Here below some basic MCQ’s about “Haloalkanes and Haloarenes” with answer explained in details for exam practice. Let’s check one by one.
Question 1: Nomenclature
Which of the following is the correct IUPAC name for CH₃-CH₂-CHCl-CH₃?
A) 2-Chlorobutane
B) 3-Chlorobutane
C) 1-Chlorobutane
D) Chloropropane
Answer: A) 2-Chlorobutane
Explanation:
Number the longest carbon chain containing the chlorine atom to give it the lowest possible number. The chlorine is attached to the second carbon of a four-carbon chain, hence the correct name is 2-Chlorobutane.
Question 2: Physical Properties
Which of the following haloalkanes has the highest boiling point?
A) CH₃Cl
B) CH₃CH₂Cl
C) (CH₃)₃CCl
D) CH₂Cl₂
Answer: D) CH₂Cl₂
Explanation:
Boiling points of haloalkanes generally increase with molecular weight and polarity. CH₂Cl₂ (dichloromethane) has more polar C-Cl bonds and can engage in dipole-dipole interactions more effectively than the other options, leading to a higher boiling point.
Question 3: Reactions – Nucleophilic Substitution
Which reagent is most suitable for the conversion of 1-chloropropane to 1-propanol?
A) NaOH (aqueous)
B) NaOH (alcoholic)
C) KOH (aqueous)
D) KOH (alcoholic)
Answer: A) NaOH (aqueous)
Explanation:
Aqueous NaOH promotes SN1 or SN2 nucleophilic substitution to replace the chlorine with a hydroxyl group, forming 1-propanol. Alcoholic NaOH is more likely to act as a base, favoring elimination reactions instead.
Question 4: Reactions – Elimination
When 2-chlorobutane is treated with alcoholic KOH, which major product is formed?
A) 2-Butanol
B) 1-Butene
C) cis-2-Butene
D) trans-2-Butene
Answer: D) trans-2-Butene
Explanation:
Alcoholic KOH favors elimination (E2 mechanism). The more stable alkene (trans-2-butene) is the major product due to less steric hindrance and greater stability compared to cis isomer or 1-butene.
Question 5: Properties – Reactivity
Which haloalkane is least reactive towards nucleophilic substitution?
A) CH₃Cl
B) CH₃CH₂Cl
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: D) (CH₃)₃CCl
Explanation:
Tertiary haloalkanes like (CH₃)₃CCl are less reactive towards nucleophilic substitution due to steric hindrance, making it difficult for nucleophiles to attack the carbon atom bonded to the leaving group.
Question 6: Nomenclature – Haloarenes
What is the IUPAC name for chlorobenzene?
A) Benzene chloride
B) Chlorobenzene
C) Monochlorobenzene
D) Chlorophenyl
Answer: B) Chlorobenzene
Explanation:
The correct IUPAC name follows the convention of naming the substituent first followed by the parent aromatic ring. Thus, Chlorobenzene is the proper name.
Question 7: Reactions – Haloarenes
Which reaction is commonly used to convert chlorobenzene to nitrobenzene?
A) Electrophilic substitution
B) Nucleophilic substitution
C) Friedel-Crafts acylation
D) Halogenation
Answer: B) Nucleophilic substitution
Explanation:
Chlorobenzene undergoes nucleophilic aromatic substitution when treated with a strong nitronium ion (NO₂⁺) source under appropriate conditions to form nitrobenzene.
Question 8: Physical Properties – Solubility
Which of the following haloalkanes is most soluble in water?
A) CH₃Cl
B) C₂H₅Cl
C) C₃H₇Cl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
Explanation:
Smaller haloalkanes like CH₃Cl have higher solubility in water due to their ability to form hydrogen bonds and have a greater polarity relative to their size. Larger haloalkanes are less soluble due to increased hydrophobic character.
Question 9: Nomenclature – Multiple Substituents
What is the correct IUPAC name for CH₃-CHCl-CHBr-CH₃?
A) 2-Chloro-3-bromobutane
B) 3-Chloro-2-bromobutane
C) 2-Bromo-3-chlorobutane
D) 3-Bromo-2-chlorobutane
Answer: A) 2-Chloro-3-bromobutane
Explanation:
Number the chain to give the substituents the lowest possible numbers. Here, chlorine gets position 2 and bromine position 3, so the name is 2-Chloro-3-bromobutane.
Question 10: Reactions – Dehalogenation
Which reagent is used for the dehydrohalogenation of 2,3-dibromobutane to form an alkene?
A) NaOH
B) KOH
C) Zn/AcOH
D) KI in acetone
Answer: B) KOH
Explanation:
KOH (especially alcoholic KOH) is commonly used for dehydrohalogenation reactions, eliminating hydrogen and halogen atoms to form alkenes. In this case, treating 2,3-dibromobutane with KOH would result in the formation of but-2-ene.
Question 11: Nomenclature
What is the IUPAC name for CH₃-CH₂-CBr₂-CH₃?
A) 2,3-Dibromobutane
B) 2,2-Dibromobutane
C) 3,3-Dibromobutane
D) 1,2-Dibromobutane
Answer: B) 2,2-Dibromobutane
Explanation:
Identify the longest carbon chain and assign numbers to substituents to give them the lowest possible numbers. Both bromine atoms are attached to the second carbon, so the correct name is 2,2-Dibromobutane.
Question 12: Physical Properties
Which haloalkane is expected to have the lowest solubility in water?
A) CH₃Br
B) C₂H₅Br
C) C₃H₇Br
D) (CH₃)₃CBr
Answer: D) (CH₃)₃CBr
Explanation:
As the carbon chain length increases, solubility in water decreases due to increased hydrophobic character. (CH₃)₃CBr (tert-Butyl bromide) has the largest alkyl group, making it the least soluble in water.
Question 13: Reactions – Nucleophilic Substitution
Which haloalkane will react fastest in an SN2 reaction?
