Hinsberg Reagent and Test - Meaning, Preparation, Procedure, FAQs

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Hinsberg Reagent and Test:

Hinsberg reagent can be described as an alternate name for benzene sulfonyl chloride. This name is given for the usage of its Hinsberg test to detect and distinguish primary, secondary, tertiary amines of a given sample. This reagent is an organosulfur compound, and the Hinsberg reagent formula (chemical formula) C₆H₅SO₂Cl.The Hinsberg reagent is a colourless oil that has a thick consistency and is soluble in organic solvents.

This Story also Contains

Hinsberg Reagent and Test:
What is Hinsberg Reagent?
Preparation of Hinsberg Reagent
The Hinsberg Test:
Principle of Hinsberg Test:
Mechanism of Hinsberg Test:
Procedure for Hinsberg Test:
Hinsberg Reaction Pathways
Amine Determination Using Hindsberg Reagent:

What is Hinsberg Reagent?

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

An organosulfur compound is what this reagent is. C₆H₅SO₂Cl l is the chemical formula for this substance. Hinsberg reagent has the appearance of a colourless, thick oil.

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

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Preparation of Hinsberg Reagent

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

Reacting benzene with chloro sulfuric acid is another technique to make the needed Heisenberg reagent (chemical reagent formula HSO₃Cl). Both of these approaches for preparing the needed reagent are shown in the diagram below.

Preparation of Hinsberg Reagent

Source: Self made using Chemdraw software

The Hinsberg Test:

The Hinsberg test is a chemical reagent reaction that determines if an amine is primary, secondary, or tertiary. Oscar Heinrich Daniel Hinsberg, a German chemist, was the first to report this reaction in 1890.

The amines operate as nucleophiles in the Hinsberg test, attacking the electrophile (sulfonyl chloride). This causes the chloride to be displaced, resulting in the formation of sulfonamides. When primary and secondary amines combine to generate sulfonamides, the resulting sulfonamide is insoluble and precipitates as a solid from the solution.

Principle of Hinsberg Test:

The Hinsberg test is based on the production of sulfonamide. An amine reacts with benzene sulfonyl chloride in the Hinsberg test. Because tertiary amines can not produce stable sulfonamides, if a product occurs, the amine is either a primary or secondary amine. It's a primary amine if the sulfonamide that develops dissolves in aqueous sodium hydroxide solution.

It's a secondary amine if the sulfonamide is insoluble in aqueous sodium hydroxide and hydrogen chloride. Because it has an acidic hydrogen atom on the nitrogen, the sulfonamide of a primary amine is soluble in an aqueous base. The base sodium hydroxide absorbs this hydrogen atom, forming a sulfonamide sodium salt. The benzene sulfonyl chloride does not react with tertiary amine.

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

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Mechanism of Hinsberg Test:

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

Procedure for Hinsberg Test:

In a big test tube, add 8-10 drops of amine.

Benzene sulfonyl chloride, 10 drops
10 mL NaOH (at a concentration of 10%)
To combine, vigorously shake the ingredients (use a cork)
Examine the solution for the existence of a single layer (primary amine) or a double layer (secondary amine).
If there is a double layer, use a separatory funnel to remove the bottom aqueous layer and examine if the organic layer is soluble in 5% HCl (If it is not soluble, then secondary amine is present)

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Hinsberg Reaction Pathways

When benzene sulfonyl chloride reacts with primary amines, a sulfonamide product is formed that is alkali soluble. The following diagram depicts this reaction.

Hinsberg Reaction Pathways

When benzene sulfonyl chloride reacts with secondary amines, a sulfonamide product is formed that is not alkali soluble. Below is an example of this type of reaction.

Hinsberg Reaction Pathways

Between a tertiary amine and the benzene sulfonyl chloride reagent, no such reaction occurs. Sulfonyl chloride hydrolysis is aided by tertiary amines. This reaction produces salts that are water soluble.

