The reaction of primary amines, secondary amines, **amines and sulfonyl chloride is collectively referred to as the Hinsberg reaction, which is usually carried out under alkaline conditions.
In the presence of alkali, primary and secondary amines can also react with benzenesulfonyl chloride to form benzenesulfonamide. The benzene sulfonamide produced by the primary amine is weakly acidic due to the influence of the sulfonyl group on the amino group, so it can be soluble in alkali and become salt.
The benzene sulfonamide produced by the secondary amine cannot be salted without hydrogen atoms on the amino group. **Amines and benzenesulfonyl chloride do not work. Therefore, benzenesulfonyl chloride (or p-toluenesulfonyl chloride) is often used to separate the mixture of three amines.
Mechanism of reaction
Under the action of the base, the N-H bond in the amine is dissociated, and the N atom is negatively charged, and this negatively charged base country attacks the sulfur in the radium-yl chloride, and then eliminates the chlorine, that is, through an addition-elimination process to obtain the morning end product.
Because the benzene sulfonyl group is a strong electron-withdrawing group, the hydrogen atom on the benzenesulfonamide ammonia generated from primary amines is affected by it and has a certain acidity, which can react with sodium hydroxide to form sodium salt soluble in water. The benzenesulfonamide produced by secondary amine has no hydrogen atoms on it, and cannot react with the base to form salts, so it cannot be dissolved in the aqueous solution of the alkali. This property can be used to identify or isolate the amine and the right amine.
Reaction experience
In the process of separating primary, secondary, **amines, we can separate them by their reactivity properties.
Response limitations
1. Higher aliphatic primary amines and aliphatic primary amines with more than six carbon atoms react with benzenesulfonyl chloride to form the corresponding benzenesulfonamide, which is completely insoluble in alkaline solution.
The benzenesulfonylcyclooctamine derivative was prepared in the laboratory and found that the derivative was not soluble in a 10% sodium hydroxide solution. This was followed by the synthesis of a series of naphthalamide derivatives of C5 C10 and tert-butylamine and 24.The results show that the benzenesulfonamine derivative of 4-trimethyl-2-aminopentane is insoluble or slightly soluble in 10% Na0H solution, but the solubility is larger in 10% KoH solution
2. Unknown amines are undetectable for both sexes.
For example, methylamine teribenzoate reacts with C6H5SO2Cl in alkaline medium as follows, and the product is dissolved in alkali and precipitates free acid when acidified. The phenomenon is the same as that of primary amines, so it can be mistaken for primary amines.
3. Based on the analysis of the reaction between tertiary amine and tert-aniline and C6H5SO2Cl, the reaction between tertiary amine and C6H5SO2Cl is very slow due to the insoluble of tertiary amine in the alkaline medium of the Hinsburg reaction, coupled with the stereo-effect and low nucleophilicity of tertiary amine. The decomposition of C6H5SO2Cl by alkali OH- in the Hingsberg reaction can effectively compete with the reaction of tertiary amine and C6H5SO2Cl. Although the tertiary amine reacts but can be recovered in the end, the tertiary aniline can also be recovered, but there is a large loss.
4. Many secondary amines with large stereo effect need to be heated to react, because many tertiary aromatic amines also react with C6H5SO2Cl when heated. Therefore, secondary amines with large stereo effects cannot be used as unknowns.