A) CH₃Cl
B) CH₃CH₂Cl
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
Explanation:
SN2 reactions are favored by primary haloalkanes due to less steric hindrance. CH₃Cl is a methyl chloride, making it the most reactive in SN2 among the options.
Question 14: Reactions – Halogen Exchange
What is the product when 1-chloropropane is treated with excess NaI in acetone?
A) 1-Iodopropane
B) 2-Iodopropane
C) Propanol
D) No reaction
Answer: A) 1-Iodopropane
Explanation:
This is a Finkelstein reaction, where chloride is replaced by iodide. 1-Chloropropane reacts with NaI in acetone to form 1-Iodopropane and NaCl, which precipitates out.
Question 15: Properties – Reactivity
Which haloalkane is most susceptible to elimination (E2) reaction?
A) CH₃Cl
B) CH₃CH₂Cl
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: D) (CH₃)₃CCl
Explanation:
Tertiary haloalkanes like (CH₃)₃CCl are highly susceptible to E2 elimination due to the stability of the resulting tertiary alkene and the steric hindrance that disfavors SN2 reactions.
Question 16: Nomenclature – Haloarenes
What is the IUPAC name for o-dichlorobenzene?
A) 1,2-Dichlorobenzene
B) 1,3-Dichlorobenzene
C) 1,4-Dichlorobenzene
D) 2,3-Dichlorobenzene
Answer: A) 1,2-Dichlorobenzene
Explanation:
In ortho (o-) substitution, the substituents are adjacent, occupying positions 1 and 2. Hence, the IUPAC name is 1,2-Dichlorobenzene.
Question 17: Reactions – Haloarenes
Which of the following is a common method to prepare chlorobenzene?
A) Chlorination of benzene using Cl₂ and FeCl₃
B) Nitration of benzene followed by reduction
C) Friedel-Crafts alkylation of benzene
D) Hydrogenation of benzoyl chloride
Answer: A) Chlorination of benzene using Cl₂ and FeCl₃
Explanation:
Chlorobenzene is commonly prepared by the chlorination of benzene in the presence of a Lewis acid catalyst like FeCl₃.
Question 18: Physical Properties – Boiling Point
Which of the following haloalkanes has the highest boiling point?
A) CH₃CH₂Cl
B) CH₃CHClCH₃
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: A) CH₃CH₂Cl
Explanation:
Boiling points increase with molecular weight and polarity. CH₃CH₂Cl has hydrogen bonding capabilities and less branching compared to other options, resulting in a higher boiling point.
Question 19: Nomenclature – Substituted Haloarenes
What is the IUPAC name for 4-bromo-1-chlorobenzene?
A) 1-Bromo-4-chlorobenzene
B) 4-Bromo-1-chlorobenzene
C) 2-Bromo-1-chlorobenzene
D) 3-Bromo-1-chlorobenzene
Answer: B) 4-Bromo-1-chlorobenzene
Explanation:
Numbering starts to give the substituents the lowest possible numbers. In this case, 1-chloro and 4-bromo are the correct positions, so the name is 4-Bromo-1-chlorobenzene.
Question 20: Reactions – Hydrolysis
What is the product when 1-bromobutane undergoes hydrolysis?
A) Butan-1-ol
B) Butan-2-ol
C) Butanal
D) Butanoic acid
Answer: A) Butan-1-ol
Explanation:
Hydrolysis of 1-bromobutane (a primary haloalkane) with aqueous NaOH leads to substitution, forming butan-1-ol via an SN2 mechanism.
Question 21: Nomenclature
What is the IUPAC name for CH₃-CH(Br)-CH₂-CH₃?
A) 1-Bromobutane
B) 2-Bromobutane
C) 3-Bromobutane
D) Bromobutane
Answer: B) 2-Bromobutane
Explanation:
Number the longest chain to give the substituent the lowest possible number. The bromine is on the second carbon, so the name is 2-Bromobutane.
Question 22: Physical Properties – Density
Which haloalkane has a density greater than water?
A) CH₃Cl
B) C₂H₅Cl
C) C₃H₇Cl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
Explanation:
Haloalkanes generally have densities greater than water due to the presence of heavy halogen atoms. CH₃Cl (methyl chloride) has a density greater than water.
Question 23: Reactions – Dehydrohalogenation
What is the major product when 2-chloro-2-methylpropane is treated with a strong base?
A) 2-Methylpropene
B) 1-Methylpropene
C) 2,2-Dimethylpropane
D) 1,2-Dimethylpropene
Answer: A) 2-Methylpropene
Explanation:
Treatment with a strong base leads to elimination. 2-Chloro-2-methylpropane forms 2-Methylpropene as the major product due to the formation of the more stable tertiary alkene.
Question 24: Properties – Reactivity
Which of the following factors does NOT affect the reactivity of haloalkanes in nucleophilic substitution reactions?
A) Nature of the carbon atom bonded to the halogen
B) Strength of the C-X bond
C) Solvent used
D) Color of the haloalkane
Answer: D) Color of the haloalkane
Explanation:
Reactivity in SN reactions is influenced by the carbon’s substitution (primary, secondary, tertiary), the C-X bond strength, and the solvent type. Color has no effect on reactivity.
Question 25: Nomenclature – Multiple Halogens
What is the IUPAC name for CH₃-CHCl-CHCl-CH₃?
A) 2,3-Dichlorobutane
B) 2,2-Dichlorobutane
C) 1,3-Dichlorobutane
D) 1,2-Dichlorobutane
Answer: A) 2,3-Dichlorobutane
Explanation:
Number the chain to assign the lowest numbers to the substituents. Chlorines are on the 2nd and 3rd carbons, hence 2,3-Dichlorobutane.
Question 26: Reactions – Radical Halogenation
Which haloalkane is formed predominantly when methane undergoes bromination?
A) Chloromethane
B) Bromomethane
C) Methyl chloride
D) No reaction occurs
Answer: B) Bromomethane
Explanation:
When methane undergoes bromination (a radical substitution), bromomethane (CH₃Br) is formed.
