Q.1 Which of the following is a primary haloalkane?
CH3CH2Cl
CH3CHClCH3
CCl4
CH3CCl3
Explanation - A primary haloalkane has the halogen attached to a carbon which is bonded to only one other carbon. CH3CH2Cl fits this definition.
Correct answer is: CH3CH2Cl
Q.2 Which reagent is commonly used for the free radical chlorination of methane?
Cl2 / hv
HCl / heat
NaCl / H2SO4
Cl2 / heat only
Explanation - Free radical chlorination requires chlorine and ultraviolet light (hv) to initiate the radical chain reaction.
Correct answer is: Cl2 / hv
Q.3 Which of the following reactions is an example of nucleophilic substitution?
CH3CH2Br + OH- → CH3CH2OH + Br-
CH3CH3 + Cl2 → CH3CH2Cl + HCl
C6H5Br + Fe → C6H5FeBr
CH3CH2OH → CH2=CH2 + H2O
Explanation - Nucleophilic substitution involves the replacement of a leaving group (here Br-) by a nucleophile (OH-).
Correct answer is: CH3CH2Br + OH- → CH3CH2OH + Br-
Q.4 Which of the following haloalkanes undergoes SN1 reaction fastest?
CH3CH2Br
CH3CH2CH2Br
(CH3)3CBr
CH3CHBrCH3
Explanation - Tertiary haloalkanes like (CH3)3CBr form more stable carbocations, favoring the SN1 mechanism.
Correct answer is: (CH3)3CBr
Q.5 What is the major product of the reaction: CH3CH2Br + KOH (alc)?
CH3CH2OH
CH2=CH2
CH3CH2OK
CH3CH2Br
Explanation - Alcoholic KOH causes dehydrohalogenation (elimination) of ethyl bromide to form ethene.
Correct answer is: CH2=CH2
Q.6 Which of the following is least reactive in nucleophilic substitution reactions?
CH3Cl
CH3Br
CH3I
CH3F
Explanation - C–F bond is very strong and hence CH3F is least reactive in nucleophilic substitution.
Correct answer is: CH3F
Q.7 Which of the following reagents converts haloarenes to phenols?
NaOH (aq) / heat
KOH (alc) / heat
H2 / Pd
Br2 / FeBr3
Explanation - Aromatic halides react with aqueous NaOH at high temperature to give phenols.
Correct answer is: NaOH (aq) / heat
Q.8 The bond dissociation energy of C–Cl in CH3Cl is approximately:
338 kJ/mol
432 kJ/mol
328 kJ/mol
210 kJ/mol
Explanation - The C–Cl bond in methyl chloride requires around 338 kJ/mol to break homolytically.
Correct answer is: 338 kJ/mol
Q.9 Which of the following is true for chlorobenzene?
Undergoes SN1 easily
Undergoes nucleophilic substitution under normal conditions
Does not easily undergo nucleophilic substitution
Highly reactive towards electrophilic substitution
Explanation - The C–Cl bond in chlorobenzene is strengthened by resonance; hence it resists nucleophilic substitution.
Correct answer is: Does not easily undergo nucleophilic substitution
Q.10 Which of the following reagents converts an alkyl halide to an alcohol via SN2 mechanism?
NaOH (aq)
H2O / heat
NaNH2
KCN
Explanation - Aqueous NaOH acts as a nucleophile, replacing the halide in a primary haloalkane via SN2.
Correct answer is: NaOH (aq)
Q.11 Which of the following is an example of a secondary haloalkane?
CH3CHClCH3
CH3CH2Cl
CH3Cl
CCl4
Explanation - A secondary haloalkane has the halogen attached to a carbon bonded to two other carbons. CH3CHClCH3 fits this.
Correct answer is: CH3CHClCH3
Q.12 Which halogen gives the fastest reaction in SN2 with a primary haloalkane?
F
Cl
Br
I
Explanation - Iodide is the best leaving group due to its large size and weak C–I bond, making SN2 faster.
Correct answer is: I
Q.13 Which of the following compounds will undergo E2 elimination most readily?
CH3CH2Br with alcoholic KOH
CH3CH2Br with H2O
CH3CH2Cl with aq NaOH
CH3CH2I with H2O
Explanation - Alcoholic KOH is a strong base favoring E2 elimination of a primary haloalkane to give an alkene.
