Mnemonics: Organic Chemistry : Some Basic Principles & Techniques | Chemistry Class 11 - NEET PDF Download

Introduction

Understanding the principles of organic chemistry can be challenging, but mnemonics offer an effective method to simplify and retain complex concepts, making them easier to recall.

IUPAC Naming of Compounds

• Mnemonic: "Penny Wants Sweets First"
• Penny = Prefix (Substituents and their positions) . Start with the prefix for any substituents (halogens, alkyl groups, etc.) and their positions on the carbon chain.
• Wants = Word Root (Carbon chain length). After the prefix, identify the word root, which indicates the number of carbon atoms in the longest continuous chain (e.g., "meth-" for 1, "eth-" for 2, "prop-" for 3, etc.).
• Sweets = Suffix (Functional group). Finally, apply the suffix, which tells you the type of compound based on its functional group (e.g., -ane for alkane, -ene for alkene, -ol for alcohol, -al for aldehyde, etc.). 

Carbocation and Carbanion

• A Carbocation is a positively charged species where a carbon atom has three bonds and an empty p-orbital.
• A Carbanion is a negatively charged species where a carbon atom has an extra pair of electrons.

• Mnemonic: "Cations Love Crowds, Anions Stay Alone."
• Cations: Carbocations are stabilized by more alkyl groups (tertiary > secondary > primary).
• Love Crowds: More alkyl groups stabilize the positive charge via hyperconjugation and induction.
• Anions: Carbanions are destabilized by alkyl groups (methyl > primary > secondary > tertiary).
• Stay Alone: Fewer alkyl groups provide more stability to the negative charge.

Types of Isomerism

Different types of isomers in organic chemistry.

• Mnemonic: "Smart Scientists Can Predict Fun Structures."
• Smart: Structural isomers.
• Scientists: Stereoisomers.
• Can: Chain isomers.
• Predict: Positional isomers.
• Fun: Functional isomers.
• Structures: Spatial (geometrical) isomers.

Markovnikov’s Rule

The rule for the addition of hydrogen halides to alkenes.

• Mnemonics: More Friends, More Hydrogen."
• More Friends: Carbon with more hydrogens gets more hydrogens.
• More Hydrogen: Hydrogen adds where hydrogens are already abundant.

Anti Markovnikov's Rule

 In the presence of peroxide, the addition of hydrogen halides (like HBr) to alkenes occurs in such a way that the hydrogen atom attaches to the more substituted carbon, and the halogen attaches to the less substituted carbon.

• Mnemonic: "Anti Mark Prefers Poor Places."
• Anti: Anti-Markovnikov’s Rule.
• Mark: Opposite of Markovnikov’s Rule.
• Prefers: Peroxides initiate the reaction.
• Poor: Halogen prefers the less substituted carbon (electron-poor place).
• Places: Hydrogen bonds to the more substituted carbon.

Mnemonics serve as valuable tools in mastering organic chemistry, enhancing both comprehension and retention of key principles for practical application.