Organic Chemistry · CBSE XII · Visual Learning

Organic Chemistry
Concept Maps

Visual reaction pathways, mechanism step-cards, and memory shortcuts β€” built for students who find organic chemistry overwhelming.

πŸ”¬ Functional Groups β€” CBSE XII Quick Reference

The 11 functional groups you must recognise instantly. Each group has its own characteristic reactions β€” master these structures first.

πŸŒ€ Aromatic Foundation

Benzene Ring Foundation
KekulΓ© Delocalized
C₆H₆
Foundation of aromatic chemistry. All positions equivalent. EAS reactions preferred (not EAd).

Ch 10 β€” Haloalkanes & Haloarenes

Alkyl HalideCh 10
R X F, Cl, Br, I
R–X
X = F, Cl, Br, or I. Named haloalkane (aliphatic) or haloarene (aromatic).
Aryl HalideCh 10
X
Ar–X
Haloarenes are less reactive to nucleophilic substitution due to C–X bond resonance with ring.

Ch 11 β€” Alcohols, Phenols & Ethers

AlcoholCh 11
R O H
R–OH
–OH (hydroxyl) group. Primary, secondary, tertiary based on C bearing the OH.
PhenolCh 11
O H
Ar–OH
More acidic than alcohol (phenoxide ion stabilised by resonance with ring).
EtherCh 11
R O R'
R–O–R'
Ethers are relatively inert β€” good solvents. Cleavage occurs only with conc. HI or HBr.

Ch 12 β€” Aldehydes, Ketones & Carboxylic Acids

AldehydeCh 12
R C O H
R–CHO
Carbonyl carbon (C=O) at end of chain. Always has H on carbonyl C.
KetoneCh 12
R C R' O
R–CO–R'
Carbonyl C flanked by two carbons. Cannot be oxidised further without breaking C–C bonds.
Carboxylic AcidCh 12
R C O O H
R–COOH
Most acidic common organic group. Carboxylate anion (RCOO⁻) is resonance-stabilised.
EsterCh 12
R C O O R'
R–COO–R'
Formed from carboxylic acid + alcohol. Pleasant fruity smell. Hydrolysis gives back acid + alcohol.
AmideCh 12
R C O N H H
R–CONHβ‚‚
Weakest acid among carbonyl derivatives. C–N bond has partial double-bond character (resonance).

Ch 13 β€” Amines

Amine (Primary)Ch 13
R N H H
R–NHβ‚‚
Basic character due to lone pair on N. 1Β° > 2Β° > 3Β° basicity in gas phase, reversed in water.

πŸ—Ί Functional Group Reaction Roadmap

A visual map of organic conversions for CBSE XII. Hover/tap any group to highlight its connections. Color-coded arrows show reaction types.

Oxidation
Reduction
Substitution
Addition / Hydrolysis
Elimination
Condensation
Alkane C–H bonds only Xβ‚‚, hΞ½ Zn/HCl Alkyl Halide R–X aq. KOH PClβ‚…/SOClβ‚‚ Alcohol R–OH β˜… Central Hub PCC (1Β° alc.) NaBHβ‚„ Aldehyde R–CHO Kβ‚‚Crβ‚‚O₇ LiAlHβ‚„ Carboxylic Acid R–COOH Highest oxidation alc. KOH HX Alkene C=C Hβ‚‚O/H⁺ Hβ‚‚SOβ‚„ Kβ‚‚Crβ‚‚O₇ (2Β° alc.) NaBHβ‚„ Ketone R–CO–R' HCN Cyanohydrin R–CH(OH)–CN R'OH /H⁺ NaOH Ester R–COOR' KCN (SN2) Nitrile R–C≑N H₃O⁺ hydrolysis β†’ COOH Phenol Ar–OH aromatic analogue Primary Amine (1Β°) R–NHβ‚‚  or  Ar–NHβ‚‚ NH₃ (excess) amide β†’ Hoffmann NaNOβ‚‚/HCl (0–5Β°C, Ar only) Diazonium Salt Ar–N₂⁺ Cl⁻ Ξ²-naphthol Azo Dye Ar–N=N–Ar Sandmeyer Ar–Cl/Br CuCl/CuBr HBFβ‚„ Ar–F Balz-Sch. Hβ‚‚O, boil Ar–OH phenol ← REDUCTION Carbon Oxidation State OXIDATION β†’ C: βˆ’4 βˆ’2 βˆ’1 +1 +3 πŸ’‘ Memory Shortcuts β†’ PCC/CrO₃ stops at aldehyde from 1Β° alcohol; Kβ‚‚Crβ‚‚O₇ goes all the way to COOH β†’ NaBHβ‚„ reduces only C=O (aldehyde/ketone); LiAlHβ‚„ reduces everything (ester, amide, acid) β†’ SN2 prefers 1Β° halide (less bulky); SN1 prefers 3Β° (stable carbocation) β†’ Diazonium coupling ONLY for aromatic amines (Ar–NHβ‚‚), never aliphatic (R–NHβ‚‚)

