Class 12th ORGANIC CHEMISTRY : Make Your Basics Super Strong || Back to Basics 🔥

Brief Summary

This video serves as a bridge course for students transitioning from 11th to 12th grade, focusing on essential organic chemistry concepts needed for the 12th-grade curriculum. It covers basics like:

• Understanding organic chemistry, hydrocarbons, and their derivatives.
• Representing organic compounds through various formulas.
• Grasping fundamental concepts such as bond types, hybridization, and electronic effects.
• Nomenclature of organic compounds using IUPAC rules.
• Isomerism and its classification.
• General Organic Chemistry (GOC) concepts including reaction mechanisms, electronic effects, and attacking reagents.

The course aims to build a solid foundation, enabling students to tackle the organic chemistry portion of the 12th-grade syllabus with confidence.

Introduction

The instructor, Shura Grover, welcomes students to the NCERT Wallah platform, emphasizing that the session will cover essential organic chemistry concepts for class 12th. The bridge course is designed for students who need to strengthen their understanding of organic chemistry, especially those who found it challenging in 11th grade. The course will cover basics necessary for class 12th, addressing common myths about skipping 11th-grade organic chemistry.

Success Through Effort

The instructor encourages students to dedicate themselves to studying with determination. Success may not come with every attempt, but every success is rooted in effort.

Organic Chemistry Basics

The session will cover the basics of organic chemistry, starting with carbon and its related concepts. This includes understanding the types of bonds carbon can form, hybridization, and IUPAC nomenclature. The content will also relate to class 12th chapters such as Haloalkanes and Haloarenes, Alcohols, Phenols, and Ethers, Aldehydes, Ketones, Carboxylic Acids, and Amines.

Rules for the Session

To make the most of the session, students are advised to use a single notebook to keep their notes organized. They should also have three colored pens (blue, black, and pencil) to build and revise structures effectively. Active participation is encouraged.

What is Organic Chemistry?

Organic chemistry is defined as the study of hydrocarbons and their derivatives. Hydrocarbons are compounds containing only hydrogen and carbon. Derivatives are compounds derived from hydrocarbons by replacing one or more hydrogen atoms with other atoms or groups. For example, CH3Cl is a derivative of CH4 (methane). Organic compounds must contain at least one carbon and hydrogen atom.

Representation of Organic Compounds

Organic compounds can be represented in four ways:

1. Molecular Formula: Indicates the exact number of each type of atom in a molecule (e.g., C4H10).
2. Condensed Structural Formula: Shows carbon-carbon bonds but omits carbon-hydrogen bonds (e.g., CH3-CH2-CH2-CH3).
3. Expanded Structural Formula: Shows all bonds between all atoms (C-H and C-C).
4. Bond Line Notation: Represents compounds using lines to indicate bonds, with carbon atoms at the corners and ends of lines, and hydrogen atoms are implied.

Practice Questions: Condensed Structural Formula

Students practice converting structures into condensed structural formulas. Examples include converting ethane (CH3-CH3) and propane (CH3-CH2-CH3) into their condensed forms.

More Practice: Complex Structures

More complex structures are presented, and students are guided to represent them in condensed form, reinforcing the concept with examples like branched and cyclic compounds.

Cyclic Compounds

The lesson covers cyclic compounds, explaining how to represent them in condensed form, such as cyclopropane (CH2-CH2-CH2).

Bonds and Hybridization

Two types of bonds are explained: sigma (σ) and pi (π) bonds. A single bond is always a sigma bond. A double bond consists of one sigma and one pi bond. A triple bond consists of one sigma and two pi bonds. Each bond contains two electrons. Hybridization is calculated by counting sigma bonds and lone pairs, excluding pi bonds.

Calculating Hybridization

The method to calculate hybridization is explained:

• If the sum of sigma bonds and lone pairs is 4, the hybridization is sp3.
• If the sum is 3, the hybridization is sp2.
• If the sum is 2, the hybridization is sp.

Negative charges on carbon indicate the presence of a lone pair. Pi bonds are not considered for hybridization.

