300 short question answers on organic chemistry of class 12 - Complete revision

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25 short question-answer  on Haloalkanes :

Basic Concepts

  1. What are haloalkanes?
    → Organic compounds containing a halogen (X = F, Cl, Br, I) attached to an alkyl group.

  2. How are haloalkanes classified?
    → Based on the carbon to which halogen is attached:

    • Primary (1°): R-CH₂-X
    • Secondary (2°): R₂-CH-X
    • Tertiary (3°): R₃-C-X

  3. Which is more reactive: alkyl halides or aryl halides?
    → Alkyl halides, because aryl halides have resonance stabilization.

  4. Which is the best leaving group among halogens?
    → I⁻ (Iodide) because it is the largest and weakest base.

  5. Why do haloalkanes have higher boiling points than alkanes?
    → Due to dipole-dipole interactions and van der Waals forces.

Preparation of Haloalkanes

  1. How is chloromethane prepared from methane?
    → By free radical halogenation:
    CH₄ + Cl₂ → CH₃Cl + HCl (in sunlight)

  2. How can alcohols be converted to haloalkanes?
    → By using:

    • HCl, HBr, or HI
    • PCl₅, PCl₃, SOCl₂ (best method for Cl)

  3. What is the best method for preparing alkyl chlorides from alcohols?
    → SOCl₂ (Thionyl chloride) in pyridine as it gives pure alkyl chloride.

  4. Which method is used to prepare fluoroalkanes?
    → Swarts reaction: R-Br + AgF → R-F + AgBr

  5. How are haloalkanes prepared from alkenes?
    → By electrophilic addition of HX:

    • CH₂=CH₂ + HBr → CH₃-CH₂Br (Markovnikov's rule)

Physical & Chemical Properties

  1. Why are haloalkanes insoluble in water?
    → They cannot form strong hydrogen bonds with water.

  2. Which is more reactive: R-Cl or R-I?
    → R-I, because the C-I bond is weaker and more easily broken.

  3. What is the effect of branching on the boiling point of haloalkanes?
    → More branching lowers the boiling point due to reduced surface area.

  4. What is the order of dipole moment among CH₃F, CH₃Cl, CH₃Br, CH₃I?
    → CH₃Cl > CH₃F > CH₃Br > CH₃I due to bond polarity and size.

  5. Why are tertiary haloalkanes more reactive in SN1 reactions?
    → Due to the formation of a stable carbocation intermediate.

Reactions of Haloalkanes

  1. What happens when alkyl halides react with aqueous KOH?
    → Nucleophilic substitution:
    R-X + KOH → R-OH + KX

  2. What happens when alkyl halides react with alcoholic KOH?
    → Elimination (β-elimination) to form an alkene:
    R-CH₂-CH₂-X + alc. KOH → R-CH=CH₂ + HX

  3. Which type of haloalkane undergoes SN1 reaction fastest?
    → Tertiary (3°) alkyl halides, due to stable carbocation formation.

  4. Which type of haloalkane undergoes SN2 reaction fastest?
    → Primary (1°) alkyl halides, because steric hindrance is least.

  5. What is Wurtz reaction?
    → Alkyl halide + Na + Dry ether → Alkane
    2R-X + 2Na → R-R + 2NaX

Important Named Reactions

  1. What is Finkelstein reaction?
    → Exchange of halogens:
    R-Cl + NaI → R-I + NaCl (in acetone)

  2. What is the Sandmeyer reaction?
    → Aryl diazonium salt + Cu₂X → Aryl halide

    • C₆H₅N₂⁺Cl⁻ + Cu₂Cl₂ → C₆H₅Cl + N₂

  3. What is Swarts reaction?
    → Alkyl bromide/chloride reacts with AgF or Hg₂F₂ to form fluoroalkanes.

  4. What is the difference between SN1 and SN2 reactions?
    → SN1: Two-step, carbocation formation, tertiary > secondary > primary.
    → SN2: One-step, backside attack, primary > secondary > tertiary.

  5. How can alkyl halides be converted to Grignard reagents?
    → By reacting with Mg in dry ether:
    R-X + Mg → R-MgX (Grignard reagent)

25 short question-answer  on Haloarenes 

Basic Concepts of Haloarenes

  1. What are haloarenes?

    • Aromatic compounds in which one or more hydrogen atoms of benzene are replaced by halogen atoms.

  2. Give an example of a haloarene.

    • Chlorobenzene (C₆H₅Cl)

  3. How are haloarenes classified based on the number of halogen atoms?

    • Monohaloarenes, Dihaloarenes, and Polyhaloarenes

  4. Why do haloarenes have a higher boiling point than benzene?

    • Due to stronger dipole-dipole interactions and van der Waals forces caused by the presence of halogen atoms.

Preparation of Haloarenes

  1. Which reaction is used to prepare haloarenes from benzene?

    • Electrophilic aromatic substitution (Halogenation reaction).

  2. What is the role of FeBr₃ in the bromination of benzene?

    • It acts as a Lewis acid catalyst and generates the electrophile Br⁺ (bromonium ion).

  3. How is chlorobenzene prepared from aniline?

    • By Sandmeyer’s reaction (using CuCl/HCl).

  4. Which reaction is used to prepare aryl iodides?

    • Balz-Schiemann reaction (by treating aryl diazonium salts with KI).