βš—οΈ Carbonyl Chemistry Hub

The C=O group is the star of organic chemistry. Everything attacks the electrophilic carbon. Learn who attacks and what you get.

C=O (Carbonyl Group)

The carbon is electron-poor (Ξ΄+) β†’ nucleophiles attack it
CΞ΄+=OΞ΄βˆ’
Aldehyde (Rβˆ’CHO) is MORE reactive than Ketone (Rβˆ’COβˆ’R') because:
less steric hindrance + less electron donation to C=O
πŸ”‘ Key Principle
Nucleophilic Addition = nucleophile (Nu⁻) attacks the electrophilic C
β†’ Ο€ bond breaks β†’ O becomes O⁻ β†’ protonation β†’ product

Oxidation vs Reduction:
Aldehyde can be oxidised to COOH (Tollens, Fehling β€” positive for RCHO, NOT for Rβ‚‚CO)
Aldehyde & Ketone can both be reduced to alcohol (NaBHβ‚„)
πŸ”΅
Addition of HCN β†’ Cyanohydrin
Reagent: HCN (base catalyst)
Rβˆ’CHO + HCN β†’ Rβˆ’CH(OH)βˆ’CN
Mechanism: CN⁻ (nucleophile) attacks C of C=O β†’ tetrahedral intermediate (alkoxide) β†’ protonation by HCN β†’ cyanohydrin
πŸ’‘ Cyanohydrin contains CN group β†’ acid hydrolysis β†’ Ξ±-hydroxy acid (one more carbon than the starting aldehyde)
🟣
Grignard Reagent Addition
Reagent: R'MgX (dry ether)
HCHO β†’ 1Β° alcohol | RCHO β†’ 2Β° alcohol | Rβ‚‚CO β†’ 3Β° alcohol
RCHO + R'MgX β†’ Rβˆ’CH(OH)βˆ’R' (after H₃O⁺)
πŸ’‘ Grignard is a carbanion (R⁻ equivalent) β€” very strong nucleophile. Always write Mg in the formula. Product has one more carbon than starting carbonyl.
🟠
Aldol Condensation
Reagent: dilute NaOH (must have Ξ±-H)
Step 1: OH⁻ removes Ξ±-H β†’ enolate
Step 2: Enolate attacks C=O of another molecule
Step 3: Ξ²-hydroxy aldehyde (aldol product)
Step 4: Heat β†’ dehydration β†’ Ξ±,Ξ²-unsaturated carbonyl
2 CH₃CHO β†’ CH₃CH(OH)CHβ‚‚CHO β†’ CH₃CH=CHCHO
πŸ’‘ Memory trick: "Aldol = Alcohol + Aldehyde" β€” product has both groups initially
πŸ”΄
Cannizzaro Reaction
Reagent: conc. NaOH (no Ξ±-H!)
For aldehydes WITHOUT Ξ±-H (HCHO, PhCHO, CCl₃CHO)
One molecule is oxidised β†’ RCOO⁻ (acid)
Other is reduced β†’ RCHβ‚‚OH (alcohol)
2 HCHO + NaOH β†’ CH₃OH + HCOONa
πŸ’‘ Cannizzaro = disproportionation. Key word: "no Ξ±-H". Formaldehyde and benzaldehyde are classic examples.
πŸ”·
Reduction β€” Clemmensen vs Wolff-Kishner
C=O β†’ CHβ‚‚ (complete removal)
Clemmensen: Zn(Hg)/conc. HCl (acidic, acid-stable compound)
Wolff-Kishner: NHβ‚‚NHβ‚‚ then KOH/Ξ” (basic condition)
Rβˆ’COβˆ’R' β†’ Rβˆ’CHβ‚‚βˆ’R'
πŸ’‘ Use Clemmensen if product is acid-stable; use Wolff-Kishner if product is base-stable. Both remove the oxygen completely.
🟒
Reactions of Carboxylic Acid
RCOOH β†’ many derivatives
RCOOH + R'OH β†’ Ester (H⁺ catalyst, Fischer esterification)
RCOOH + SOClβ‚‚ β†’ RCOCl (acid chloride β€” most reactive derivative)
RCOOH + NH₃ β†’ RCONHβ‚‚ (amide β€” then Hoffmann β†’ amine)
RCOOH + LiAlHβ‚„ β†’ RCHβ‚‚OH (1Β° alcohol)
πŸ’‘ Reactivity of acid derivatives: RCOCl > RCOOH > RCONHβ‚‚. Acyl chloride reacts with everything!
🟑
Tollens vs Fehling Test
Distinguish aldehydes from ketones
Tollens (silver mirror test): RCHO + Ag(NH₃)₂⁺ β†’ RCOOH + Ag↓ (silver mirror)
Fehling: RCHO + Cu²⁺(blue) β†’ RCOOH + Cuβ‚‚O↓ (brick red ppt)
Ketones: NO reaction with either (no oxidation)
πŸ’‘ Exception: Fructose (a ketone) gives Fehling's positive because it isomerises to glucose in alkaline conditions
🩷
Acidity of Carboxylic Acids
RCOOH > phenol > alcohol
pKa: RCOOH (~4.8) < phenol (~10) < alcohol (~16)
–I group (Cl, NOβ‚‚) near COOH β†’ increases acidity (stabilises RCO₂⁻)
+I group (CH₃) β†’ decreases acidity
ClCHβ‚‚COOH > CH₃COOH > (CH₃)₃CCOOH
πŸ’‘ The closer the electron-withdrawing group to COOH, the stronger the acid. Cl at Ξ±-carbon has bigger effect than at Ξ³-carbon.