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

NCERT Chemistry Notes:

Amine Determination Using Hindsberg Reagent:

Hinsberg's reagent is benzene sulphonyl chloride, which may be used to discriminate between 1°, 2°, and 3° amines.

The primary amines, on the other hand, contain two active hydrogen ions, making it easier for them to react with benzene sulphonyl chloride and form salt, which may be dissolved in NaOH due to the remaining active hydrogen.

Because secondary amines only have one hydrogen ion, they react with Benzene sulphonyl chloride but not with NaOH. Because tertiary amines don't contain active hydrogen, they don't react with Benzene sulphonyl chloride.

The Hinsberg reaction is a test for primary, secondary, and tertiary amine detection. The amine is thoroughly shaken with Hinsberg reagent is in the presence of aqueous alkali in this test (either KOH or NaOH). A substrate is treated with a reagent containing an aqueous sodium hydroxide solution and benzene sulfonyl chloride. A soluble sulfonamide salt is formed by a primary amine.

The main amine's sulfonamide is precipitated after acidification of this salt. In the same process, a secondary amine forms an insoluble sulfonamide. A tertiary amine will stay insoluble if it does not react with the initial reagent (benzene sulfonyl chloride). This insoluble amine is transformed

Assume that a, b, and c represent primary, secondary, and tertiary amines, respectively.

In the aqueous phase, if R is considered as a methyl group (the total Rs, excluding hydrogen), then the order of basicity is b > a > c.

If R is any group other than a methyl group, then the basicity order is b > c > a.

When it comes to the gas phase, the basicity order can be written as c > b > a.

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Frequently Asked Questions (FAQs)

1. What is hinsberg reagent?

Hinsberg reagent can be described as an alternate name for benzene sulfonyl chloride. This reagent is an organosulfur compound, and the Hinsberg reagent formula (chemical formula) C₆H₅SO₂Cl. The Hinsberg reagent is a colourless oil that has a thick consistency and is soluble in organic solvents.

2. What is hinsberg test used for?

Hinsberg test to detect and distinguish primary, secondary, tertiary amines of a given sample.

3. Give a brief mechanism of hinsberg reaction

4. Give the hinsberg test for amines

In the test, the amines operate as nucleophiles in the Hinsberg test, attacking the electrophile (sulfonyl chloride). This causes the chloride to be displaced, resulting in the formation of sulfonamides. When primary and secondary amines can be distinguished bys combine to generate sulfonamides, the resulting sulfonamide is insoluble and precipitates as a solid from the solution.

5. How is hinsberg reagent prepared?

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

Reacting benzene with chloro sulfuric acid is another technique to make the needed Hinsberg reagent (chemical formula HSO₃Cl). Both of these approaches for preparing the needed reagent are shown in the diagram below.

6. Why is the Hinsberg test important in amine classification?

The Hinsberg test is crucial because it provides a simple and effective method to differentiate between primary, secondary, and tertiary amines based on their reactivity with benzenesulfonyl chloride. This distinction is important in organic synthesis and analysis.

7. How does the Hinsberg reagent react with primary amines?

Primary amines react with the Hinsberg reagent to form N-substituted benzenesulfonamides. These products are insoluble in alkali but can dissolve in acid. The reaction produces two equivalents of HCl.

8. What is the characteristic reaction of secondary amines with the Hinsberg reagent?

Secondary amines react with the Hinsberg reagent to form N,N-disubstituted benzenesulfonamides. These products are insoluble in both acid and alkali. The reaction produces one equivalent of HCl.

9. How do tertiary amines behave in the Hinsberg test?

Tertiary amines do not react with the Hinsberg reagent. They remain unreacted and form a separate layer from the reagent. This non-reactivity is a key identifier for tertiary amines.

10. What are the safety precautions when handling the Hinsberg reagent?

The Hinsberg reagent is corrosive and moisture-sensitive. Handle it in a fume hood, wear protective gloves and eyewear, and avoid skin contact or inhalation. Keep it away from water as it hydrolyzes readily.

