Hinsberg Reagent and Test

Benzene sulfonyl chloride is also known as the Hinsberg reagent. This name alludes to the way the Hinsberg test detects and distinguishes primary, secondary, and tertiary amines in a sample. C6H5SO2Cl is an organosulfur compound with the Hinsberg reagent formula (chemical formula). The Hinsberg reagent is a colourless, thick-textured oil that is organic solvent soluble.

Hinsberg Reagent and its Function

Benzene sulfonyl chloride is another name for Hinsberg reagent formula. This name comes from the Hinsberg test, which is used to detect and distinguish primary, secondary, and tertiary amines in a sample. 

This reagent is an organosulfur compound with a sulphur base. This compound’s chemical formula is C6H5SO2Cl .The Hinsberg reagent seems to be an oil that is colourless and thick. 

This reagent reacts with compounds that have reactive O-H and N-H bonds. It is used to produce sulfonamides and sulfonamide esters by reacting with amines (via reaction with alcohol).

Preparation of Hinsberg Reagent

The necessary reagent is obtained by chlorinating benzene sulfonic acid or benzene sulfonic acid salts with phosphorus oxychloride (POCl3).

Another method for producing the necessary Heisenberg reagent is to react benzene with chloro sulfuric acid (chemical reagent formula HSO3Cl). Both of these approaches for creating the needed reagent are depicted in the graphic below.

The Hinsberg Test

It uses a chemical reagent reaction to determine if an amine is primary, secondary, or tertiary. Oscar Heinrich Daniel Hinsberg, a German chemist, was the first to record this reaction in 1890.

The amines act as nucleophiles in the Hinsberg test, attacking the electrophile (sulfonyl chloride). Sulfonamides are generated as a result of the displacement of the chloride. By mixing primary and secondary amines, sulfonamides are produced. The resultant sulfonamide is insoluble and precipitates out of solution as a solid. 

Hinsberg Test Principle

The Hinsberg test is based on the production of sulfonamides. An amine interacts with benzene sulfonyl chloride in the Hinsberg test. Due to the inability of tertiary amines to form stable sulfonamides, any product produced is either a primary or secondary amine. If the resulting sulfonamide dissolves in aqueous sodium hydroxide solution, it is a primary amine. 

It is a secondary amine if the sulfonamide is insoluble in aqueous sodium hydroxide and hydrogen chloride. As  it has an acidic hydrogen atom on the nitrogen, the sulfonamide of a primary amine is soluble in an aqueous base. When the base sodium hydroxide absorbs this hydrogen atom, the sulfonamide sodium salt is created. Tertiary amine reacts with benzene sulfonyl chloride but not with benzene sulfonyl chloride.

When hydrogen chloride is acidified, it produces an insoluble solid or oil (unreacted amine) that dissolves, yielding a clear solution of the amine salt.

Mechanism of Hinsberg Test

The amine initially interacts with benzene sulfonyl chloride in an addition-elimination reaction on the highly electrophilic sulfonyl chloride derivative. The sodium sulfonamide salt is formed after the chlorine and one proton from the amine are lost in a stepwise manner in the presence of sodium hydroxide. 

For the Hinsberg Test,

1. Add 8-10 drops of amine to a big test tube.

2. Benzene sulfonyl chloride, 10 drops

3. one-tenth litre sodium hydroxide (at a concentration of 10 percent )

4. To combine the components, vigorously shake them (use a cork)

5. In the solution, look for a single layer (primary amine) or a double layer (secondary amine) (secondary amine).

6. If there is a double layer, use a separatory funnel to remove the bottom aqueous layer and check to see if the organic layer is soluble in 5% HCl (If it is not soluble, then secondary amine is present) 

Hinsberg’s Reaction Pathways

When benzene sulfonyl chloride reacts with primary amines, an alkali soluble sulfonamide product is formed. The graphic below depicts this reaction.

As a result, the Hinsberg reagent reacts differently with primary, secondary, and tertiary amines. These variations can be seen in the sulfonamide product’s alkali solubility.

Conclusion 

We conclude that the Hinsberg reagent is another name for benzene sulfonyl chloride. The Hinsberg test is used to detect and distinguish primary, secondary, and tertiary amines in a sample, hence the name. The Hinsberg reaction is an amine detection test that can identify primary, secondary, and tertiary amines. In this test, the amine is extensively shaken with Hinsberg reagent in the presence of an aqueous alkali (KOH or NaOH).