Sigma and Pi Bonds Practice

Students practice calculating the number of sigma and pi bonds in various structures, including single, double, and triple bonds.

Bond Line Notation and Hybridization

Students practice identifying sigma and pi bonds and determining the hybridization of carbon atoms in bond line notation structures.

Degree of Carbon

Carbon atoms are classified based on their degree:

• Primary (1°): Bonded to one other carbon atom.
• Secondary (2°): Bonded to two other carbon atoms.
• Tertiary (3°): Bonded to three other carbon atoms.
• Quaternary (4°): Bonded to four other carbon atoms.

Degree of Hydrogen

Hydrogen atoms are classified based on the degree of the carbon atom to which they are attached:

• Primary (1°): Attached to a primary carbon atom.
• Secondary (2°): Attached to a secondary carbon atom.
• Tertiary (3°): Attached to a tertiary carbon atom.

Quaternary hydrogen atoms do not exist.

Degree of Alkyl Halides

Alkyl halides are classified based on the degree of the carbon atom to which the halogen is attached:

• Primary (1°): Halogen attached to a primary carbon atom.
• Secondary (2°): Halogen attached to a secondary carbon atom.
• Tertiary (3°): Halogen attached to a tertiary carbon atom.

Degree of Alcohols

Alcohols are classified based on the degree of the carbon atom to which the hydroxyl (OH) group is attached:

• Primary (1°): OH group attached to a primary carbon atom.
• Secondary (2°): OH group attached to a secondary carbon atom.
• Tertiary (3°): OH group attached to a tertiary carbon atom.

Degree of Amines

Amines are classified based on the number of alkyl groups attached to the nitrogen atom:

• Primary (1°): One alkyl group attached to the nitrogen atom (RNH2).
• Secondary (2°): Two alkyl groups attached to the nitrogen atom (R2NH).
• Tertiary (3°): Three alkyl groups attached to the nitrogen atom (R3N).

IUPAC Nomenclature

Organic compounds have two types of names: common names and IUPAC names. IUPAC (International Union of Pure and Applied Chemistry) nomenclature provides a systematic way to name organic compounds.

Common System vs. IUPAC System

The common system names organic compounds based on their origin or properties. The IUPAC system follows a set of rules for naming compounds. Key prefixes include n- (straight chain), iso- (branching on the second carbon), and neo- (branching on both sides of the second carbon).

IUPAC Nomenclature Rules

The general format for IUPAC names is:

Secondary Prefix - Primary Prefix - Word Root - Primary Suffix - Secondary Suffix

• Word Root: Indicates the number of carbon atoms in the main chain (e.g., meth- for 1 carbon, eth- for 2 carbons, prop- for 3 carbons, but- for 4 carbons).
• Primary Suffix: Indicates the type of bond between carbon atoms (e.g., -ane for single bonds, -ene for double bonds, -yne for triple bonds).
• Secondary Suffix: Indicates the functional group (e.g., -ol for alcohols, -al for aldehydes, -oic acid for carboxylic acids).
• Primary Prefix: Indicates if the compound is cyclic (cyclo-).
• Secondary Prefix: Indicates substituents or side chains (e.g., chloro-, bromo-, methyl-).

IUPAC Practice

Students practice naming compounds using IUPAC rules, including examples with substituents, double bonds, and cyclic structures.

Priority Order of Functional Groups

A priority order of functional groups is presented to determine which group takes precedence as the principal functional group (secondary suffix) when multiple functional groups are present. The order includes carboxylic acids, sulfonic acids, acid anhydrides, esters, acyl halides, amides, nitriles, aldehydes, ketones, alcohols, thiols, and amines.

IUPAC Naming with Multiple Functional Groups

The lesson explains how to name compounds with multiple functional groups, using the priority order to determine the principal functional group and naming the other groups as substituents.

Isomerism

Isomerism occurs when two or more compounds have the same molecular formula but different properties. These properties can be physical or chemical.