πŸ’Š Amine Web β€” Synthesis Routes & Properties

Amines are key in CBSE because of basicity questions (5 marks), Hoffmann degradation (5 marks), and diazonium salt reactions (5 marks). Learn these three clusters.

Primary Amine (1Β°) Rβˆ’NHβ‚‚ HOW TO MAKE AMINES Alkyl Halide + NH₃ Rβˆ’X + NH₃ β†’ Rβˆ’NHβ‚‚ SN2 Nitro Reduction Arβˆ’NOβ‚‚ + Fe/HCl β†’ Arβˆ’NHβ‚‚ reduction Hoffmann Degradation RCONHβ‚‚ + Brβ‚‚/NaOH β†’ RNHβ‚‚ (βˆ’1 carbon) Gabriel Synthesis Phthalimide β†’ 1Β° amine only pure 1Β° WHAT AMINES DO Acylation β†’ Amide Rβˆ’NHβ‚‚ + RCOCl β†’ RCONHR Diazotisation (ArNHβ‚‚ only) Arβˆ’NHβ‚‚ + NaNOβ‚‚/HCl, 0–5Β°C β†’ Arβˆ’N₂⁺Cl⁻ (diazonium salt) Carbylamine Test (1Β° amines) Rβˆ’NHβ‚‚ + CHCl₃/KOH β†’ Rβˆ’NC (isocyanide, foul smell) 2Β° Amine β†’ N-nitrosoamine Rβ‚‚NH + HNOβ‚‚ β†’ Rβ‚‚Nβˆ’N=O πŸ”₯ Diazonium Salt Reactions (Most Important for Exam) ArN₂⁺Cl⁻ β†’ Arβˆ’Cl (Sandmeyer: CuCl) | Arβˆ’Br (Sandmeyer: CuBr) | Arβˆ’CN (CuCN) | Arβˆ’F (Balz-Schiemann: HBFβ‚„) ArN₂⁺Cl⁻ β†’ Arβˆ’OH (Hβ‚‚O, warm) | Arβˆ’H (H₃POβ‚‚/Hypophosphorous acid: deamination) ArN₂⁺Cl⁻ β†’ Azo dye (coupling with phenol / Ξ²-naphthol in alkaline medium β†’ Arβˆ’N=Nβˆ’Ar', coloured) πŸ’‘ Sandmeyer = Cu salt needed; Gattermann = Cu powder instead. Always learn: which Cu compound for which product.

