Question

In order to distinguish between \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}\) and \(\mathrm{C}_{6} \mathrm{H}_{5}\) \(-\mathrm{NH}_{2}\), which of the following reagents is useful? (a) \(\beta\)-naphthol (b) Hinsberg reagent (c) \(\mathrm{NaOH}\) (d) \(\mathrm{CHCl}_{3} / \mathrm{KOH}\)

Short answer

Use the Hinsberg reagent to distinguish between ethylamine and aniline.

Step-by-step solution

Understanding the Compounds

The compounds in question are ethylamine (\(\mathrm{C}_{2} \mathrm{H}_{5}\mathrm{NH}_{2}\)) and aniline (\(\mathrm{C}_{6} \mathrm{H}_{5}\)\(-\mathrm{NH}_{2}\)). Ethylamine is an aliphatic amine, while aniline is an aromatic amine.

Considering the Reagents

The task is to identify which reagent from the options can distinguish between ethylamine and aniline. We need to consider how these reagents interact with aliphatic and aromatic amines.

Analyzing Each Reagent's Reaction

- **\(\beta\)-naphthol**: It forms colored compounds with amines but does not effectively distinguish between aliphatic and aromatic.- **Hinsberg Reagent (benzene sulfonyl chloride)**: Reacts with primary amines to form sulfonamides, but only aliphatic sulfonamides remain soluble in alkali, helping differentiate.- **\(\mathrm{NaOH}\)**: Acts as a base and does not help in distinguishing.- **\(\mathrm{CHCl}_{3} / \mathrm{KOH}\) (Carbylamine reaction)**: Reacts with primary aliphatic amines like ethylamine, producing a foul smell (isocyanides or carbylamine) and not with aniline.

Selecting the Appropriate Reagent

The Hinsberg Reaction is crucial because it results in different solubility behavior between ethylamine and aniline's derivative products. The derivative from ethylamine remains soluble with alkali, whereas the one from aniline does not.

Key concepts

Hinsberg Reagent

The Hinsberg reagent, formally known as benzene sulfonyl chloride, plays a crucial role in the differentiation of primary amines. It's often used to distinguish between aliphatic and aromatic amines due to its specific reaction patterns. When a primary amine reacts with this reagent, it forms a sulfonamide. This reaction is key to identifying a primary amine.

Notably, the products of the Hinsberg test can help differentiate between aliphatic and aromatic amines due to their solubility characteristics in alkaline solutions. After the formation of sulfonamides, only those derived from aliphatic amines remain soluble in an excess of an alkaline solution, while those from aromatic amines do not. This makes the Hinsberg reagent a valuable tool in organic chemistry for identifying the nature of amines.

Primary Amines

Primary amines, defined by the presence of a nitrogen atom connected to one alkyl or aryl group, are essential in numerous organic reactions. These compounds behave uniquely and are distinct from secondary and tertiary amines due to their chemical structure and reactivity. The nitrogen atom in a primary amine has two hydrogen atoms in addition to the alkyl group.

This configuration influences how primary amines react with other compounds, such as the Hinsberg reagent. The reaction of primary amines with the Hinsberg reagent results in sulfonamide formation, a reaction that highlights their unique solubility properties when in an alkaline environment. Therefore, understanding primary amines is crucial to utilizing them effectively in chemical differentiation and other organic processes.

Aromatic Amines

Aromatic amines feature an amine group attached to an aromatic ring, such as a phenyl group. These compounds, like aniline ( C_6H_5NH_2), have unique characteristics due to the influence of the aromatic ring on the amino group. This connection modulates their reactivity compared to aliphatic amines and contributes to their unique behavior in reactions.

For example, in the presence of the Hinsberg reagent, aromatic amines produce sulfonamides just like aliphatic amines. However, the aromatic sulfonamides are typically insoluble in alkaline solutions. This insolubility is a key factor in distinguishing them from aliphatic amines, whose sulfonamides generally are soluble. Thus, the specific reaction of aromatic amines forms an integral part in the identification process in organic chemistry.

Aliphatic Amines

Aliphatic amines are characterized by the amino group attached to a non-aromatic structure, usually a straight or branched carbon chain. Ethylamine ( C_2H_5NH_2) is a classic example, demonstrating how these compounds behave distinctly in various chemical reactions.

Their behavior is especially noted in the Hinsberg test, where aliphatic amines react to form sulfonamides that are soluble in alkali. This solubility is crucial for differentiating them from their aromatic counterparts, like aniline, whose sulfonamide derivatives do not dissolve in alkaline solutions. Understanding these differences is essential for students learning about organic compound classification and reaction identification.

• Aliphatic amines are more reactive with longer chains.
• They generally have higher boiling points compared to other amine types.

This makes them incredibly important in fields requiring precise organic synthesis and differentiation techniques.