This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Hyperconjugation”.
1. Which of the following is known as Baker-Nathan effect?
a) Mesomeric effect
b) Inductive effect
c) Hyperconjugation
d) Electromeric effect
View Answer
Explanation: Hyperconjugation is also known as Baker-Nathan effect. Hyperconjugation is the stabilising interaction that results from the interaction of the electrons in a σ-bond (usually C-H or C-C) with an adjacent empty or partially filled p-orbital or a π-orbital to give an extended molecular orbital that increases the stability of the system.
2. Hyperconjugation involves the delocalisation of __________
a) σ bond orbital
b) π bond orbital
c) Both σ and π bond orbital
d) None of the mentioned
View Answer
Explanation: Hyperconjugation involves the delocalisation of σ bond orbital. It is the stabilising interaction that results from the interaction of the electrons in a σ-bond (usually C-H or C-C) with an adjacent empty or partially filled p-orbital or a π-orbital to give an extended molecular orbital that increases the stability of the system.
3. Number of hyperconjugation structures in isopropyl radical is __________
a) 3
b) 6
c) 9
d) 12
View Answer
Explanation: Number of hyperconjugation structures in isopropyl radical is 6. Isopropyl is C3H7.
4. The resonance energy (kCal/mol) of tertiary butyl is __________
a) 9
b) 10
c) 11
d) 12
View Answer
Explanation: The resonance energy of tertiary butyl is 12 kCal/mol. It is also called tert-butanol, is the simplest tertiary alcohol, with a formula of (CH3)3COH It is one of the four isomers of butanol.
5. Larger the number of hyperconjugation structures, the stability of free radicals will __________
a) Increase
b) Decrease
c) Remains same
d) None of the mentioned
View Answer
Explanation: Larger the number of hyperconjugation structures, greater will be the stability of free radicals.
6. Which of the following is a consequence of Baker-Nathan effect?
a) It is helpful in explaining the directive influence of alkyl groups in aromatic alkyl benzene
b) It is helpful in explaining the relative stability of alkenes
c) It is helpful in explaining the relative stabilities of alkyl carbocations
d) All of the mentioned
View Answer
Explanation: Baker-Nathan effect is helpful in explaining the directive influence of alkyl groups in aromatic alkyl benzene. It is helpful in explaining the relative stability of alkenes and relative stabilities of alkyl carbocations.
7. On increasing the number of α-hydrogens, the number of hyperconjugation structures will __________
a) Decrease
b) Increase
c) Remains same
d) None of the mentioned
View Answer
Explanation: On increasing the number of α-hydrogens, the number of hyperconjugation structures will increase. Hyperconjugation is directly proportional to the number of α-hydrogens. α-hydrogen is the hydrogen atom attached to the carbon which is attached to a functional group.
8. When the contributing structure contains the same number of two-electron bonds as the normal lewis formula, it will be __________
a) Heterovalent hyperconjugation
b) Sacrificial hyperconjugation
c) Isovalent hyperconjugation
d) All of the mentioned
View Answer
Explanation: When the contributing structure contains the same number of two-electron bonds as the normal lewis formula, it will be isovalent hyperconjugation.
9. The compound that can be most readily sulphonated is __________
a) Benzene
b) Toluene
c) Nitrobenzene
d) Chlorobenzene
View Answer
Explanation: The compound that can be most readily sulphonated is toluene. Toulene contains a methyl group with benzene ring and is a colorless, water-insoluble liquid with the smell associated with paint thinners.
10. Ethene is devoid of any alpha hydrogen so hyperconjugation is not possible.
a) True
b) False
View Answer
Explanation: Ethene is devoid of any alpha hydrogen so hyperconjugation is not possible because the presence of alpha hydrogen is the necessary condition for hyperconjugation.
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