Basicity Order Reference

CompoundTypepKbWhy
(CH₃)β‚‚NH2Β° aliphatic3.27Best +I effect + best solvation of conjugate acid in water
CH₃NHβ‚‚1Β° aliphatic3.38+I effect from one methyl group
(CH₃)₃N3Β° aliphatic4.22Steric hindrance prevents good solvation of (CH₃)₃NH⁺
NH₃–4.74No +I substituents
C₆Hβ‚…NHβ‚‚ (aniline)1Β° aromatic9.40Lone pair delocalised into benzene ring β†’ unavailable to donate to H⁺
4-NOβ‚‚βˆ’C₆Hβ‚„βˆ’NHβ‚‚1Β° aromatic13.0–NOβ‚‚ withdraws electrons further β†’ even less basic
Exam trick for gas phase vs aqueous: In gas phase, order is (CH₃)₃N > (CH₃)β‚‚NH > CH₃NHβ‚‚ (purely inductive). In aqueous, (CH₃)β‚‚NH wins because trimethylammonium ion ((CH₃)₃NH⁺) is bulky and poorly solvated. CBSE usually asks aqueous basicity β€” answer is 2Β° > 1Β° > 3Β°.

πŸ”¬ Reaction Mechanisms β€” Step by Step

For full marks, draw curly arrows and name each intermediate. These 4 mechanisms cover ~20 marks in CBSE exam.

SN1 vs SN2 β€” Nucleophilic Substitution
5 marks

SN1 (Unimolecular)

  • Rate = k[Rβˆ’X] only
  • 2-step: ionisation β†’ Nu attack
  • Carbocation intermediate
  • 3Β° substrate preferred (stable C⁺)
  • Racemisation of product
  • Polar protic solvent (Hβ‚‚O, ROH)
  • Weak nucleophile (Hβ‚‚O)

SN2 (Bimolecular)