Physical Properties of Haloarenes

  1. Why are haloarenes less soluble in water?

    • Due to their non-polar nature and inability to form hydrogen bonds with water.

  2. How does the boiling point of haloarenes change with an increase in halogen size?

  • Boiling point increases in the order Fluoro < Chloro < Bromo < Iodo.

Chemical Reactions of Haloarenes

  1. Why do haloarenes undergo electrophilic substitution instead of nucleophilic substitution?
  • The delocalization of lone pairs of halogen into the benzene ring reduces the partial positive charge on carbon, making it less susceptible to nucleophilic attack.
  1. What is the major product when chlorobenzene is nitrated with concentrated HNO₃ and H₂SO₄?
  • p-Nitrochlorobenzene and o-Nitrochlorobenzene (para is the major product).
  1. Why do haloarenes show low reactivity towards nucleophilic substitution reactions?
  • Due to resonance stabilization and partial double bond character of C-X bond.
  1. What happens when chlorobenzene reacts with NaOH at 623K and 300 atm pressure?
  • It forms sodium phenoxide, which on acidification gives phenol.
  1. What is the product of the reaction of bromobenzene with Mg in dry ether?
  • Phenyl magnesium bromide (Grignard reagent).

Special Reactions of Haloarenes

  1. What is Fittig reaction?
  • When haloarenes react with sodium in dry ether, they form a biaryl compound (e.g., biphenyl).
  1. What is the Wurtz-Fittig reaction?
  • A reaction between aryl halides and alkyl halides in presence of Na/dry ether to form alkylated benzene.
  1. What is the product when chlorobenzene is treated with Na metal in liquid ammonia?
  • Benzyne intermediate is formed, leading to nucleophilic substitution reactions.
  1. What is the effect of electron-withdrawing groups (-NO₂) on nucleophilic substitution of haloarenes?
  • They increase reactivity by stabilizing the intermediate carbanion.
  1. Which product is obtained when p-dichlorobenzene is heated with NaNH₂ in liquid ammonia?
  • p-Phenylenediamine

Application-Based Questions

  1. Why is chlorobenzene less reactive than benzyl chloride towards nucleophilic substitution?
  • Chlorobenzene is stabilized by resonance, while benzyl chloride forms a stable benzyl carbocation.
  1. Which is more reactive towards SN1, benzyl chloride or chlorobenzene?
  • Benzyl chloride, as it forms a stable benzyl carbocation.
  1. Why does fluorobenzene show lower reactivity than chlorobenzene?
  • Due to stronger C-F bond (high bond dissociation energy).
  1. How can you distinguish between chlorobenzene and benzyl chloride?
  • Aqueous NaOH test: Benzyl chloride undergoes hydrolysis, while chlorobenzene does not.
  1. What is the product of chlorobenzene when treated with methyl chloride in the presence of AlCl₃?
  • p-Chlorotoluene (Friedel-Crafts alkylation).


25 short question-answer on Alcohol

Basic Concepts

  1. What is the general formula of alcohols?

    • CnH2n+1OH (for monohydric alcohols)

  2. How are alcohols classified based on the number of hydroxyl (-OH) groups?

    • Monohydric, Dihydric, Trihydric, and Polyhydric alcohols

  3. How are alcohols classified based on the nature of the carbon attached to the -OH group?

    • Primary (1°), Secondary (2°), and Tertiary (3°) alcohols

  4. Which type of hybridization is shown by the oxygen in alcohols?

    • sp³ hybridization

Preparation of Alcohols

  1. Name two methods for the preparation of alcohols from alkenes.

    • Acid-catalyzed hydration and Hydroboration-oxidation

  2. Which reagent is used in hydroboration-oxidation of alkenes to form alcohols?

    • BH₃·THF followed by H₂O₂/NaOH

  3. What is the major product in acid-catalyzed hydration of alkenes?

    • Markovnikov alcohol (OH attaches to the more substituted carbon).

  4. Which reagent is used to convert aldehydes and ketones to alcohols?

    • LiAlH₄ (Lithium Aluminium Hydride) or NaBH₄ (Sodium Borohydride)

  5. Which reagent is used to convert carboxylic acids to primary alcohols?

    • LiAlH₄ (NaBH₄ does not reduce carboxylic acids).

  6. What is the product of the reaction between Grignard reagent and formaldehyde?

    • Primary alcohol

Physical Properties of Alcohols

  1. Why do alcohols have a higher boiling point than alkanes of similar molecular mass?

    • Due to hydrogen bonding.

  2. Which alcohol is most soluble in water?

    • Methanol (CH₃OH), as it has the smallest alkyl group.

  3. What happens to the solubility of alcohols in water as the carbon chain increases?

    • Solubility decreases due to increased hydrophobic character.

Chemical Reactions of Alcohols

  1. What is Lucas' test used for?

    • To distinguish between primary, secondary, and tertiary alcohols using ZnCl₂/HCl.

  2. Which alcohol reacts fastest in Lucas' test?

    • Tertiary alcohol (forms turbidity immediately).

  3. What is the product when an alcohol reacts with sodium metal?

    • Sodium alkoxide and hydrogen gas (H₂).