Question 27: Physical Properties – Intermolecular Forces
Which haloalkane exhibits hydrogen bonding?
A) CH₃Cl
B) CH₃CH₂Br
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
Explanation:
Hydrogen bonding occurs when hydrogen is bonded to highly electronegative atoms like chlorine. CH₃Cl can engage in hydrogen bonding due to the C-Cl bond.
Question 28: Reactions – Substitution Specificity
Which haloalkane is least likely to undergo nucleophilic substitution under standard conditions?
A) CH₃Br
B) CH₃CH₂Br
C) (CH₃)₂CHBr
D) (CH₃)₃CBr
Answer: D) (CH₃)₃CBr
Explanation:
(CH₃)₃CBr (tert-Butyl bromide) is a tertiary haloalkane that favors elimination over substitution due to steric hindrance, making it least likely to undergo nucleophilic substitution.
Question 29: Nomenclature – Aromatic Substituents
What is the IUPAC name for a benzene ring substituted with two bromine atoms at the 1st and 3rd positions?
A) 1,2-Dibromobenzene
B) 1,3-Dibromobenzene
C) 1,4-Dibromobenzene
D) 2,3-Dibromobenzene
Answer: B) 1,3-Dibromobenzene
Explanation:
Two substituents at positions 1 and 3 on a benzene ring are referred to as 1,3-Dibromobenzene.
Question 30: Reactions – Electrophilic Substitution
Which of the following is a product when chlorobenzene undergoes nitration?
A) Nitrochlorobenzene
B) Chloronitromethane
C) 1,4-Dichlorobenzene
D) 1,3-Dinitrobenzene
Answer: A) Nitrochlorobenzene
Explanation:
Nitration of chlorobenzene introduces a nitro group to form Nitrochlorobenzene through electrophilic aromatic substitution.
Question 31: Physical Properties – Vapor Pressure
Which haloalkane has the highest vapor pressure at room temperature?
A) CH₃Cl
B) CH₃CH₂Cl
C) C₂H₅CHCl₂
D) (CH₃)₃CCl
Answer: D) (CH₃)₃CCl
Explanation:
Higher molecular weight and branching (as in (CH₃)₃CCl) generally lead to lower boiling points and higher vapor pressures.
Question 32: Nomenclature – Substituent Priority
What is the correct IUPAC name for CH₃-CH(Br)-CH₂-Cl?
A) 1-Bromo-3-chloropropane
B) 2-Bromo-1-chloropropane
C) 1-Chloro-3-bromopropane
D) 3-Chloro-1-bromopropane
Answer: B) 2-Bromo-1-chloropropane
Explanation:
Number the chain to give the substituents the lowest possible numbers. Chlorine gets position 1 and bromine position 2, resulting in 2-Bromo-1-chloropropane.
Question 33: Reactions – Halogenation Specificity
Which haloalkane is formed when ethylene reacts with chlorine?
A) Ethyl chloride
B) 1,2-Dichloroethane
C) Vinyl chloride
D) Ethanol
Answer: B) 1,2-Dichloroethane
Explanation:
Addition of chlorine to ethylene (an alkene) yields 1,2-Dichloroethane through an addition reaction.
Question 34: Properties – Reactivity Order
Arrange the following haloalkanes in order of decreasing reactivity towards SN2 reactions: CH₃Cl > CH₃CH₂Cl > (CH₃)₂CHCl > (CH₃)₃CCl
A) CH₃Cl > CH₃CH₂Cl > (CH₃)₂CHCl > (CH₃)₃CCl
B) (CH₃)₃CCl > (CH₃)₂CHCl > CH₃CH₂Cl > CH₃Cl
C) CH₃CH₂Cl > CH₃Cl > (CH₃)₂CHCl > (CH₃)₃CCl
D) CH₃Cl > (CH₃)₂CHCl > CH₃CH₂Cl > (CH₃)₃CCl
Answer: A) CH₃Cl > CH₃CH₂Cl > (CH₃)₂CHCl > (CH₃)₃CCl
Explanation:
SN2 reactivity decreases with increasing steric hindrance. Methyl chloride (CH₃Cl) is the most reactive, followed by primary, secondary, and then tertiary haloalkanes.
Question 35: Nomenclature – Binary Halo Compounds
Which of the following is the correct name for C₂H₅Cl?
A) Ethyl chloride
B) 1-Chloroethane
C) Both A and B
D) Dichloroethane
Answer: C) Both A and B
Explanation:
Both Ethyl chloride and 1-Chloroethane are correct IUPAC names for C₂H₅Cl.
Question 36: Reactions – Substitution Mechanism
Which mechanism is predominantly followed by tertiary haloalkanes in nucleophilic substitution?
A) SN1
B) SN2
C) E1
D) E2
Answer: A) SN1
Explanation:
Tertiary haloalkanes favor the SN1 mechanism due to the stability of the tertiary carbocation intermediate.
Question 37: Physical Properties – Boiling Point Trend
Which statement correctly describes the boiling point trend of haloalkanes?
A) Boiling points decrease with increasing molecular weight
B) Boiling points increase with increasing molecular weight
C) Boiling points remain the same irrespective of molecular weight
D) Boiling points are independent of molecular structure
Answer: B) Boiling points increase with increasing molecular weight
Explanation:
As molecular weight increases, so do London dispersion forces, leading to higher boiling points.
Question 38: Nomenclature – Prefixes and Suffixes
What is the IUPAC name for CH₃-CH₂-CH₂-CH₂-Br?
A) 1-Bromobutane
B) 2-Bromobutane
C) 3-Bromobutane
D) Butyl bromide
Answer: A) 1-Bromobutane
Explanation:
The bromine is attached to the first carbon of the four-carbon chain, so the correct name is 1-Bromobutane.
Question 39: Reactions – Solvent Effects
Which solvent favors the SN2 reaction mechanism for haloalkanes?
A) Polar protic
B) Polar aprotic
C) Non-polar
D) Any solvent
Answer: B) Polar aprotic
Explanation:
Polar aprotic solvents stabilize cations but do not solvate anions effectively, enhancing nucleophilicity and favoring the SN2 mechanism.
