On Sulphonfluoresceïn and some of its Derivatives 3

On Sulphonfluoresceïn and some of its Derivatives 3

The chloride thus obtained was treated with strong aqueous ammonia.

The conversion to the sulphamide does not take place so readily as

in case of the pure o-chloride obtained from the sulphonic acid and

phosphorus pentachloride.

 

After standing about two days the whole of the oily chloride had

solidified to a yellowish brown mass. The excess of ammonia was

driven off by gentle heating on the water bath and the mass then

boiled with water. Not enough water was added at first for complete

solution but when the first portion was saturated it was poured

off through a filter and from it the amide separated in yellowish

feathery crystals which melted at 105°-125° and consisted therefore

as shown by Fahlberg (Am. Ch. Jour. Vol. I. p. 170) of a mixture

of o- and p-sulphonamides. It was recrystallized and from it was

obtained a portion melting at 153°-5° and one at 108°-20°.

 

Since this mixture cannot be completely separated by

recrystallization another method was suggested. Remsen has shown that

K_{2}Cr_{2}O_{7} in acid solution does not oxidize the methyl group in

 

 

CH_{3}

╱

C_{6}H_{4}

╲

SO_{2}NH_{2} (o)

 

but does oxidize that in

 

CH_{3}

╱

C_{6}H_{4}

╲

SO_{2}NH_{2} (p).

 

It was thought that in a mixture of the two the former might be left

unchanged while the latter was oxidized to p-sulphamine benzoic acid.

 

To test this 15 gr of the mixture, melting at 105°-125°, was heated

with 40 gr K_{2}Cr_{2}O_{7}, 55 gr H_{2}SO_{4} and 2 vols. of water

for about two hours. It was then tested and shown to be still a

mixture of p-& o-amides, since it was again heated for several

hours with half the original quantity of oxidizing mixture, then

diluted, filtered and washed. The white crystalline residue was

treated with sodium carbonate to dissolve the benzoic para-sulphamide

and the residue was found to be pure toluene o-sulphonamide melting

at 153°-155°. The small quantity remaining, 3 gr., indicated that

part of the o-amide had been completely broken down by the strong

oxidizing agent, though the proportion of o-& p-amides in the

original mixtures was known only approximately. The evolution of gas

during the oxidation would point to the same conclusion.

 

Although this effects a complete separation it is hardly economical

since it will be shown later that a separation can be conveniently

effected after the oxidation with KMnO_{4} so that the o-amide

contained in the mixture need not be lost.

 

The original mass was treated with successive portions of water

till nothing remained but a black tarry substance. The amide which

separated from these extracts was perfectly white and melted at

153-5°. It was therefore regarded as practically pure o-amide. The

yield in amide melting above 153° was a little over one sixth the

weight of toluene used.

 

The amide obtained in this way was oxidized in the manner already

described. It was found however that there was always some benzoic

p-sulphamide in the solution of the oxidation, due to the slight

admixture of p- with the o-amide used. This is thrown down with

the sulphinide on acidifying the solution and may be removed by

re-crystallization since it is somewhat less soluble in hot and cold

water than sulphinide.

 

A better way to effect the separation, however, was found to be

the following. After having evaporated the solution containing the

products of oxidation, nearly neutralized with HCl, to about one

fifth its original volume, it is made very slightly acid and allowed

to cool. In this way very nearly all the benzoic p-sulphamide is

separated from the solution and none of the sulphinide. After

filtering, strong HCl is added and the sulphinide then separates

in its characteristic form. This indicates that sulphinide forms

an alkaline salt which is not decomposed by diluted HCl while the

p-sulphamide does not.

 

The mixture of amides meeting at 105°-120° was oxidized and the

products separated in this way gave about equal quantities of

sulphinide and benzoic p-sulphamide.

 

When toluene is treated with chlorsulphonic acid there are formed

besides the ortho- and para- chlorides also ortho and para sulphonic

acids. These of course are in solution in the water from which the

chlorides separated. In order to recover the ortho-acid, the solution

was neutralized with chalk forming the calcium salt: this converted

into the potassium salt which by evaporating the solution to dryness

was obtained as a white crystalline powder. When treated with PCl_{5}

in the manner already described this gave a mixture of ortho and para

sulphonchlorides consisting of about ⅓ ortho and ⅔ para.