11. What is the significance of the HCl produced in the Hinsberg reaction?

The production of HCl is significant because the number of equivalents produced helps distinguish between primary and secondary amines. Primary amines produce two equivalents of HCl, while secondary amines produce only one.

12. What is the chemical nature of the N-H bond in the sulfonamide products?

The N-H bond in sulfonamide products is acidic due to the electron-withdrawing effect of the sulfonyl group. This acidity allows the products from primary amines to dissolve in strong bases.

13. How does the solubility of reaction products help in amine identification?

The solubility of the reaction products in acid and base helps identify the amine type. Primary amine products dissolve in acid, secondary amine products are insoluble in both acid and base, while tertiary amines don't form products and remain as a separate layer.

14. How does the steric hindrance of amines affect their reactivity in the Hinsberg test?

Steric hindrance can affect the reactivity of amines in the Hinsberg test. More sterically hindered amines (e.g., bulky secondary amines) may react more slowly or incompletely, potentially leading to misinterpretation of results.

15. What are some limitations of the Hinsberg test?

Limitations include potential incomplete reactions with sterically hindered amines, difficulty in distinguishing between closely related amines, and the test's ineffectiveness with very weak bases or certain aromatic amines.

16. How does the Hinsberg test relate to the concept of acid-base chemistry?

The Hinsberg test involves acid-base reactions at multiple stages: the initial reaction produces HCl (an acid), which is neutralized by the base. The solubility of products in acid or base also relies on acid-base properties of the sulfonamides formed.

17. How does the Hinsberg test demonstrate the concept of chemoselectivity in organic reactions?

The Hinsberg test is chemoselective as it specifically reacts with amines but not with other functional groups like alcohols or thiols under the same conditions. This selectivity is crucial for its use in amine identification.

18. How does the Hinsberg test relate to the concept of protecting groups in organic synthesis?

The sulfonamide products of the Hinsberg test can act as protecting groups for amines in organic synthesis. The N-S bond can be cleaved under specific conditions, making it a reversible protection strategy.

19. Can the Hinsberg test be used to distinguish between primary and secondary enamines?

Enamines are less reactive than simple amines in the Hinsberg test due to resonance stabilization. While primary enamines might react slowly, secondary enamines are generally unreactive, behaving more like tertiary amines in this test.

20. How does the Hinsberg test illustrate the concept of kinetics versus thermodynamics in organic reactions?

The Hinsberg test demonstrates kinetic differences between primary, secondary, and tertiary amines. Primary amines react fastest, followed by secondary amines, while tertiary amines are kinetically unreactive despite being often more thermodynamically basic.

21. What is the chemical basis for the formation of N-substituted benzenesulfonamides?

The formation of N-substituted benzenesulfonamides occurs through a nucleophilic substitution reaction. The amine acts as a nucleophile, attacking the electrophilic sulfur atom of the sulfonyl chloride, displacing the chloride ion.

22. What is the mechanism of the Hinsberg reaction with primary amines?

The mechanism involves nucleophilic attack by the amine on the sulfur atom, followed by elimination of HCl. A second equivalent of the amine then removes the remaining proton, forming the final N-substituted benzenesulfonamide and another HCl molecule.

23. How does the basicity of amines influence their reactivity in the Hinsberg test?

More basic amines generally react more readily with the Hinsberg reagent. Aliphatic amines, being more basic than aromatic amines, typically react faster and more completely.

24. How does the electronic nature of substituents on the benzene ring of the reagent affect its reactivity?

Electron-withdrawing groups on the benzene ring increase the electrophilicity of the sulfur atom, enhancing reactivity. Conversely, electron-donating groups decrease reactivity by reducing the electrophilicity of the sulfur.

25. What happens if water is present during the Hinsberg test?

Water can hydrolyze the Hinsberg reagent, forming benzenesulfonic acid. This can interfere with the test results and reduce the effectiveness of the reagent. Therefore, anhydrous conditions are preferred.

