potassium 4-acetamidobenzenesulfonate

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Properties of substance:

potassium 4-acetamidobenzenesulfonate

Group of substances:

inorganic

Empirical formula (Hill's system for organic substances):

C₈H₈KNO₄S

Structural formula as text:

CH3CONHC6H4SO3K

Synthesis 1:

Reference: Euklid Sakellarios. Uber ein bequemes Verfahren zur Darstellung des o-Nitro-anilins im Laboratorium. (Bearbeitet von Demosthenes Jatrides.) / Chemische Berichte. - 1925. - Vol. 58, No. 10 pp. 2287 [doi: 10.1002/cber.19250581008]

2H₂NC₆H₄SO₃H + K₂CO₃ → 2H₂NC₆H₄SO₃K + H₂O + CO₂
H₂NC₆H₄SO₃K + (CH₃CO)₂O → CH₃CONHC₆H₄SO₃K + CH₃COOH

173 g (1 mole) of anhydrous sulfanilic acid and 69 g (0.5 mole) of potassium carbonate are dissolved in hot water. Once the solution reaches 50°C, 112 g (1.1 mole) of acetic anhydride is slowly added with vigorous stirring. The addition rate is adjusted to maintain the temperature at 65—70°C, preventing it from exceeding 70°C with external cooling.

When all the acetic anhydride has been added and the temperature begins to drop, the reaction is considered complete. To check for unreacted sulfanilic acid, a sample is taken, dissolved in water, and mixed with a few drops of hydrochloric acid and a sodium nitrite solution. The resulting reaction mixture is poured into an alkaline solution of 2-naphthol. If acetylation is incomplete, the characteristic orange coloration of naphthol orange appears. If the test is negative, the acetylation is considered complete.

The mixture is now cooled, causing the potassium salt of N-acetyl-4-sulfanilic acid to precipitate. After a few hours, the precipitation is complete, and the product is filtered and dried on a water bath, yielding 230 g of potassium 4-(acetamido)benzenesulfonate (89.8% of theoretical yield). Further concentration of the mother liquor yields additional 22 g, bringing the total amount to 252 g (98.5% of theoretical yield). The product is sufficiently pure for further processing into o-nitroaniline.

For analysis, 25 g of the substance was recrystallized from 10 g of water. When the air-dried substance had been heated to 125°C, it showed no loss in weight, confirming that the salt is free of crystallization water.

Anal. Calcd. For CH3CONHC6H4SO3K: S, 12.67; K, 15.45. Found: S, 12.63; K, 15.42.

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