Class 11 : Chemistry (In English) – Chapter 8: Organic Chemistry-some basic principles and techniques

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On June 21, 2025

EXPLANATION & SUMMARY

🔵 Introduction
Organic Chemistry 🧪 is the chemistry of carbon compounds (excluding simple oxides like CO, CO₂, carbonates, etc.). Carbon, due to its tetravalency (4 bonds) and catenation (ability to form chains), creates an enormous variety of compounds 🌍 — fuels, plastics, medicines, DNA, proteins. To study this vast field systematically, we need fundamental rules, nomenclature, classification, electronic effects, and techniques.
This chapter lays down the basic language of Organic Chemistry 📝.

🟢 General Characteristics of Organic Compounds
Carbon is tetravalent (forms 4 bonds).
Shows catenation: ability to form long chains, rings, branches.
Bonds are strong covalent bonds.
Variety in hybridization → sp³ (alkanes), sp² (alkenes), sp (alkynes).
Exhibits isomerism (same formula, different structure).

🔵 Classification of Organic Compounds
1️⃣ Open Chain Compounds (Acyclic)
Straight or branched chains.
Example: CH₃–CH₂–CH₃ (propane).
2️⃣ Closed Chain Compounds (Cyclic)
Ring structures:
Alicyclic (cycloalkanes, e.g., cyclohexane).
Aromatic (benzene, C₆H₆).
3️⃣ Based on Functional Group
Alcohols (–OH), Aldehydes (–CHO), Ketones (–CO–), Carboxylic acids (–COOH), Amines (–NH₂), etc.
4️⃣ Based on Saturation
Saturated: single bonds only (alkanes).
Unsaturated: double/triple bonds (alkenes/alkynes).

🟡 Nomenclature of Organic Compounds
IUPAC rules provide systematic names 🌍.
✔ Steps for IUPAC Naming:
Select longest carbon chain → parent name.
Number the chain → lowest locants for substituents.
Identify and name substituents.
Place substituents alphabetically with positions.
Add suffix for functional group.
Examples:
CH₃–CH₂–CH₃ → Propane.
CH₂=CH–CH₃ → Prop-1-ene.
CH₃–CH(OH)–CH₃ → Propan-2-ol.
💡 Functional Group Priority Order: Carboxylic acid > Aldehyde > Ketone > Alcohol > Alkene > Alkyne > Alkane.

🔴 Isomerism
Compounds with same molecular formula but different arrangements.
Structural Isomerism
Chain (butane vs isobutane).
Position (but-1-ene vs but-2-ene).
Functional group (alcohol vs ether).
Metamerism (ethers, ketones with different alkyl groups).
Tautomerism (keto–enol equilibrium).
Stereoisomerism
Geometrical (cis–trans in alkenes).
Optical (chiral carbon with 4 different groups → enantiomers).

🟢 Electronic Displacements in Covalent Bonds
These effects explain reactivity of organic molecules ⚡.
1️⃣ Inductive Effect (I-effect)
Electron displacement along sigma bond due to electronegativity differences.
–I groups (–NO₂, –Cl) withdraw electrons.
+I groups (–CH₃, –C₂H₅) release electrons.
Influences acidity/basicity.
2️⃣ Electromeric Effect (E-effect)
Temporary electron shift in double bond when attacking reagent approaches.
3️⃣ Resonance Effect
Delocalization of electrons represented by resonance structures.
Example: Benzene (delocalized π electrons → stability).
4️⃣ Hyperconjugation
Delocalization of σ-electrons of C–H bond adjacent to double bond or carbocation.
“No bond resonance.”
Explains stability of carbocations, alkenes.

🔵 Types of Organic Reactions
1️⃣ Substitution → one atom/group replaced.
Example: CH₄ + Cl₂ → CH₃Cl + HCl.
2️⃣ Addition → molecules add across double/triple bonds.
Example: CH₂=CH₂ + H₂ → CH₃–CH₃.
3️⃣ Elimination → atoms/groups removed forming double/triple bonds.
Example: CH₃–CH₂–Br → CH₂=CH₂ + HBr.
4️⃣ Rearrangement → atoms/groups rearrange within molecule.
Example: Pinacol–Pinacolone rearrangement.

🟡 Reaction Intermediates
Organic reactions often proceed through unstable intermediates:
Carbocations (C⁺): positively charged carbon.
Carbanions (C⁻): negatively charged carbon.
Free radicals (C•): carbon with unpaired electron.
Carbenes: neutral, divalent carbon species.
Stability order:
Carbocation: 3° > 2° > 1° > CH₃⁺ (due to +I and hyperconjugation).
Carbanion: CH₃⁻ > 1° > 2° > 3° (due to destabilizing +I).
Free radical: 3° > 2° > 1° > CH₃•.

🔴 Purification of Organic Compounds
Since organic compounds are often obtained with impurities, purification techniques are essential.
1️⃣ Crystallization → purification based on solubility differences.
2️⃣ Sublimation → separation of sublimable solids (camphor, iodine).
3️⃣ Distillation
Simple distillation (different b.p.).
Fractional distillation (close b.p.).
Steam distillation (volatile compounds).
Distillation under reduced pressure (high b.p. compounds).
4️⃣ Chromatography → separation based on adsorption/partition.
5️⃣ Differential Extraction → organic vs aqueous layer separation.

🟢 Detection of Elements in Organic Compounds
Lassaigne’s Test: Fusion with sodium → extract tested for elements.
Nitrogen: NaCN formed → Prussian blue with Fe²⁺/Fe³⁺.
Sulphur: Na₂S → black ppt with Pb²⁺.
Halogens: NaX → white ppt with AgNO₃.

🔵 Quantitative Analysis
Carbon & Hydrogen → CO₂, H₂O produced, measured.
Nitrogen → Kjeldahl’s method.
Halogens → Carius method (AgX formed).
Sulphur & Phosphorus → converted to sulphate/phosphate, weighed.

🟡 Empirical and Molecular Formula
Empirical formula → simplest whole-number ratio.
Molecular formula = (Empirical formula) × n
n = Molar mass / Empirical formula mass.
Example: Acetic acid → Empirical = CH₂O, Molecular = C₂H₄O₂.

🔴 Significance of the Chapter
Provides foundation for naming and classifying compounds.
Explains stability and reactivity (inductive, resonance, hyperconjugation).
Introduces types of reactions and intermediates.
Essential purification and detection techniques.
Lays base for advanced organic topics (hydrocarbons, functional groups, biomolecules).

✨ Conclusion
Organic chemistry is vast but logical 🌍. This chapter equips us with the grammar of organic language — how to name, classify, analyze, and understand carbon compounds. It provides the stepping stone to the whole world of medicines, fuels, plastics, and biomolecules.

📌 Organic Chemistry – Some Basic Principles and Techniques
🔵 General Features
Carbon shows tetravalency and catenation.
Variety of compounds due to hybridization, functional groups.
🟢 Classification
Open chain, closed chain (alicyclic, aromatic).
Based on saturation: alkanes, alkenes, alkynes.
Based on functional groups: alcohols, aldehydes, acids, amines.
🔴 Nomenclature (IUPAC)
Longest chain, numbering, substituents, functional group priority.
Examples: propan-1-ol, but-2-ene.
🟡 Isomerism
Structural: chain, position, functional.
Stereoisomerism: geometrical, optical.
💡 Electronic Effects
Inductive effect (–I, +I).
Electromeric effect.
Resonance (delocalization).
Hyperconjugation (no-bond resonance).
📚 Reactions
Substitution, addition, elimination, rearrangement.
Intermediates: carbocations, carbanions, free radicals, carbenes.
🌟 Purification Techniques
Crystallization, sublimation, distillation, chromatography, extraction.
🧪 Elemental Analysis
Lassaigne’s Test for N, S, X.
Quantitative: C, H (CO₂/H₂O measurement), N (Kjeldahl), halogens (Carius).
📍 Formulas
Empirical vs molecular formula.
Relation: n = Molar mass / Empirical mass.
✨ Importance
Basis for studying all organic reactions.
Explains structure, reactivity, and analysis.
Provides lab techniques essential for chemistry.

📝 Quick Recap:
✔ Organic chemistry studies carbon compounds (except CO, CO₂, etc.).
✔ Compounds classified into open/closed chain, saturated/unsaturated, functional group-based.
✔ IUPAC rules → systematic naming of molecules.
✔ Isomerism (structural, stereoisomerism) gives diversity.
✔ Electronic effects (inductive, resonance, hyperconjugation) explain reactivity.
✔ Organic reactions: substitution, addition, elimination, rearrangement.
✔ Intermediates: carbocations, carbanions, radicals, carbenes.
✔ Purification techniques: crystallization, distillation, chromatography.
✔ Elemental detection (Lassaigne’s test) and quantitative analysis provide formulas.
✔ Foundation chapter for all organic chemistry.

