11. Which of the following compounds exhibits position isomerism?
A. Butan-1-ol and Butan-2-ol
B. Ethanol and Dimethyl ether
C. Propanal and Propanone
D. Ethanoic acid and Methyl methanoate
Answer: A. Butan-1-ol and Butan-2-ol
Explanation:
Position isomerism occurs when the functional group occupies different positions on the same carbon chain. In Butan-1-ol and Butan-2-ol, the hydroxyl (-OH) group is at different positions in the carbon chain.
12. Which of the following is the most reactive towards nucleophilic substitution via the SN2 mechanism?
A. CH₃Cl
B. CH₃CH₂Cl
C. (CH₃)₃CCl
D. C₆H₅CH₂Cl
Answer: A. CH₃Cl
Explanation:
In the SN2 mechanism, reactivity increases as the steric hindrance decreases. Methyl halides like CH₃Cl have the least steric hindrance, making them the most reactive toward SN2 reactions.
13. Which one of the following is a pair of chain isomers?
A. Pentane and 2-Methylbutane
B. Pentan-2-one and Pentan-3-one
C. Ethanol and Ethanoic acid
D. Propan-1-ol and Propan-2-ol
Answer: A. Pentane and 2-Methylbutane
Explanation:
Chain isomerism occurs when the carbon skeleton of a molecule is arranged differently. Pentane and 2-Methylbutane are chain isomers because they differ in the branching of their carbon chain.
14. Which of the following reactions involves a free radical mechanism?
A. Bromination of benzene
B. Halogenation of methane
C. Esterification of carboxylic acids
D. Hydrolysis of alkyl halides
Answer: B. Halogenation of methane
Explanation:
The halogenation of alkanes, such as methane, proceeds via a free radical mechanism, involving initiation, propagation, and termination steps where free radicals are formed and consumed.
15. Which of the following compounds exhibits geometrical isomerism?
A. 1-Butene
B. But-2-yne
C. But-2-ene
D. 2-Methylpropene
Answer: C. But-2-ene
Explanation:
Geometrical isomerism occurs due to restricted rotation around a double bond, where different groups are attached to the double-bonded carbons. But-2-ene has cis and trans isomers due to the arrangement of substituents around the double bond.
16. Which of the following reactions will proceed via an SN1 mechanism?
A. 2-Bromo-2-methylpropane with OH⁻
B. Methyl bromide with OH⁻
C. Chloromethane with CN⁻
D. Bromoethane with OH⁻
Answer: A. 2-Bromo-2-methylpropane with OH⁻
Explanation:
Tertiary alkyl halides, like 2-Bromo-2-methylpropane, undergo nucleophilic substitution through the SN1 mechanism due to the stability of the tertiary carbocation formed during the reaction.
17. The IUPAC name of the compound CH₃CH₂COCH₃ is:
A. Propan-2-one
B. Butan-2-one
C. Butanone
D. Butanal
Answer: B. Butan-2-one
Explanation:
The compound contains four carbon atoms, with a ketone group (-CO) attached to the second carbon atom. Thus, the correct name is butan-2-one.
18. Which of the following compounds exhibits optical isomerism?
A. 2-Butanol
B. 2-Methylpropane
C. But-2-ene
D. 1-Butanol
Answer: A. 2-Butanol
Explanation:
Optical isomerism occurs when a molecule contains a chiral center, a carbon atom attached to four different groups. In 2-butanol, the second carbon is chiral, making the molecule optically active.
19. Which of the following pairs can be classified as tautomers?
A. Acetone and Propan-2-ol
B. Ethanol and Acetic acid
C. Acetone and Propanal
D. Acetone and Enol
Answer: D. Acetone and Enol
Explanation:
Tautomers are isomers of a compound that differ in the position of a proton and the connectivity of atoms. Acetone (keto form) and enol are keto-enol tautomers.
20. Which of the following will undergo electrophilic aromatic substitution most readily?
A. Nitrobenzene
B. Benzene
C. Toluene
D. Chlorobenzene
Answer: C. Toluene
Explanation:
Toluene has a methyl group (-CH₃), which is an electron-donating group. This activates the benzene ring towards electrophilic substitution, making toluene more reactive than benzene and other substituted benzene rings with electron-withdrawing groups.
Leave a comment