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Organic Reactions

GATE Chemistry - Organic Reactions including substitutions, additions, eliminations, named reactions, and reagent properties

15 Questions Published
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Questions

Question 1 Multiple Choice (Single Answer)

Assertion: When acetylene reacts with methylmagnesium bromide, hydrogen is evolved.
Reason: Grignard reagent is an organometallic compound of Mg+2.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
Question 2 Multiple Choice (Single Answer)

Which of the following statements is/are false?
A. Dehydration of 1-methylcyclohexanol with H2SO4 gives methylenecyclohexane.
B. Lewisite is obtained by addition of AlCl3 to ethyne.
C. Lindlar’s catalyst is palladium supported over calcium carbonate partially poisoned by addition of lead acetate.

  1. Only A
  2. Only B
  3. A and B
  4. B and C
  5. A and C
Question 3 Multiple Choice (Single Answer)

Which of the following statements is/are true?
A. Benzene reacts with isobutyl chloride in presence of anhydrous AlCl3 to give isobutylbenzene.
B. Reduction of 2-butyne with NaNH2 in liquid NH3 gives cis-2-butene.
C. Baeyer’s reagent can be used to distinguish cyclopropane from propene.

  1. Only A
  2. Only B
  3. A and B
  4. A and C
  5. Only C
Question 4 Multiple Choice (Single Answer)

Assertion: Benzene reacts with Cl2 in presence of light to form BHC.
Reason: BHC is also called gammexane or 666.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
Question 5 Multiple Choice (Single Answer)

Assertion: Lewisite is less poisonous than mustard gas.
Reason: Lewisite is obtained by the action of aluminium trichloride with acetylene in presence of anhydrous AsCl3.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
Question 6 Multiple Choice (Single Answer)

Assertion: Benzene does not decolourise Br2 water.
Reason: Benzene is stabilized by resonance due to delocalization of π-electrons.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
Question 7 Multiple Choice (Single Answer)

Assertion: In Kolbe’s electrolytic method, if there are n-carbon atoms in the parent acid, the alkane produced will have (n-1) carbon atoms.
Reason: Ethylene and acetylene cannot be prepared by this method.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
Question 8 Multiple Choice (Single Answer)

Assertion: Treatment of 1, 3-dibromopropane with zinc produces cyclopropane.
Reason: The reaction of alkyl halides with zinc dust is called frankland reaction.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
Question 9 Multiple Choice (Single Answer)

Assertion: Propene is more reactive than ethene towards electrophilic addition reactions.
Reason: Hyperconjugation effect of the CH3 group increases the electron density in the double bond.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
Question 10 Multiple Choice (Single Answer)

Assertion: During cracking of alkanes, C-C rather than C-H bonds break.
Reason: The bond dissociation energy of C-C bond is lower than that of C-H bond.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
Question 11 Multiple Choice (Single Answer)

Assertion: Addition of HBr to HC ≡ C − CH2 − CH = CH2 gives HC ≡ C − CH2 − CHBr − CH3 and not H2C = CBr − CH2 − CHBr − CH3.
Reason: A triple bond is less reactive than a double bond.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
Question 12 Multiple Choice (Single Answer)

Assertion: Activation fuels contain a high percentage of highly branched chain alkanes.
Reason: The octane number of branched chain alkanes is lower than that of straight chain alkanes.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
Question 13 Multiple Choice (Single Answer)

Assertion: 1-Chlorobutane on heating with alcoholic KOH undergoes dehydrohalogenation to yield 1-butene as the major product.
Reason: The reaction does not occur through carbocation intermediate but instead occurs by a concerted mechanism.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
Question 14 Multiple Choice (Single Answer)

Assertion: 1-Butenol on dehydration with conc. H2SO4 mainly produces 1-butene.
Reason: The initially formed primary carbocation rearranges to more stable secondary carbocation before losing a proton to form 2-butene as the major product.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
Question 15 Multiple Choice (Single Answer)

Assertion: The octane number of branched chain hydrocarbon is higher than that of unbranched chain hydrocarbons.
Reason: The branched chain hydrocarbons are more volatile than unbranched chain hydrocarbons.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
  5. Both A and R are false.
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