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QUESTIONS FROM TEXTBOOK

🔵 Q8.1
What are hybridisation states of each carbon atom in the following compounds?
CH₂=C=O, CH₃CH=CH₂, CH₃COCH₃, CH₂=CHCN, C₆H₆
🟢 Answer
Let’s examine each carbon atom:
(i) CH₂=C=O
First C (CH₂): sp² (forms 3 σ bonds: 2 with H, 1 with next C)
Second C (=O): sp (forms 2 σ bonds: 1 with first C, 1 with O)
O: sp (not asked)
(ii) CH₃–CH=CH₂
C₁ (CH₃): sp³
C₂ (CH=): sp²
C₃ (=CH₂): sp²
(iii) CH₃–CO–CH₃
Terminal CH₃ carbons: sp³
Central carbonyl C: sp²
(iv) CH₂=CH–CN
C₁ (CH₂): sp²
C₂ (CH=): sp²
C₃ (–CN): sp (triple bond)
(v) C₆H₆ (Benzene)
Each carbon: sp² hybridised
Planar hexagonal structure with delocalised π electrons
✔ Final:
Compound Hybridisation of Carbons
CH₂=C=O sp², sp
CH₃CH=CH₂ sp³, sp², sp²
CH₃COCH₃ sp³, sp², sp³
CH₂=CHCN sp², sp², sp
C₆H₆ all sp²

🔵 Q8.2
Indicate the σ and π bonds in the following molecules:
C₂H₆, C₃H₈, CH₂=CH₂, CH≡CH, CH₂=CHCN, CH₃NO₂, HCONH₂
🟢 Answer
👉 Rule:
Single bond = 1 σ
Double bond = 1 σ + 1 π
Triple bond = 1 σ + 2 π
Now count bonds:
(i) C₂H₆
All single → 7 σ, 0 π
(ii) C₃H₈
All single → 10 σ, 0 π
(iii) CH₂=CH₂
1 C=C double = 1 σ + 1 π
4 C–H = 4 σ
→ Total: 5 σ + 1 π
(iv) CH≡CH
1 C≡C triple = 1 σ + 2 π
2 C–H = 2 σ
→ 3 σ + 2 π
(v) CH₂=CH–CN
C=C double = 1 σ + 1 π
C–C single = 1 σ
C≡N triple = 1 σ + 2 π
C–H = 3 σ
→ Total = 6 σ + 3 π
(vi) CH₃NO₂
3 C–H = 3 σ
1 C–N = 1 σ
2 N–O = 1 σ + 1 σ
1 π (delocalised between N=O bonds)
→ 6 σ + 1 π
(vii) HCONH₂
C=O → 1 σ + 1 π
C–N, C–H, N–H all single
→ 7 σ + 1 π

🔵 Q8.3
Write bond line formulas for the following:
Isopropyl alcohol, 2,3-Dimethylbutanal, Heptan-4-one
🟢 Answer
💠 (i) Isopropyl alcohol (C₃H₈O):
Bond-line:
OH
|
CH3–CH–CH3
💠 (ii) 2,3-Dimethylbutanal (C₆H₁₂O):
CH3
|
CH3–CH–CH–CH=O
|
CH3
💠 (iii) Heptan-4-one (C₇H₁₄O):
CH3–CH2–CO–CH2–CH2–CH2–CH3

🔵 Q8.4
Give IUPAC names of the following compounds:
(a)
CH3
|
CH3–CH–CH2–CH3
(b)
CH3–CH2–CH2–CN
(c)
CH3–CH(Br)–CH2–CH3
(d)
CH3–CH(Cl)–CH2–CH(Br)–CH3
(e)
CH3–CH=CH–CH2–CH3
(f)
ClCH2–CH(OH)–CH3
🟢 Answer
(a) 2-Methylbutane
(b) Butanenitrile
(c) 2-Bromobutane
(d) 2-Chloro-4-bromopentane
(e) Pent-2-ene
(f) 3-Chloro-2-propanol

🔵 Q8.5
Which of the following represents correct IUPAC name?
(a) 2,2-Dimethylpentane or 2-Dimethylpentane
(b) 2,4,7-Trimethyloctane or 2,5,7-Trimethyloctane
(c) 2-Chloro-4-methylpentane or 4-Chloro-2-methylpentane
(d) But-3-yn-1-ol or But-4-ol-1-yne
🟢 Answer
✅ Correct IUPAC:
(a) 2,2-Dimethylpentane (lowest locants)
(b) 2,4,7-Trimethyloctane (sum of locants lowest)
(c) 2-Chloro-4-methylpentane (alphabetical order + low locants)
(d) But-3-yn-1-ol (OH gets priority, lowest number)

🔵 Q8.6
Draw formulas for first five members of homologous series:
(a) Carboxylic acids (R–COOH)
(b) Ketones (R–CO–R’)
(c) Alkenes (CₙH₂ₙ)
🟢 Answer
(a) Carboxylic acids:
HCOOH (Methanoic)
CH₃COOH (Ethanoic)
C₂H₅COOH (Propanoic)
C₃H₇COOH (Butanoic)
C₄H₉COOH (Pentanoic)
(b) Ketones:
(Not exist for 1C, 2C)
3C: CH₃COCH₃ (propanone)
4C: CH₃COC₂H₅ (butan-2-one)
5C: CH₃COC₃H₇ (pentan-2-one)
6C: C₂H₅COC₂H₅ (hexan-3-one)
(c) Alkenes:
C₂H₄ (Ethene)
C₃H₆ (Propene)
C₄H₈ (Butene)
C₅H₁₀ (Pentene)
C₆H₁₂ (Hexene)

🔵 Q8.7
Give condensed and bond line structural formulas and identify functional groups (if any) for:
(a) 2,2,4-Trimethylpentane
(b) 2-Hydroxy-1,2,3-propane tricarboxylic acid
(c) Hexanedial
🟢 Answer
(a) 2,2,4-Trimethylpentane (Iso-octane)
Condensed: CH₃–C(CH₃)₂–CH(CH₃)–CH₂–CH₃
Functional group: Alkane
(b) 2-Hydroxy-1,2,3-propane tricarboxylic acid (Citric acid)
Condensed: HOOC–CH₂–C(OH)(COOH)–CH₂–COOH
Functional groups: –COOH and –OH
(c) Hexanedial
Condensed: OHC–(CH₂)₄–CHO
Functional group: –CHO (aldehyde ×2)

🔵 Question 8.8:
Identify the functional groups in the following compounds:
(a) ![Compound 1](CHO, OH, OMe on benzene)
(b) ![Compound 2](NH₂ and OCH₂CH₂N(C₂H₅)₂)
(c)
🟢 Answer:
✔ (a) Functional groups:
–CHO (Aldehyde)
–OH (Hydroxyl / Alcohol)
–OCH₃ (Methoxy / Ether)
✔ (b) Functional groups:
–NH₂ (Amino group)
–OCH₂CH₂N(C₂H₅)₂ (Ether and tertiary amine group)
✔ (c) Functional groups:
–CH=CH– (Alkene)
–NO₂ (Nitro group)
🧠 Hence, each compound contains multiple functional groups responsible for its reactivity.

🔵 Question 8.9:
Which of the two is expected to be more stable and why?
(i) O⁻CH₂CH₂O⁻
(ii) CH₃CH₂O⁻
🟢 Answer:
✔ Compound (i) O⁻CH₂CH₂O⁻ is less stable because of negative–negative charge repulsion between two adjacent oxyanions.
✔ Compound (ii) CH₃CH₂O⁻ is more stable as it has only one negative charge, and the –CH₃ group donates electrons slightly by +I effect, dispersing the charge.
💡 Conclusion: CH₃CH₂O⁻ is more stable due to less repulsion and charge delocalisation.

🔵 Question 8.10:
Explain why alkyl groups act as electron donors when attached to a π system.
🟢 Answer:
✔ Alkyl groups show +I effect (inductive effect), pushing electron density through σ-bonds.
✔ When attached to a π-system (like a benzene ring), this extra electron density is delocalised into the ring, stabilising positive charge.
✔ Hence, alkyl groups act as electron donors by inductive effect and sometimes hyperconjugation.
💡 Example: In toluene, –CH₃ donates electrons into benzene ring, activating it toward electrophilic substitution.

🔵 Question 8.11:
Draw the resonance structures for the following compounds. Show electron shift using curved-arrow notation.
(a) C₆H₅OH
(b) C₆H₅NO₂
(c) CH₂=CH–CHO
(d) C₆H₅–CHO
(e) C₆H₅–CH=CH₂
🟢 Answer:
✔ (a) Phenol (C₆H₅OH):
– Lone pair on oxygen delocalises into ring → ortho/para resonance forms with negative charge on ring atoms.
✔ (b) Nitrobenzene (C₆H₅NO₂):
– Electrons of ring delocalise toward –NO₂ group (electron-withdrawing) → decreased electron density on ring (especially ortho/para).
✔ (c) Acrolein (CH₂=CH–CHO):
– π-electrons shift toward oxygen → resonance form CH₂–CH=CH–O⁻ ↔ CH₂=CH–CH=O⁺.
✔ (d) Benzaldehyde (C₆H₅–CHO):
– π-bond of –CHO interacts with aromatic ring; resonance reduces charge on carbon.
✔ (e) Styrene (C₆H₅–CH=CH₂):
– π-electrons conjugate with aromatic ring → resonance stabilisation across ring and double bond.
💡 Resonance = delocalisation of π-electrons → stabilisation of molecule.

🔵 Question 8.12:
What are electrophiles and nucleophiles? Explain with examples.
🟢 Answer:
✔ Electrophiles:
→ Electron-deficient species, seek electrons.
→ Act as Lewis acids.
🧪 Examples: H⁺, NO₂⁺, BF₃, AlCl₃.
✔ Nucleophiles:
→ Electron-rich species, donate electrons.
→ Act as Lewis bases.
🧪 Examples: OH⁻, CN⁻, NH₃, H₂O.
💡 In a reaction, nucleophile attacks electrophilic centre.

🔵 Question 8.13:
Identify reagents in bold as nucleophiles or electrophiles:
(a) CH₃COOH + HO⁻ → CH₃COO⁻ + H₂O
(b) CH₃CH=CH₂ + H⁺ → CH₃CH⁺–CH₃
(c) C₆H₆ + CH₃⁺ → C₆H₆CH₃
(d) CH₃Cl + :OH⁻ → CH₃OH + Cl⁻
🟢 Answer:
✔ (a) HO⁻ → Nucleophile (donates electron pair).
✔ (b) H⁺ → Electrophile (accepts electrons).
✔ (c) CH₃⁺ → Electrophile (positively charged carbocation).
✔ (d) :OH⁻ → Nucleophile (attacks carbon).

🔵 Question 8.14:
Classify the following reactions as per type:
(a) CH₃CH₂Br + HS⁻ → CH₃CH₂SH + Br⁻
(b) (CH₃)₂C=CH₂ + HCl → (CH₃)₂CCl–CH₃
(c) CH₃CH₂Br + HO⁻ → CH₂=CH₂ + H₂O + Br⁻
(d) (CH₃)₃C–CH₂OH + HBr → (CH₃)₃CBrCH₂CH₃ + H₂O
🟢 Answer:
✔ (a) Nucleophilic substitution (Br replaced by SH).
✔ (b) Electrophilic addition (H⁺, Cl⁻ added).
✔ (c) Elimination reaction (dehydrohalogenation).
✔ (d) Nucleophilic substitution (–OH replaced by –Br).

