Class 11 Chemistry – Organic Chemistry: Some Basic Principles and Techniques

CBSE 2026–27 | NCERT-aligned free study resource

Nature of Organic Compounds

Organic chemistry studies carbon compounds. Carbon’s tetravalency and ability to form chains and rings lead to enormous structural diversity.

Classification

Organic compounds may be classified by carbon skeleton and functional groups. Homologous series contain compounds with the same functional group and a common general formula, with successive members differing by CH₂.

Nomenclature

IUPAC naming requires identifying the parent chain, principal functional group, substituents, numbering and appropriate suffix/prefix. Accurate naming depends on choosing the correct parent structure and lowest possible locants.

Isomerism

Structural isomerism occurs when compounds have the same molecular formula but different connectivity. Common forms include chain, position and functional isomerism. Stereoisomerism concerns different spatial arrangements.

Electronic Effects

Inductive effect, resonance and hyperconjugation help explain stability and reactivity of organic molecules.

Reaction Intermediates

Carbocations, carbanions and free radicals are important intermediates. Their stability depends on structural and electronic factors.

Purification and Analysis

Common techniques include crystallisation, sublimation, distillation, differential extraction and chromatography. Qualitative analysis identifies elements or functional groups, while quantitative analysis determines composition.

MCQs

1. The characteristic reactive part of an organic molecule is often its: (A) functional group (B) neutron (C) nucleus (D) isotope only. Answer: A.
2. Members of a homologous series differ successively by: (A) CH (B) CH₂ (C) H₂O (D) CO₂. Answer: B.
3. Chromatography can be used for: (A) separation of components (B) measuring atomic number (C) nuclear fission (D) determining gravity. Answer: A.

Practice

1. Name structures using basic IUPAC rules.
2. Identify types of structural isomerism.
3. Choose an appropriate purification technique for a mixture.

HOTS

Explain why two compounds with the same molecular formula can have different physical and chemical properties.

Revision

Carbon skeleton → functional group → IUPAC name → isomerism → electronic effects → intermediates → purification.