51. Which of the following is the correct IUPAC name for CH₃CH₂COOCH₃?
A. Methyl ethanoate
B. Methyl propanoate
C. Ethyl methanoate
D. Propyl methanoate
Answer: B. Methyl propanoate
Explanation:
The compound is an ester where the alkyl group attached to the oxygen is methyl, and the acid part is propanoic acid, making the name methyl propanoate.
52. Which of the following compounds exhibits cis-trans isomerism?
A. 2-Butene
B. Butane
C. Ethyne
D. 1-Butene
Answer: A. 2-Butene
Explanation:
Cis-trans (geometrical) isomerism occurs due to restricted rotation around a double bond, with different groups attached to the double-bonded carbons. 2-Butene has both cis and trans forms.
53. Which of the following is an example of a nucleophilic substitution reaction?
A. Reaction of methyl chloride with NaOH
B. Hydrogenation of alkenes
C. Nitration of benzene
D. Addition of HCl to ethene
Answer: A. Reaction of methyl chloride with NaOH
Explanation:
The reaction of methyl chloride (CH₃Cl) with NaOH involves the substitution of the chloride ion with a hydroxide ion (OH⁻), a nucleophile, making it a nucleophilic substitution reaction.
54. Which of the following exhibits keto-enol tautomerism?
A. Acetone
B. Benzene
C. Ethanol
D. Methane
Answer: A. Acetone
Explanation:
Keto-enol tautomerism occurs when a compound containing a carbonyl group (such as acetone) is in equilibrium with its enol form, where a hydrogen atom shifts from the alpha carbon to the oxygen.
55. Which of the following is an example of a dehydration reaction?
A. Conversion of ethanol to ethene
B. Hydrolysis of esters
C. Oxidation of alcohols
D. Hydrogenation of alkenes
Answer: A. Conversion of ethanol to ethene
Explanation:
Dehydration is the removal of water (H₂O) from a compound. When ethanol is heated with an acid catalyst, it undergoes dehydration to form ethene and water.
56. Which of the following will undergo nucleophilic substitution the slowest via an SN2 mechanism?
A. Methyl chloride
B. Ethyl chloride
C. Isopropyl chloride
D. Tert-butyl chloride
Answer: D. Tert-butyl chloride
Explanation:
The SN2 mechanism requires backside attack by the nucleophile. Tert-butyl chloride has significant steric hindrance due to three bulky methyl groups, making it the slowest to undergo SN2 substitution.
57. The correct order of reactivity of the following compounds in the SN1 mechanism is:
A. Methyl chloride > Ethyl chloride > Isopropyl chloride > Tert-butyl chloride
B. Tert-butyl chloride > Isopropyl chloride > Ethyl chloride > Methyl chloride
C. Isopropyl chloride > Methyl chloride > Ethyl chloride > Tert-butyl chloride
D. Ethyl chloride > Methyl chloride > Tert-butyl chloride > Isopropyl chloride
Answer: B. Tert-butyl chloride > Isopropyl chloride > Ethyl chloride > Methyl chloride
Explanation:
In the SN1 mechanism, the reactivity is determined by the stability of the carbocation formed. Tertiary carbocations are the most stable, followed by secondary, primary, and methyl carbocations.
58. Which of the following is an example of an electrophilic addition reaction?
A. Addition of HCl to ethene
B. Reaction of methyl chloride with KCN
C. Nitration of benzene
D. Hydrolysis of esters
Answer: A. Addition of HCl to ethene
Explanation:
Electrophilic addition involves the attack of an electrophile on an electron-rich species like an alkene. In the addition of HCl to ethene, the H⁺ (electrophile) adds to the double bond, followed by the chloride ion.
59. Which of the following compounds is optically active?
A. 2-Chlorobutane
B. 1-Chlorobutane
C. 2-Methylpropane
D. 2-Butene
Answer: A. 2-Chlorobutane
Explanation:
Optical activity is exhibited by compounds with a chiral center. 2-Chlorobutane has a carbon atom attached to four different groups, making it chiral and optically active.
60. Which of the following is the major product in the dehydration of 2-methylpropan-2-ol?
A. 2-Methylpropene
B. 1-Butene
C. 2-Butene
D. But-1-yne
Answer: A. 2-Methylpropene
Explanation:
Dehydration of alcohols proceeds via an elimination reaction. According to Zaitsev’s rule, the more substituted alkene is formed as the major product, which in this case is 2-Methylpropene.
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