The Hinsberg reaction is a chemical test for the detection of primary, secondary and tertiary

amines In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such ...

. The reaction was first described by Oscar Hinsberg in 1890. In this test, the amine is shaken well with Hinsberg reagent in the presence of aqueous alkali (either KOH or NaOH). A reagent containing an aqueous sodium hydroxide solution and

benzenesulfonyl chloride Benzenesulfonyl chloride is an organosulfur compound with the formula C6H5SO2Cl. It is a colourless viscous oil that dissolves in organic solvents, but reacts with compounds containing reactive N-H and O-H bonds. It is mainly used to prepare sulfo ...

is added to a substrate. A

primary amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such ...

will form a soluble sulfonamide salt. Acidification of this salt then precipitates the sulfonamide of the primary amine. A secondary amine in the same reaction will directly form an insoluble sulfonamide. A tertiary amine will not react with the original reagent(benzene sulfonyl chloride) and will remain insoluble. After adding dilute acid this insoluble amine is converted to a soluble

ammonium salt The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary ...

. Hinsberg test Is Used to distinguish between 1,2,3 degree amine with help of sulphonly cloride In this way the reaction can distinguish between the three types of amines. Tertiary amines are able to react with benzenesulfonyl chloride under a variety of conditions; the test described above is not absolute. The Hinsberg test for amines is valid only when reaction speed, concentration, temperature, and solubility are taken into account.

Reactions

Amines serve as nucleophiles in attacking the sulfonyl chloride electrophile, displacing chloride. The sulfonamides resulting from primary and secondary amines are poorly soluble and precipitate as solids from solution. :PhSO₂Cl + 2 RR'NH → PhSO₂NRR' + R'NH₂⁺l⁻ Hinsberg reaction, primary amine

For primary amines (R' = H), the initially formed sulfonamide is deprotonated by base to give a water-soluble sulfonamide salt (Na hSO₂NR. :PhSO₂N(H)R + NaOH → Na⁺ hSO₂NR⁻+ H₂O Hinsberg reaction, secondary amine

Tertiary amines promote hydrolysis of the sulfonyl chloride functional group, which affords water-soluble sulfonate salts. :PhSO₂Cl + R₃N + H₂O → R₃NH⁺ hSO+ HCl Hinsberg reaction, tertiary amine

References

External links

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Chemical tests