Loading PDF...
Chapter Analysis
Advanced19 pages • EnglishQuick Summary
This chapter on Amines, discusses their classification into primary, secondary, and tertiary categories based on substitution on the nitrogen atom. It covers the preparation of amines through various methods such as reduction of nitro compounds and the Gabriel synthesis. The chapter also explores the chemical properties of amines, including their basicity which is influenced by both inductive and solvation effects, and their reactions like alkylation and acylation. Key emphasis is on the practical significance of amines in the synthesis of dyes and medicines.
Key Topics
- •Classification of amines
- •Preparation methods of amines
- •Basicity of amines
- •Reactions of amines
- •Diazonium salts
- •Hinsberg test for amines
- •Electrophilic substitution in aromatic amines
Learning Objectives
- ✓Classify amines based on their structure
- ✓Name amines using IUPAC and common naming systems
- ✓Describe the preparation methods for amines
- ✓Understand and explain the basicity of amines
- ✓Identify amines using chemical tests
- ✓Discuss the industrial applications of diazonium salts
Questions in Chapter
Write IUPAC names of the following compounds and classify them into primary, secondary and tertiary amines.
Page 278
Give one chemical test to distinguish between the following pairs of compounds.
Page 279
Account for the following.
Page 279
Arrange the following in decreasing order of the pKb values.
Page 279
How will you convert:
Page 279
Describe a method for the identification of primary, secondary and tertiary amines.
Page 279
Write short notes on the following:
Page 279
Additional Practice Questions
Explain the carbylamine reaction and its importance.
mediumAnswer: The carbylamine reaction involves the formation of isocyanides by heating aliphatic or aromatic primary amines with chloroform and ethanolic potassium hydroxide. This reaction is important as it provides a test method for primary amines due to the formation of foul-smelling isocyanides.
Differentiate between the solubility of amines and alcohols in water.
mediumAnswer: Amines are generally soluble in water due to hydrogen bonding with water molecules, but their solubility decreases with an increase in molecular size. On the other hand, alcohols are more polar and form stronger hydrogen bonds, thus are usually more soluble in water than amines of similar molecular weights.
Discuss the role of hydrogen bonding in determining the boiling points of amines.
mediumAnswer: Primary and secondary amines engage in intermolecular hydrogen bonding due to the presence of hydrogen atoms attached to nitrogen. This increases the boiling point. Tertiary amines, lacking hydrogen atoms attached to nitrogen, do not engage in this type of bonding, generally resulting in lower boiling points compared to primary and secondary amines.
Describe the method of preparation of aniline using nitrobenzene.
easyAnswer: Aniline can be prepared by the reduction of nitrobenzene using hydrogen gas in the presence of nickel, palladium or platinum catalysts. Alternatively, iron filings and hydrochloric acid can also be used as reducing agents.
Explain why aromatic amines are generally weaker bases than aliphatic amines.
hardAnswer: Aromatic amines are weaker bases than aliphatic amines because the nitrogen's lone pair of electrons is delocalized across the aromatic ring, reducing its availability to bond with protons. The electron withdrawing nature of the aromatic ring also makes it less basic.