🔵 Question 8.15:
What is the relationship between the following pairs of structures?
(a) CH₃–CH₂–CH=CH₂ and CH₂=CH–CH₂–CH₃
(b) CH₃CH=CH₂ and CH₂=CHCH₃
(c) CH₃CH₂OH and CH₃CH₂OH
🟢 Answer:
✔ (a) Geometrical isomers (cis–trans).
✔ (b) Structural isomers (different structure but same formula).
✔ (c) Same compound (identical).
💡 Relationship classification depends on connectivity and spatial arrangement.

🔵 Question 8.16:
For the following bond cleavages, use curved-arrows to show the electron flow and classify each as homolysis or heterolysis. Identify the reactive intermediate produced as free radical, carbocation, or carbanion.
(a) CH₃–O–CH₃ → CH₃O• + •OCH₃
(b) R–O–H → R–O⁻ + H⁺
(c) R–Br → R⁺ + Br⁻
(d) C₆H₆–E → C₆H₆⁺ + E⁻
🟢 Answer:
✔ (a) Equal sharing of electrons → Homolytic cleavage → Forms free radicals (CH₃O• and •OCH₃).
✔ (b) Unequal sharing → Heterolytic cleavage → Forms carbanion (R–O⁻) and cation (H⁺).
✔ (c) Heterolytic cleavage → Gives carbocation (R⁺) and anion (Br⁻).
✔ (d) Heterolytic cleavage → Gives carbocation (C₆H₆⁺) and anion (E⁻).
💡 Homolysis → equal electron division → free radicals.
💡 Heterolysis → unequal electron division → ions (R⁺/R⁻).

🔵 Question 8.17:
Explain the terms Inductive effect and Electromeric effect. Which effect explains the following order of acidity?
(a) Cl₃CCOOH > Cl₂CHCOOH > ClCH₂COOH
(b) CH₃CH₂COOH > (CH₃)₂CHCOOH > (CH₃)₃CCOOH
🟢 Answer:
✔ Inductive effect (+I/–I): Permanent displacement of σ-electrons along a chain.
–I effect: Electron-withdrawing groups (Cl) increase acidity.
+I effect: Electron-donating alkyl groups decrease acidity.
✔ Electromeric effect: Temporary electron shift in π-bonds when an attacking reagent approaches.
✔ (a) Cl atoms show –I effect, pulling electrons from –COOH → stabilises conjugate base → more acidic.
➡ Order: Cl₃CCOOH > Cl₂CHCOOH > ClCH₂COOH
✔ (b) Alkyl groups show +I effect, donate electrons → destabilise conjugate base → less acidic.
➡ Order: CH₃CH₂COOH > (CH₃)₂CHCOOH > (CH₃)₃CCOOH
💡 Thus, inductive effect explains both orders.

🔵 Question 8.18:
Give a brief description of the principles of the following techniques, taking an example in each case:
(a) Crystallisation
(b) Distillation
(c) Chromatography
🟢 Answer:
✔ (a) Crystallisation:
Used for purification of solids.
Principle: Substance dissolves in a solvent at high temperature and crystallises upon cooling.
🧪 Example: Purification of benzoic acid.
✔ (b) Distillation:
Used for liquid purification.
Principle: Based on difference in boiling points.
🧪 Example: Separation of acetone and water.
✔ (c) Chromatography:
Used for mixture separation.
Principle: Components distribute differently between stationary and mobile phase.
🧪 Example: Separation of pigments from ink.

🔵 Question 8.19:
Describe the method used to separate two compounds with different solubilities in a solvent S.
🟢 Answer:
✔ Fractional Crystallisation:
Based on difference in solubility.
Dissolve both solids in hot solvent S.
Cool slowly → less soluble compound crystallises first.
Filter → crystallise second compound from filtrate.
💡 Example: Separation of KNO₃ and NaCl.

🔵 Question 8.20:
What is the difference between distillation, distillation under reduced pressure, and steam distillation?
🟢 Answer:
✔ Distillation:
→ Used for liquids with different boiling points.
→ Example: Water & alcohol.
✔ Reduced pressure distillation:
→ For high boiling liquids that decompose at normal bp.
→ Low pressure lowers bp.
→ Example: Glycerol.
✔ Steam distillation:
→ For temperature-sensitive liquids immiscible with water.
→ Boil below 100°C.
→ Example: Essential oils.

🔵 Question 8.21:
Discuss the chemistry of Lassaigne’s test.
🟢 Answer:
✔ Used to detect N, S, and halogens in organic compounds.
✔ Organic compound fused with Na metal → converts covalent elements into ionic forms:
NaCN, Na₂S, NaX.
✔ Aqueous extract = Lassaigne’s extract.
✔ Test each ion separately:
NaCN → Prussian blue test
Na₂S → Black ppt with Pb²⁺
NaX → AgX ppt with AgNO₃.

🔵 Question 8.22:
Differentiate between principles of nitrogen estimation by Dumas method and Kjeldahl’s method.
🟢 Answer:
✔ Dumas Method:
Organic sample burnt in excess O₂.
N converted to N₂ gas → measured.
Suitable for all compounds.
✔ Kjeldahl Method:
Compound digested with conc. H₂SO₄ → NH₃ formed.
NH₃ absorbed in acid → titrated.
Not suitable for N in ring (NO₂, N=N).
💡 Dumas → gaseous estimation; Kjeldahl → titrimetric.

🔵 Question 8.23:
Discuss the principle of estimation of halogens, sulphur, and phosphorus present in an organic compound.
🟢 Answer:
✔ Principle:
Fuse compound with Na metal → convert into ionic forms:
NaX (halogen), Na₂S (sulphur), Na₃PO₄ (phosphorus).
✔ Extract ions → test quantitatively.
➡ Halogens: Precipitated with AgNO₃ → weighed as AgX.
➡ Sulphur: Precipitated as BaSO₄ → weighed.
➡ Phosphorus: Precipitated as MgNH₄PO₄ → ignited to Mg₂P₂O₇ → weighed.
💡 Method = Gravimetric analysis.

🔵 Question 8.24:
Explain the principle of paper chromatography.
🟢 Answer:
✔ Paper chromatography separates components of a mixture based on their different partitioning between two phases:
Stationary phase: Thin film of water molecules adsorbed on the cellulose of filter paper.
Mobile phase: A solvent (or solvent mixture) moving through the paper by capillary action.
✔ Each component has a distinct partition coefficient (K), so it travels a different distance.
✔ The retention factor (Rf) identifies compounds:
Rf = (distance moved by substance) ÷ (distance moved by solvent front)
💡 Example: Separation of amino acids using a mixture of n-butanol : acetic acid : water.

🔵 Question 8.25:
Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?
🟢 Answer:
✔ To acidify the extract and destroy interfering ions like CN⁻ and S²⁻ that could form misleading precipitates (AgCN or Ag₂S).
✔ HNO₃ oxidises these ions to volatile products (HCN, H₂S), ensuring only halide ions remain.
✔ Then AgNO₃ gives characteristic precipitates:
AgCl → white AgBr → pale-cream AgI → yellow.

🔵 Question 8.26:
Explain the reason for fusion with metallic sodium when testing nitrogen, sulphur, and halogens.
🟢 Answer:
✔ In organic compounds, N, S, and halogens are covalently bound and not directly testable.
✔ Fusion with sodium metal converts them into ionic, water-soluble salts:
NaCN, Na₂S, NaX (X = Cl, Br, I).
✔ These dissolve in water to form Lassaigne’s extract, enabling specific ionic tests.

🔵 Question 8.27:
Name a suitable technique to separate a mixture of calcium sulphate and camphor.
🟢 Answer:
✔ Sublimation
Camphor sublimes (solid → vapour → solid).
Calcium sulphate is non-volatile.
✔ Gentle heating → camphor vapour condenses on a cool surface → separated from residue.

🔵 Question 8.28:
Explain why an organic liquid vaporises below its boiling point during steam distillation.
🟢 Answer:
✔ For immiscible liquids (organic compound + water), total vapour pressure = P(organic) + P(water).
✔ Boiling occurs when total pressure = atmospheric pressure → at a lower temperature than each component’s individual boiling point.
✔ Thus, steam distillation allows distillation without decomposition of heat-sensitive substances (e.g. essential oils).

🔵 Question 8.29:
Will CCl₄ give a white precipitate of AgCl on heating with AgNO₃? Give reason.
🟢 Answer:
❌ No.
✔ Chlorine atoms in CCl₄ are covalently bonded, not ionised.
✔ AgNO₃ reacts only with free Cl⁻ ions; hence no AgCl precipitate forms.
✔ Detection requires conversion to ionic chloride via sodium fusion.

🔵 Question 8.30:
Why is a KOH solution used to absorb CO₂ evolved during carbon estimation?
🟢 Answer:
✔ In the combustion method, carbon forms CO₂.
✔ Potassium hydroxide absorbs CO₂ completely, producing potassium carbonate:
2 KOH + CO₂ → K₂CO₃ + H₂O
✔ This ensures accurate quantitative measurement of carbon.

🔵 Question 8.31:
What do you understand by the term hybridisation? Explain sp³, sp², and sp hybridisation with examples.
🟢 Answer:
✔ Hybridisation = Process of mixing atomic orbitals of nearly equal energy on the same atom to form new equivalent orbitals called hybrid orbitals.
(i) sp³ Hybridisation:
1 s + 3 p orbitals → 4 sp³ orbitals.
Geometry: Tetrahedral; angle = 109.5°.
Example: CH₄ (each C–H bond = sp³–s σ bond).
(ii) sp² Hybridisation:
1 s + 2 p → 3 sp² orbitals.
Geometry: Trigonal planar; angle = 120°.
Example: C₂H₄ (ethylene).
(iii) sp Hybridisation:
1 s + 1 p → 2 sp orbitals.
Geometry: Linear; angle = 180°.
Example: C₂H₂ (acetylene).
💡 Hybridisation explains shape and bond angles.

🔵 Question 8.32:
What are resonance structures? Draw resonance structures for benzene.
🟢 Answer:
✔ When a molecule can be represented by two or more Lewis structures differing only in position of electrons, not atoms → such structures are resonance forms.
✔ The actual molecule is a hybrid of all forms and more stable.
Example: Benzene (C₆H₆):
Two Kekulé structures:
Alternating double bonds starting at C₁–C₂
Alternating double bonds starting at C₂–C₃
💡 Actual benzene: all C–C bonds equal (140 pm), electron delocalised over ring.