Question 40: Properties – Reactivity Order in SN1
Arrange the following haloalkanes in order of decreasing reactivity towards SN1 reactions: (CH₃)₃CCl > (CH₃)₂CHCl > CH₃CH₂Cl > CH₃Cl
A) (CH₃)₃CCl > (CH₃)₂CHCl > CH₃CH₂Cl > CH₃Cl
B) CH₃Cl > CH₃CH₂Cl > (CH₃)₂CHCl > (CH₃)₃CCl
C) (CH₃)₂CHCl > (CH₃)₃CCl > CH₃Cl > CH₃CH₂Cl
D) CH₃CH₂Cl > CH₃Cl > (CH₃)₂CHCl > (CH₃)₃CCl
Answer: A) (CH₃)₃CCl > (CH₃)₂CHCl > CH₃CH₂Cl > CH₃Cl
Explanation:
SN1 reactivity increases with the stability of the carbocation. Tertiary > secondary > primary > methyl.
Question 41: Nomenclature – Cycloalkanes
What is the IUPAC name for CH₂Cl-CH₂Cl in a cyclohexane ring?
A) 1,2-Dichlorocyclohexane
B) 1,3-Dichlorocyclohexane
C) 1,4-Dichlorocyclohexane
D) Dichlorocyclohexane
Answer: A) 1,2-Dichlorocyclohexane
Explanation:
When two chlorines are on adjacent carbons in a cyclohexane ring, the name is 1,2-Dichlorocyclohexane.
Question 42: Reactions – Substitution vs. Elimination
Which condition favors elimination over substitution in haloalkane reactions?
A) Polar protic solvent
B) Strong nucleophile
C) Weak base
D) Strong bulky base
Answer: D) Strong bulky base
Explanation:
A strong bulky base favors elimination (E2) over substitution (SN2) due to steric hindrance which makes it difficult for the base to approach the carbon.
Question 43: Physical Properties – Molecular Shape
Which haloalkane has a bent molecular shape around the carbon atom bonded to the halogen?
A) CH₃Cl
B) C₂H₅Cl
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
Explanation:
CH₃Cl has a tetrahedral geometry around the carbon, but considering only the substituents, the shape around the C-Cl bond appears bent due to the presence of lone pairs on chlorine.
Question 44: Nomenclature – Common Names
Which common name corresponds to 1,1-dichloroethane?
A) Ethylene dichloride
B) Vinyl chloride
C) Dichloroethylene
D) Ethylidene chloride
Answer: D) Ethylidene chloride
Explanation:
1,1-Dichloroethane is commonly known as Ethylidene chloride.
Question 45: Reactions – Side Reactions
What side reaction may occur during the SN2 substitution of a primary haloalkane?
A) Rearrangement
B) Carbocation formation
C) Elimination
D) No side reaction
Answer: C) Elimination
Explanation:
Although SN2 is favored in primary haloalkanes, elimination (E2) can occur as a side reaction, especially under strong base conditions.
Question 46: Properties – Reactivity Order in SN2
Which of the following haloalkanes is least reactive towards SN2 reactions?
A) CH₃Br
B) CH₃CH₂Br
C) (CH₃)₂CHBr
D) (CH₃)₃CBr
Answer: D) (CH₃)₃CBr
Explanation:
(CH₃)₃CBr (tert-Butyl bromide) is the least reactive towards SN2 due to significant steric hindrance around the carbon atom bonded to the bromine.
Question 47: Nomenclature – Position Numbers
What is the IUPAC name for CH₃-CH₂-CHBr-CH₂-Cl?
A) 3-Bromo-4-chlorobutane
B) 2-Bromo-4-chlorobutane
C) 3-Bromo-1-chlorobutane
D) 1-Bromo-3-chlorobutane
Answer: C) 3-Bromo-1-chlorobutane
Explanation:
Number the chain to give the substituents the lowest possible numbers. Chlorine is on carbon 1 and bromine on carbon 3, resulting in 3-Bromo-1-chlorobutane.
Question 48: Reactions – Formation of Alkenes
Which product is formed when 2-bromopropane undergoes dehydrohalogenation?
A) Propene
B) 1-Propanol
C) 2-Propanol
D) Propane
Answer: A) Propene
Explanation:
2-Bromopropane undergoes dehydrohalogenation to form Propene through the elimination of HBr.
Question 49: Physical Properties – Dipole Moment
Which haloalkane has the highest dipole moment?
A) CH₃Cl
B) CH₃CH₂Cl
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
Explanation:
CH₃Cl has the highest dipole moment among the listed haloalkanes due to the high polarity of the C-Cl bond and minimal molecular symmetry.
Question 50: Reactions – Synthesis
Which reagent is used to synthesize chlorobenzene from benzene?
A) HCl
B) Cl₂ with FeCl₃
C) NaCl
D) HCl with AlCl₃
Answer: B) Cl₂ with FeCl₃
Explanation:
Chlorobenzene is synthesized by the chlorination of benzene using Cl₂ in the presence of a FeCl₃ catalyst.
Question 51: Nomenclature – Substituent Prefix
What is the IUPAC name for CH₃-CH₂-CH₂-CH₂-CH₂-Br?
A) 1-Bromopentane
B) 2-Bromopentane
C) 3-Bromopentane
D) Pentyl bromide
Answer: A) 1-Bromopentane
Explanation:
The bromine is attached to the first carbon of the five-carbon chain, making the correct name 1-Bromopentane.
Question 52: Reactions – Halide Exchange
What is the product when 1-chloropropane is treated with excess NaI in acetone?
A) 1-Iodopropane
B) 2-Iodopropane
C) Propanol
D) No reaction
Answer: A) 1-Iodopropane
Explanation:
In a Finkelstein reaction, 1-chloropropane reacts with NaI in acetone to produce 1-Iodopropane and NaCl precipitates out.
Question 53: Properties – Solubility Trend
Which of the following haloalkanes is most soluble in water?
