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.
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