  4. What is the product when ethanol is heated with concentrated H₂SO₄ at 170°C?

    • Ethene (alkene formation via dehydration).

  5. Which reagent is used for oxidation of primary alcohols to aldehydes?

    • PCC (Pyridinium chlorochromate)

  6. Which reagent is used for oxidation of primary alcohols to carboxylic acids?

    • K₂Cr₂O₇/H₂SO₄ or KMnO₄.

  7. What is the product when phenol reacts with bromine water?

    • 2,4,6-Tribromophenol (white precipitate).

Special Reactions of Alcohols

  1. What is the main product when tertiary butyl alcohol reacts with concentrated HCl?

    • Tert-butyl chloride (via SN1 mechanism).

  2. Which alcohol shows the highest reactivity towards acid-catalyzed dehydration?

    • Tertiary alcohols (due to stable carbocation formation).

  3. What is the product when ethanol is treated with Cu at 300°C?

    • Acetaldehyde (CH₃CHO) via dehydrogenation.

  4. What is the product when methanol is heated with HI?

    • Methyl iodide (CH₃I).

  5. How will you distinguish between ethanol and methanol using a simple test?

    • Iodoform test: Ethanol gives a yellow precipitate of CHI₃, methanol does not.


25 short question-answer  on Phenol 

Basic Concepts of Phenol

  1. What is the chemical formula of phenol?

    • C₆H₅OH

  2. How is phenol different from alcohols?

    • Phenol has an -OH group directly attached to an aromatic ring, making it more acidic than alcohols.

  3. Why is phenol more acidic than ethanol?

    • Due to resonance stabilization of the phenoxide ion after deprotonation.

  4. Which type of hybridization does the oxygen in phenol exhibit?

    • sp³ hybridization

Preparation of Phenol

  1. What is the Dow’s process for phenol preparation?

    • Chlorobenzene reacts with NaOH at 623 K and 300 atm to form sodium phenoxide, which on acidification gives phenol.

  2. Which industrial method is used to manufacture phenol?

    • Cumene process (oxidation of cumene followed by acid treatment).

  3. What is the main reactant in the cumene process?

    • Cumene (Isopropylbenzene)

  4. How can phenol be prepared from benzene sulfonic acid?

    • By fusing benzene sulfonic acid with NaOH at high temperature.

  5. Which reagent is used to prepare phenol from diazonium salt?

    • H₂O or Cu₂O in acidic medium.

Physical Properties of Phenol

  1. Why is phenol soluble in water?
  • Due to hydrogen bonding with water molecules.
  1. Why does phenol have a higher boiling point than benzene?
  • Due to intermolecular hydrogen bonding.
  1. What is the state of pure phenol at room temperature?
  • It is a white crystalline solid.

Chemical Reactions of Phenol

  1. What is the product when phenol reacts with bromine water?
  • 2,4,6-Tribromophenol (white precipitate).
  1. What happens when phenol is treated with concentrated HNO₃?
  • It forms 2,4,6-Trinitrophenol (Picric acid).
  1. What is the major product when phenol undergoes nitration with dilute HNO₃?
  • o-Nitrophenol and p-Nitrophenol (para is the major product).
  1. Why does phenol show electrophilic substitution more easily than benzene?
  • Due to the activating effect of the -OH group, which increases electron density at ortho and para positions.
  1. What is the product of the reaction between phenol and Zn metal?
  • Benzene (C₆H₆) and ZnO.
  1. What happens when phenol reacts with FeCl₃?
  • It gives a violet-colored complex, used as a test for phenol.
  1. What is the Kolbe’s reaction?
  • Phenol reacts with NaOH and CO₂ to form salicylic acid.
  1. What is the Reimer-Tiemann reaction?
  • Phenol reacts with CHCl₃ and NaOH to form salicylaldehyde.

Application-Based Questions

  1. Why is phenol more reactive than benzene towards electrophilic substitution?
  • Due to the +M (resonance donating) effect of the -OH group.
  1. Which product is obtained when phenol is treated with NaOH followed by an alkyl halide?
  • Ether (Williamson ether synthesis).
  1. How can you distinguish phenol from alcohols?
  • FeCl₃ test: Phenol gives a violet color, alcohols do not.
  1. What happens when phenol is heated with zinc dust?
  • It forms benzene.
  1. Why does phenol turn pink on exposure to air?
  • Due to slow oxidation forming quinones.


25 short question-answer  on Ethers 

Basic Concepts of Ethers

  1. What is the general formula of ethers?

    • R-O-R'

  2. How are ethers classified?

    • Symmetrical (same alkyl groups) and Unsymmetrical (different alkyl groups).

  3. Give an example of a symmetrical ether.

    • Dimethyl ether (CH₃-O-CH₃)

  4. Give an example of an unsymmetrical ether.

    • Ethyl methyl ether (CH₃-O-C₂H₅)

  5. Why do ethers have low boiling points compared to alcohols?

    • They cannot form hydrogen bonds with themselves.

Preparation of Ethers

  1. Which reaction is commonly used to prepare ethers?

    • Williamson Ether Synthesis

  2. Which reagents are used in Williamson Ether Synthesis?

    • Alkoxide (R-O⁻) and Alkyl halide (R-X)

  3. Why are tertiary alkyl halides not used in Williamson Ether Synthesis?

    • They undergo elimination instead of substitution.

