IIT-JEE MAINS 2027 cheat sheet for Organic Chemistry! 📱 Practice 1 Lakh+ PYQs on ExamBhai.com! - Free Study Material

Chapter Summary: General Organic Chemistry & Reaction Mechanisms

Mastering Organic Chemistry for IIT-JEE Mains 2027 requires a firm grasp of electronic effects, stereochemistry, and core reaction mechanisms. Below is a structured breakdown of fundamental concepts and formulas.

1. Electronic Effects

• Inductive Effect (I-effect): Permanent displacement of $\sigma$-electrons along a carbon chain due to electronegativity differences. Group order for $-I$: $-NO_2 > -F > -Cl > -Br > -I > -OH$.
• Resonance / Mesomeric Effect (M-effect): Delocalization of $\pi$-electrons. $+M$ groups increase electron density on the ring (e.g., $-OH, -NH_2$), whereas $-M$ groups withdraw density (e.g., $-NO_2, -CHO$).
• Hyperconjugation: Delocalization of $\sigma$-electrons of a $C-H$ bond with an adjacent vacant $p$-orbital or $\pi$-system. Number of $\alpha$-hydrogens directly dictates alkene and carbocation stability.

2. Key Reaction Types & Rules

• Electrophilic Addition: Addition of $\text{HX}$ to asymmetric alkenes follows Markovnikov's rule, proceeding via the most stable carbocation intermediate: $CH_3-CH=CH_2 + HCl \to CH_3-CH(Cl)-CH_3$.
• Nucleophilic Substitution: $S_N1$ reactions involve a two-step process with carbocation formation (Order: $3^\circ > 2^\circ > 1^\circ$), while $S_N2$ proceeds via a single-step inversion mechanism (Order: $1^\circ > 2^\circ > 3^\circ$).

3. Representative Molecular Structure

Consider the structure of crotonaldehyde formed via aldol condensation followed by dehydration of acetaldehyde:

```smiles CC=CC(=O)H ```
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