A) CH₃Br
B) C₂H₅Br
C) C₃H₇Br
D) (CH₃)₃CBr
Answer: A) CH₃Br
Explanation:
Smaller haloalkanes like CH₃Br have higher solubility in water due to greater polarity and less hydrophobic character.
Question 54: Nomenclature – Multiple Substituents Priority
What is the correct IUPAC name for CH₃-CCl₂-CH₂-Cl?
A) 1,1,2-Trichloropropane
B) 1,2,3-Trichloropropane
C) 1,1-Dichloro-3-chloropropane
D) 1,1,3-Trichloropropane
Answer: A) 1,1,2-Trichloropropane
Explanation:
Assign numbers to give the substituents the lowest possible numbers. There are two chlorines on carbon 1 and one on carbon 2, so the name is 1,1,2-Trichloropropane.
Question 55: Reactions – Aromatic Substitution
Which position on chlorobenzene is most susceptible to nitration?
A) Ortho and para positions
B) Meta position
C) Only ortho
D) Only para
Answer: B) Meta position
Explanation:
Chlorine is an ortho/para director but deactivates the benzene ring, making the meta position relatively more susceptible to nitration due to steric hindrance at ortho and para positions.
Question 56: Physical Properties – Boiling Points
Which haloalkane has the lowest boiling point?
A) CH₃Cl
B) CH₃CH₂Cl
C) CH₃CH₂CH₂Cl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
Explanation:
CH₃Cl has the lowest boiling point among the listed haloalkanes due to its smaller size and fewer intermolecular forces.
Question 57: Nomenclature – Functional Groups
In haloarenes, the halogen substituent is considered a(n):
A) Functional group
B) Parent group
C) Suffix
D) Inert group
Answer: A) Functional group
Explanation:
In haloarenes, the halogen acts as a functional group, influencing the compound’s chemical properties and nomenclature.
Question 58: Reactions – Nucleophilic Aromatic Substitution
Which of the following is necessary for nucleophilic aromatic substitution to occur?
A) Electron-donating groups
B) Electron-withdrawing groups
C) High temperature
D) Basic conditions
Answer: B) Electron-withdrawing groups
Explanation:
Electron-withdrawing groups stabilize the intermediate anion in nucleophilic aromatic substitution, making the reaction feasible.
Question 59: Properties – Reactivity of Haloarenes
Which haloarene is more reactive towards nucleophilic aromatic substitution?
A) Chlorobenzene
B) Nitrochlorobenzene
C) Methylchlorobenzene
D) Dimethylchlorobenzene
Answer: B) Nitrochlorobenzene
Explanation:
Nitro groups are strong electron-withdrawing groups, increasing the reactivity of the aromatic ring towards nucleophilic substitution.
Question 60: Reactions – Preparation of Haloalkanes
Which of the following methods can be used to prepare a primary haloalkane?
A) Reaction of alcohol with PBr₅
B) Reaction of aldehyde with HCl
C) Dehydration of alcohol
D) Hydrogenation of alkene
Answer: A) Reaction of alcohol with PBr₅
Explanation:
Primary alcohols react with PBr₅ to form primary haloalkanes via substitution.
Question 61: Nomenclature – Isomer Identification
Which of the following haloalkanes is an isomer of 2-chlorobutane?
A) 1-chloropropane
B) 1-chloro-2-methylpropane
C) 2-chloro-2-methylpropane
D) 1,2-dichlorobutane
Answer: B) 1-chloro-2-methylpropane
Explanation:
1-Chloro-2-methylpropane has the same molecular formula as 2-chlorobutane but a different structure, making them isomers.
Question 62: Reactions – Synthesis of Haloarenes
Which reagent is used to synthesize bromobenzene from benzene?
A) Br₂ with FeBr₃
B) HBr with peroxides
C) NaBr with H₂SO₄
D) Br₂ with AlCl₃
Answer: A) Br₂ with FeBr₃
Explanation:
Bromobenzene is synthesized by the bromination of benzene using Br₂ in the presence of a FeBr₃ catalyst.
Question 63: Physical Properties – Methyl Halides
Which methyl halide has the highest boiling point?
A) CH₃F
B) CH₃Cl
C) CH₃Br
D) CH₃I
Answer: D) CH₃I
Explanation:
Boiling points increase with increasing molecular weight and polarizability. CH₃I has the highest boiling point among methyl halides due to its larger atomic size.
Question 64: Nomenclature – Multiple Functional Groups
What is the IUPAC name for CH₃-CHCl-CHBr-CH₃?
A) 2-Chloro-3-bromobutane
B) 3-Chloro-2-bromobutane
C) 2-Bromo-3-chlorobutane
D) Both A and C
Answer: D) Both A and C
Explanation:
Both 2-Chloro-3-bromobutane and 2-Bromo-3-chlorobutane are correct as the numbering can start from either end, providing the same set of locants.
Question 65: Reactions – Reactivity of Haloalkanes
Which haloalkane is most likely to undergo E2 elimination?
A) CH₃CH₂Cl
B) (CH₃)₂CHCl
C) (CH₃)₃CCl
D) CH₃Cl
Answer: C) (CH₃)₃CCl
Explanation:
(CH₃)₃CCl is a tertiary haloalkane, which readily undergoes E2 elimination due to the formation of a stable tertiary alkene.
Question 66: Properties – Physical State
Which haloalkane is a gas at room temperature?
A) CH₃Cl
B) C₂H₅Cl
C) C₃H₇Cl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
Explanation:
CH₃Cl (methyl chloride) is a gas at room temperature due to its small molecular size and low boiling point.
Question 67: Nomenclature – Binary Naming
What is the common name for 1-bromoethane?
A) Ethyl bromide
B) Ethylene bromide
C) Bromoethane
D) Both A and C
Answer: D) Both A and C
Explanation:
1-Bromoethane is commonly known as Ethyl bromide or simply Bromoethane.
