On Sulphonfluoresceïn and some of its Derivatives 2

On Sulphonfluoresceïn and some of its Derivatives 2

┌─ ┌─

│ CH_{3} │ CH_{3}

1. C_{6}H_{3} ┤ SO_{3} + HNaSO_{3} = C_{6}H_{3}┤ SO_{2}ONa

│ \ │

│ N═N │ N═NSO_{3}H

└─ └─

┌─

│ CH_{3}

2. C_{6}H_{3} ┤ SO_{2}ONa + HNaSO_{3} + H_{2}O

│ N═NSO_{3}H

└─ ┌─

│ CH_{3}

= C_{6}H_{3} ┤ SO_{2}ONa + HNaSO_{4}.

│ NH-NHSO_{3}H

└─

 

To the hot solution an excess of conc. HCl is added when the

hydrazine compound separates in a few moments in lustrous yellow

scales which completely fill the solution. On the addition of the HCl

a large amount of SO_{2} is given off from the excess of HNaSO_{3} and

the solution becomes deep red. When the hydrazine has separated the

mother liquor is again yellow.

 

The reaction is represented as follows:

 

┌─

│CH_{3}

C_{6}H_{6}┤SO_{2}ONa + HCl + H_{2}O

│NH-NHSO_{3}H

└─

┌─

│CH_{3}

= C_{6}H_{3}┤SO_{2}OH + H_{2}SO_{4} + NaCl

│NH-NH_{2}

└─

 

The yield of hydrazine when both the diazo and the NaHSO_{3} are

freshly prepared is practically quantitative.

 

The hydrazine thus prepared was treated with a hot 10% solution of

copper sulphate till a permanent blue color was obtained in the

solution. Nitrogen is evolved and the copper sulphate is reduced to

cuprous oxide which is precipitated as a red powder. The reaction is

as follows.

 

┌─

│CH_{3}

C_{6}H_{3}┤SO_{2}OH + 2CuSO_{4} + H_{2}O

│NH-NH_{2}

└─

┌─

= C_{6}H_{4}┤CH_{3} + Cu_{2}O + N_{2} + 2H_{2}SO_{4}

│SO_{2}OH

└─

 

Chalk was added to the solution to precipitate the H_{2}SO_{4} and

form a calcium salt of toluene-o-sulphonic acid. From this the

sodium salt was made by adding a slight excess of Na_{2}SO_{3} and

evaporating to dryness. The salt is very soluble being deliquescent

in the air while the corresponding potassium salt is not. From 1538

gr. of para-nitro-toluene, 655 gr. of toluene ortho-sodium sulphonate

were obtained.

 

Having thus obtained the toluene ortho-sulphonic acid the next

step in the problem was to find a convenient method for converting

this into ortho-sulph-benzoic acid. Two ways present themselves

for accomplishing this end. (1) direct oxidation of this salt and

(2) conversion into benzoic sulphinide from which the acid may be

obtained. Both of these methods were tried.

 

 

Oxidation of toluene-o-sodium sulphonate.

 

┌─

C_{6}H_{4}─┤CH_{3}

│SO_{2}ONa

└─

 

The sodium salt of toluene-o-sulphonic acid is oxidized to

ortho-sulphobenzoic acid with considerable difficulty by KMnO_{4} in

neutral solution.

 

Thus two experiments showed that the oxidation was not complete after

24 hours boiling with excess of permanganate. If the solution be made

alkaline however, the oxidation is completed in a few hours, yet the

greatest difficulty still remains in the separation of the free acid

from the products of oxidation in the solution. If HCl be added to

the solution the acid salt

 

COOH

╱

C_{6}H_{4}

╲

SO_{2}OK

 

is formed and this has nearly the same solubility as the KCl also

present. A better method therefore is to add a slight excess of

H_{2}SO_{4} and evaporate nearly to dryness. In this way are formed

sulphates and the free acid presumably. The mixture is heated with

alcohol (95%) which extracts the acid leaving the greater part of

the manganese salts. This extract is evaporated and reextracted

with alcohol. To this solution BaCO_{3} is added to precipitate the

H_{2}SO_{4} and form the Barium salt of the o-sulphobenzoic acid. The

solution is filtered from the BaSO_{4} and just enough H_{2}SO_{4}

is added to exactly precipitate the barium. The solution should

thus contain only the free acid sought, which crystallizes out on

evaporating to a small volume. While the method is theoretically

possible it presents so many difficulties that it is practically

useless. The yield is extremely small; only enough acid being

obtained in this way to show that it was possible.

 

 

Formation of Sulphinide from toluene-o-sodium sulphonate.