  4. How is diethyl ether prepared industrially?

    • By heating ethanol with H₂SO₄ at 140°C.

  5. What is the major product when excess ethanol reacts with H₂SO₄ at 140°C?

    • Diethyl ether (C₂H₅-O-C₂H₅).

Physical Properties of Ethers

  1. Why are ethers soluble in water?
  • They form hydrogen bonds with water.
  1. Why do ethers have lower boiling points than alcohols?
  • Lack of intermolecular hydrogen bonding.

Chemical Reactions of Ethers

  1. What happens when ethers react with HI?
  • They undergo cleavage to form alcohol and alkyl halide.
  1. What is the major product when ethyl methyl ether reacts with HI?
  • Methyl iodide (CH₃I) and ethanol (C₂H₅OH).
  1. Which ether shows the fastest cleavage with HI?
  • Methyl tert-butyl ether (due to formation of stable tert-butyl carbocation).
  1. Why do ethers resist reaction with nucleophiles?
  • Due to the absence of a good leaving group.
  1. What is the product when diethyl ether is exposed to air for a long time?
  • Peroxides (explosive ether peroxides).
  1. What happens when ethers react with phosphorus pentachloride (PCl₅)?
  • They form alkyl chlorides and POCl₃.

Special Reactions of Ethers

  1. What is the major product when anisole (methoxybenzene) undergoes bromination?
  • p-Bromoanisole (major) and o-Bromoanisole.
  1. Why does anisole undergo electrophilic substitution more readily than benzene?
  • Due to the +M effect of the -OCH₃ group.
  1. What is the product of anisole when treated with HI?
  • Iodomethane (CH₃I) and phenol (C₆H₅OH).

Application-Based Questions

  1. Why do ethers act as good solvents?
  • They are chemically inert and dissolve both polar and nonpolar compounds.
  1. How can you distinguish between ether and alcohol?
  • Alcohol gives a positive Lucas test, ether does not.
  1. What is the structure of crown ethers used for?
  • Encapsulating metal cations (used in phase transfer catalysis).
  1. What happens when ether vapors are passed over hot Al₂O₃?
  • They undergo dehydration to form alkenes.


25 short question-answer on Amines 

Basic Concepts

  1. What are amines?
    → Amines are organic compounds derived from ammonia (NH₃) by replacing one or more hydrogen atoms with alkyl or aryl groups.

  2. How are amines classified?
    → Based on the number of alkyl/aryl groups attached to nitrogen:

    • Primary (1°) amine: R-NH₂
    • Secondary (2°) amine: R₂-NH
    • Tertiary (3°) amine: R₃-N

  3. Which amine has the highest boiling point?
    → Primary amines (1°) due to strong hydrogen bonding.

  4. Which amine is least soluble in water?
    → Tertiary amines (3°), as they cannot form hydrogen bonds with water.

  5. Why are amines basic in nature?
    → Due to the presence of a lone pair of electrons on nitrogen, which can accept a proton (H⁺).

Preparation of Amines

  1. How are amines prepared by the reduction of nitro compounds?
    → Nitro compounds (-NO₂) can be reduced to amines (-NH₂) using:

    • Sn/HCl
    • Fe/HCl
    • Catalytic hydrogenation (H₂/Pd)

  2. Write the reaction of the Gabriel Phthalimide synthesis.
    → Phthalimide + Alkyl halide + Base → Primary Amine

  3. Why is Gabriel Phthalimide synthesis not suitable for making aromatic amines?
    → Aryl halides do not undergo nucleophilic substitution easily.

  4. What is Hofmann Bromamide reaction?
    → Amide + Br₂ + NaOH → Primary Amine (R-NH₂)

    • Example: CH₃CONH₂ → CH₃NH₂

  5. What is the product when an amide is treated with LiAlH₄?
    → LiAlH₄ reduces amides to primary amines.

Physical & Chemical Properties

  1. Which is more basic: NH₃ or CH₃NH₂?
    → CH₃NH₂ (methylamine) because the methyl group (+I effect) increases electron density on nitrogen.

  2. What is the effect of resonance on the basicity of aniline?
    → Resonance decreases basicity because the lone pair of nitrogen is delocalized into the benzene ring.

  3. Arrange NH₃, CH₃NH₂, (CH₃)₂NH, and (CH₃)₃N in increasing order of basicity in aqueous medium.
    → NH₃ < (CH₃)₃N < CH₃NH₂ < (CH₃)₂NH

  4. What happens when aniline reacts with Br₂ water?
    → 2,4,6-Tribromoaniline is formed as a white precipitate.

  5. What is Carbylamine reaction?
    → Primary amine + CHCl₃ + KOH → Isocyanide (foul smell)

  • Used to test for primary amines.

  1. Why do tertiary amines not undergo acylation?
    → Tertiary amines (R₃N) lack a hydrogen atom to react with acyl halides.

  2. What is the Hinsberg test used for?
    → To distinguish between 1°, 2°, and 3° amines using Hinsberg reagent (benzenesulfonyl chloride, C₆H₅SO₂Cl).

  3. What happens when aniline reacts with HNO₂ at 0°C?
    → It forms benzenediazonium chloride (C₆H₅N₂⁺Cl⁻).

Reactions of Amines

  1. What is diazotization?
    → The reaction of primary aromatic amines with NaNO₂ + HCl at 0-5°C to form diazonium salts.

