Question

Classify each amine reaction as acid-base or condensation and list its products. \begin{equation}\begin{array}{l}{\text { a. } \mathrm{CH}_{3} \mathrm{NHCH}_{3}+\mathrm{HCl} \longrightarrow} \\ {\text { b. } \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}+\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOH} \longrightarrow} \\ {\text { c. } \mathrm{CH}_{3} \mathrm{NH}_{2}+\mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow}\end{array}\end{equation}

Short answer

Reaction a: Acid-base, products are [CH_3NH_2^+CH_3]Cl^-. Reaction b: Condensation, products are CH_3CH_2CONHCH_2CH_3 and H_2O. Reaction c: Acid-base, product is [CH_3NH_3^+]HSO_4^-.

Step-by-step solution

Identify Type of Reaction for a

An amine reacting with a strong acid like HCl often undergoes an acid-base reaction. The lone pair of electrons on the nitrogen atom of the amine can accept a proton from HCl.

Determine Products for Reaction a

The amine \( CH_3NHCH_3 \) will accept a proton from HCl to form the corresponding ammonium chloride salt. The product is \( [CH_3NH_2^+CH_3]Cl^- \).

Identify Type of Reaction for b

When an amine reacts with a carboxylic acid, it typically undergoes a condensation reaction called amidation, where an amide bond is formed by the elimination of water.

Determine Products for Reaction b

The amine \( CH_3CH_2NH_2 \) reacts with the carboxylic acid \( CH_3CH_2COOH \) to form an amide and water. The products are \( CH_3CH_2CONHCH_2CH_3 \) (an amide) and \( H_2O \).

Identify Type of Reaction for c

An amine reacting with a strong acid like \( H_2SO_4 \) is an acid-base reaction. The amine can accept a proton from \( H_2SO_4 \).

Determine Products for Reaction c

The amine \( CH_3NH_2 \) will accept a proton from \( H_2SO_4 \) to form the corresponding ammonium salt. The product is \( [CH_3NH_3^+]HSO_4^- \).

Key concepts

Acid-Base Reaction

In the study of organic chemistry, understanding acid-base reactions is crucial for grasping the behavior of amines. These compounds feature a nitrogen with a lone electron pair, which can act as a base by accepting a proton from an acid.

For instance, when we observe the reaction of an amine with hydrochloric acid (HCl), the amine nitrogen donates its lone electron pair to capture a hydrogen ion from the acid, forming an ammonium salt. This process can be seen in part 'a' of the exercise, where the amine, \( CH_3NHCH_3 \), interacts with HCl leading to the production of \( [CH_3NH_2^+CH_3]Cl^- \). Similarly in part 'c', the amine \( CH_3NH_2 \) reacts with sulfuric acid \( H_2SO_4 \) to form \( [CH_3NH_3^+]HSO_4^- \).

These reactions are fundamental in organic syntheses and are critical for forming various functional materials, including dyes, pharmaceuticals, and polymers.

Condensation Reaction

Condensation reactions are another exciting aspect of organic transformations involving amines. When an amine and a carboxylic acid react, they typically undergo this reaction type, resulting in the formation of an amide bond and the release of water.

Here's how it happens: the nitrogen from the amine and the carbonyl carbon from the acid join together, ejecting a water molecule in the process. This can be observed in part 'b' of the exercise, where the amine \( CH_3CH_2NH_2 \) and the carboxylic acid \( CH_3CH_2COOH \) combine to form \( CH_3CH_2CONHCH_2CH_3 \) and \( H_2O \).

Applications of Condensation Reactions

Condensation reactions are widely utilized in the manufacture of polyamides and polyesters, which are essential to the textile and plastic industry. Understanding this process is invaluable not only for chemical synthesis but also for applications in material science and engineering.

Amidation Process

The amidation process is a specific type of condensation reaction where an amine reacts with a carboxylic acid to form an amide. It's the core step in creating peptides and proteins essential for life. The part 'b' of the provided exercise illustrates an amidation reaction, where ethylamine \( CH_3CH_2NH_2 \) and ethanoic acid \( CH_3CH_2COOH \) synthesize an amide \( CH_3CH_2CONHCH_2CH_3 \) and water \( H_2O \).

In practical terms, amidation is vital in pharmaceutical synthesis, crafting complex molecules for drug development. Mastering the intricacies of this reaction helps students understand how large biological molecules are constructed from simpler building blocks.

Ammonium Salts

Ammonium salts are the products of acid-base reactions involving amines. They are formed when an amine accepts a proton from an acid, with the nitrogen atom in the amine being converted from a neutral \( NH_2 \) group to a positively charged \( NH_3^+ \) group.

Our exercise demonstrates the formation of ammonium salts in reactions 'a' and 'c'. Ammonium salts have diverse applications, including use as fertilizers, in pharmaceuticals, and as cleaning agents. Their study is significant for students aiming to work in various sectors of the chemical industry, as they are foundational compounds in a vast array of chemical processes.