  • Rate = k[Rβˆ’X][Nu⁻]
  • 1-step: concerted backside attack
  • No intermediate (transition state only)
  • 1Β° substrate preferred (less steric)
  • Walden inversion (R β†’ S or vice versa)
  • Polar aprotic solvent (DMSO, acetone)
  • Strong nucleophile (CN⁻, OH⁻)
SN1: R₃Cβˆ’X β†’ [R₃C⁺] + X⁻ β†’ R₃Cβˆ’Nu Step 1: slow (rate-determining) | Step 2: fast Nu⁻ attacks flat carbocation from BOTH sides β†’ racemic mixture (50:50) SN2: Nu⁻ + Rβˆ’X β†’ [NuΒ·Β·Β·CΒ·Β·Β·X]‑ β†’ Nuβˆ’R + X⁻ One concerted step. Nu attacks from BACK β†’ configuration inverts (like umbrella flipping)
Aldol Condensation β€” Complete Mechanism
5 marks
1
Deprotonation of Ξ±-carbon: OH⁻ removes the Ξ±-H (H on carbon next to C=O) β†’ forms enolate ion (carbanion)
CH₃CHO + OH⁻ β†’ ⁻CHβ‚‚CHO + Hβ‚‚O
2
Nucleophilic attack: Enolate carbon attacks the electrophilic C=O of the second aldehyde molecule
⁻CHβ‚‚CHO + CH₃CHO β†’ [CH₃CH(O⁻)CHβ‚‚CHO]
3
Protonation β†’ Aldol product: The alkoxide O⁻ picks up H⁺ from water β†’ Ξ²-hydroxy aldehyde
β†’ CHβ‚ƒβˆ’CH(OH)βˆ’CHβ‚‚βˆ’CHO (3-hydroxybutanal)
4
Dehydration (on heating) β†’ Condensation product: Loss of Hβ‚‚O from Ξ²-hydroxy group β†’ Ξ±,Ξ²-unsaturated carbonyl
CHβ‚ƒβˆ’CH(OH)βˆ’CHβ‚‚βˆ’CHO β†’ CHβ‚ƒβˆ’CH=CHβˆ’CHO + Hβ‚‚O (but-2-enal)
Key terms: Aldol product = Ξ²-hydroxy aldehyde (step 3 product, cold). Aldol condensation product = Ξ±,Ξ²-unsaturated carbonyl (step 4, on heating).
Condition for aldol: Compound MUST have Ξ±-H. Formaldehyde (HCHO) has no Ξ±-H β†’ Cannizzaro instead.
Hoffmann Bromamide Degradation β€” 4-Step Mechanism
5 marks
1
N-Bromination: Brβ‚‚ + NaOH β†’ NaOBr. NaOBr brominates the nitrogen of the amide
RCONHβ‚‚ + Brβ‚‚/NaOH β†’ RCONHBr (N-bromoamide)
2
Deprotonation: NaOH removes Nβˆ’H β†’ forms anion (RCON⁻Br)
RCONHBr + NaOH β†’ RCON⁻Br + Hβ‚‚O
3
Isocyanate formation: Br⁻ leaves β†’ nitrogen migrates with its lone pair β†’ Rβˆ’N=C=O (isocyanate, KEY intermediate!)
RCON⁻Br β†’ Rβˆ’N=C=O + Br⁻
This is why the product has ONE LESS CARBON β€” the C=O of isocyanate is lost next
4
Hydrolysis of isocyanate: Hβ‚‚O attacks β†’ carbamic acid β†’ decarboxylation β†’ primary amine
Rβˆ’N=C=O + Hβ‚‚O β†’ Rβˆ’NHβˆ’COOH β†’ Rβˆ’NHβ‚‚ + COβ‚‚
Memory: "Hoffmann = one less carbon". RCONHβ‚‚ (n carbons) β†’ RNHβ‚‚ (nβˆ’1 carbons).
Example: Ethanamide (CH₃CONHβ‚‚) β†’ Methylamine (CH₃NHβ‚‚)
Nucleophilic Addition to C=O β€” General Mechanism
3–5 marks
1
Polarisation of C=O: Oxygen is more electronegative β†’ C is Ξ΄+ (electrophilic)
CΞ΄+= OΞ΄βˆ’ ←→ ⁺Cβˆ’O⁻ (resonance)
2
Nucleophile attacks C: Nu⁻ donates electron pair to C β†’ Ο€ bond breaks β†’ O becomes O⁻ (alkoxide)
Nu⁻ + Rβˆ’CHO β†’ Rβˆ’CH(Nu)βˆ’O⁻ (tetrahedral intermediate)
3
Protonation: O⁻ picks up H⁺ (from solvent or acid) β†’ final product
Rβˆ’CH(Nu)βˆ’O⁻ + H⁺ β†’ Rβˆ’CH(Nu)βˆ’OH
Nu⁻ = CN⁻ β†’ Cyanohydrin
Rβˆ’CH(OH)βˆ’CN β†’ hydrolyse β†’ Ξ±-hydroxy acid
Nu⁻ = RMgX β†’ Grignard
β†’ 1Β°, 2Β° or 3Β° alcohol depending on carbonyl type
Nu = NHβ‚‚OH β†’ Oxime
Rβ‚‚C=O + Hβ‚‚NOH β†’ Rβ‚‚C=Nβˆ’OH + Hβ‚‚O
Nu = RNHβ‚‚ β†’ Imine (Schiff base)
Rβˆ’CHO + R'NHβ‚‚ β†’ Rβˆ’CH=Nβˆ’R' + Hβ‚‚O

🌿 Biomolecules β€” Visual Quick Maps

7 marks from biomolecules. Focus on: types + linkages + bonds + function. Don't memorise structures β€” memorise the logic.

