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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 Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent ...
. 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 Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly caustic base and a ...
solution and benzenesulfonyl chloride 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 Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent ...
will form a soluble
sulfonamide In organic chemistry, the sulfonamide functional group (also spelled sulphonamide) is an organosulfur group with the structure . It consists of a sulfonyl group () connected to an amine group (). Relatively speaking this group is unreactive. ...
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 amm ...
. 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 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 Tertiary amines promote hydrolysis of the sulfonyl chloride functional group, which affords water-soluble sulfonate salts. :PhSO2Cl + R3N + H2O → R3NH+ hSO+ HCl


References


External links

{{cc * Laboratory procedure
science.csustan.edu
Chemical tests