  2. What happens when diazonium salts are treated with Cu₂Cl₂ (Sandmeyer reaction)?
    → The diazonium group (-N₂⁺) is replaced by -Cl to form chlorobenzene.

  3. What is the product of aniline with excess methyl iodide (CH₃I)?
    → Quaternary ammonium salt (C₆H₅N(CH₃)₃⁺ I⁻).

  4. What is the product when aniline is treated with acetic anhydride?
    → Acetanilide (C₆H₅NHCOCH₃).

  5. What is the product of aniline with bromine water?
    → 2,4,6-Tribromoaniline (white precipitate).

  6. What happens when amines react with nitrous acid (HNO₂)?

  • 1° amines: Form diazonium salts.
  • 2° amines: Form N-nitrosoamines (yellow oily layer).
  • 3° amines: Form water-soluble nitrite salts.
  1. How can aniline be converted to benzene?
    → Aniline → Benzene diazonium chloride → Benzene
  • Use H₃PO₂ (hypophosphorous acid) to remove N₂.

25 short question-answer pairs  Aldehydes 

Basic Concepts of Aldehydes

  1. What is the general formula of aldehydes?

    • R-CHO

  2. Which functional group is present in aldehydes?

    • -CHO (Formyl group)

  3. Give an example of an aldehyde.

    • Formaldehyde (HCHO) or Acetaldehyde (CH₃CHO)

  4. Why are aldehydes more reactive than ketones?

    • Due to less steric hindrance and stronger electrophilic nature of the carbonyl carbon.

  5. Why do aldehydes have higher boiling points than alkanes but lower than alcohols?

    • They have dipole-dipole interactions but lack hydrogen bonding.

Preparation of Aldehydes

  1. How can aldehydes be prepared from primary alcohols?

    • By oxidation using PCC (Pyridinium chlorochromate).

  2. Which reagent is used to prepare aldehydes from acyl chlorides?

    • Rosenmund’s reduction (H₂, Pd/BaSO₄, poisoned with sulfur or quinoline).

  3. Which reagent is used to prepare aldehydes from nitriles?

    • Partial reduction using DIBAL-H (Diisobutylaluminium hydride).

  4. Which reaction converts benzene to benzaldehyde?

    • Gattermann-Koch reaction (CO, HCl, AlCl₃, CuCl).

  5. Which reaction converts alkynes to aldehydes?

    • Hydroboration-oxidation (BH₃, H₂O₂/NaOH).

Physical Properties of Aldehydes

  1. Why are lower aldehydes soluble in water?
  • Due to hydrogen bonding with water molecules.
  1. Why does formaldehyde exist as a gas, while benzaldehyde is a liquid?
  • Formaldehyde has a lower molecular weight, leading to weaker intermolecular forces.

Chemical Reactions of Aldehydes

  1. What is the product of the reaction of aldehydes with 2,4-DNP?
  • Hydrazone derivative (yellow/orange precipitate).
  1. What is the product of the reaction of aldehydes with Fehling’s solution?
  • Red precipitate of Cu₂O (Positive test for aldehydes).
  1. What happens when aldehydes react with Tollen’s reagent?
  • Silver mirror is formed due to Ag deposition.
  1. Which reagent is used to differentiate aldehydes and ketones?
  • Tollen’s reagent (Aldehydes give a silver mirror test).
  1. What is the Cannizzaro reaction?
  • Self-oxidation and reduction of aldehydes without alpha-hydrogen using NaOH to form alcohol and carboxylic acid.
  1. What is the product when an aldehyde reacts with HCN?
  • Cyanohydrin (-OH and -CN group on the same carbon).
  1. What is the product when formaldehyde undergoes aldol condensation?
  • Formaldehyde does not undergo aldol condensation (no α-hydrogen).
  1. What is the product when aldehydes react with Grignard reagent?
  • Secondary alcohols (except formaldehyde, which gives primary alcohols).

Special Reactions of Aldehydes

  1. What is the product of the reaction between benzaldehyde and acetophenone in NaOH?
  • Benzalacetophenone (Crossed aldol condensation).
  1. What is the major product when acetaldehyde reacts with NaOH and I₂?
  • Iodoform (Yellow precipitate, CHI₃).
  1. What is the product when benzaldehyde reacts with aniline?
  • Schiff base (C=N bond formation).
  1. How can you distinguish formaldehyde and acetaldehyde?
  • Iodoform test: Acetaldehyde gives a yellow precipitate, formaldehyde does not.
  1. Which aldehyde gives a positive Fehling’s test but not a positive iodoform test?
  • Formaldehyde (HCHO).

25 short question-answer pairs  Ketones 

Basic Concepts of Ketones

  1. What is the general formula of ketones?

    • R-CO-R'

  2. Which functional group is present in ketones?

    • Carbonyl group (C=O) attached to two alkyl or aryl groups.

  3. Give an example of a simple ketone.

    • Acetone (CH₃COCH₃).

  4. Why are ketones less reactive than aldehydes?

    • Due to steric hindrance and reduced electrophilicity of the carbonyl carbon.