🍬 Carbohydrates
MonosaccharidesGlucose, Fructose, Galactose β€” cannot be hydrolysed further
DisaccharidesSucrose (Glu+Fru), Maltose (Glu+Glu), Lactose (Glu+Gal)
PolysaccharidesStarch, Cellulose, Glycogen
Starch linkageΞ±-1,4 (amylose straight) + Ξ±-1,6 (amylopectin branched)
Cellulose linkageΞ²-1,4 β€” linear, indigestible. Structural role in plants
Reducing sugarHas free βˆ’CHO or open-chain keto: Glucose, Fructose, Maltose, Lactose
Non-reducingSucrose β€” both anomeric carbons used in glycosidic bond
πŸ’‘ Test: reducing sugars give Tollens/Fehling positive. Sucrose does NOT β€” it has no free βˆ’CHO or βˆ’OH at C1.
🧬 Proteins
MonomerAmino acids (Hβ‚‚Nβˆ’CHRβˆ’COOH) β€” 20 types, linked by peptide bonds (βˆ’COβˆ’NHβˆ’)
1Β° StructureSequence of amino acids. Bond: peptide (covalent). Determined by DNA.
2Β° StructureΞ±-helix or Ξ²-pleated sheet. Bond: H-bonds (between C=O and N-H of chain)
3Β° Structure3D folding. Bonds: disulphide (–S–S–), H-bonds, hydrophobic, ionic
4Β° StructureMultiple subunits. E.g., Haemoglobin (2Ξ± + 2Ξ²). Non-covalent forces.
DenaturationDisrupts 2Β°, 3Β°, 4Β° (NOT 1Β°). Heat, acid, organic solvents. Loses activity.
πŸ’‘ Memory: "1234 = primary(peptide), secondary(H-bond), tertiary(disulphide), quaternary(subunits)"
πŸ§ͺ Nucleic Acids
MonomerNucleotide = nitrogenous base + pentose sugar + phosphate group
DNA sugarsDeoxyribose (2β€²-H); RNA: Ribose (2β€²-OH)
DNA basesAdenine (A), Guanine (G), Cytosine (C), Thymine (T)
RNA basesA, G, C, Uracil (U) β€” no thymine
Watson-CrickA=T (2 H-bonds), G≑C (3 H-bonds). Anti-parallel strands.
DNA vs RNADNA: double-stranded, T instead of U, deoxyribose. RNA: single-stranded, ribose
πŸ’‘ "AT 2, GC 3" β€” A pairs with T (2 bonds), G pairs with C (3 bonds). More GC = stronger/harder to denature DNA.
πŸ”‘ Enzymes & Vitamins
Enzyme natureProteins (globular). Act as biological catalysts β€” specific to one reaction.
Active sitePocket on enzyme where substrate binds. Complementary shape to substrate.
Lock & KeyRigid active site matches substrate exactly (like lock and key)
Induced FitActive site changes shape slightly to embrace substrate β€” more accurate model
Fat-solubleVitamins A, D, E, K β€” stored in fatty tissues
Water-solubleVitamins B-complex, C β€” not stored, need regular intake
πŸ’‘ "Fat-soluble ADEK, water-soluble B&C" β€” common exam question about deficiency diseases links to which vitamin.

Key Distinctions Examiners Love to Ask

Question PatternAnswer
Starch vs CelluloseStarch: Ξ±-1,4 glycosidic bonds, energy storage, digestible. Cellulose: Ξ²-1,4, structural, not digestible by humans
DNA vs RNADNA: double-stranded, deoxyribose, thymine; RNA: single-stranded, ribose, uracil
Why sucrose is non-reducingBoth C-1 of glucose and C-2 of fructose are involved in glycosidic bond β†’ no free βˆ’CHO or free anomeric βˆ’OH
What is mutarotation?Change in optical rotation when Ξ± or Ξ²-D-glucose dissolves in water β†’ equilibrium mixture via open-chain form
What happens in denaturation?2Β°/3Β°/4Β° structure disrupted, NOT primary. Loses biological activity. Boiling egg white is classic example.
Essential amino acidsCannot be synthesised by body, must come from diet. 10 out of 20 amino acids are essential.

πŸ“ Key Diagrams β€” Must-Know Visuals

6 high-yield visual concepts that unlock marks across Haloalkanes, Stereochemistry, and Mechanism questions.

SN2 β€” Nucleophilic Substitution Mechanism Haloalkanes β€’ 5 marks
BEFORE TRANSITION STATE ‑ AFTER (Inverted) Nu⁻ C X R₁ Rβ‚‚ R₃ Nu⁻ attacks from BACK (180Β° to X) Nu C X ‑ R₁ Rβ‚‚ R₃ C is spΒ²-like (flat). Partial bonds shown as dashed. Nu C X⁻ R₁ Rβ‚‚ R₃ Walden Inversion β€” like umbrella turning inside-out

πŸ’‘ SN2 only happens with 1Β° substrates (unhindered). 3Β° substrates prefer SN1 instead. Backside attack = inversion of configuration = R becomes S or vice versa.

