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Case Study Questions for Class 11 Chemistry Chapter 13 Hydrocarbons
Case Study Questions
Question 1:
The rotation of carbon-carbon single bond (s-bond), due to cylindrical symmetry of s-MOs (molecular orbitals) long internuclear axis, in alkanes results into different spatial arrangements of atoms in space, that are interconvertible. These arrangements are called conformations.
However, weak repulsive interaction are present between the adjacent bonds in alkanes so the rotation of C—C single bond is not completely free and is hindered by a small energy barriers of 1-20 kJ mol-1. The repulsive interaction between the adjacent bond is due to electron cloud. The two types of conformations are very common, i.e., staggered and eclipsed.
The conformation in which the hydrogen atoms attached to the two carbon atoms are as far apart as possible is called the staggered conformation. The conformations in which the hydrogen atoms attached to the two carbon atoms are as closed as possible is called eclipsed conformation. Any intermediate conformation between the above two is called skew or gauche conformation
(i) The electronic distribution of the sigma molecular orbital is symmetrical around the internuclear axis of C-C bond which permits free rotation around C-C bond. Such spatial arrangements of atoms in which conversion of one another takes place by rotation around C-C bond is known as
(a) rotamers
(b) conformers
(c) conformations
(d) All of these
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Answer: d(ii) The possible rotamers of ethane is/are
(a) 2
(b) 3
(c) 4
(d) ∞
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Answer: d(iii) The different conformations of ethane cannot be separated and isolated because
(a) small energy barrier
(b) large energy barrier
(c) Both (a) and (b)
(d) Neither (a) nor (b)
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Answer: aOr
The repulsive interaction between the electron clouds, which affects stability of a conformation is termed as
(a) torsional strain
(b) dihedral angle
(c) torsional angle
(d) conformation
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Answer: a(iv) Which form of ethane has the least torsional strain?
(a) Staggered
(b) Skew boat
(c) Eclipsed
(d) Boat
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Answer: aRelated Posts
Class 11 Chemistry Case Study Questions
Chapter 1 Some Basic Concepts of Chemistry Case Study Questions
Chapter 2 Structure of The Atom Case Study Questions
Chapter 3 Classification of Elements and Periodicity in Properties Case Study Questions
Chapter 4 Chemical Bonding and Molecular Structure Case Study Questions
Chapter 5 States of Matter Case Study Questions
Chapter 6 Thermodynamics Case Study Questions
Chapter 7 Equilibrium Case Study Questions
Chapter 8 Redox Reactions Case Study Questions
Chapter 9 Hydrogen Case Study Questions
Chapter 10 The s-Block Elements Case Study Questions
Chapter 11 The p-Block Elements Case Study Questions
Chapter 12 Organic Chemistry: Some Basic Principles and Techniques Case Study Questions
Chapter 13 Hydrocarbons Case Study Questions
Chapter 14 Environmental Chemistry Case Study Questions