Question 68: Reactions – Synthesis Pathway
Which sequence of reactions can convert 1-propanol to 1-propyl bromide?
A) Dehydration followed by bromination
B) Oxidation followed by substitution
C) Sulfonation followed by elimination
D) Conversion to tosylate followed by substitution
Answer: D) Conversion to tosylate followed by substitution
Explanation:
1-Propanol can be converted to 1-propyl tosylate and then undergo nucleophilic substitution with NaBr to form 1-propyl bromide.
Question 69: Properties – Molecular Dipole
Which haloalkane has the smallest dipole moment?
A) CH₃Cl
B) CH₃CH₂Cl
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: D) (CH₃)₃CCl
Explanation:
(CH₃)₃CCl has the smallest dipole moment due to its symmetrical, highly branched structure, which reduces overall molecular polarity.
Question 70: Reactions – Haloalkane Hydrolysis
What type of reaction is involved in converting 2-chloropropane to 2-propanol?
A) Elimination
B) Nucleophilic substitution
C) Electrophilic addition
D) Radical substitution
Answer: B) Nucleophilic substitution
Explanation:
Conversion of 2-chloropropane to 2-propanol involves an SN2 or SN1 nucleophilic substitution where the chlorine is replaced by a hydroxyl group.
Question 71: Nomenclature – Naming Haloalkenes
What is the IUPAC name for CH₂=CH-CH₂-Cl?
A) 1-Chloropropene
B) 2-Chloropropene
C) Chloroethene
D) Vinyl chloride
Answer: B) 2-Chloropropene
Explanation:
The chlorine is attached to the second carbon in the propene chain, so the name is 2-Chloropropene.
Question 72: Reactions – Synthesis of Haloarenes
Which reagent is used to convert toluene to p-chlorotoluene?
A) Cl₂ with FeCl₃
B) HCl with AlCl₃
C) NaCl with UV light
D) SOCl₂
Answer: A) Cl₂ with FeCl₃
Explanation:
Chlorination of toluene with Cl₂ in the presence of FeCl₃ selectively forms p-Chlorotoluene due to the directing effects of the methyl group.
Question 73: Physical Properties – Comparison with Alkanes
Compared to alkanes, haloalkanes generally have:
A) Higher boiling points
B) Lower boiling points
C) Similar boiling points
D) No systematic difference
Answer: A) Higher boiling points
Explanation:
Haloalkanes have higher boiling points than alkanes of similar molecular weight due to dipole-dipole interactions and increased molecular polarity.
Question 74: Nomenclature – Cyclohexane Derivatives
What is the IUPAC name for 1,4-dichlorocyclohexane?
A) cis-1,4-Dichlorocyclohexane
B) trans-1,4-Dichlorocyclohexane
C) 1,4-Dichlorocyclohexane
D) Both A and B depending on stereochemistry
Answer: D) Both A and B depending on stereochemistry
Explanation:
1,4-Dichlorocyclohexane can exist as cis or trans isomers, so the IUPAC name includes the stereochemistry: cis-1,4-Dichlorocyclohexane or trans-1,4-Dichlorocyclohexane.
Question 75: Reactions – Effect of Substituents
How does the presence of a nitro group on a haloarene affect its reactivity towards nucleophilic substitution?
A) Increases reactivity
B) Decreases reactivity
C) No effect
D) Depends on the position
Answer: A) Increases reactivity
Explanation:
A nitro group is a strong electron-withdrawing group that activates the aromatic ring towards nucleophilic substitution by stabilizing the intermediate.
Question 76: Properties – Haloalkane Types
Which type of haloalkane is CH₃CHBrCH₃?
A) Primary
B) Secondary
C) Tertiary
D) Methyl
Answer: B) Secondary
Explanation:
The carbon bonded to the bromine is attached to two other carbon atoms, making it a secondary haloalkane.
Question 77: Nomenclature – Di- and Tri-substituted Haloalkanes
What is the IUPAC name for CH₃-CCl₂-CH₂-CH₃?
A) 2,2-Dichlorobutane
B) 1,2-Dichlorobutane
C) 3,3-Dichlorobutane
D) 1,1-Dichlorobutane
Answer: A) 2,2-Dichlorobutane
Explanation:
Both chlorine atoms are on the second carbon of a four-carbon chain, so the name is 2,2-Dichlorobutane.
Question 78: Reactions – Substituent Effects
Which substituent on a benzene ring deactivates it towards electrophilic substitution?
A) -OH
B) -NH₂
C) -NO₂
D) -CH₃
Answer: C) -NO₂
Explanation:
The -NO₂ group is a strong electron-withdrawing group that deactivates the benzene ring towards electrophilic substitution.
Question 79: Physical Properties – Hydrogen Halides
Which hydrogen halide has the highest boiling point?
A) HCl
B) HBr
C) HI
D) HF
Answer: D) HF
Explanation:
HF has the highest boiling point among hydrogen halides due to strong hydrogen bonding between molecules.
Question 80: Nomenclature – Chiral Haloalkanes
What is the IUPAC name for CH₃-CH(Cl)-CH₂-Br?
A) 2-Chloro-3-bromopropane
B) 2-Bromo-3-chloropropane
C) 2-Chloro-1-bromopropane
D) 1-Chloro-2-bromopropane
Answer: D) 1-Chloro-2-bromopropane
Explanation:
Number the chain to give substituents the lowest numbers. Chlorine is on carbon 1 and bromine on carbon 2, making the name 1-Chloro-2-bromopropane.
Question 81: Reactions – Preparation of Methyl Halides
Which reagent is used to convert methanol to methyl chloride?
A) HCl
B) PCl₅
C) SOCl₂
D) All of the above
Answer: D) All of the above
Explanation:
Methanol can be converted to methyl chloride using HCl, PCl₅, or SOCl₂ through substitution reactions.
Question 82: Properties – Reactivity in E1 Mechanism
Which haloalkane is most likely to undergo E1 elimination?