🔵 Question 8.33:
Define electromeric effect and differentiate it from inductive effect.
🟢 Answer:
✔ Electromeric effect (E-effect):
Temporary shift of π electrons toward one atom under the attack of a reagent.
Reversible, only in presence of attacking reagent.
Example:
C=O + H⁺ → C⁺–O⁻ (π electrons shift to O).
✔ Inductive effect (I-effect):
Permanent displacement of σ-electrons due to electronegativity difference; transmitted along chain.
Feature Electromeric Inductive
Nature Temporary Permanent
Electrons shifted π σ
Condition Only when reagent attacks Always present
Example C=O + H⁺ –NO₂ shows –I

🔵 Question 8.34:
What is hyperconjugation? Explain with an example.
🟢 Answer:
✔ Definition: Delocalisation of σ-electrons of C–H bond adjacent to a double bond or positive centre into π-system or vacant p-orbital.
✔ Known as no-bond resonance.
Example: Propene (CH₃–CH=CH₂):
C–H σ bond of CH₃ overlaps with π bond → stabilisation.
✔ More hyperconjugative structures = greater stability.
Order (carbocation): 3° > 2° > 1° > CH₃⁺.
💡 Explains stability of alkenes and carbocations.

🔵 Question 8.35:
What is carbocation? Classify and discuss stability order.
🟢 Answer:
✔ Carbocation = species with positive charge on carbon (C⁺), sp² hybridised, planar.
Types:
Primary (1°): charge on C attached to 1 C
Secondary (2°): charge on C attached to 2 C
Tertiary (3°): charge on C attached to 3 C
Stability order:
3° > 2° > 1° > CH₃⁺
(because of +I effect and hyperconjugation)
Example: (CH₃)₃C⁺ most stable.

🔵 Question 8.36:
Define free radical. Discuss its structure and stability.
🟢 Answer:
✔ Free radical = species with odd electron (unpaired), electrically neutral.
✔ Carbon is sp² hybridised; geometry = planar; unpaired electron in p orbital.
Stability order:
3° > 2° > 1° > CH₃•
Due to hyperconjugation and inductive effect.
Example: CH₃•, C₂H₅•, (CH₃)₂CH•, (CH₃)₃C•.

🔵 Question 8.37:
Define carbanion. Discuss its structure and stability.
🟢 Answer:
✔ Carbanion = species with negative charge on carbon (C⁻), with lone pair.
✔ Hybridisation: sp³; geometry: pyramidal.
Stability order:
CH₃⁻ > 1° > 2° > 3°
Because alkyl groups donate electrons (+I) → destabilise negative charge.
💡 Electron-withdrawing groups increase stability.

🔵 Question 8.38:
Explain electrophilic substitution reaction with example.
🟢 Answer:
✔ Reaction where an electrophile replaces a hydrogen atom in an aromatic compound.
Example:
Nitration of benzene:
C₆H₆ + HNO₃ → C₆H₅NO₂ + H₂O (in presence of H₂SO₄)
Electrophile = NO₂⁺.
Mechanism:
Generation of electrophile
Attack on ring
Loss of proton → substitution product.

🔵 Question 8.39:
Explain nucleophilic substitution reaction with example.
🟢 Answer:
✔ Reaction in which a nucleophile replaces another atom/group (usually halide).
Example:
CH₃Br + OH⁻ → CH₃OH + Br⁻
Nucleophile: OH⁻; leaving group: Br⁻.
Types: SN1 (2-step) and SN2 (1-step).

🔵 Question 8.40:
Explain elimination reaction with example.
🟢 Answer:
✔ In elimination, two atoms/groups are removed from adjacent carbons forming multiple bond.
Example:
CH₃CH₂Br + KOH (alc.) → CH₂=CH₂ + HBr + K⁺Br⁻
Called dehydrohalogenation.
💡 Competes with substitution; favoured by strong base and heat.

NEET QUESTIONS FROM THIS LESSON

🔵 Question 1:
The IUPAC name of CH₃–CH₂–CH=CH₂ is:
🔴 ① Butane
🟢 ② But-1-ene
🟡 ③ But-2-ene
🔵 ④ Prop-1-ene
🟢 Answer: ② But-1-ene
📘 Exam: NEET
📅 Year: 2016 | Set: M

🔵 Question 2:
The IUPAC name of CH₃–CH₂–OH is:
🔴 ① Ethanol
🟢 ② Ethyl alcohol
🟡 ③ Methanol
🔵 ④ Propanol
🟢 Answer: ① Ethanol
📘 Exam: AIPMT
📅 Year: 2002 | Set: A

🔵 Question 3:
The correct order of C–H bond length in CH₄, C₂H₄, C₂H₂ is:
🔴 ① CH₄ > C₂H₄ > C₂H₂
🟢 ② C₂H₂ > C₂H₄ > CH₄
🟡 ③ CH₄ > C₂H₂ > C₂H₄
🔵 ④ C₂H₄ > CH₄ > C₂H₂
🟢 Answer: ① CH₄ > C₂H₄ > C₂H₂
📘 Exam: NEET
📅 Year: 2019 | Set: Q2

🔵 Question 4:
Which of the following has sp³ hybridisation at carbon?
🔴 ① Ethane
🟢 ② Ethene
🟡 ③ Ethyne
🔵 ④ Benzene
🟢 Answer: ① Ethane
📘 Exam: AIPMT
📅 Year: 2005 | Set: B

🔵 Question 5:
The hybridisation of carbon in CO₂ is:
🔴 ① sp
🟢 ② sp²
🟡 ③ sp³
🔵 ④ sp³d
🟢 Answer: ① sp
📘 Exam: NEET
📅 Year: 2018 | Set: P1

🔵 Question 6:
Which of the following has resonance?
🔴 ① CH₄
🟢 ② Benzene
🟡 ③ C₂H₆
🔵 ④ C₂H₅OH
🟢 Answer: ② Benzene
📘 Exam: AIPMT
📅 Year: 2003 | Set: A

🔵 Question 7:
Which of the following is the most stable carbocation?
🔴 ① CH₃⁺
🟢 ② CH₃–CH₂⁺
🟡 ③ (CH₃)₂CH⁺
🔵 ④ (CH₃)₃C⁺
🟢 Answer: ④ (CH₃)₃C⁺
📘 Exam: NEET
📅 Year: 2012 | Set: P

🔵 Question 8:
Which of the following carbocations is most stable due to resonance?
🔴 ① Benzyl
🟢 ② Allyl
🟡 ③ Tert-butyl
🔵 ④ Isopropyl
🟢 Answer: ① Benzyl
📘 Exam: NEET
📅 Year: 2017 | Set: O2

🔵 Question 9:
The stability order of free radicals is:
🔴 ① 3° > 2° > 1° > CH₃
🟢 ② 1° > 2° > 3°
🟡 ③ CH₃ > 1° > 2° > 3°
🔵 ④ 2° > 3° > 1°
🟢 Answer: ① 3° > 2° > 1° > CH₃
📘 Exam: AIPMT
📅 Year: 2006 | Set: C

🔵 Question 10:
The correct order of acidity is:
🔴 ① CH≡CH > CH₂=CH₂ > CH₃–CH₃
🟢 ② CH₃–CH₃ > CH₂=CH₂ > CH≡CH
🟡 ③ CH₂=CH₂ > CH≡CH > CH₃–CH₃
🔵 ④ CH≡CH > CH₃–CH₃ > CH₂=CH₂
🟢 Answer: ① CH≡CH > CH₂=CH₂ > CH₃–CH₃
📘 Exam: NEET
📅 Year: 2014 | Set: Q

🔵 Question 11:
The general formula of alkanes is:
🔴 ① CnH₂n
🟢 ② CnH₂n+2
🟡 ③ CnH₂n–2
🔵 ④ CnH₂n+1
🟢 Answer: ② CnH₂n+2
📘 Exam: AIPMT
📅 Year: 2001 | Set: B

🔵 Question 12:
The IUPAC name of CH₃–C≡CH is:
🔴 ① Propene
🟢 ② Propyne
🟡 ③ Propane
🔵 ④ Ethyne
🟢 Answer: ② Propyne
📘 Exam: NEET
📅 Year: 2018 | Set: R

🔵 Question 13:
Which type of isomerism is shown by CH₃–O–CH₃ and CH₃–CH₂–OH?
🔴 ① Chain isomerism
🟢 ② Functional group isomerism
🟡 ③ Position isomerism
🔵 ④ Geometrical isomerism
🟢 Answer: ② Functional group isomerism
📘 Exam: AIPMT
📅 Year: 2007 | Set: A

🔵 Question 14:
Which of the following compounds shows geometrical isomerism?
🔴 ① CH₂=CH₂
🟢 ② CH₃–CH=CH–CH₃
🟡 ③ CH≡CH
🔵 ④ CH₄
🟢 Answer: ② CH₃–CH=CH–CH₃
📘 Exam: NEET
📅 Year: 2015 | Set: Q

🔵 Question 15:
In which of the following, resonance is present?
🔴 ① Ethene
🟢 ② Benzene
🟡 ③ Ethyne
🔵 ④ Propane
🟢 Answer: ② Benzene
📘 Exam: AIPMT
📅 Year: 2008 | Set: C

🔵 Question 16:
The general formula of alkenes is:
🔴 ① CnH₂n+2
🟢 ② CnH₂n
🟡 ③ CnH₂n–2
🔵 ④ CnH₂n+1
🟢 Answer: ② CnH₂n
📘 Exam: NEET
📅 Year: 2016 | Set: O

🔵 Question 17:
Which of the following is an electrophile?
🔴 ① NH₃
🟢 ② H⁺
🟡 ③ OH⁻
🔵 ④ Cl⁻
🟢 Answer: ② H⁺
📘 Exam: AIPMT
📅 Year: 2002 | Set: C

🔵 Question 18:
Which of the following shows hyperconjugation?
🔴 ① Propene
🟢 ② Propane
🟡 ③ Ethane
🔵 ④ Ethyne
🟢 Answer: ① Propene
📘 Exam: NEET
📅 Year: 2013 | Set: P

🔵 Question 19:
Which of the following represents chain isomerism?
🔴 ① C₄H₁₀ (n-butane and isobutane)
🟢 ② C₂H₆O (ethanol and dimethyl ether)
🟡 ③ C₂H₄ (ethylene and acetylene)
🔵 ④ CH₄
🟢 Answer: ① C₄H₁₀ (n-butane and isobutane)
📘 Exam: NEET
📅 Year: 2017 | Set: S

