This set of Class 11 Chemistry Chapter 12 Multiple Choice Questions & Answers (MCQs) focuses on “Fundamental Concepts in Organic Reaction Mechanism”.
1. Free radicals are formed during homolytic fission.
a) true
b) false
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Explanation: In homolytic fission, one of the electrons of the shared pair in covalent bond goes with each of the bonded atoms, the neutral chemical species such formed, is called free radical. Generally, homolytic fission takes place in non-polar, covalent molecules in the presence of Sunlight or high-temperature free radicals are highly reactive, neutral and electron deficient species which are formed here.
2. Nucleophilic reagents behave as ______________
a) water
b) lewis base
c) lewis acid
d) salt
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Explanation: Nucleophilic reagents are electron rich species,s they behave as Lewis bases. They attack at electron deficient area and in case of the same nucleophilic site, nucleophilicity parallels basicity that is as well as a city increases nucleophilicity also increases.
3. Carbocations bear a ______________ charge.
a) no
b) negative
c) positive
d) 0
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Explanation: Carbocations are the product of hydrolysis and contain a carbon bearing positive charge, these are electron deficient species. Carbocations contain 6 electrons in their valence shell, these are also planner chemical species with sp2 hybridization and an Empty p-orbital.
4. What is the hybridization of singlet carbene?
a) sp
b) sp3
c) sp3d
d) sp2
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Explanation: In a singlet carbon, the carbon atom is sp2 hybridized, the unhybridized orbitals contain no electrons and a hybridized orbital contains two electrons. Singlet carbene has a brain structure and is less stable than a triplet carbine.
5. Which of the following is false regarding inductive effect?
a) temporary effect
b) propagates through a carbon chain
c) permanent effect
d) groups having high electron affinity than hydrogen show the negative inductive effect
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Explanation: Inductive effect is a permanent effect and it propagates through carbon chain atoms or group having greater electron affinity than hydrogen, are said to have electronic track thing or negative inductive effect and vice versa. Inductive effect is just like shifting of shared pair of electrons in polar covalent molecules.
6. In a molecule, when displacement of electron pair is away from the group it is ______________ electromeric effect.
a) zero
b) negative
c) positive
d) no
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Explanation: Electromeric effect is defined as the polarity produced in a multiple bonded compounds as a reagent approaches it in the presence of attacking agent, the 2 π electrons are completely transferred to any one of them and this effect is temporary. It is positive electromeric effect to when the displacement of electron pair is away from the atom or group and vice versa.
7. Baker Nathan effect is related to ______________
a) inductive effect
b) electromeric effect
c) hyperconjugation
d) resonance
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Explanation: Hyperconjugation involves delocalization of Sigma electrons of a carbon-hydrogen bond of an alkyl group attached directly to an atom of unsaturated system or to an atom with an ancient π orbital. It is calso called no Bond formation or Baker Nathan effect.
8. Resonating structures are also known as ______________ forms.
a) canonical
b) inductor
c) electromeric
d) nucleophilic
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Explanation: When all the properties of a molecule cannot be shown by a single structure and two or more structures are required to show all the properties of that molecule, then the structures are called resonating structures are canonical forms and the molecule is referred to as resonance hybrid.
9. What is obtained by thermolysis of azides?
a) free radicals
b) carbocation
c) arene
d) nitrene
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Explanation: Nitrenes are obtained by the thermolysis of azides. They are neutral monovalent nitrogen species in which nitrogen atom has 2 and shared pair of electrons with a monovalent atom or group attached and they are as reactive as carbenes.
10. If the total number of bonds between two atoms is 3 the total number of resonating structures is 2 what is the bond order?
a) 0.5
b) 1.5
c) 2.5
d) 3.5
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Explanation: Bond order is given by the formula that the total number of bonds between two atoms / the total number of resonating structures, the bond order = 3/2 = 1.5, we can say that there is a relation between resonance and bond order through this equation.
Sanfoundry Global Education & Learning Series – Chemistry – Class 11.
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