Carbocation Stability Order SN1 β€’ E1 β€’ 5 marks
C⁺ H H H CH₃⁺ Methyl Least Stable C⁺ H H R RCH₂⁺ 1Β° Primary C⁺ H R R Rβ‚‚CH⁺ 2Β° Secondary C⁺ R R R R₃C⁺ 3Β° β€” MOST STABLE INCREASING STABILITY β†’

πŸ’‘ More alkyl groups = more hyperconjugation + +I inductive effect β†’ disperses positive charge. Benzyl (C₆H₅–CH₂⁺) and allyl (CHβ‚‚=CH–CH₂⁺) are also highly stable due to resonance.

Inductive Effect β€” Electron Push & Pull Acidity β€’ Reactivity
βˆ’I Effect (Electron Withdrawal) F CHβ‚‚ COOH Ξ΄βˆ’ Ξ΄+ Ξ΄+ βˆ’I Groups: –F, –Cl, –NOβ‚‚, –CN, –COOH ↑ Increases acidity of COOH group F–CH₂–COOH (fluoroacetic acid) +I Effect (Electron Donation) CH₃ CHβ‚‚ COOH Ξ΄+ Ξ΄βˆ’ +I Groups: –CH₃, –Cβ‚‚Hβ‚…, –alkyl ↓ Decreases acidity of COOH group CH₃–CH₂–COOH (propanoic acid)

πŸ’‘ The -I effect of halogens explains: FCHβ‚‚COOH > ClCHβ‚‚COOH > BrCHβ‚‚COOH > CH₃COOH (acidity order). More electronegative = stronger -I = more acidic.

Benzene Ring β€” Ortho / Meta / Para EAS β€’ Boards favourite
1 (substituent) 1 2 2 β€” ortho 6 6 β€” ortho 3 3 β€” meta 5 5 β€” meta 4 4 β€” para KekulΓ© structure 1 1 2 3 4 5 6 Delocalized structure (more accurate) ortho=1,2 | meta=1,3 | para=1,4

πŸ’‘ In EAS: –OH, –NHβ‚‚, –CH₃ are ortho/para directors. –NOβ‚‚, –COOH, –CHO are meta directors. Board questions often ask to predict position of substitution.

Aldol Condensation β€” Complete Mechanism Carbonyl β€’ 5 marks
1 Ξ±-H Removal CH₃–CHO + OH⁻ ⁻CHβ‚‚CHO (enolate) OH⁻ removes Ξ±-H β†’ carbanion (enolate) Base removes Ξ±-hydrogen adjacent to C=O 2 Nucleophilic Attack ⁻CHβ‚‚CHO attacks C=O alkoxide intermediate ⁻CHβ‚‚CHO + CH₃CHO Enolate is the nucleophile C–C bond forms here 3 Aldol Product Ξ²-hydroxyaldehyde formed: CH₃–CH(OH)–CH₂–CHO β˜… This is the ALDOL product –OH on Ξ²-carbon 3-hydroxybutanal No heat needed for this step 4 Dehydration –Hβ‚‚O (on heating): CH₃–CH=CH–CHO + Hβ‚‚O crotonaldehyde Ξ±,Ξ²-unsaturated aldehyde Ξ” (heat) drives water loss conjugated C=C–C=O system more stable (extended Ο€)

πŸ’‘ Aldol needs Ξ±-H (HCHO and (CH₃)₃CCHO have no Ξ±-H β†’ Cannizzaro instead). Heating drives dehydration. Crossed aldol = mix of two different aldehydes (less useful, not asked in CBSE boards usually).

Hybridisation β€” Shapes & Bond Angles Bonding β€’ Geometry
spΒ³ C H H H H 109.5Β° CHβ‚„ (methane) TETRAHEDRAL spΒ² C H H C Ο€ 120Β° CHβ‚‚=CHβ‚‚, C=O TRIGONAL PLANAR sp H C C H 180Β° CH≑CH (ethyne), COβ‚‚ 2 sp + 2 unhybridised p orbitals LINEAR

πŸ’‘ Carbocation (R₃C⁺) is spΒ² hybridised β€” it's flat/planar (that's why Nu can attack from both sides β†’ racemisation in SN1). In SN2 the transition state is also spΒ²-like.