26. How is the Hinsberg reagent prepared?

The Hinsberg reagent is typically prepared by reacting benzenesulfonic acid with phosphorus pentachloride (PCl5) or thionyl chloride (SOCl2). This reaction replaces the -OH group of the sulfonic acid with a chlorine atom.

27. How does the concept of electron-withdrawing groups apply to the Hinsberg reagent?

The sulfonyl group (-SO2Cl) in benzenesulfonyl chloride is strongly electron-withdrawing. This increases the electrophilicity of the sulfur atom, making it more reactive towards nucleophilic attack by amines.

28. What is the environmental impact of the Hinsberg test?

The Hinsberg test produces chlorinated organic compounds and uses strong bases, which can be environmentally harmful if not disposed of properly. Modern labs often seek greener alternatives or proper waste management protocols.

29. How does the Hinsberg test differentiate between primary and secondary aromatic amines?

Primary aromatic amines form sulfonamides that are soluble in alkali due to the acidic N-H proton. Secondary aromatic amines form products insoluble in both acid and alkali. This solubility difference allows differentiation.

30. Can the Hinsberg test distinguish between aromatic and aliphatic amines?

No, the Hinsberg test cannot directly distinguish between aromatic and aliphatic amines. It only differentiates between primary, secondary, and tertiary amines regardless of whether they are aromatic or aliphatic.

31. How does the Hinsberg test relate to the concept of nucleophilicity?

The Hinsberg test demonstrates the nucleophilic nature of amines. Primary and secondary amines act as nucleophiles, attacking the electrophilic sulfur atom of the reagent. The strength of the nucleophile affects the reaction rate.

32. What is the significance of the insolubility of secondary amine products in both acid and base?

The insolubility of secondary amine products in both acid and base is due to the lack of acidic hydrogens and the presence of two alkyl groups. This unique solubility behavior is key to identifying secondary amines in the Hinsberg test.

33. How does the Hinsberg test compare to other methods of amine classification?

The Hinsberg test is more definitive than some other methods like the acetylation test. It provides clear distinctions between primary, secondary, and tertiary amines, whereas other tests might only distinguish between primary and non-primary amines.

34. Why is an excess of base used in the Hinsberg test?

An excess of base (usually NaOH) is used to neutralize the HCl produced during the reaction and to create an alkaline environment. This helps in distinguishing between the products formed by different types of amines.

35. What is the role of shaking in the Hinsberg test procedure?

Shaking ensures thorough mixing of the reagents and promotes complete reaction. It helps in the formation of the sulfonamide products and ensures that all of the amine has reacted with the Hinsberg reagent.

36. How does temperature affect the Hinsberg test?

Temperature can affect the rate of reaction in the Hinsberg test. Higher temperatures generally increase the reaction rate but may also lead to side reactions. The test is typically performed at room temperature for consistent results.

37. Can the Hinsberg test be used for amino acids?

The Hinsberg test can be used for amino acids, but interpretation may be complicated due to the presence of both amine and carboxylic acid groups. The test is more commonly used for simpler amine compounds.

38. Can the Hinsberg test be used to quantify amines?

While primarily qualitative, the Hinsberg test can be adapted for semi-quantitative analysis. By measuring the amount of HCl produced or the weight of the sulfonamide product, one can estimate the quantity of amine present.

39. Can the Hinsberg test be used for cyclic amines?

Yes, the Hinsberg test can be used for cyclic amines. Cyclic secondary amines like piperidine will form insoluble products, while cyclic tertiary amines like N-methylpiperidine will not react.

40. How does the Hinsberg test relate to the concept of electrophiles in organic chemistry?

The Hinsberg reagent acts as an electrophile in the reaction. The sulfur atom, being electron-deficient due to the electronegative chlorine and oxygen atoms, is susceptible to nucleophilic attack by the amine.

