71. Which of the following compounds will undergo nucleophilic substitution most easily?
A. Methyl bromide
B. Ethyl bromide
C. Isopropyl bromide
D. Tert-butyl bromide
Answer: A. Methyl bromide
Explanation:
In the SN2 mechanism, nucleophilic substitution occurs more easily with less steric hindrance. Methyl bromide, being the least sterically hindered, undergoes substitution most easily.
72. Which of the following is an example of a condensation reaction?
A. Aldol reaction
B. Hydrogenation of alkenes
C. Nitration of benzene
D. Oxidation of alcohols
Answer: A. Aldol reaction
Explanation:
In the Aldol reaction, two carbonyl compounds combine to form a β-hydroxy ketone or aldehyde, with the elimination of water, making it a condensation reaction.
73. Which of the following is the major product in the reaction of propene with HBr in the absence of peroxides?
A. 1-Bromopropane
B. 2-Bromopropane
C. Propanol
D. 2-Bromobutane
Answer: B. 2-Bromopropane
Explanation:
According to Markovnikov’s rule, in the absence of peroxides, the bromine atom will add to the more substituted carbon (the carbon with fewer hydrogen atoms), forming 2-bromopropane.
74. Which of the following undergoes an E2 elimination reaction?
A. 2-Bromopropane with KOH in ethanol
B. Ethyl chloride with NaOH in water
C. Benzyl chloride with NaCN
D. Chloromethane with NH₃
Answer: A. 2-Bromopropane with KOH in ethanol
Explanation:
The reaction of 2-bromopropane with KOH in ethanol undergoes an E2 elimination mechanism, resulting in the formation of propene.
75. Which of the following is an electrophilic addition reaction?
A. Addition of HCl to ethene
B. Nitration of benzene
C. Reduction of alkenes
D. Free radical chlorination
Answer: A. Addition of HCl to ethene
Explanation:
In the addition of HCl to ethene, the electrophilic hydrogen ion (H⁺) adds to the double bond, followed by the nucleophilic attack of chloride ion (Cl⁻), making it an electrophilic addition reaction.
76. Which of the following compounds exhibits geometrical isomerism?
A. 2-Butene
B. Ethane
C. 1-Butanol
D. Benzene
Answer: A. 2-Butene
Explanation:
Geometrical isomerism arises due to restricted rotation around a double bond. In 2-butene, the arrangement of the substituents around the double bond leads to cis and trans isomers.
77. Which of the following compounds is the most acidic?
A. Acetic acid
B. Ethanol
C. Methane
D. Ethene
Answer: A. Acetic acid
Explanation:
Acetic acid is a carboxylic acid, and the -COOH group donates a proton (H⁺), making it more acidic than alcohols (ethanol), hydrocarbons (methane), or alkenes (ethene).
78. Which of the following will undergo SN1 reaction most readily?
A. Methyl bromide
B. Ethyl bromide
C. Isopropyl bromide
D. Tert-butyl bromide
Answer: D. Tert-butyl bromide
Explanation:
The SN1 reaction mechanism proceeds via the formation of a carbocation intermediate. Tert-butyl bromide forms a stable tertiary carbocation, making it the most reactive in SN1 reactions.
79. Which of the following is the most basic compound?
A. Aniline
B. Ammonia
C. Methylamine
D. Dimethylamine
Answer: D. Dimethylamine
Explanation:
Basicity in amines increases with the electron-donating effects of alkyl groups. Dimethylamine, having two methyl groups, is more basic than ammonia, methylamine, and aniline.
80. Which of the following compounds exhibits both geometrical and optical isomerism?
A. 2-Butene
B. 2-Chlorobutane
C. 1,2-Dichlorocyclopropane
D. 1,3-Butadiene
Answer: C. 1,2-Dichlorocyclopropane
Explanation:
1,2-Dichlorocyclopropane exhibits both geometrical isomerism (cis-trans) due to restricted rotation in the ring and optical isomerism if the compound has non-superimposable mirror images.
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