The Proscience Portal

Aldehyde Ketones L 2

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ASSIGNMENT

Section A: Multiple Choice Questions (1 mark each)

  1. Etard reaction converts toluene into:
    a) Benzoic acid b) Benzyl chloride c) Benzaldehyde d) Benzyl alcohol
  2. Which reagent is used in Friedel–Crafts acylation?
    a) ZnCl₂ b) AlCl₃ c) H₂SO₄ d) FeCl₃
  3. Side chain chlorination of toluene gives:
    a) Chlorobenzene b) Benzyl chloride c) o-Chlorotoluene d) Benzaldehyde
  4. Which of the following can reduce esters to aldehydes selectively?
    a) LiAlH₄ b) NaBH₄ c) DIBAL-H d) H₂/Ni
  5. Ketones can be prepared from acid chlorides using:
    a) Grignard reagent b) Gattermann reaction c) Dialkylcadmium d) NaBH₄

Section B: Assertion and Reason (1 mark each)

  1. Assertion: Etard reaction uses chromyl chloride as oxidising agent.
    Reason: It selectively oxidises methyl group of aromatic ring.
  2. Assertion: Gattermann–Koch reaction gives benzaldehyde.
    Reason: It involves CO + HCl in presence of AlCl₃/CuCl.
  3. Assertion: Friedel–Crafts acylation is not used on deactivated rings.
    Reason: Electron-withdrawing groups reduce reactivity of benzene ring.
  4. Assertion: DIBAL-H is used at –78°C for aldehyde formation.
    Reason: Low temperature prevents further reduction of ester to alcohol.
  5. Assertion: Benzyl chloride is formed during side chain halogenation.
    Reason: Chlorination occurs at benzylic position in light or heat.

Section C: One Word Answer (1 mark each)

  1. Which compound is needed along with CO and HCl in Gattermann-Koch reaction?
  2. Write the IUPAC name of benzyl chloride.
  3. Name the reagent used in Etard reaction.
  4. What is the product of Friedel–Crafts acylation of benzene with acetyl chloride?
  5. What is the intermediate formed in Friedel–Crafts acylation?

Section D: Two Mark Questions

  1. Write the balanced equation for Etard reaction starting from toluene.
  2. Write one preparation of ketone using dialkylcadmium.

Section E: Three Mark Questions

a) Explain side chain chlorination of toluene with equation.
b) Write the mechanism of Friedel–Crafts acylation using acetyl chloride.
c) Give one equation showing the conversion of ester to aldehyde using DIBAL-H.

KEY

Section A: Multiple Choice Questions

  1. (c) Benzaldehyde
  2. (b) AlCl₃
  3. (b) Benzyl chloride
  4. (c) DIBAL-H
  5. (c) Dialkylcadmium

Section B: Assertion and Reason

  1. (i) Both A and R are true and R is the correct explanation
  2. (i) Both A and R are true and R is the correct explanation
  3. (i) Both A and R are true and R is the correct explanation
  4. (i) Both A and R are true and R is the correct explanation
  5. (i) Both A and R are true and R is the correct explanation

Section C: One Word Answers

  1. Answer: AlCl₃/CuCl
  2. Answer: Chloromethylbenzene
  3. Answer: CrO₂Cl₂ (Chromyl chloride)
  4. Answer: Acetophenone
  5. Answer: Acylium ion (R–C≡O⁺)

Section D: Two Mark Questions

  1. Answer:
    C₆H₅CH₃ + CrO₂Cl₂ → C₆H₅CH(Cl)₂ (Etard complex) → C₆H₅CHO (Benzaldehyde)
  2. Answer:
    RCOCl + (R’)₂Cd → RCOR’ (ketone)
    Example: CH₃COCl + (CH₃)₂Cd → CH₃COCH₃

Section E: Three Mark Questions

18a. Answer:
C₆H₅CH₃ + Cl₂ → C₆H₅CH₂Cl (benzyl chloride)
Further chlorination → C₆H₅CHCl₂ → C₆H₅CCl₃ (in presence of UV light)

18b. Mechanism of Friedel–Crafts Acylation:
CH₃COCl + AlCl₃ → CH₃C⁺=O (acylium ion)
C₆H₆ + CH₃C⁺=O → C₆H₅COCH₃ (acetophenone)

18c. DIBAL-H Reaction:
RCOOR’ + DIBAL-H (–78°C) → RCHO (aldehyde)
Example: CH₃COOC₂H₅ + DIBAL-H → CH₃CHO