 

The second method for obtaining free o-sulphobenzoic acid from

toluene-ortho-sulphonic acid is by the conversion of the latter first

into benzoic sulphinide and then into the free acid. The sulphinide

was made essentially as described by Remsen (Am. Ch. Jour. Vol. I.

p. 428) with a few changes in the details as follows.

 

┌─

The salt C_{6}H_{4}┤CH_{3} finely pulverized and in portions

│SO_{2}ONa

└─

 

of from 10 to 50 gr. was placed in a Florence flask; an equivalent

quantity of PCl_{5} added; An inverted condenser was then attached

and the flask shaken. The action takes place at once and involves

sufficient heat to distill off the oxychloride formed in the

reaction. This being returned to the flask by the condenser furnishes

a liquid medium in which the reaction takes place more readily and

completely than when it is not present. It is best to cool the flask

at first and afterwards heat gently on the water bath. The reaction

which takes place may be represented as follows.

 

┌─ ┌─

│CH_{3} │CH_{3}

C_{6}H_{4}┤SO_{2}ONa + PCl_{5} = C_{6}H_{4}┤SO_{2}Cl + POCl_{3} + NaCl.

└─ └─

 

On the addition of water the chloride separates as a light yellow

oil. This is washed with water and concentrated aqueous ammonia

added, which forms toluene-o-sulphonamide thus.

 

CH_{3} CH_{3}

╱ ╱

C_{6}H_{4} + NH_{3} = C_{6}H_{4} + HCl.

╲ ╲

SO_{2}Cl SO_{2}NH_{2}

 

The reaction is accompanied by a slight evolution of heat and the

formation, apparently, of an intermediate product having a yellowish

color, which passes over on longer standing into the white amide.

After standing several hours the excess of ammonia was driven off

by very gentle heating on the water bath. If the heat is too high

a large amount of a tarry product is formed and the yield of amide

is correspondingly small. In any case some of this tarry product is

formed. When nearly all the ammonia had been driven off the mass was

boiled with water which dissolves everything except the tar. The

hot solution was filtered through charcoal and on cooling the amide

separated in white feathery crystals which melt at 155°-156°.

 

The amide thus obtained was oxidized as described by Remsen (loc. cit.)

with potassium permanganate in neutral solution. The proportions are

10 gr amide. 40 gr KMnO_{4} and 1 L. water. The oxidation was usually

effected in from four to six hours.

 

To obtain the sulphinide from this solution after oxidation, the

latter, after filtration from the precipitated oxides of manganese,

was slightly acidified with HCl and evaporated to about one fourth

its original volume. On the addition of concentrated HCl to this

solution, the sulphinide separated out in white or slightly yellowish

feather shaped crystals melting at 212° and having the characteristic

intensely sweet taste.

 

 

Formation of Sulphinide from Toluene by means

of the chlorsulphonic acid reaction.

 

Before passing on to the methods used for converting the sulphinide

into free acid another method should be described by which

the former was obtained in larger quantities and much more easily

than by the one above described.

 

Beckurts and Otto (Ber. XI. 2061) found that by treatment of toluene

with sulphuryl hydroxy-chloride or chlorsulphonic acid, ClSO_{2}OH,

both o- and p- and as they supposed also m-toluene sulphonchlorides

were formed together with the corresponding sulphonic acid.

 

Claesson and Wallin (Ber. XII. p. 1848) repeated the work reaching

practically the same results and finally Noyes (Am. Ch. Jour. Vol.

VIII. p. 176) employed the reaction as a convenient method for

obtaining toluene o-sulphon-chloride.

 

Chlorsulphonic acid is made by passing dry HCl over solid sulphuric

acid so long as it continues to be absorbed. Since no solid sulphuric

acid was at hand, ordinary fuming Nordhausen acid was taken and

from one of two equal portions the SO_{3} was driven over into

the other. HCl was passed into the latter and the resulting

chlorsulphonic acid distilled off at about 156°.

 

This was placed in a flask, provided with a drop funnel and exit

tube, in portions of 150 gr. and to each portion 60 gr. of toluene

was added, very slowly, with constant shaking, the temperature

being kept near 10°. The action is violent and if any toluene is

allowed to collect on the surface of the liquid it is apt to produce

disastrous results. Large quantities of HCl are given off and the

liquid in the flask assumes a brown color. When all the toluene has

been added, it is poured into a large quantity of ice water, when

the sulphon-chlorides separate out, the ortho- as a heavy oil and

the para- as a white crystalline solid. After allowing to stand some

time in order that as much of the para-chloride might crystallize as

possible the ortho- was drawn off and subjected to a freezing

temperature for several hours. By this means more of the p-chloride

was removed and the operation was replicated as long as any crystals

continued to form, generally two or three times. In this way the

greater part of the para- may be removed, though some still remains

dissolved in the liquid chloride, which cannot be removed by repeated freezings.