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) 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
😑 View Answer Rough Work Error
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 :
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