250+ TOP MCQs on Organic Reactions and Answers

Organic Chemistry Multiple Choice Questions on “Organic Reactions”.

1. Identify the one which does not come under the organic addition reaction?
a) Hydration
b) Dehydration
c) Halogenation
d) Hydrohalogenation
Answer: b
Clarification: Dehydration comes under elimination reaction and hence it does not come under addition reaction.

2. Choose the correct one which will react faster in the SN2 nucleophilic substitution reaction?
a) CH₂ – CH = CH₂ = Br
b) CH₂ = CH – CH₂ – Br
c) CH₂ = CH – CH₂ = Br
d) CH = CH₂ – CH₂ – Br
Answer: b
Clarification: The carbocation character in the transition state causes stabilization of the resonance and hence CH₂ = CH – CH₂ – Br (2- bromobutane) is the one which will react faster compared to the others.

3. What will be the reactivity of chlorobenzene in an electrophilic substitution reaction with benzene?
a) Reacts very slowly than benzene
b) Reacts in the same way as benzene
c) Reacts faster than benzene
d) Does not react with benzene
Answer: a
Clarification: The rate of the reaction depends on the electron density in the ring and here in this case resonance is not favorable and the electronegativity dipole dominates. This slows down the reactivity of chlorobenzene.

4. Alcohol on refluxing with Cr₂O₇ gives ____________
a) Ester
b) Aldehyde
c) Sugar
d) Carboxylic acid
Answer: d
Clarification: Alcohol (R-OH), when it is refluxed with Cr₂O₇, it forms carboxylic acid (R-COOH).

5. Alkene under high temperature and high-pressure forms ___________
a) Alcohol
b) Polyalkyne
c) Polyalkane
d) Polyalkene
Answer:c
Clarification: Alkenes undergoes polymerization reaction under high temperature and pressure to form poly alkanes -(C-C)-n.

6. Identify the one which on reaction with carboxylic acid at high temperature gives Ester?
a) Ketone
b) Alcohol
c) Aldehyde
d) Sugars
Answer: b
Clarification: Alcohols on reaction with carboxylic acid at high temperature, in the presence of sulphuric acid gives Ester.

7. Select the correct statement regarding carboxylic acids.
a) They form acyl chlorides on reaction with PCl₅
b) Aldehydes in the presence of H⁺/Cr₂O₇ forms carboxylic acids
c) They combine with alcohols to form esters
d) Upon polymerization, they form polymers
Answer: d
Clarification: Carboxylic acids do not undergo polymerization reaction.

8. Primary alcohols undergo what reaction to form alkenes?
a) Elimination
b) Oxidation
c) Reduction
d) Hydrolysis
Answer: a
Clarification: Upon elimination or dehydration, the primary alcohols form alkenes.

9. Carbonyl compounds especially ketones undergo reduction to form __________
a) Primary alcohols
b) Secondary alcohols
c) Alkanes
d) Alkenes
Answer: b
Clarification: Ketones in the presence of NaBH₄ undergoes reduction to form secondary alcohols.

10. Primary amides get converted into primary amines by _________
a) Addition
b) Oxidation
c) Reduction
d) Acylation
Answer: b
Clarification: Primary amides upon heating in the presence of hydrogen and nickel catalyst, gets reduced to form primary amines.