  5. Why do ketones have higher boiling points than alkanes but lower than alcohols?

    • They have dipole-dipole interactions but lack hydrogen bonding.

Preparation of Ketones

  1. How can ketones be prepared from secondary alcohols?

    • By oxidation using PCC, K₂Cr₂O₇, or KMnO₄.

  2. Which reagent is used to prepare ketones from acid chlorides?

    • Rosenmund reduction (H₂, Pd/BaSO₄, poisoned with sulfur or quinoline).

  3. Which reaction converts nitriles into ketones?

    • Grignard reagent followed by hydrolysis.

  4. Which reaction converts benzene to acetophenone?

    • Friedel-Crafts acylation (RCOCl, AlCl₃).

  5. What is the major product when alkynes undergo hydration in the presence of Hg²⁺ and H₂SO₄?

    • Ketones (via keto-enol tautomerism).

Physical Properties of Ketones

  1. Why are lower ketones soluble in water?
  • Due to hydrogen bonding with water molecules.
  1. Why do ketones have a distinct smell?
  • Due to their volatile nature and polarity.

Chemical Reactions of Ketones

  1. What is the product of the reaction of ketones with 2,4-DNP?
  • Hydrazone derivative (orange/yellow precipitate).
  1. Do ketones give a positive Fehling’s test?
  • No, because they cannot be easily oxidized.
  1. Do ketones react with Tollen’s reagent?
  • No, as they do not have a hydrogen directly attached to the carbonyl carbon.
  1. What happens when ketones react with hydrogen cyanide (HCN)?
  • Cyanohydrins are formed (-OH and -CN on the same carbon).
  1. Which ketone gives a positive iodoform test?
  • Methyl ketones like Acetone (CH₃COCH₃).
  1. What is the product when ketones undergo reduction with NaBH₄ or LiAlH₄?
  • Secondary alcohols.
  1. What happens when ketones react with Grignard reagents?
  • Tertiary alcohols are formed.
  1. What happens when ketones react with NH₂-NH₂ (Hydrazine) in the presence of KOH?
  • Wolff-Kishner reduction, forming alkanes.

Special Reactions of Ketones

  1. What is the product of aldol condensation of ketones?
  • β-Hydroxy ketones, which further dehydrate to α,β-unsaturated ketones.
  1. What is the major product when ketones react with NaOH and I₂?
  • Iodoform (CHI₃, yellow precipitate).
  1. Which reaction converts ketones to alkanes?
  • Clemmensen reduction (Zn/Hg, HCl) or Wolff-Kishner reduction.
  1. How can you distinguish ketones from aldehydes?
  • Ketones do not give Fehling’s or Tollen’s test, aldehydes do.
  1. Which ketone is the most reactive in nucleophilic addition?
  • Acetone (smallest steric hindrance and more electrophilic carbonyl carbon).

25 short question-answer on Carboxylic Acids 

Basic Concepts of Carboxylic Acids

  1. What is the general formula of carboxylic acids?

    • R-COOH

  2. Which functional group is present in carboxylic acids?

    • Carboxyl group (-COOH)

  3. Give an example of a simple carboxylic acid.

    • Formic acid (HCOOH) or Acetic acid (CH₃COOH).

  4. Why are carboxylic acids more acidic than alcohols?

    • Due to resonance stabilization of the carboxylate anion (R-COO⁻).

  5. Why do carboxylic acids have higher boiling points than alcohols?

    • Due to strong intermolecular hydrogen bonding (dimer formation).

Preparation of Carboxylic Acids

  1. How can carboxylic acids be prepared from primary alcohols?

    • By oxidation using KMnO₄ or K₂Cr₂O₇.

  2. How can carboxylic acids be prepared from alkylbenzenes?

    • By oxidation with KMnO₄ (Side-chain oxidation).

  3. Which reaction converts nitriles to carboxylic acids?

    • Hydrolysis of nitriles using H₃O⁺ or NaOH.

  4. How can carboxylic acids be prepared from Grignard reagents?

    • By reacting RMgX with CO₂, followed by acid hydrolysis.

  5. Which reaction converts aldehydes to carboxylic acids?

    • Oxidation using Tollen’s reagent, Fehling’s solution, or KMnO₄.

Physical Properties of Carboxylic Acids

  1. Why are lower carboxylic acids soluble in water?
  • Due to hydrogen bonding with water molecules.
  1. What is the nature of hydrogen bonding in carboxylic acids?
  • Intermolecular hydrogen bonding, leading to dimer formation.

Chemical Reactions of Carboxylic Acids

  1. What happens when carboxylic acids react with bases?
  • They form carboxylate salts (RCOO⁻ Na⁺).
  1. What happens when carboxylic acids react with PCl₅ or SOCl₂?
  • They form acid chlorides (RCOCl).
  1. Which reagent is used to reduce carboxylic acids to primary alcohols?
  • LiAlH₄ (Lithium Aluminium Hydride).
  1. What is the product when formic acid undergoes oxidation?
  • Carbon dioxide and water.
  1. Which test confirms the presence of carboxyl groups?
  • Reaction with NaHCO₃ (Effervescence due to CO₂ formation).
  1. Which carboxylic acid gives a positive silver mirror test?
  • Formic acid (HCOOH) as it behaves like an aldehyde.
  1. What happens when carboxylic acids react with alcohols in the presence of H₂SO₄?
  • Esterification (Formation of esters).
  1. What is the major product when acetic acid reacts with NH₃ (Ammonia)?
  • Ammonium acetate (CH₃COONH₄).

