Sulfonic acids are produced through the sulfonation process. Sulfur trioxide is usually the sulfonating agent. The wide application of this method is the production of alkylbenzene sulfonic acids. Sulphonic acids are strong acids. They are usually listed as one million times stronger than the corresponding carboxylic acid. For example, p-Toluenesulfonic acid and methanesulfonic acid have pKa values of -2.8 and -1.9, respectively, while those of benzoic acid and acetic acid are 4.20 and 4.76, respectively. However, as a result of their strong acidity, their pKa values cannot be measured directly, and the commonly quoted values must be considered as indirect estimates with considerable uncertainty. For example, various sources have reported the pKa of methanesulfonic acid as high as -0.6 or as low as -6.5. Sulfonic acids react with solid sodium chloride (salt) to form sodium sulfonate and hydrogen chloride. This property indicates an acidity two or three times that of HCl(g), whose pKa has recently been accurately determined (pKaaq = -5.9).

Because of their polarity, sulfonic acids are usually crystalline solids or viscous, high-boiling liquids. They are also usually colorless and non-oxidizing, which makes them suitable for use as acid catalysts in organic reactions. Their polarity, along with their high acidity, makes short-chain sulfonic acids soluble in water, while longer-chain acids have detergent-like properties.

The structure of sulfonic acids is illustrated by the prototype, methanesulfonic acid. The sulfonic acid group, RSO2OH, has a tetrahedral sulfur center, meaning that the sulfur is centered on four atoms: three oxygens and one carbon. The overall geometry of the sulfur center is reminiscent of that of sulfuric acid.

Sulphonic acid purity measurement method

The percentage purity of sulfonic acid: The best method to determine its purity percentage is the titration method. Hyamine with a normality of 0.004 is used as a titrant. The working method is that first one gram of the acid is weighed in 100 cc and Its exact weight is recorded. In the next step, by adding about 30 cc of distilled water to the mixture and completely dissolving it, it is titrated with 0.1 normal sodium (NaOH) with phenol reagent to determine the acid value. Then the solution in the mixture, which Transfer the pale pink color to a 500 cc flask and make up to volume. Then, with a pipette, transfer 5 cc of the solution to a Nessler (containing 15 cc of distilled water, 15 cc of indicator mix, and 10 cc of chloroform) and Hayamin, we headline.