41. Can the Hinsberg test be used to distinguish between different primary amines?

The Hinsberg test alone cannot distinguish between different primary amines. However, the melting points or other properties of the resulting sulfonamides can be used for further identification.

42. What role does the concentration of the base play in the Hinsberg test?

The concentration of the base (usually NaOH) should be sufficient to neutralize the HCl produced and create an alkaline environment. Too low a concentration may lead to incomplete reaction or misinterpretation of results.

43. How does the Hinsberg test illustrate the concept of leaving groups in organic reactions?

In the Hinsberg reaction, the chloride ion acts as a leaving group. Its ability to leave easily, being a good leaving group, facilitates the nucleophilic substitution reaction with the amine.

44. What is the Hinsberg reagent?

The Hinsberg reagent is benzenesulfonyl chloride (C6H5SO2Cl). It's an organic compound used to distinguish between primary, secondary, and tertiary amines in organic chemistry.

45. What is the chemical structure of benzenesulfonyl chloride?

Benzenesulfonyl chloride has the formula C6H5SO2Cl. It consists of a benzene ring attached to a sulfonyl chloride group (-SO2Cl).

46. What structural features of benzenesulfonyl chloride make it an effective reagent for the Hinsberg test?

The key features are the electrophilic sulfonyl group (-SO2Cl) and the good leaving group (Cl-). The benzene ring provides stability and makes the reagent less reactive towards hydrolysis compared to simpler sulfonyl chlorides.

47. How does the Hinsberg test demonstrate the difference in reactivity between nitrogen and oxygen nucleophiles?

The Hinsberg test showcases the superior nucleophilicity of nitrogen compared to oxygen. Amines readily react with the reagent, while alcohols (oxygen nucleophiles) do not under the same conditions.

48. Can the Hinsberg test be used to distinguish between primary, secondary, and tertiary amides?

No, the Hinsberg test is not effective for distinguishing between amides. Amides are much less nucleophilic than amines and do not react with benzenesulfonyl chloride under the conditions of the Hinsberg test.

49. How does the concept of resonance apply to the products formed in the Hinsberg test?

In the sulfonamide products, resonance occurs between the nitrogen lone pair and the sulfur-oxygen double bonds. This resonance stabilizes the product and contributes to the acidity of the N-H bond in primary amine products.

50. Can the Hinsberg test be adapted for use with gas chromatography or other analytical techniques?

Yes, the Hinsberg test can be adapted for use with analytical techniques. The sulfonamide products can be analyzed by gas chromatography, HPLC, or mass spectrometry for more precise identification or quantification of amines.

51. What are the potential side reactions in the Hinsberg test?

Potential side reactions include hydrolysis of the reagent in the presence of water, formation of benzenesulfonic acid, and possible reactions with very nucleophilic aromatic rings in certain amines.

52. What is the role of organic solvents in the Hinsberg test?

Organic solvents like ether are often used in the Hinsberg test to dissolve the amine and reagent, ensuring good mixing and reaction. The choice of solvent can affect reaction rate and product solubility.

53. How does the Hinsberg test relate to the concept of functional group interconversion?

The Hinsberg test converts amines into sulfonamides, demonstrating functional group interconversion. This transformation changes the reactivity and properties of the nitrogen-containing group significantly.

54. Can the Hinsberg test be used to distinguish between aliphatic and aromatic amines within the same class (e.g., primary aliphatic vs. primary aromatic)?

While the Hinsberg test doesn't directly distinguish between aliphatic and aromatic amines of the same class, the reactivity and properties of the resulting sulfonamides can provide clues. Aromatic amines generally react more slowly and form more stable sulfonamides.

55. What is the significance of the Hinsberg test in the historical development of organic chemistry?

The Hinsberg test, developed by Oscar Hinsberg in 1890, was a significant advancement in organic analysis. It provided a reliable method for distinguishing between different classes of amines, which was crucial for the development of organic synthesis and pharmaceutical chemistry in the early 20th century.