COOC₆H₄.CH₃
/
Cal. for C₆H₃——SO₂OC₆H₄.CH₃
\
NO₂
Found.
I II
C = 59.08 59.06
H = 3.98 4.52
S = 7.49 7.43
4. The Action of Hydroquinone upon the Symmetrical Chloride of
Paranitroorthosulphobenzoic Acid.
Action with hydroquinone occurs at 120°-135°, the mixture at the same
time becoming dark colored and viscous.
On cooling, the product was powdered and treated with dilute alkali.
It readily dissolved, without residue, forming a dark red solution.
In concentrated solution the addition of acid produces a voluminous
precipitate, dark brown in color, which when washed, and dried in paper
forms an almost black powder. A dilute solution of this powder is dark
red when alkaline, orange-yellow when acid.
From the way in which this powder was obtained, and owing to the fact
that its solubility prevented repeated washing, it was evident that it
would not give close analytical results for a calculated formula. It
was thought, however, that analysis would give a general idea of the
composition.
Analysis of different specimens gave results for sulphur which averaged
about 5.5%. The percentage required for the formula
C[C₆H₃(OH)₂]₂
/ \
/ O
/ /
C₆H₃——SO₂
\
NO₂
which represents the simplest sulphonfluoresceïn, is 7.43.
The compound could hardly have been so far from pure as to occasion
such a discrepancy in results as this. It would appear, therefore, that
more than two molecules of hydroquinone enter into the reaction with
one molecule of the chloride. Should four molecules be involved in the
reaction, leading to a compound of some such formula as
C[C₆H₃(OH)₂]
/ \
/ O
/ /
C₆H₃——SO[C₆H₃(OH)₂]₂
\
NO₂
the theoretical percentage of sulphur would be 6.00 which corresponds
much more closely with the results obtained.
This is in accord with the observations of a number of workers in
this laboratory—Lyman, Gilpin, Linn and others—who have worked on
various sulphonfluoresceïns, and have found that in many cases four,
six and even eight phenol residues condense with one molecule of the
anhydrous acid. Lyman[22] especially describes a tetra hydroquinone
sulphonfluoresceïn derived from orthosulphoparatoluic acid. No etherial
salt was observed.
[22] Am. Chem. Journ. XVI-525
5. The Action of Resorcin upon the Symmetrical Chloride of
Paranitroorthosulphobenzoic Acid.
The reaction of resorcin with the chloride is a much cleaner one
and proceeds more easily than in the case just described, leading
apparently to an individual compound which is well characterized.
During the reaction, which is complete at 125°, the mixture becomes
almost perfectly solid, and when cool, it is quite brittle. It was
reduced to a reddish powder in a mortar and dissolved in sodium
hydroxide, there being no insoluble residue. By the addition of
hydrochloric acid, the sulphonfluoresceïn was thrown down as a
chocolate-brown precipitate, which was filtered off, washed to
neutral reaction on a filter, and dried on paper. In this condition
it is a light chocolate-brown powder. In dilute alkaline solution it
possesses a slight fluorescence being pink by transmitted and yellow be
reflected light, suggesting eosin in a general way. It is interesting
to note that the sulphonfluoresceïn of orthosulphobenzoic acid
possesses a fluorescence that can hardly be distinguished from ordinary
fluoresceïn and that the introduction of a nitro group into the acid
residue produces much of the same effect as do the four bromine atoms
in eosin. In acid solution the color is reddish-orange.
Analysis of the compound, prepared as above described, gave the
following results.
I. 0.1745 gram gave 0.3339 gram of CO₂ and
0.059 gram H₂O.
II. 0.1467 gram gave 0.2820 gram CO₂ and
0.0432 gram H₂O.
III. 0.1732 gram gave 0.3345 gram CO₂ and
0.0571 gram H₂O.