HALOALKANES AND HALOARENES
MOST EXPECTED AND MOST IMPORTANT QUESTIONS{CBSE}
IUPAC NAMING ,BASIC CONCEPTS AND REACTIONS
1. Write IUPAC name of (CH₃)₃CCH₂Br.
Answer: 1-bromo-2,2-dimethylpropane
2. Write IUPAC name of CH₂=CH-CH₂Br.
Answer: 3-bromoprop-1-ene
3. Write IUPAC name of 3-chloro-2,2-dimethylbutane.
Answer: 3-chloro-2,2-dimethylbutane
4. Why is CH₂=CH–CH₂–Cl more easily hydrolyzed than CH₃–
CH₂–CH₂–Cl?
Answer: Allylic carbocation is resonance-stabilized .
5. Explain why chloroform is kept in dark bottles.
Answer: Light causes reaction with oxygen forming toxic
phosgene; dark bottles prevent it.
6. Write a stereochemical difference between SN1 and SN2.
Answer: SN1 gives racemic mixture; SN2 results in inversion of
configuration .
7. Write IUPAC name of (CH₃)₂CH–CH(Cl)CH₃.
Answer: 2-chloro-3-methylbutane
, 8. Which reacts faster: a tertiary or primary halide in SN1?
Answer: Tertiary, due to more stable carbocation
9. Name ambident nucleophiles with example.
Answer: Nucleophiles that can attack via two sites; example:
⁻CN (attacks via C or N)
10. CH₃Br vs CH₃I: which reacts faster in SN2 with OH⁻?
Answer: CH₃I, since iodide is a better leaving group
REACTIVITY ,MECHANISM AND PHYSICAL PROPERTIES
11. Arrange: 2-bromo-2-methylbutane, 1-bromopentane,
2-bromopentane in increasing SN2 reactivity.
Answer: 2-bromo-2-methylbutane < 2-bromopentane <
1-bromopentane
12. Which hydrocarbon C₅H₁₂ gives one monochloro product
only? Identify it.
Answer: 2,2-dimethylpropane (neopentane)
13. Identify chiral molecule in a pair (e.g., 2-chlorobutane).
Answer: 2-chlorobutane is chiral
14. SN2 reaction faster: CH₃CH₂Br or a tertiary halide?
Answer: CH₃CH₂Br (primary halide with less steric hindrance)
MOST EXPECTED AND MOST IMPORTANT QUESTIONS{CBSE}
IUPAC NAMING ,BASIC CONCEPTS AND REACTIONS
1. Write IUPAC name of (CH₃)₃CCH₂Br.
Answer: 1-bromo-2,2-dimethylpropane
2. Write IUPAC name of CH₂=CH-CH₂Br.
Answer: 3-bromoprop-1-ene
3. Write IUPAC name of 3-chloro-2,2-dimethylbutane.
Answer: 3-chloro-2,2-dimethylbutane
4. Why is CH₂=CH–CH₂–Cl more easily hydrolyzed than CH₃–
CH₂–CH₂–Cl?
Answer: Allylic carbocation is resonance-stabilized .
5. Explain why chloroform is kept in dark bottles.
Answer: Light causes reaction with oxygen forming toxic
phosgene; dark bottles prevent it.
6. Write a stereochemical difference between SN1 and SN2.
Answer: SN1 gives racemic mixture; SN2 results in inversion of
configuration .
7. Write IUPAC name of (CH₃)₂CH–CH(Cl)CH₃.
Answer: 2-chloro-3-methylbutane
, 8. Which reacts faster: a tertiary or primary halide in SN1?
Answer: Tertiary, due to more stable carbocation
9. Name ambident nucleophiles with example.
Answer: Nucleophiles that can attack via two sites; example:
⁻CN (attacks via C or N)
10. CH₃Br vs CH₃I: which reacts faster in SN2 with OH⁻?
Answer: CH₃I, since iodide is a better leaving group
REACTIVITY ,MECHANISM AND PHYSICAL PROPERTIES
11. Arrange: 2-bromo-2-methylbutane, 1-bromopentane,
2-bromopentane in increasing SN2 reactivity.
Answer: 2-bromo-2-methylbutane < 2-bromopentane <
1-bromopentane
12. Which hydrocarbon C₅H₁₂ gives one monochloro product
only? Identify it.
Answer: 2,2-dimethylpropane (neopentane)
13. Identify chiral molecule in a pair (e.g., 2-chlorobutane).
Answer: 2-chlorobutane is chiral
14. SN2 reaction faster: CH₃CH₂Br or a tertiary halide?
Answer: CH₃CH₂Br (primary halide with less steric hindrance)