🔵 Question 20:
Which has the highest boiling point?
🔴 ① CH₃–CH₂–OH
🟢 ② CH₃–O–CH₃
🟡 ③ CH₄
🔵 ④ C₂H₆
🟢 Answer: ① CH₃–CH₂–OH
📘 Exam: AIPMT
📅 Year: 2006 | Set: A

🔵 Question 21:
The IUPAC name of CH₃–CH₂–CHO is:
🔴 ① Ethanol
🟢 ② Propanal
🟡 ③ Propanone
🔵 ④ Acetone
🟢 Answer: ② Propanal
📘 Exam: NEET
📅 Year: 2011 | Set: Q

🔵 Question 22:
Which of the following is most acidic?
🔴 ① CH₄
🟢 ② C₂H₆
🟡 ③ CH≡CH
🔵 ④ C₂H₄
🟢 Answer: ③ CH≡CH
📘 Exam: AIPMT
📅 Year: 2005 | Set: C

🔵 Question 23:
Which of the following is nucleophile?
🔴 ① H⁺
🟢 ② OH⁻
🟡 ③ NO₂⁺
🔵 ④ BF₃
🟢 Answer: ② OH⁻
📘 Exam: NEET
📅 Year: 2019 | Set: M

🔵 Question 24:
The IUPAC name of CH₃–CO–CH₃ is:
🔴 ① Propanal
🟢 ② Propanone
🟡 ③ Ethanal
🔵 ④ Butanone
🟢 Answer: ② Propanone
📘 Exam: AIPMT
📅 Year: 2004 | Set: B

🔵 Question 25:
The hybridisation of carbon in benzene is:
🔴 ① sp
🟢 ② sp²
🟡 ③ sp³
🔵 ④ dsp²
🟢 Answer: ② sp²
📘 Exam: NEET
📅 Year: 2020 | Set: O2

🔵 Question 26:
Which one of the following is most stable?
🔴 ① Benzyl carbocation
🟢 ② Allyl carbocation
🟡 ③ Tert-butyl carbocation
🔵 ④ Ethyl carbocation
🟢 Answer: ① Benzyl carbocation
📘 Exam: NEET
📅 Year: 2016 | Set: R

🔵 Question 27:
The IUPAC name of CH₃–CH₂–C≡CH is:
🔴 ① Butyne
🟢 ② But-1-yne
🟡 ③ But-2-yne
🔵 ④ Propyne
🟢 Answer: ② But-1-yne
📘 Exam: AIPMT
📅 Year: 2009 | Set: C

🔵 Question 28:
Which of the following does not show resonance?
🔴 ① Benzene
🟢 ② CO₃²⁻
🟡 ③ CH₄
🔵 ④ NO₂⁻
🟢 Answer: ③ CH₄
📘 Exam: NEET
📅 Year: 2018 | Set: P1

🔵 Question 29:
Which of the following is most stable free radical?
🔴 ① CH₃•
🟢 ② C₂H₅•
🟡 ③ (CH₃)₂CH•
🔵 ④ (CH₃)₃C•
🟢 Answer: ④ (CH₃)₃C•
📘 Exam: AIPMT
📅 Year: 2002 | Set: A

🔵 Question 30:
What type of isomerism is exhibited by C₂H₆O (ethanol and dimethyl ether)?
🔴 ① Chain
🟢 ② Functional group
🟡 ③ Position
🔵 ④ Geometrical
🟢 Answer: ② Functional group
📘 Exam: NEET
📅 Year: 2017 | Set: Q

🔵 Question 31:
Which of the following is most reactive towards electrophilic substitution?
🔴 ① Benzene
🟢 ② Toluene
🟡 ③ Nitrobenzene
🔵 ④ Chlorobenzene
🟢 Answer: ② Toluene
📘 Exam: AIPMT
📅 Year: 2008 | Set: C

🔵 Question 32:
Which of the following is most stable due to resonance?
🔴 ① Allyl carbocation
🟢 ② Benzyl carbocation
🟡 ③ Tert-butyl carbocation
🔵 ④ Vinyl carbocation
🟢 Answer: ② Benzyl carbocation
📘 Exam: NEET
📅 Year: 2013 | Set: S

🔵 Question 33:
The hybridisation of carbon in CH₂=CH₂ is:
🔴 ① sp³
🟢 ② sp²
🟡 ③ sp
🔵 ④ dsp²
🟢 Answer: ② sp²
📘 Exam: AIPMT
📅 Year: 2006 | Set: B

🔵 Question 34:
Which one is nucleophile?
🔴 ① BF₃
🟢 ② OH⁻
🟡 ③ NO₂⁺
🔵 ④ H⁺
🟢 Answer: ② OH⁻
📘 Exam: NEET
📅 Year: 2012 | Set: P

🔵 Question 35:
Which has the maximum number of σ bonds?
🔴 ① Ethane
🟢 ② Ethene
🟡 ③ Ethyne
🔵 ④ Benzene
🟢 Answer: ① Ethane
📘 Exam: NEET
📅 Year: 2019 | Set: M

🔵 Question 36:
The IUPAC name of CH₃–CHO is:
🔴 ① Ethanal
🟢 ② Ethanol
🟡 ③ Methanal
🔵 ④ Ethane
🟢 Answer: ① Ethanal
📘 Exam: AIPMT
📅 Year: 2003 | Set: C

🔵 Question 37:
Which of the following represents position isomerism?
🔴 ① But-1-ene and But-2-ene
🟢 ② n-Butane and Isobutane
🟡 ③ Ethanol and Dimethyl ether
🔵 ④ Acetic acid and Methyl formate
🟢 Answer: ① But-1-ene and But-2-ene
📘 Exam: NEET
📅 Year: 2018 | Set: O1

🔵 Question 38:
The compound showing tautomerism is:
🔴 ① Acetone
🟢 ② Phenol
🟡 ③ Acetaldehyde
🔵 ④ Ethane
🟢 Answer: ③ Acetaldehyde
📘 Exam: AIPMT
📅 Year: 2005 | Set: A

🔵 Question 39:
Which type of isomerism is shown by CH₃–CH=CH–CH₃ (cis and trans)?
🔴 ① Functional
🟢 ② Geometrical
🟡 ③ Chain
🔵 ④ Optical
🟢 Answer: ② Geometrical
📘 Exam: NEET
📅 Year: 2014 | Set: Q

🔵 Question 40:
The correct IUPAC name of isopropyl alcohol is:
🔴 ① Propan-2-ol
🟢 ② Propan-1-ol
🟡 ③ Methanol
🔵 ④ Ethanol
🟢 Answer: ① Propan-2-ol
📘 Exam: NEET
📅 Year: 2020 | Set: R2

🔵 Question 41:
Which one is the least stable carbocation?
🔴 ① CH₃⁺
🟢 ② C₂H₅⁺
🟡 ③ (CH₃)₂CH⁺
🔵 ④ (CH₃)₃C⁺
🟢 Answer: ① CH₃⁺
📘 Exam: AIPMT
📅 Year: 2007 | Set: B

🔵 Question 42:
The IUPAC name of CH₃–C(CH₃)₂–CH₃ is:
🔴 ① n-Butane
🟢 ② Isobutane (2-methylpropane)
🟡 ③ Neopentane
🔵 ④ Pentane
🟢 Answer: ② Isobutane (2-methylpropane)
📘 Exam: NEET
📅 Year: 2011 | Set: O

🔵 Question 43:
The order of stability of carbocations is:
🔴 ① 3° > 2° > 1° > CH₃⁺
🟢 ② 1° > 2° > 3° > CH₃⁺
🟡 ③ CH₃⁺ > 1° > 2° > 3°
🔵 ④ 2° > 3° > 1° > CH₃⁺
🟢 Answer: ① 3° > 2° > 1° > CH₃⁺
📘 Exam: NEET
📅 Year: 2015 | Set: P

🔵 Question 44:
Which compound shows optical isomerism?
🔴 ① CH₃–CHCl–CH₃
🟢 ② CH₃–CHCl–COOH
🟡 ③ CH₄
🔵 ④ C₂H₆
🟢 Answer: ② CH₃–CHCl–COOH
📘 Exam: NEET
📅 Year: 2017 | Set: Q

🔵 Question 45:
The IUPAC name of CH₃–CH₂–CH₂–OH is:
🔴 ① Ethanol
🟢 ② Propan-1-ol
🟡 ③ Methanol
🔵 ④ Propan-2-ol
🟢 Answer: ② Propan-1-ol
📘 Exam: AIPMT
📅 Year: 2001 | Set: A

🔵 Question 46:
The hybridisation of carbon in acetylene is:
🔴 ① sp³
🟢 ② sp²
🟡 ③ sp
🔵 ④ dsp²
🟢 Answer: ③ sp
📘 Exam: NEET
📅 Year: 2016 | Set: M

🔵 Question 47:
Which of the following shows mesomeric effect?
🔴 ① –OH
🟢 ② –NO₂
🟡 ③ –NH₂
🔵 ④ All of these
🟢 Answer: ④ All of these
📘 Exam: NEET
📅 Year: 2019 | Set: Q2

🔵 Question 48:
The IUPAC name of CH₃–COOH is:
🔴 ① Ethanoic acid
🟢 ② Acetic acid
🟡 ③ Methanoic acid
🔵 ④ Propanoic acid
🟢 Answer: ① Ethanoic acid
📘 Exam: AIPMT
📅 Year: 2004 | Set: B

🔵 Question 49:
Which of the following is an electrophile?
🔴 ① NO₂⁺
🟢 ② OH⁻
🟡 ③ NH₃
🔵 ④ Cl⁻
🟢 Answer: ① NO₂⁺
📘 Exam: NEET
📅 Year: 2018 | Set: S

🔵 Question 50:
Which of the following is the most stable resonance structure?
🔴 ① Benzene
🟢 ② Ethane
🟡 ③ Propane
🔵 ④ Methane
🟢 Answer: ① Benzene
📘 Exam: AIPMT
📅 Year: 2006 | Set: C

