Process for Transforming Rhodols and Rhodol Esters into Dyestuffs Fast to Soap.
Year: 1899

page_text: Process for Transforming Rhodols and Rhodol Esters into Dyestuffs
Fast to Soap.
I, OLIVER IMRAY, of Birkbeck Bank Chambers, Southampton Buildings, in the
County of London, Chartered Patent Agent, do hereby declare the nature of this
invention (as communicated to me froin abroad by The Farbwerke vormals:
Meister Lucius and Brüning, of Hoechst a/Main, in the Empire of Germany,
Chemical Manufacturers), to be as follows:-
The Basler Chemische Fabrik in its application for Letters Patent B.20717/22
describes new dyestuffs which may be obtained by treating rhodols with alcohols and
nineral acids and which are to be considered as rhodol esters. These esters are not
fast to soap.
My foreign correspondents have found that from these rhodols and rhodol esters
on alkylation, either alkaline or neutral, dyestuffs may be obtained which are quite
fast to soap and are thus distinguished from those described in the application above
referred to. As alkylating agent dimethyl sulphate is best employed, but alkyl
halides may also be used. Either the rhodols or the rhodol esters may serve as
primary material; the dyestuffs resulting in both cases seem to be identical.
Besides the fastness to soap of the tints produced on cotton treated with
tannin, the dyestuffs are also distinguished from the rhodol esters in the
application above referred to by their not being precipitated from an aqueous solution
by soda or sodium acetate.
For the formation of these dyestuffs it is necessary that the alkylation should take
place with a free rhodol base, a rhodol alkali salt or a free rhodol ester, preferably
with an addition of alkali, such as sodium carbonate.

page_text: hydroxyl group and that the dyestuffs obtained after substituting for the hydroxyl
hydrogen an alkyl group (methyl, ethyl, benzyl), of the type
yield on calico, treated with tannin, dyes thoroughly fast to soap. Compounds of this
kind have not been known hitherto. They are obtained by alkaline or neutral
alkylation of the rhodols or rhodolcarboxylic esters; they may also be obtained by
etherification of the hitherto unknown rhodol-hydroxylethers:

page_text: mixed with 20 parts of soda-ash are brought into reaction with 30 parts of dimethyl-
sulphate as described in Ib. The methylether-ethylester obtained in this manner
has no characteristic distinction from the methylether-methylester described in I.
The tints obtained with both dyestuns cannot be distinguished from each other.
The tints obtained with both dyestuns cannot be distinguished from each other.
b. From diethyl-rhodol-hydroxyl-methylether.
If in Example Ic diethyl sulphate be substituted for dimethyl sulphate, the above
described methylether-ethylester is obtained in the same manner.
III. (RESORCINOL)-DIMETHYL-RHODOL-METHYLETHER-METHYLESTER.
The manufacture is exactly the same as in Example Ia bc, the dimethyl-
rhodol derivative being substituted for the diethyl derivative. There are
no characteristic distinctions from the corresponding diethyl compound, only
the methyl compound dyes somewhat more vividly; the hydrochloride is still
more readily soluble than that of the diethyl compound. The dimethyl-rhodol-
methylether, insoluble in alkali and obtained by heating dimethyl-rhodol-methylether-
methylester with soda-lye is similar in every respect to the corresponding diethyl-
rhodol compound.
IV. (RESORCINOL) -DIETHYL-RHODOL-BENZYLETHER-METHYLESTER.
84 parts by weight of the hydrochloride of diethyl-rhodol are dissolved in 200
parts of water and 70 parts of soda-lye of 40° Bé. specific gravity and this solution is
boiled for some time in a vessel provided with an inverted condenser, 50 parts of
benzyl chloride being added; insoluble diethyl-rhodol-benzylether separated. The
latter, when dried and pulverised, is mixed with dimethyl sulphate (1 part) and best
with soda-ash (part) and heated for about 1 hour to 80°-90° C. The pulverised.
mass is mixed with hydrochloric acid and diluted with water until completely
dissolved; the solution is then filtered and the dyestuff is salted out. The vivid,
yellow-red dyes obtained on calico treated with tannin can hardly be distinguished
from those of the corresponding methylether-methylester. The hydrochloride is a
brittle mass, readily soluble in water, not precipitated by a solution of sodium
carbonate; soda-lye hydrolyses the compound, yielding the diethyl-rhodol-benzyletber
which is insoluble in alkali, soluble in acids and separates as a resinous body which
gradually solidifies and is easily soluble in alcohol, ether and benzene.
V. (RESORCINOL)-MONO-ETHYL-RHODOL-METHYLETHER-METHYLESTER.
The monoethyl-rhodol is best obtained by heating para-toluene-sulphofluoresceine
with the hydrochloride of monoethylamine, zinc chloride and some quick-lime at
200° C. and eliminating small quantities of diethylrhodamine by heating with an
excess of sodium carbonate solution. The monoethyl-rhodol is soluble in a solution
of sodium carbonate with yellow-red colour and strong fluorescence. Acetic acid
precipitates the brick-red monoethyl-rhodol base which dissolves in very dilute
mineral acids with a reddish-yellow colour and strong fluorescence.
The manufacture of monoethyl-rhodol-methylether-methylester by means of
dimethyl sulphate is in this case also quite similar to the manufacture from diethyl-
rhodol, Ex. Ia-c. The hydrochloride, readily soluble in water, dyes much yellower
than the corresponding diethyl compound; the solutions, in contrast with those of
the latter have a yellow fluorescence.
VI. (HYDROQUINONE)-DIETHYL-RIODOL-METHYLETHER-METHYLESTER.
We have found, that the hitherto unknown hydroquinone-diethyl-rhodol may be
chiained by condensation of diethyl metasamnidooxybenzoylbenzoic acid and hydro-