SUBJECT : CHEMISTRY DATE : 19/04/2020
DPP NO. : 02
BATCH : AM
By : Yogesh Sir
TOPIC : HYPERCONJUGATION
This set of Engineering Chemistry Multiple Choice Ques- 6. Which of the following is a consequence of Baker-
tions & Answers (MCQs) focuses on “Hyperconjugation”. Nathan effect?
1. Which of the following is known as Baker-Nathan ef- (a) It is helpful in explaining the directive influence of
fect? alkyl groups in aromatic alkyl benzene
(a) Mesomeric effect (b) It is helpful in explaining the relative stability of
alkenes
(b) Inductive effect
(c) It is helpful in explaining the relative stabilities of
(c) Hyperconjugation alkyl carbocations
(d) Electromeric effect (d) All of the mentioned
2. Hyperconjugation involves the delocalisation of 7. On increasing the number of a-hydrogens, the number
__________ of hyperconjugation structures will __________
(a) bond orbital (a) Decrease
(b) bond orbital (b) Increase
(c) Both s and p bond orbital (c) Remains same
(d) None of the mentioned (d) None of the mentioned
3. Number of hyperconjugation structures in isopropyl radi- 8. When the contributing structure contains the same num-
cal is __________ ber of two-electron bonds as the normal lewis formula,
(a) 3 it will be __________
(b) 6 (a) Heterovalent hyperconjugation
(c) 9 (b) Sacrificial hyperconjugation
(d) 12 (c) Isovalent hyperconjugation
4. The resonance energy (kCal/mol) of tertiary butyl is (d) All of the mentioned
__________ 9. The compound that can be most readily sulphonated is
(a) 9 __________
(b) 10 (a) Benzene
(c) 11 (b) Toluene
(d) 12 (c) Nitrobenzene
5. Larger the number of hyperconjugation structures, the (d) Chlorobenzene
stability of free radicals will __________ 10. Ethene is devoid of any alpha hydrogen so
(a) Increase hyperconjugation is not possible.
(b) Decrease (a) True
(c) Remains same (b) False
(d) None of the mentioned
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ANSWER KEY
1. (c)
2. (a)
3. ( b)
4. (d)
5.(a)
6. (d)
7. (b)
8. (c)
9. (b)
10. (a)
SOLUTION
1. Explanation: Hyperconjugation is also known as Baker- 6. Explanation: Baker-Nathan effect is helpful in explain-
Nathan effect. Hyperconjugation is the stabilising inter- ing the directive influence of alkyl groups in aromatic
action that results from the interaction of the electrons alkyl benzene. It is helpful in explaining the relative sta-
in a s-bond (usually C-H or C-C) with an adjacent empty bility of alkenes and relative stabilities of alkyl
or partially filled p-orbital or a p-orbital to give an ex- carbocations.
tended molecular orbital that increases the stability of
7. Explanation: On increasing the number of -hydro-
the system.
gens, the number of hyperconjugation structures will
2. Explanation: Hyperconjugation involves the increase. Hyperconjugation is directly proportional to
delocalisation of s bond orbital. It is the stabilising inter- the number of a-hydrogens. a-hydrogen is the hydro-
action that results from the interaction of the electrons gen atom attached to the carbon which is attached to a
in a s-bond (usually C-H or C-C) with an adjacent empty functional group.
or partially filled p-orbital or a p-orbital to give an ex-
8. Explanation: When the contributing structure contains
tended molecular orbital that increases the stability of
the same number of two-electron bonds as the normal
the system.
lewis formula, it will be isovalent hyperconjugation.
3. Explanation: Number of hyperconjugation structures in
9. Explanation: The compound that can be most readily
isopropyl radical is 6. Isopropyl is C3H7.
sulphonated is toluene. Toulene contains a methyl group
4. Explanation: The resonance energy of tertiary butyl is with benzene ring and is a colorless, water-insoluble
12 kCal/mol. It is also called tert-butanol, is the sim- liquid with the smell associated with paint thinners.
plest tertiary alcohol, with a formula of (CH3)3COH It is
10. Explanation: Ethene is devoid of any alpha hydrogen so
one of the four isomers of butanol.
hyperconjugation is not possible because the presence
5. Explanation: Larger the number of hyperconjugation of alpha hydrogen is the necessary condition for
structures, greater will be the stability of free radicals. hyperconjugation.
Purushottam Bhavan, 1st Floor, Bsides CMD College, Near Loins Club, Bilaspur - 495001, Chhattisgarh.
Ph. 07752-224440, 412404 2