A) CH₃CH₂Cl
B) (CH₃)₂CHCl
C) (CH₃)₃CCl
D) CH₃Cl
Answer: C) (CH₃)₃CCl
Explanation:
(CH₃)₃CCl (tert-Butyl chloride) readily undergoes E1 elimination due to the formation of a stable tertiary carbocation.
Question 83: Nomenclature – Haloalkanes with Branches
What is the IUPAC name for (CH₃)₂CH-CH₂-Br?
A) 1-Bromo-2-methylpropane
B) 2-Bromo-2-methylpropane
C) 1-Bromo-3-methylpropane
D) 3-Bromo-1-methylpropane
Answer: A) 1-Bromo-2-methylpropane
Explanation:
Number the chain to give the substituent the lowest possible number. Bromine is on carbon 1 and the methyl group on carbon 2, resulting in 1-Bromo-2-methylpropane.
Question 84: Reactions – Effect of Leaving Group
Which haloalkane has the best leaving group for substitution reactions?
A) CH₃F
B) CH₃Cl
C) CH₃Br
D) CH₃I
Answer: D) CH₃I
Explanation:
Iodide (I⁻) is the best leaving group among the halides due to its large size and weak base strength, making CH₃I the best for substitution reactions.
Question 85: Physical Properties – Polarity
Which haloalkane is nonpolar?
A) CH₃Cl
B) CH₃CH₂Cl
C) (CH₃)₃CCl
D) None of the above
Answer: D) None of the above
Explanation:
All haloalkanes have polar C-X bonds, making them polar molecules. Hence, none are completely nonpolar.
Question 86: Nomenclature – Common vs IUPAC Names
What is the common name for 2,2-dichloropropane?
A) Propylene dichloride
B) Propan-2,2-dichloride
C) Both A and B
D) Propane-2,2-dichloride
Answer: C) Both A and B
Explanation:
Both Propylene dichloride and Propan-2,2-dichloride are accepted names for 2,2-Dichloropropane.
Question 87: Reactions – SN1 Mechanism
Which of the following conditions favor the SN1 mechanism in haloalkane reactions?
A) Primary haloalkane, polar aprotic solvent
B) Tertiary haloalkane, polar protic solvent
C) Methyl haloalkane, non-polar solvent
D) Secondary haloalkane, high concentration of nucleophile
Answer: B) Tertiary haloalkane, polar protic solvent
Explanation:
SN1 is favored by tertiary haloalkanes and polar protic solvents that stabilize the carbocation intermediate.
Question 88: Properties – Comparison with Alcohols
Compared to corresponding alcohols, haloalkanes have:
A) Higher boiling points
B) Lower boiling points
C) Similar boiling points
D) Variable boiling points
Answer: B) Lower boiling points
Explanation:
Haloalkanes have lower boiling points than corresponding alcohols because they can only engage in dipole-dipole interactions, whereas alcohols can form hydrogen bonds, leading to higher boiling points.
Question 89: Nomenclature – Priority of Substituents
In 3-bromo-2-chloropentane, which substituent has priority in numbering?
A) Bromine
B) Chlorine
C) Both have equal priority
D) It depends on the alphabetical order
Answer: C) Both have equal priority
Explanation:
When substituents have equal priority, numbering is done to give the lowest set of locants, not based on alphabetical order.
Question 90: Reactions – Competitive Reactions
In the reaction of 2-bromopropane with NaOH, which product is major?
A) 2-Propanol
B) Propene
C) 1-Propanol
D) No reaction
Answer: A) 2-Propanol
Explanation:
With a secondary haloalkane and NaOH, nucleophilic substitution (SN2 or SN1) predominates, forming 2-Propanol as the major product.
Question 91: Physical Properties – Intermolecular Forces
Which haloalkane exhibits hydrogen bonding?
A) CH₃Cl
B) CH₃CH₂Cl
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
Explanation:
Hydrogen bonding occurs when hydrogen is directly bonded to highly electronegative atoms like nitrogen, oxygen, or fluorine. In haloalkanes, chlorine is sufficiently electronegative to allow for hydrogen bonding in smaller haloalkanes. CH₃Cl can form hydrogen bonds due to the presence of the hydrogen atom bonded to carbon, which is attached to the electronegative chlorine, making it capable of weak hydrogen bonding interactions.
Question 92: Nomenclature
What is the IUPAC name for CH₃-CH₂-CH₂-Br?
A) 1-Bromopropane
B) 2-Bromopropane
C) 1-Bromo-2-propane
D) 3-Bromopropane
Answer: A) 1-Bromopropane
Explanation:
Identify the longest carbon chain, which is three carbons (propane). The bromine is attached to the first carbon, so the correct name is 1-Bromopropane.
Question 93: Physical Properties – Boiling Point
Which haloalkane has the lowest boiling point?
A) CH₃Cl
B) CH₃CH₂Cl
C) CH₃CH₂CH₂Cl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
Explanation:
Boiling points increase with molecular size and intermolecular forces. CH₃Cl (methyl chloride) is the smallest haloalkane among the options and thus has the lowest boiling point due to weaker van der Waals forces.
Question 94: Reactions – SN1 Mechanism
Which haloalkane is most likely to undergo an SN1 reaction?
A) CH₃Cl
B) CH₃CH₂Cl
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: D) (CH₃)₃CCl
Explanation:
SN1 reactions are favored by tertiary haloalkanes due to the stability of the carbocation intermediate. (CH₃)₃CCl is a tertiary chloride and thus most likely to undergo an SN1 reaction.
Question 95: Reactions – SN2 Mechanism
Which haloalkane is least likely to undergo an SN2 reaction?
A) CH₃I
B) CH₃CH₂Br
C) (CH₃)₂CHCl
D) (CH₃)₃CBr
Answer: D) (CH₃)₃CBr
Explanation:
SN2 reactions are hindered by steric hindrance. (CH₃)₃CBr is a tertiary haloalkane with significant steric hindrance, making it the least likely to undergo an SN2 reaction.
Question 96: Nomenclature – Substituted Haloarenes
What is the IUPAC name for 3-chlorotoluene?
