Engineering Chemistry MCQ (Hyperconjugation)

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Engineering Chemistry MCQ (Hyperconjugation)

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1. Which of the following is known as Baker-Nathan effect?
a) Mesomeric effect
b) Inductive effect
c) Hyperconjugation
d) Electromeric effect
Answer: c
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
Answer: a
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
Answer: b
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
Answer: d
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
Answer: a
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
Answer: d
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
Answer: b
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
Answer: c
Explanation: When the contributing structure contains the same number of twoelectron 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
Answer: b
Explanation: The compound that can be most readily sulphonated is toluene.
Toulene contains a methyl group with benzene ring and is a colorless, waterinsoluble 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
Answer: a
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.