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.
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