Organic ChemistryHigh Yield (2-3 Qs in JEE)

Hydrocarbons (Alkanes, Alkenes, Alkynes) Formulas

Markovnikov & anti-Markovnikov additions, ozonolysis, Wurtz reaction, Friedel-Crafts alkylation/acylation, and acidic nature of alkynes.

8 Formulas•514+ Questions in Bank

Core Formulas & Mathematical Identities

R-\text{CH}=\text{CH}_2 + \text{HX} \longrightarrow R-\text{CH(X)}-\text{CH}_3 \quad (\text{Markovnikov})

Electrophile H⁺ adds to form the more stable carbocation intermediate.

Examiner Tip: In presence of peroxide (R₂O₂), HBr adds anti-Markovnikov via free radical mechanism.

R_1 R_2 \text{C}=\text{C} R_3 R_4 \xrightarrow{\text{1. } O_3, \; \text{2. } Zn / H_2O} R_1 R_2 \text{C}=\text{O} + R_3 R_4 \text{C}=\text{O}

Cleaves carbon-carbon double bonds to form carbonyl compounds.

Examiner Tip: Reductive ozonolysis uses Zn/H₂O or (CH₃)₂S to prevent oxidation of aldehydes to carboxylic acids.

2 \text{ R-X} + 2 \text{Na} \xrightarrow{\text{dry ether}} \text{R-R} + 2 \text{NaX}

Coupling of alkyl halides to produce symmetrical alkanes.

Examiner Tip: Methane (CH₄) cannot be prepared by the Wurtz reaction.

\text{C}_6\text{H}_6 + \text{R-Cl} \xrightarrow{\text{anh. AlCl}_3} \text{C}_6\text{H}_5\text{R}, \quad \text{C}_6\text{H}_6 + \text{RCOCl} \xrightarrow{\text{anh. AlCl}_3} \text{C}_6\text{H}_5\text{COR}

Electrophilic aromatic substitution on benzene ring.

Examiner Tip: Acylation avoids carbocation rearrangement and polyalkylation.

\text{R-C}\equiv\text{CH} + \text{NaNH}_2 \longrightarrow \text{R-C}\equiv\text{C}^- \text{Na}^+ + \text{NH}_3

Terminal alkyne hydrogen is acidic due to 50% s-character of sp hybridized carbon.

Examiner Tip: Gives red precipitate with ammoniacal Cu₂Cl₂ and white precipitate with Tollen's reagent.

\text{R-C}\equiv\text{C-R}' \xrightarrow{\text{H}_2 / \text{Pd-CaCO}_3 \text{ (Lindlar)}} \text{cis-alkene}, \quad \text{R-C}\equiv\text{C-R}' \xrightarrow{\text{Na / liq. } \text{NH}_3 \text{ (Birch)}} \text{trans-alkene}

Syn-addition catalytic hydrogenation versus anti-addition dissolving metal reduction to control alkene geometry.

Examiner Tip: Birch reduction of benzene gives non-conjugated 1,4-cyclohexadiene.

\text{OMDM: } \text{R-CH=CH}_2 \xrightarrow{\text{1. Hg(OAc)}_2/\text{H}_2\text{O}, \; \text{2. NaBH}_4} \text{Markovnikov (no rearr.)}, \quad \text{HBO: } \xrightarrow{\text{1. B}_2\text{H}_6, \; \text{2. H}_2\text{O}_2/\text{OH}^-} \text{Anti-Markovnikov (syn)}

Two non-rearranging pathways for regioselective water addition across carbon-carbon double bonds.

Examiner Tip: OMDM avoids carbocation ring expansions and hydride/methyl shifts.

\text{Aromatic: Planar, cyclic, conjugated, } (4n + 2)\pi e^-, \quad \text{Anti-Aromatic: Planar, cyclic, conjugated, } 4n\pi e^-

Stability criteria based on cyclic π-electron delocalization. Anti-aromatic compounds are destabilized relative to open-chain analogs.

Examiner Tip: Cyclooctatetraene (8 π electrons) adopts a non-planar tub conformation to avoid anti-aromaticity, behaving as non-aromatic.

Frequently tested misconceptions in Hydrocarbons (Alkanes, Alkenes, Alkynes)

•Forgetting peroxide effect (Kharasch effect) applies ONLY to HBr, NOT to HCl or HI.
•Ozonolysis in reductive (Zn/H₂O) conditions gives aldehydes/ketones; oxidative (H₂O₂) gives carboxylic acids.