Special Reactions of Carboxylic Acids

  1. What is the product of decarboxylation of carboxylic acids?
  • Alkanes (RCOOH → RH + CO₂, using soda lime).
  1. What is the reaction of carboxylic acids with sodium metal?
  • Formation of sodium carboxylate and hydrogen gas.
  1. How can carboxylic acids be converted into ketones?
  • Using organolithium reagents (RLi).
  1. How can carboxylic acids be converted into amides?
  • By reacting with NH₃ to form ammonium salts, followed by heating.
  1. Which carboxylic acid is stronger: formic acid or acetic acid?
  • Formic acid, due to the absence of an electron-donating alkyl group.

25 short question-answer on Carboxylic Acid Derivatives 

Basic Concepts of Carboxylic Acid Derivatives

  1. What are carboxylic acid derivatives?

    • Compounds derived from carboxylic acids by replacing the -OH group with another functional group.

  2. Name the four main types of carboxylic acid derivatives.

    • Acid chlorides (RCOCl), esters (RCOOR’), amides (RCONH₂), and anhydrides (RCO-O-COR’).

  3. Which acid derivative is the most reactive?

    • Acid chlorides (due to the presence of an electronegative Cl atom).

  4. Which acid derivative is the least reactive?

    • Amides (due to resonance stabilization).

  5. What is the general order of reactivity of carboxylic acid derivatives?

    • Acid chlorides > Anhydrides > Esters > Amides.

Preparation of Carboxylic Acid Derivatives

  1. How can acid chlorides be prepared from carboxylic acids?

    • By reaction with SOCl₂, PCl₃, or PCl₅.

  2. Which reagent is used to prepare esters from carboxylic acids?

    • Alcohol and H₂SO₄ (Fischer esterification).

  3. How can anhydrides be prepared from carboxylic acids?

    • By dehydration using P₂O₅ or heating two molecules of carboxylic acid.

  4. Which reagent is used to prepare amides from carboxylic acids?

    • NH₃ (Ammonia) or amines followed by heating.

  5. How can esters be prepared from acid chlorides?

    • By reaction with alcohols (RCOCl + R’OH → RCOOR’ + HCl).

Physical Properties of Carboxylic Acid Derivatives

  1. Why do acid chlorides have lower boiling points than carboxylic acids?
  • They cannot form hydrogen bonds.
  1. Why are amides more stable than other derivatives?
  • Due to resonance between the carbonyl oxygen and nitrogen.

Chemical Reactions of Carboxylic Acid Derivatives

  1. What happens when acid chlorides react with water?
  • They hydrolyze to form carboxylic acids.
  1. What is the product of the reaction of acid chlorides with ammonia?
  • Amides (RCOCl + NH₃ → RCONH₂ + HCl).
  1. Which carboxylic acid derivative is hydrolyzed most easily?
  • Acid chlorides, due to the presence of a highly electronegative Cl atom.
  1. Which reagent can reduce acid chlorides to primary alcohols?
  • LiAlH₄ (Lithium Aluminium Hydride).
  1. What happens when esters react with aqueous NaOH?
  • Saponification (Formation of carboxylate salt and alcohol).
  1. What is the product when anhydrides react with alcohols?
  • Esters and carboxylic acids.
  1. What is the major product when esters react with Grignard reagents?
  • Tertiary alcohols.
  1. What happens when amides are heated strongly?
  • They form nitriles (RCONH₂ → RCN + H₂O).

Special Reactions of Carboxylic Acid Derivatives

  1. Which reaction converts esters to alcohols?
  • Reduction using LiAlH₄.
  1. What is the product of the reaction of acid chlorides with Grignard reagents?
  • Tertiary alcohols (via ketone intermediate).
  1. What happens when esters undergo hydrolysis in acidic medium?
  • They form carboxylic acids and alcohols.
  1. Which reaction converts amides to amines?
  • Hofmann degradation (Br₂ + NaOH).
  1. Which carboxylic acid derivative is used in peptide bond formation?
  • Amides (-CONH- bond in proteins).

25 short question-answer  on Benzene Diazonium Chloride (BDC) 

Basic Concepts of Benzene Diazonium Chloride

  1. What is the molecular formula of benzene diazonium chloride?

    • C₆H₅N₂Cl

  2. How is benzene diazonium chloride prepared?

    • By reacting aniline (C₆H₅NH₂) with NaNO₂ and HCl at 0-5°C (Diazotization reaction).

  3. Why is diazotization carried out at low temperatures (0-5°C)?

    • Because benzene diazonium chloride is unstable at higher temperatures and decomposes.

  4. What is the hybridization of the diazonium (-N₂⁺) group in benzene diazonium chloride?

    • sp hybridized.

  5. Why is benzene diazonium chloride soluble in water?

    • Due to its ionic nature.

Physical and Chemical Properties

  1. Why is benzene diazonium chloride unstable?

    • It readily decomposes to release nitrogen gas.

  2. What happens when benzene diazonium chloride is heated in the presence of water?

    • Phenol (C₆H₅OH) is formed.

