Common Types of Organic Reactions(Substitution, Addition, Elimination, and Rearrangement) NEET Questions

Organic Chemistry - Some Basic Principles of Organic Chemistry
Common Types of Organic Reactions(Substitution, Addition, Elimination, and Rearrangement)

Common Types of Organic Reactions(Substitution, Addition, Elimination, and Rearrangement) MCQ Questions


13.
Halogenation of alkanes (e.g., CH4 + Br2 → CH3Br + HBr) involves which key intermediate?
A.
Carbenes
B.
Carbanions
C.
Free radicals (Br• and CH3•)
D.
Carbocations
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ANSWER :
C. Free radicals (Br• and CH3•)
14.
Which of the following is NOT a substitution reaction?
A.
C6H6 + Br2 (FeBr3) → C6H5Br + HBr
B.
C2H5Cl + KOH(aq) → C2H5OH + KCl
C.
CH2=CH2 + Br2 → CH2BrCH2Br
D.
CH4 + Cl2 (hν) → CH3Cl + HCl
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ANSWER :
C. CH2=CH2 + Br2 → CH2BrCH2Br
15.
In the reaction C6H5–H + Cl2/FeCl3 → C6H5–Cl + HCl, the actual electrophile is:
A.
Cl•
B.
Cl⁺ (from FeCl4⁻ ion-pair)
C.
Cl⁻
D.
FeCl3
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ANSWER :
B. Cl⁺ (from FeCl4⁻ ion-pair)
16.
In SN1 reactions, racemisation of an optically active substrate occurs because:
A.
The carbocation intermediate is planar (sp²) and is attacked from both faces
B.
Both nucleophile and leaving group are on the same face
C.
The reaction goes through a concerted mechanism
D.
The substrate has no chirality
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ANSWER :
A. The carbocation intermediate is planar (sp²) and is attacked from both faces
17.
Polar protic solvents (water, alcohols) generally favour:
A.
Only E2
B.
Only free-radical reactions
C.
SN2 over SN1
D.
SN1 over SN2
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ANSWER :
D. SN1 over SN2
18.
Which of the following statements about SN2 is INCORRECT?
A.
It results in inversion of stereochemistry
B.
It is a one-step concerted reaction
C.
Rate depends only on substrate concentration
D.
It involves backside attack of the nucleophile
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ANSWER :
C. Rate depends only on substrate concentration
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