A) 3-Chloromethylbenzene
B) 1-Chloro-3-methylbenzene
C) 3-Chloro-1-methylbenzene
D) 1-Methyl-3-chlorobenzene
Answer: D) 1-Methyl-3-chlorobenzene
Explanation:
In substituted haloarenes, the substituents are named with their positions. 3-Chlorotoluene translates to 1-Methyl-3-chlorobenzene, indicating a methyl group at position 1 and a chlorine at position 3 on the benzene ring.
Question 97: Reactions – Hydrohalogenation
What is the product when 2-methylpropene undergoes hydrohalogenation with HBr?
A) 2-Bromo-2-methylpropane
B) 1-Bromo-2-methylpropane
C) 2-Bromo-1-methylpropane
D) 1-Bromo-3-methylpropane
Answer: A) 2-Bromo-2-methylpropane
Explanation:
Hydrohalogenation follows Markovnikov’s rule, where the hydrogen atom attaches to the carbon with more hydrogen atoms, and the halogen attaches to the more substituted carbon. Thus, 2-methylpropene reacts with HBr to form 2-Bromo-2-methylpropane.
Question 98: Properties – Reactivity Order
Arrange the following haloalkanes in order of increasing reactivity towards nucleophilic substitution (SN2): CH₃Br, CH₃CH₂Br, (CH₃)₂CHBr, (CH₃)₃CBr.
A) (CH₃)₃CBr < (CH₃)₂CHBr < CH₃CH₂Br < CH₃Br
B) CH₃Br < CH₃CH₂Br < (CH₃)₂CHBr < (CH₃)₃CBr
C) (CH₃)₂CHBr < (CH₃)₃CBr < CH₃Br < CH₃CH₂Br
D) CH₃CH₂Br < CH₃Br < (CH₃)₂CHBr < (CH₃)₃CBr
Answer: A) (CH₃)₃CBr < (CH₃)₂CHBr < CH₃CH₂Br < CH₃Br
Explanation:
SN2 reactivity decreases with increasing steric hindrance. (CH₃)₃CBr (tertiary) is least reactive, followed by (CH₃)₂CHBr (secondary), CH₃CH₂Br (primary), and CH₃Br (methyl) being the most reactive.
Question 99: Reactions – Elimination (E2)
Which product is formed when 2-bromo-2-methylpropane undergoes E2 elimination?
A) 2-Methylpropene
B) 1-Methylpropene
C) 2,3-Dimethylpropene
D) 1,2-Dimethylpropene
Answer: A) 2-Methylpropene
Explanation:
E2 elimination leads to the formation of the most stable alkene. 2-Bromo-2-methylpropane eliminates a hydrogen and bromine from adjacent carbons to form 2-Methylpropene, the most stable tertiary alkene.
Question 100: Nomenclature – Haloarenes
What is the IUPAC name for p-fluorotoluene?
A) 1-Fluoro-4-methylbenzene
B) 4-Fluoro-1-methylbenzene
C) Both A and B
D) 1-Methyl-4-fluorobenzene
Answer: C) Both A and B
Explanation:
Both 1-Fluoro-4-methylbenzene and 4-Fluoro-1-methylbenzene are correct IUPAC names for p-fluorotoluene, as the numbering can start from either substituent to give the lowest possible numbers.
Question 101: Reactions – Aromatic Substitution
Which directing group does a chloro substituent on benzene exhibit in electrophilic aromatic substitution?
A) Ortho/Para Director
B) Meta Director
C) Both Ortho and Meta Director
D) Neither Ortho nor Meta Director
Answer: A) Ortho/Para Director
Explanation:
Chlorine is an electron-withdrawing group due to its electronegativity but donates electron density through resonance. Thus, it is an Ortho/Para Director in electrophilic aromatic substitution reactions.
Question 102: Physical Properties – Solvent Effects
Which solvent is most favorable for SN2 reactions of haloalkanes?
A) Water
B) Methanol
C) Acetone
D) Toluene
Answer: C) Acetone
Explanation:
Polar aprotic solvents like acetone stabilize the cations without solvating the nucleophile, thereby enhancing the rate of SN2 reactions. Water and methanol are polar protic and can hinder SN2 by stabilizing the nucleophile, while toluene is non-polar.
Question 103: Reactions – Nucleophilic Aromatic Substitution
Which of the following haloarenes is most reactive towards nucleophilic aromatic substitution?
A) Chlorobenzene
B) 4-Chloronitrobenzene
C) 2-Chlorotoluene
D) 3-Chlorotoluene
Answer: B) 4-Chloronitrobenzene
Explanation:
Electron-withdrawing groups like nitro groups activate haloarenes towards nucleophilic substitution by stabilizing the negative charge in the intermediate. 4-Chloronitrobenzene has a nitro group para to the chlorine, making it highly reactive towards nucleophilic aromatic substitution.
Question 104: Nomenclature – Cyclic Haloalkanes
What is the IUPAC name for cyclohexyl chloride?
A) Chlorocyclohexane
B) Cyclohexane chloride
C) 1-Chlorocyclohexane
D) Both A and C
Answer: D) Both A and C
Explanation:
Both Chlorocyclohexane and 1-Chlorocyclohexane are correct IUPAC names for cyclohexyl chloride, as the chlorine substituent is understood to be at position 1 in a monosubstituted cyclohexane.
Question 105: Reactions – Dehalogenation
Which reagent is used for the dehalogenation of vicinal dihalides to form alkenes?
A) NaOH
B) KOH
C) Zn/Acetic Acid
D) KI in acetone
Answer: C) Zn/Acetic Acid
Explanation:
Zn/Acetic Acid is commonly used to remove vicinal dihalides and form alkenes through dehalogenation. It facilitates the elimination of two halogen atoms from adjacent carbons, resulting in the formation of a double bond.
Question 106: Physical Properties – Vapor Pressure
Which haloalkane has the highest vapor pressure at room temperature?
A) CH₃Cl
B) CH₃CH₂Cl
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
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