JEE MAINS QUESTIONS FROM THIS LESSON

🔵 Question 1
Which of the following has highest boiling point?
🔴 ① CH₃CH₂OH
🟢 ② CH₃OCH₃
🟡 ③ C₂H₆
🔵 ④ CH₃CHO
🟢 Answer: ① CH₃CH₂OH (due to H-bonding)
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Morning

🔵 Question 2
The correct IUPAC name of CH₃–CH(OH)–CH₃ is:
🔴 ① 2-hydroxypropane
🟢 ② Propan-2-ol
🟡 ③ Isopropyl alcohol
🔵 ④ Propyl alcohol
🟢 Answer: ② Propan-2-ol
📘 Exam: JEE Main
📅 Year: 2014 | Shift: Morning

🔵 Question 3
The compound which will show metamerism is:
🔴 ① C₂H₆
🟢 ② C₄H₁₀O
🟡 ③ C₃H₈
🔵 ④ CH₄
🟢 Answer: ② C₄H₁₀O (ethers)
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Evening

🔵 Question 4
Which of the following is an example of functional isomerism?
🔴 ① C₂H₆O : CH₃CH₂OH & CH₃OCH₃
🟢 ② CH₃CH₂CH₃ & CH₃CH(CH₃)₂
🟡 ③ Butane & 2-methylpropane
🔵 ④ Hexane & 2,2-dimethylbutane
🟢 Answer: ① C₂H₆O : alcohol & ether
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Evening

🔵 Question 5
The number of possible isomers of C₄H₁₀O is:
🔴 ① 6
🟢 ② 7
🟡 ③ 8
🔵 ④ 9
🟢 Answer: ② 7
📘 Exam: JEE Main
📅 Year: 2013 | Shift: Morning

🔵 Question 6
The hybridisation of carbon in CH₂=CH₂ is:
🔴 ① sp³
🟢 ② sp²
🟡 ③ sp
🔵 ④ dsp²
🟢 Answer: ② sp²
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Evening

🔵 Question 7
Which reagent is used to detect nitrogen in organic compounds by Lassaigne’s test?
🔴 ① CuSO₄
🟢 ② FeSO₄
🟡 ③ AgNO₃
🔵 ④ NaOH
🟢 Answer: ② FeSO₄ (Prussian blue test)
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Morning

🔵 Question 8
Which one gives positive Lassaigne’s test for sulphur?
🔴 ① Na₂SO₄
🟢 ② Thiourea
🟡 ③ Glucose
🔵 ④ Urea
🟢 Answer: ② Thiourea
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Morning

🔵 Question 9
The correct IUPAC name of CH₃–C≡C–CH₃ is:
🔴 ① 2-butyne
🟢 ② 1-butyne
🟡 ③ Ethyne
🔵 ④ Propyne
🟢 Answer: ① 2-butyne
📘 Exam: JEE Main
📅 Year: 2014 | Shift: Evening

🔵 Question 10
Which of the following is aromatic according to Huckel’s rule?
🔴 ① Cyclobutadiene
🟢 ② Benzene
🟡 ③ Cyclooctatetraene
🔵 ④ Cyclopropenyl cation
🟢 Answer: ② Benzene (4n+2 rule, n=1)
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Morning

🔵 Question 11
The IUPAC name of (CH₃)₂CH–CH₃ is:
🔴 ① Butane
🟢 ② 2-methylpropane
🟡 ③ Isobutane
🔵 ④ Pentane
🟢 Answer: ② 2-methylpropane
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Evening

🔵 Question 12
The molecular formula C₄H₆ corresponds to:
🔴 ① Alkane
🟢 ② Alkyne or cyclic alkene
🟡 ③ Alkene
🔵 ④ Aromatic
🟢 Answer: ② Alkyne or cyclic alkene
📘 Exam: JEE Main
📅 Year: 2013 | Shift: Evening

🔵 Question 13
Which element is detected by sodium fusion test using AgNO₃?
🔴 ① Sulphur
🟢 ② Halogen
🟡 ③ Oxygen
🔵 ④ Nitrogen
🟢 Answer: ② Halogen
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Morning

🔵 Question 14
Which of the following is geometrical isomerism?
🔴 ① CH₂=CHCl
🟢 ② CHCl=CHCl
🟡 ③ CH₄
🔵 ④ C₂H₆
🟢 Answer: ② CHCl=CHCl
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Evening

🔵 Question 15
Which of the following has highest resonance energy?
🔴 ① Benzene
🟢 ② Naphthalene
🟡 ③ Anthracene
🔵 ④ Toluene
🟢 Answer: ① Benzene
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Morning

🔵 Question 16
The π bond is formed by:
🔴 ① End-on overlap of orbitals
🟢 ② Sidewise overlap of orbitals
🟡 ③ Overlap of s and p
🔵 ④ Overlap of s and s
🟢 Answer: ② Sidewise overlap of orbitals
📘 Exam: JEE Main
📅 Year: 2014 | Shift: Morning

🔵 Question 17
Which is the correct increasing order of stability?
🔴 ① Allyl > Benzyl > 3° carbocation
🟢 ② 3° carbocation > Benzyl > Allyl
🟡 ③ Benzyl > Allyl > 3° carbocation
🔵 ④ 3° carbocation > Allyl > Benzyl
🟢 Answer: ② 3° carbocation > Benzyl > Allyl
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Evening

🔵 Question 18
Which of the following is most acidic?
🔴 ① Ethyne
🟢 ② Ethene
🟡 ③ Ethane
🔵 ④ Benzene
🟢 Answer: ① Ethyne
📘 Exam: JEE Main
📅 Year: 2013 | Shift: Morning

🔵 Question 19
The correct order of –I effect is:
🔴 ① –NO₂ > –Cl > –CH₃ > –OCH₃
🟢 ② –CH₃ > –OCH₃ > –Cl > –NO₂
🟡 ③ –Cl > –NO₂ > –OCH₃ > –CH₃
🔵 ④ –OCH₃ > –CH₃ > –Cl > –NO₂
🟢 Answer: ① –NO₂ > –Cl > –CH₃ > –OCH₃
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Morning

🔵 Question 20
In which case hyperconjugation is observed?
🔴 ① CH₃–CH=CH₂
🟢 ② CH₂=CH₂
🟡 ③ CH≡CH
🔵 ④ CH₄
🟢 Answer: ① CH₃–CH=CH₂
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Evening

🔵 Question 21
Which of the following compounds shows tautomerism?
🔴 ① CH₃CHO
🟢 ② CH₃COCH₃
🟡 ③ CH₃COOH
🔵 ④ CH₄
🟢 Answer: ① CH₃CHO (Aldehyde ↔ enol)
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Morning

🔵 Question 22
The compound with highest dipole moment is:
🔴 ① CH₃Cl
🟢 ② CH₂Cl₂
🟡 ③ CHCl₃
🔵 ④ CCl₄
🟢 Answer: ② CH₂Cl₂
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Evening

🔵 Question 23
Which carbonium ion is most stable?
🔴 ① CH₃⁺
🟢 ② C₂H₅⁺
🟡 ③ (CH₃)₃C⁺
🔵 ④ C₆H₅⁺
🟢 Answer: ③ (CH₃)₃C⁺
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Evening

🔵 Question 24
The reagent used in estimation of halogen in organic compounds by Carius method is:
🔴 ① Conc. HNO₃
🟢 ② Fuming HNO₃ + AgNO₃
🟡 ③ NaOH
🔵 ④ HCl
🟢 Answer: ② Fuming HNO₃ + AgNO₃
📘 Exam: JEE Main
📅 Year: 2014 | Shift: Morning

🔵 Question 25
The correct order of +I effect is:
🔴 ① –CH₃ < –C₂H₅ < –C₃H₇ < –C(CH₃)₃
🟢 ② –C(CH₃)₃ < –C₂H₅ < –CH₃ < –C₃H₇
🟡 ③ –CH₃ < –C₃H₇ < –C₂H₅ < –C(CH₃)₃
🔵 ④ –CH₃ < –C₂H₅ < –C(CH₃)₃ < –C₃H₇
🟢 Answer: ① –CH₃ < –C₂H₅ < –C₃H₇ < –C(CH₃)₃
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Morning

🔵 Question 26
Which of the following has highest percentage of carbon?
🔴 ① CH₄
🟢 ② C₂H₂
🟡 ③ C₆H₆
🔵 ④ C₂H₆
🟢 Answer: ③ C₆H₆
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Evening

🔵 Question 27
The compound CH₃–CH₂–C≡CH shows:
🔴 ① Chain isomerism
🟢 ② Position isomerism
🟡 ③ Functional isomerism
🔵 ④ Geometrical isomerism
🟢 Answer: ② Position isomerism
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Morning

🔵 Question 28
Which of the following is aromatic?
🔴 ① Cyclopentadienyl anion
🟢 ② Cyclopropenyl cation
🟡 ③ Cyclooctatetraene
🔵 ④ Cyclobutadiene
🟢 Answer: ② Cyclopropenyl cation (4n+2 rule, n=0)
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Morning

🔵 Question 29
Which of the following is most stable?
🔴 ① Vinyl carbocation
🟢 ② Allyl carbocation
🟡 ③ Benzyl carbocation
🔵 ④ Methyl carbocation
🟢 Answer: ③ Benzyl carbocation
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Evening

🔵 Question 30
The IUPAC name of isobutyl alcohol is:
🔴 ① Butan-1-ol
🟢 ② Butan-2-ol
🟡 ③ 2-methylpropan-1-ol
🔵 ④ 2-methylpropan-2-ol
🟢 Answer: ③ 2-methylpropan-1-ol
📘 Exam: JEE Main
📅 Year: 2014 | Shift: Evening

🔵 Question 31
The type of hybridisation in CH₄, NH₃ and H₂O is:
🔴 ① sp³, sp², sp²
🟢 ② sp³, sp³, sp³
🟡 ③ sp², sp³, sp³
🔵 ④ sp³, sp², sp³
🟢 Answer: ② sp³, sp³, sp³
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Evening

🔵 Question 32
The decreasing order of acidity is:
🔴 ① CH≡CH > CH₂=CH₂ > CH₃–CH₃
🟢 ② CH₃–CH₃ > CH₂=CH₂ > CH≡CH
🟡 ③ CH₂=CH₂ > CH≡CH > CH₃–CH₃
🔵 ④ CH≡CH > CH₃–CH₃ > CH₂=CH₂
🟢 Answer: ① CH≡CH > CH₂=CH₂ > CH₃–CH₃
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Morning