Types of Isomerism

Isomerism is classified into two main types:

1. Structural Isomerism: Compounds have the same molecular formula but different structures.
2. Stereo Isomerism: Compounds have the same molecular formula and structure but different arrangements of atoms in space.

Structural Isomerism Types

Structural isomerism includes:

• Chain Isomerism: Different arrangement of the carbon chain.
• Position Isomerism: Different positions of functional groups or multiple bonds.
• Functional Isomerism: Different functional groups.
• Ring-Chain Isomerism: Compounds can exist in both ring and chain forms.
• Metamerism: Different alkyl groups around the same functional group.
• Tautomerism: Isomers that differ in the position of a proton and a double bond, often seen in carbonyl compounds.

Chain Isomerism Explained

Chain isomers have the same molecular formula but differ in the arrangement of the carbon chain.

Positional Isomerism Explained

Positional isomers have the same molecular formula and carbon chain arrangement but differ in the position of functional groups or multiple bonds.

Functional Isomerism Explained

Functional isomers have the same molecular formula but different functional groups.

Ring Chain Isomerism Explained

Ring-chain isomers have the same molecular formula but can exist in both ring and chain forms.

Metamerism Explained

Metamers have the same molecular formula but different alkyl groups around the same functional group.

Tautomerism Explained

Tautomers are isomers that differ in the position of a proton and a double bond, often seen in carbonyl compounds.

Isomerism Practice Questions

Students practice identifying types of isomerism in given examples.

Stereo Isomerism Introduction

Stereo isomers have the same molecular formula and structure but different arrangements of atoms in space.

Chiral Centers

A chiral center (or chiral carbon) is an sp3 hybridized carbon atom bonded to four different groups. The presence of a chiral center does not guarantee optical activity.

Mirror Images and Superimposability

The concepts of superimposable and non-superimposable mirror images are introduced. Non-superimposable mirror images are chiral and can exhibit optical activity.

General Organic Chemistry (GOC) Introduction

The final section introduces General Organic Chemistry (GOC), which explains the flow of reactions and the electronic effects that influence them.

Reaction Mechanisms

A chemical reaction involves a substrate and an attacking reagent. The mixture of these two forms the reactant. Before forming the product, the reaction goes through a transition state or an intermediate stage.

Electronic Effects

Electronic effects, including inductive, resonance, mesomeric, hyperconjugation, and electromeric effects, are studied within the substrate. Attacking reagents are either electrophiles or nucleophiles. Intermediates include carbocations, carbanions, and carbon free radicals.

Bond Fission

Bond fission (breaking of bonds) occurs in two ways:

1. Homolytic Cleavage: Each atom takes one electron, resulting in radicals.
2. Heterolytic Cleavage: One atom takes both electrons, resulting in ions (carbocations and carbanions).

Inductive Effect

The inductive effect is a distance-dependent effect (valid up to four carbon atoms) caused by electronegativity differences. It can be either +I (electron-donating) or -I (electron-withdrawing).

Resonance Effect

Resonance involves the delocalization of pi electrons in conjugated systems. Resonating structures are created to explain properties that a single structure cannot.

Mesomeric Effect

The mesomeric effect is similar to the resonance effect but is unidirectional due to the presence of a specific group. It can be either +M (electron-donating) or -M (electron-withdrawing).

Electromeric Effect

The electromeric effect is a temporary effect that occurs in the presence of an attacking reagent on a multiple bond system.

Hyperconjugation

Hyperconjugation involves the delocalization of sigma electrons. It requires the presence of alpha hydrogen atoms (hydrogen atoms on the carbon atom adjacent to a double bond).

Electrophiles and Nucleophiles

• Electrophiles: Electron-loving species (positive charge or electron-deficient).
• Nucleophiles: Nucleus-loving species (negative charge or electron-rich).

The lesson explains how nucleophiles attack positive centers and electrophiles attack negative centers in chemical reactions.

Conclusion and Farewell

The instructor summarizes the topics covered and encourages students to practice and solve NCERT questions. The session concludes with motivational lines and a farewell.