by the
process referred to in the second claim, into colouring matters soluble in water, by
reating the said colouring matters soluble in alcohol with diluted sulphuric acid, such
s of 80 per cent., and in transforming the sulphonic acids thus obtained into-
lkaline salts, substantially as described.
4. As new products:
a) The colouring matters of the rhodamine series soluble in alcohol constituted
by the bases or the salts of the following bodies: dimethyl ortho tolyl rhod-
amine, methyl ethyl ortho tolyl rhodamine, ethyl ortho tolyl rhodamine, phenyl
ortho tolyl rhodamine, methyl phenyl ortho tolyl rhodamine, ethyl phenyl
ortho tolyl rhodamine, methyl tolyl ortho tolyl rhodamine, ethyl tolyl ortho
tolyl rhodamine, ortho tolyl homo rhodamine, methyl ortho toly! homo
rhodamine, phenyl ortho tolyl homo rhodamine, and tolyl ortho tolyl homo.
rhodamine;
b) The colouring matters of the series of rhodol soluble in alcohol constituted
by the bases or the salts of ortho tolyl rhodol;
c) The colouring matters, soluble in water constituted by the alkaline salts of
the sulpho derivatives of the colouring matters mentioned under a) and b),
whatever means may be employed for sulphonising the said colouring matters.
soluble in alcohol.
5. The use of the intermediate product referred to in the first claim for the pro-
duction of colouring matters of the series of the rhodamines and of rhodol, substantially
as described.
Dated this 3rd day of September 1896.
ABEL & IMKAY,
Agents for the Applicant.