🔵 Question 33
Which of the following is a heteroatom?
🔴 ① C
🟢 ② H
🟡 ③ O
🔵 ④ Both H and C
🟢 Answer: ③ O
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Evening

🔵 Question 34
The compound CH₃–CH₂–O–CH₃ is an example of:
🔴 ① Alcohol
🟢 ② Ether
🟡 ③ Aldehyde
🔵 ④ Ester
🟢 Answer: ② Ether
📘 Exam: JEE Main
📅 Year: 2013 | Shift: Morning

🔵 Question 35
Which is the correct decreasing order of dipole moment?
🔴 ① CH₃Cl > CH₂Cl₂ > CHCl₃ > CCl₄
🟢 ② CH₂Cl₂ > CH₃Cl > CCl₄ > CHCl₃
🟡 ③ CCl₄ > CHCl₃ > CH₂Cl₂ > CH₃Cl
🔵 ④ CH₃Cl > CHCl₃ > CH₂Cl₂ > CCl₄
🟢 Answer: ① CH₃Cl > CH₂Cl₂ > CHCl₃ > CCl₄
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Evening

🔵 Question 36
Which of the following carbocations is least stable?
🔴 ① 1° carbocation
🟢 ② 2° carbocation
🟡 ③ 3° carbocation
🔵 ④ Allyl carbocation
🟢 Answer: ① 1° carbocation
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Morning

🔵 Question 37
Which of the following shows geometrical isomerism?
🔴 ① But-2-ene
🟢 ② Prop-1-ene
🟡 ③ Ethane
🔵 ④ Propane
🟢 Answer: ① But-2-ene
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Evening

🔵 Question 38
The IUPAC name of isopentane is:
🔴 ① 2-methylbutane
🟢 ② 3-methylbutane
🟡 ③ Pentane
🔵 ④ 2,2-dimethylpropane
🟢 Answer: ① 2-methylbutane
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Morning

🔵 Question 39
Hybridisation of carbon in acetylene is:
🔴 ① sp³
🟢 ② sp²
🟡 ③ sp
🔵 ④ dsp²
🟢 Answer: ③ sp
📘 Exam: JEE Main
📅 Year: 2013 | Shift: Evening

🔵 Question 40
Which among the following is most basic?
🔴 ① NH₃
🟢 ② C₆H₅NH₂
🟡 ③ (CH₃)₃N
🔵 ④ CH₃NH₂
🟢 Answer: ③ (CH₃)₃N
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Morning

🔵 Question 41
Toluene undergoes electrophilic substitution easily compared to benzene because of:
🔴 ① –CH₃ shows –I effect
🟢 ② –CH₃ shows +I effect and hyperconjugation
🟡 ③ –CH₃ withdraws electrons
🔵 ④ None
🟢 Answer: ② –CH₃ shows +I effect and hyperconjugation
📘 Exam: JEE Main
📅 Year: 2014 | Shift: Morning

🔵 Question 42
Which of the following is optically active?
🔴 ① 2-butanol
🟢 ② 2-propanol
🟡 ③ Ethanol
🔵 ④ Methanol
🟢 Answer: ① 2-butanol (chiral carbon)
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Morning

🔵 Question 43
The resonance hybrid is:
🔴 ① More stable than canonical forms
🟢 ② Less stable than canonical forms
🟡 ③ Same as canonical forms
🔵 ④ Unstable
🟢 Answer: ① More stable than canonical forms
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Morning

🔵 Question 44
Which of the following acids is strongest?
🔴 ① CH₃COOH
🟢 ② CCl₃COOH
🟡 ③ ClCH₂COOH
🔵 ④ HCOOH
🟢 Answer: ② CCl₃COOH (–I effect of 3 Cl)
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Evening

🔵 Question 45
Which effect explains stability of carbocations?
🔴 ① Inductive effect
🟢 ② Hyperconjugation
🟡 ③ Resonance
🔵 ④ All
🟢 Answer: ④ All
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Evening

🔵 Question 46
Which among the following is mesomeric effect group?
🔴 ① –NO₂
🟢 ② –CH₃
🟡 ③ –C₂H₅
🔵 ④ –H
🟢 Answer: ① –NO₂ (–M effect)
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Evening

🔵 Question 47
Which is the correct decreasing order of inductive effect?
🔴 ① –I: F > Cl > Br > I
🟢 ② –I: I > Br > Cl > F
🟡 ③ +I: CH₃ < C₂H₅ < C₃H₇ < C(CH₃)₃
🔵 ④ Both ① and ③
🟢 Answer: ④ Both ① and ③
📘 Exam: JEE Main
📅 Year: 2013 | Shift: Morning

🔵 Question 48
The number of resonance structures of carbonate ion (CO₃²⁻) is:
🔴 ① 1
🟢 ② 2
🟡 ③ 3
🔵 ④ 4
🟢 Answer: ③ 3
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Evening

🔵 Question 49
The IUPAC name of tert-butyl alcohol is:
🔴 ① 2-methylpropan-1-ol
🟢 ② 2-methylpropan-2-ol
🟡 ③ Butan-2-ol
🔵 ④ Butan-1-ol
🟢 Answer: ② 2-methylpropan-2-ol
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Morning

🔵 Question 50
Which one is not a resonance structure of benzene?
🔴 ① Kekule forms
🟢 ② Dewar structures
🟡 ③ Circular π-cloud
🔵 ④ Isolated double bonds
🟢 Answer: ④ Isolated double bonds
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Morning

JEE ADVANCED QUESTIONS FROM THIS LESSON

🔵 Question 1:
The element which is always present in all organic compounds is:
🔴 ① Hydrogen
🟢 ② Carbon
🟡 ③ Oxygen
🔵 ④ Nitrogen
🟢 Answer: ② Carbon
🎯 Difficulty: NEET

🔵 Question 2:
The general method of separating a mixture of two volatile liquids with different boiling points is:
🔴 ① Filtration
🟢 ② Distillation
🟡 ③ Sublimation
🔵 ④ Crystallization
🟢 Answer: ② Distillation
🎯 Difficulty: NEET

🔵 Question 3:
The functional group –CHO belongs to:
🔴 ① Alcohol
🟢 ② Aldehyde
🟡 ③ Ketone
🔵 ④ Ester
🟢 Answer: ② Aldehyde
🎯 Difficulty: NEET

🔵 Question 4:
The functional group –COOH is called:
🔴 ① Aldehyde
🟢 ② Carboxylic acid
🟡 ③ Ester
🔵 ④ Amine
🟢 Answer: ② Carboxylic acid
🎯 Difficulty: NEET

🔵 Question 5:
The IUPAC name of CH₃–CH₂–OH is:
🔴 ① Methanol
🟢 ② Ethanol
🟡 ③ Propanol
🔵 ④ Butanol
🟢 Answer: ② Ethanol
🎯 Difficulty: NEET

🔵 Question 6:
The process of purification of organic solids which sublime is:
🔴 ① Crystallization
🟢 ② Sublimation
🟡 ③ Chromatography
🔵 ④ Distillation
🟢 Answer: ② Sublimation
🎯 Difficulty: NEET

🔵 Question 7:
The technique used for separating colored substances is:
🔴 ① Filtration
🟢 ② Chromatography
🟡 ③ Crystallization
🔵 ④ Distillation
🟢 Answer: ② Chromatography
🎯 Difficulty: NEET

🔵 Question 8:
The hybridisation of carbon in methane (CH₄) is:
🔴 ① sp
🟢 ② sp³
🟡 ③ sp²
🔵 ④ dsp²
🟢 Answer: ② sp³
🎯 Difficulty: NEET

🔵 Question 9:
The formula of benzene is:
🔴 ① C₂H₄
🟢 ② C₆H₆
🟡 ③ C₆H₁₂
🔵 ④ C₅H₁₀
🟢 Answer: ② C₆H₆
🎯 Difficulty: NEET

🔵 Question 10:
The compound CH₃–COOH contains which functional group?
🔴 ① Ketone
🟢 ② Carboxyl
🟡 ③ Aldehyde
🔵 ④ Alcohol
🟢 Answer: ② Carboxyl
🎯 Difficulty: NEET

🔵 Question 11:
Toluene is also known as:
🔴 ① Methylbenzene
🟢 ② Ethylbenzene
🟡 ③ Phenol
🔵 ④ Aniline
🟢 Answer: ① Methylbenzene
🎯 Difficulty: NEET

🔵 Question 12:
The homologous series differs by:
🔴 ① CH₂ group
🟢 ② CH₃ group
🟡 ③ OH group
🔵 ④ COOH group
🟢 Answer: ① CH₂ group
🎯 Difficulty: NEET

🔵 Question 13:
The term “isomerism” refers to:
🔴 ① Same molecular and structural formula
🟢 ② Same molecular formula but different structures
🟡 ③ Same compounds
🔵 ④ Different molecular formula
🟢 Answer: ② Same molecular formula but different structures
🎯 Difficulty: NEET

🔵 Question 14:
The IUPAC name of acetone is:
🔴 ① Ethanal
🟢 ② Propanone
🟡 ③ Butanone
🔵 ④ Methanal
🟢 Answer: ② Propanone
🎯 Difficulty: NEET

🔵 Question 15:
Which is an aromatic compound?
🔴 ① C₂H₆
🟢 ② C₆H₆
🟡 ③ C₃H₈
🔵 ④ C₂H₂
🟢 Answer: ② C₆H₆
🎯 Difficulty: NEET

🔵 Question 16:
The functional group present in alcohols is:
🔴 ① –COOH
🟢 ② –OH
🟡 ③ –CHO
🔵 ④ –C=O
🟢 Answer: ② –OH
🎯 Difficulty: NEET

🔵 Question 17:
The method used for determining molecular mass of volatile liquids is:
🔴 ① Duma’s method
🟢 ② Victor Meyer’s method
🟡 ③ Kjeldahl’s method
🔵 ④ Lassaigne’s test
🟢 Answer: ② Victor Meyer’s method
🎯 Difficulty: NEET

🔵 Question 18:
The brown ring test is used to detect:
🔴 ① Sulphur
🟢 ② Nitrogen
🟡 ③ Halogen
🔵 ④ Phosphorus
🟢 Answer: ② Nitrogen
🎯 Difficulty: NEET