 

 

Formation of Orthosulphobenzoic acid from Sulphinide.

 

Benzoic sulphinide may be converted into a sulpho-benzoic

acid (1) by boiling with Ba(OH)_{2}, (2) by heating in a closed tube

with conc. HCl or (3) by evaporating on the water bath with HCl.

 

1. Three gramms of sulphinide were boiled in a flask connected

with an inverted condenser for about two days with an excess of

Ba(OH)_{2}. There was formed in the flask a hard mineral-like mass

which was insoluble in water and cold diluted HCl but dissolved in

hot HCl with effervesence. This was a Barium salt, probably basic (?)

of ortho sulphobenzoic acid. There was also formed an easily soluble

barium salt of that acid. The former was dissolved in H_{2}SO_{4}

and treated with BaCO_{3}; the filtrate from the BaSO_{4} which

contained a soluble barium salt was added to that above mentioned and

the barium exactly precipitated with H_{2}SO_{4} and the filtrate

evaporated to dryness giving the free acid but not in a perfectly

pure condition.

 

2. 2.75 gr. of sulphinide was sealed up in a tube with pure conc. HCl

and heated two hours to 150°. On cooling nothing separated; the liquid

was evaporated to dryness giving 3.2 gr of acid and ammonium

chloride. The reaction taking place here may be represented thus:

 

CO COOH

╱ ╲ ╱

C_{6}H_{4} NH + 2H_{2}O + HCl = C_{6}H_{4} + NH_{4}Cl.

╲ ╱ ╲

SO_{2} SO_{2}OH

 

3. A more convenient method for obtaining the acid than either of

the above, is to heat the sulphinide with conc. HCl on the water

bath for two days. Then evaporate to dryness and dissolve the

residue in a small quantity of water. If the sulphinide contained

any para-sulphamide, as is usually the case, this will be left

undissolved and most of the NH_{4}Cl will crystallize on standing.

This solution by slow evaporation deposits large colorless crystals

of the free acid.

 

This acid is soluble in about two parts of cold water, very

difficultly soluble in absolute alcohol and almost completely

insoluble in ether. It does not melt under 250° but considerably

above that it melts, at first apparently without change and then

with slight sublimation of a very deliquescent substance, probably

the anhydride.

 

Two determinations of the S. made by Mr. A. F. Linn, gave the

following results.

 

I ·1358 gr substance gave ·1855 gr BaSO_{4} representing 15·72% S.

 

II ” ” ” ” ” ”

 

COOH

╱

Calculated for the formula C_{6}H_{4} = 15·84% S.

╲

SO_{2}OH

 

 

[Illustration]

 

A crystallographic examination of the acid showed it to belong to the

orthorhombic system. Axial ratio: a: b: c = ·8507: 1: ·8121.

Planes. Ρ and αΡὰ.

 

┌─

┌─ │ Edge X = 131° 8'

│ Ρ ^ Ρ ─┤ ” Y = 82° 18'

│ │ ” Z = 118° 40'

Angles measured ─┤ └─

│

│ Ρ ^ αΡὰ = 114° 38'

└─

 

The crystals are up to 8 mm in length. The pyramidal faces are

generally etched so that the image is poor.

 

 

 

 

Sulphonfluoresceïn.

 

 

Several attempts had already been made to obtain from the action

of o-sulphobenzoic acid and resorcin a substance analogous to the

fluoresceïn obtained by Baeyer[1] from phthalic anhydride and

resorcin but while a strongly fluorescent substance was easily

obtained, no definite compound could be separated from it. Thus

Palmer obtained, by heating together the above named substances to

160°(?) a solid mass, part soluble in water and part insoluble as a

dark brown amorphous powder. Both parts gave a strong fluorescence

with alkalis. He was unable however to obtain the substance itself or

any derivative in a crystalline form.

 

[1] Annalin. No. 183. S. 1. No. 202. S. 36 & S. 153.

Berichte. No. IV. S. 457. 555. 658. 662.

” ” VIII. S. 66. 146.