  3. What is the main gas evolved when benzene diazonium chloride decomposes?

    • Nitrogen gas (N₂).

  4. What happens when benzene diazonium chloride reacts with CuCl?

    • Chlorobenzene (C₆H₅Cl) is formed (Sandmeyer reaction).

  5. What is the role of CuBr in the reaction with benzene diazonium chloride?

  • It replaces the -N₂⁺ group with -Br (Formation of bromobenzene).

Reactions of Benzene Diazonium Chloride

  1. What is formed when benzene diazonium chloride reacts with KI?
  • Iodobenzene (C₆H₅I).
  1. What is the product of the reaction of benzene diazonium chloride with CuCN?
  • Benzonitrile (C₆H₅CN).
  1. Which reaction converts benzene diazonium chloride to fluorobenzene?
  • Balz-Schiemann reaction (Using HBF₄ and heat).
  1. What is the major product when benzene diazonium chloride reacts with H₃PO₂?
  • Benzene (C₆H₆), by reduction.
  1. What happens when benzene diazonium chloride reacts with β-naphthol?
  • An azo dye (Orange-red colored compound) is formed.

Special Reactions of Benzene Diazonium Chloride

  1. What type of reaction is involved in the formation of azo dyes?
  • Coupling reaction with phenols or aromatic amines.
  1. What happens when benzene diazonium chloride reacts with aniline?
  • Azo compound (C₆H₅-N=N-C₆H₄NH₂) is formed (Yellow to orange dye).
  1. Which reagent is used to replace the -N₂⁺ group with hydrogen?
  • H₃PO₂ (Hypophosphorous acid).
  1. Which reaction is used to replace the -N₂⁺ group with a halogen?
  • Sandmeyer reaction (For Cl, Br, CN) and Balz-Schiemann reaction (For F).
  1. What happens when benzene diazonium chloride is treated with ethanol?
  • Benzene is formed as nitrogen gas is released.

Applications and Uses of Benzene Diazonium Chloride

  1. What is the industrial significance of benzene diazonium chloride?
  • Used in dye synthesis (Azo dyes).
  1. Why is benzene diazonium chloride important in organic synthesis?
  • It helps in introducing halogens, cyanide, and other functional groups into benzene.
  1. Which dye is formed when benzene diazonium chloride reacts with phenol?
  • p-Hydroxyazobenzene (Orange azo dye).
  1. How is benzene diazonium chloride used to prepare phenyl hydrazine?
  • By reduction using SnCl₂/HCl.
  1. Why is benzene diazonium chloride considered a good intermediate in organic synthesis?
  • It allows multiple transformations without affecting the benzene ring.

25 short question-answer  on Biomolecules 

Carbohydrates

  1. What are biomolecules?

    • Organic molecules essential for life, including carbohydrates, proteins, lipids, and nucleic acids.

  2. What is the general formula of carbohydrates?

    • (CH₂O)ₙ

  3. What are the three main types of carbohydrates?

    • Monosaccharides, disaccharides, and polysaccharides.

  4. Which monosaccharides form sucrose?

    • Glucose and fructose.

  5. Which carbohydrate is the storage form of energy in animals?

    • Glycogen.

  6. Which test is used to detect the presence of reducing sugars?

    • Benedict’s test or Fehling’s test.

  7. What is the structural difference between starch and cellulose?

    • Starch has α-glycosidic bonds, while cellulose has β-glycosidic bonds.

Proteins and Amino Acids

  1. What are amino acids?

    • Organic compounds containing both amino (-NH₂) and carboxyl (-COOH) functional groups.

  2. How many amino acids are commonly found in proteins?

    • 20.

  3. What is a peptide bond?

  • A covalent bond between the carboxyl group of one amino acid and the amino group of another.
  1. What are the two main types of proteins based on structure?
  • Fibrous and globular proteins.
  1. What is the primary structure of a protein?
  • The sequence of amino acids in a polypeptide chain.
  1. Which reagent is used in the Biuret test for proteins?
  • Copper sulfate (CuSO₄).
  1. What happens when proteins are heated or exposed to extreme pH?
  • They denature (lose their structure and function).

Enzymes

  1. What are enzymes?
  • Biological catalysts that speed up chemical reactions.
  1. What is the active site of an enzyme?
  • The region where the substrate binds and the reaction occurs.
  1. Which model explains enzyme-substrate interaction?
  • Lock and Key model and Induced Fit model.
  1. What are coenzymes?
  • Organic non-protein molecules that assist enzyme function (e.g., vitamins).
  1. Which enzyme converts glucose into ethanol and CO₂?
  • Zymase.

Nucleic Acids (DNA & RNA)

  1. What are the components of a nucleotide?
  • A nitrogenous base, a sugar (ribose or deoxyribose), and a phosphate group.
  1. Which nitrogenous bases are found in DNA?
  • Adenine (A), Thymine (T), Cytosine (C), Guanine (G).
  1. What is the function of mRNA?
  • It carries genetic information from DNA to ribosomes for protein synthesis.
  1. Which bond holds the two strands of DNA together?
  • Hydrogen bonds.
  1. What is the full form of ATP?
  • Adenosine Triphosphate.
  1. Which enzyme is responsible for DNA replication?
  • DNA polymerase.


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