Correct answer is: CH3CH2Br with alcoholic KOH
Q.14 Which of the following is a tertiary haloalkane?
(CH3)3CBr
CH3CH2Br
CH3CHClCH3
CH3CH2CH2Br
Explanation - A tertiary haloalkane has the halogen attached to a carbon bonded to three other carbons. (CH3)3CBr is tertiary.
Correct answer is: (CH3)3CBr
Q.15 Which of the following is a characteristic reaction of haloarenes?
Electrophilic substitution
Nucleophilic substitution under mild conditions
Free radical halogenation
Dehydrohalogenation
Explanation - Haloarenes typically undergo electrophilic substitution rather than nucleophilic substitution due to resonance stabilization.
Correct answer is: Electrophilic substitution
Q.16 Which of the following conditions favors SN1 over SN2?
Tertiary haloalkane with polar protic solvent
Primary haloalkane with polar aprotic solvent
Primary haloalkane with strong nucleophile
Secondary haloalkane with aprotic solvent
Explanation - SN1 is favored by tertiary carbons (stable carbocation) and polar protic solvents that stabilize ions.
Correct answer is: Tertiary haloalkane with polar protic solvent
Q.17 Which of the following is formed when CH3CH2Cl reacts with KCN in ethanol?
CH3CH2CN
CH3CH2OH
CH2=CH2
CH3CH2NH2
Explanation - KCN acts as a nucleophile, replacing Cl to form a nitrile via SN2 mechanism.
Correct answer is: CH3CH2CN
Q.18 Which of the following haloalkanes undergoes fastest reaction with OH- in aqueous solution?
CH3CH2Br
CH3CH2Cl
CH3CH2I
CH3CH2F
Explanation - Iodide is the best leaving group due to weak C–I bond, making substitution fastest.
Correct answer is: CH3CH2I
Q.19 Which of the following compounds is expected to be most reactive in benzyne mechanism?
C6H5F
C6H5Cl
C6H5Br
C6H5I
Explanation - Fluorobenzene reacts via benzyne mechanism because F is highly electronegative and can facilitate elimination under strong base conditions.
Correct answer is: C6H5F
Q.20 Which of the following reagents is used for dehalogenation of alkyl halides to alkanes?
Zn/acid
NaOH (aq)
KOH (alc)
H2/Pd
Explanation - Zn in acid reduces alkyl halides to alkanes by replacing halogen with hydrogen.
Correct answer is: Zn/acid
Q.21 Which of the following undergoes fastest SN2 reaction?
CH3CH2Br
CH3CHBrCH3
CH3CBr3
CH3CH2CH2Br
Explanation - Primary haloalkanes undergo SN2 fastest because steric hindrance is minimal.
Correct answer is: CH3CH2Br
Q.22 Which of the following haloalkanes undergoes E1 elimination readily?
(CH3)3CBr
CH3CH2Br
CH3CH2Cl
CH3CH2I
Explanation - Tertiary haloalkanes form stable carbocations and undergo E1 elimination easily.
Correct answer is: (CH3)3CBr
Q.23 Which of the following is true for alkyl halides?
They can undergo nucleophilic substitution
They are highly acidic
They react with acids to form alkanes
They do not react with bases
Explanation - Alkyl halides react with nucleophiles to replace the halogen in substitution reactions.
Correct answer is: They can undergo nucleophilic substitution
Q.24 Which of the following compounds is aromatic halide?
C6H5Cl
CH3Cl
CH3CH2Br
CH3CCl3
Explanation - C6H5Cl is a haloarene, where the halogen is attached to an aromatic ring.
Correct answer is: C6H5Cl
Q.25 Which of the following is a leaving group in nucleophilic substitution?
Cl-
CH3-
OH- (neutral)
H+
Explanation - Halide ions like Cl-, Br-, I- are good leaving groups in nucleophilic substitution.
Correct answer is: Cl-
Q.26 Which of the following haloalkanes is most prone to SN1 reaction?
(CH3)3CBr
CH3CH2Br
CH3CH2Cl
CH3CH2I
Explanation - Tertiary haloalkanes like (CH3)3CBr form stable carbocations, favoring SN1 mechanism.
Correct answer is: (CH3)3CBr