🔵 Question 19:
The functional group –NH₂ belongs to:
🔴 ① Alcohols
🟢 ② Amines
🟡 ③ Amides
🔵 ④ Aldehydes
🟢 Answer: ② Amines
🎯 Difficulty: NEET

🔵 Question 20:
Which technique separates a non-volatile impurity from an organic liquid?
🔴 ① Sublimation
🟢 ② Distillation
🟡 ③ Filtration
🔵 ④ Crystallisation
🟢 Answer: ② Distillation
🎯 Difficulty: NEET

🔵 Question 21:
The functional group –COOR is of:
🔴 ① Amine
🟢 ② Ester
🟡 ③ Aldehyde
🔵 ④ Ketone
🟢 Answer: ② Ester
🎯 Difficulty: NEET

🔵 Question 22:
Which of the following is a heteroatom?
🔴 ① C
🟢 ② H
🟡 ③ O
🔵 ④ Both (③) and (④)
🟢 Answer: ③ O
🎯 Difficulty: NEET

🔵 Question 23:
The reagent used to detect halogens in Lassaigne’s test is:
🔴 ① AgNO₃
🟢 ② FeSO₄
🟡 ③ Na₂S₂O₃
🔵 ④ KMnO₄
🟢 Answer: ① AgNO₃
🎯 Difficulty: NEET

🔵 Question 24:
The IUPAC name of CH₃–CH₂–COOH is:
🔴 ① Ethanoic acid
🟢 ② Propanoic acid
🟡 ③ Methanoic acid
🔵 ④ Butanoic acid
🟢 Answer: ② Propanoic acid
🎯 Difficulty: NEET

🔵 Question 25:
The functional isomer of ethanol is:
🔴 ① Methanol
🟢 ② Dimethyl ether
🟡 ③ Propanol
🔵 ④ Ethanoic acid
🟢 Answer: ② Dimethyl ether
🎯 Difficulty: NEET

🔵 Question 26:
The IUPAC name of tert-butyl alcohol is:
🔴 ① 2-butanol
🟢 ② 2-methylpropan-2-ol
🟡 ③ 1-butanol
🔵 ④ 2-propanol
🟢 Answer: ② 2-methylpropan-2-ol
🎯 Difficulty: JEE Main

🔵 Question 27:
Which of the following pairs are functional isomers?
🔴 ① CH₃–CH₂–OH and CH₃–O–CH₃
🟢 ② CH₄ and C₂H₆
🟡 ③ CH₃–CHO and CH₃–COOH
🔵 ④ C₂H₆ and C₂H₄
🟢 Answer: ① CH₃–CH₂–OH and CH₃–O–CH₃
🎯 Difficulty: JEE Main

🔵 Question 28:
Which of the following has sp² hybridised carbon?
🔴 ① CH₄
🟢 ② C₂H₄
🟡 ③ C₂H₂
🔵 ④ C₂H₆
🟢 Answer: ② C₂H₄
🎯 Difficulty: JEE Main

🔵 Question 29:
Which of the following is an electrophile?
🔴 ① NH₃
🟢 ② AlCl₃
🟡 ③ H₂O
🔵 ④ OH⁻
🟢 Answer: ② AlCl₃
🎯 Difficulty: JEE Main

🔵 Question 30:
Which statement is true about resonance?
🔴 ① Resonance structures exist in isolation
🟢 ② The real molecule is a hybrid of resonance structures
🟡 ③ Resonance decreases stability
🔵 ④ Resonance makes bond lengths unequal
🟢 Answer: ② The real molecule is a hybrid of resonance structures
🎯 Difficulty: JEE Main

🔵 Question 31:
The IUPAC name of acetic acid is:
🔴 ① Ethanoic acid
🟢 ② Methanoic acid
🟡 ③ Propanoic acid
🔵 ④ Butanoic acid
🟢 Answer: ① Ethanoic acid
🎯 Difficulty: JEE Main

🔵 Question 32:
Which of the following is an example of geometrical isomerism?
🔴 ① C₂H₂
🟢 ② C₂H₄Cl₂
🟡 ③ CH₄
🔵 ④ C₂H₆
🟢 Answer: ② C₂H₄Cl₂
🎯 Difficulty: JEE Main

🔵 Question 33:
Among the following, which is a nucleophile?
🔴 ① H⁺
🟢 ② OH⁻
🟡 ③ BF₃
🔵 ④ AlCl₃
🟢 Answer: ② OH⁻
🎯 Difficulty: JEE Main

🔵 Question 34:
The order of stability of carbocations is:
🔴 ① 1° > 2° > 3°
🟢 ② 3° > 2° > 1°
🟡 ③ 2° > 3° > 1°
🔵 ④ 2° > 1° > 3°
🟢 Answer: ② 3° > 2° > 1°
🎯 Difficulty: JEE Main

🔵 Question 35:
Which of the following is a heterolytic fission?
🔴 ① Formation of free radicals
🟢 ② Formation of carbocations and anions
🟡 ③ Breaking into atoms
🔵 ④ None
🟢 Answer: ② Formation of carbocations and anions
🎯 Difficulty: JEE Main

🔵 Question 36:
Which of the following has highest boiling point?
🔴 ① CH₃OH
🟢 ② CH₃CH₂CH₃
🟡 ③ CH₃OCH₃
🔵 ④ CH₃CHO
🟢 Answer: ① CH₃OH
🎯 Difficulty: JEE Main

🔵 Question 37:
Which of the following shows tautomerism?
🔴 ① CH₃CH₂OH
🟢 ② CH₃–CO–CH₂–H
🟡 ③ CH₄
🔵 ④ C₂H₆
🟢 Answer: ② CH₃–CO–CH₂–H
🎯 Difficulty: JEE Main

🔵 Question 38:
Which of the following gives a positive test with Tollens’ reagent?
🔴 ① CH₃–CH₂–OH
🟢 ② HCHO
🟡 ③ CH₃–CO–CH₃
🔵 ④ CH₃–O–CH₃
🟢 Answer: ② HCHO
🎯 Difficulty: JEE Main

🔵 Question 39:
Which of the following is the strongest acid?
🔴 ① CH₃COOH
🟢 ② CCl₃COOH
🟡 ③ CH₂ClCOOH
🔵 ④ ClCH₂CH₂COOH
🟢 Answer: ② CCl₃COOH
🎯 Difficulty: JEE Main

🔵 Question 40:
The reagent used to test unsaturation in hydrocarbons is:
🔴 ① Br₂ in CCl₄
🟢 ② KMnO₄ solution
🟡 ③ Both (①) and (②)
🔵 ④ AgNO₃ solution
🟢 Answer: ③ Both (①) and (②)
🎯 Difficulty: JEE Main

🚀 Advanced-level (Q41–Q50):

🔵 Question 41:
Which of the following shows optical isomerism?
🔴 ① 1-chloropropane
🟢 ② 2-chlorobutane
🟡 ③ 2-methylpropane
🔵 ④ n-butane
🟢 Answer: ② 2-chlorobutane
🎯 Difficulty: JEE Advanced

🔵 Question 42:
The order of +I effect of alkyl groups is:
🔴 ① –CH₃ < –C₂H₅ < –C₃H₇ < –C(CH₃)₃ 🟢 ② –C(CH₃)₃ < –C₃H₇ < –C₂H₅ < –CH₃ 🟡 ③ –CH₃ > –C₂H₅ > –C₃H₇ > –C(CH₃)₃
🔵 ④ –CH₃ = –C₂H₅ = –C₃H₇
🟢 Answer: ① –CH₃ < –C₂H₅ < –C₃H₇ < –C(CH₃)₃
🎯 Difficulty: JEE Advanced

🔵 Question 43:
Which of the following carbanions is most stable?
🔴 ① CH₃⁻
🟢 ② C₆H₅⁻
🟡 ③ CH₂=CH⁻
🔵 ④ C₂H₅⁻
🟢 Answer: ② C₆H₅⁻
🎯 Difficulty: JEE Advanced

🔵 Question 44:
The inductive effect decreases with:
🔴 ① Increase in chain length
🟢 ② Decrease in chain length
🟡 ③ Branching
🔵 ④ Presence of double bonds
🟢 Answer: ① Increase in chain length
🎯 Difficulty: JEE Advanced

🔵 Question 45:
The acidity order of substituted benzoic acids is:
🔴 ① p-NO₂ > p-Cl > H > p-CH₃
🟢 ② p-CH₃ > H > p-Cl > p-NO₂
🟡 ③ H > p-Cl > p-NO₂ > p-CH₃
🔵 ④ H > p-CH₃ > p-Cl > p-NO₂
🟢 Answer: ① p-NO₂ > p-Cl > H > p-CH₃
🎯 Difficulty: JEE Advanced

🔵 Question 46:
Which effect explains the higher acidity of formic acid compared to acetic acid?
🔴 ① Resonance effect
🟢 ② Inductive effect
🟡 ③ Hyperconjugation
🔵 ④ Steric effect
🟢 Answer: ② Inductive effect
🎯 Difficulty: JEE Advanced

🔵 Question 47:
Which type of fission is involved in free radical halogenation?
🔴 ① Heterolytic
🟢 ② Homolytic
🟡 ③ Ionic
🔵 ④ None
🟢 Answer: ② Homolytic
🎯 Difficulty: JEE Advanced

🔵 Question 48:
Among CH₄, NH₃, H₂O, and HF, which shows maximum hydrogen bonding?
🔴 ① CH₄
🟢 ② NH₃
🟡 ③ H₂O
🔵 ④ HF
🟢 Answer: ④ HF
🎯 Difficulty: JEE Advanced

🔵 Question 49:
Which of the following compounds is aromatic?
🔴 ① Cyclobutadiene
🟢 ② Benzene
🟡 ③ Cyclooctatetraene
🔵 ④ Cyclopentadienyl cation
🟢 Answer: ② Benzene
🎯 Difficulty: JEE Advanced

🔵 Question 50:
The correct order of stability of free radicals is:
🔴 ① 1° > 2° > 3°
🟢 ② 3° > 2° > 1°
🟡 ③ 2° > 3° > 1°
🔵 ④ 1° = 2° = 3°
🟢 Answer: ② 3° > 2° > 1°
🎯 Difficulty: JEE Advanced

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