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Questions and Answers
What type of conformation of butane has larger groups positioned 180° from each other?
What type of conformation of butane has larger groups positioned 180° from each other?
What phenomenon causes an increase in energy when atoms are forced too close to one another?
What phenomenon causes an increase in energy when atoms are forced too close to one another?
How many 60° rotations are needed to return to the original conformation in butane?
How many 60° rotations are needed to return to the original conformation in butane?
In terms of energy, how do staggered conformations compare to eclipsed conformations?
In terms of energy, how do staggered conformations compare to eclipsed conformations?
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Which conformation of butane is generally higher in energy due to steric strain?
Which conformation of butane is generally higher in energy due to steric strain?
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What is the dihedral angle of the C—H bonds in the staggered conformation of ethane?
What is the dihedral angle of the C—H bonds in the staggered conformation of ethane?
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Which conformation is more stable due to lower energy?
Which conformation is more stable due to lower energy?
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What is the primary cause of increased energy in the eclipsed conformation?
What is the primary cause of increased energy in the eclipsed conformation?
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What is the energy difference between staggered and eclipsed conformers known as?
What is the energy difference between staggered and eclipsed conformers known as?
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How is torsional strain defined?
How is torsional strain defined?
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Which of the following describes the process of converting an eclipsed conformation into a staggered conformation?
Which of the following describes the process of converting an eclipsed conformation into a staggered conformation?
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In a Newman projection, how is the front carbon represented?
In a Newman projection, how is the front carbon represented?
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What is the contribution of each eclipsed C—H bond to the energy difference?
What is the contribution of each eclipsed C—H bond to the energy difference?
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Study Notes
Conformations of Acyclic Alkanes
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Conformations: Different arrangements of atoms resulting from rotation around single bonds.
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Eclipsed conformation: C-H bonds on adjacent carbons directly align.
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Staggered conformation: C-H bonds on one carbon bisect the H-C-H bond angle on the adjacent carbon.
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Dihedral angle: Angle between two bonds on adjacent atoms.
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Newman projections: End-on representations of conformations.
Ethane Conformations
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Staggered ethane: Dihedral angle of 60 degrees; More stable than eclipsed due to lower electron-electron repulsion.
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Eclipsed ethane: Dihedral angle of 0 degrees; Less stable than staggered due to higher electron-electron repulsion.
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Torsional energy: Energy difference between staggered and eclipsed conformers; ~3 kcal/mol for ethane, with each eclipsed C-H bond contributing 1 kcal/mol.
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Torsional strain: Increased energy caused by eclipsing interactions.
Butane Conformations
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Butane has six different conformations due to multiple C-C bonds capable of rotation.
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Anti conformation: Staggered conformation with two larger groups 180 degrees apart.
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Gauche conformation: Staggered conformation with two larger groups 60 degrees apart.
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Steric strain: Increased energy when atoms are forced too close; Present in gauche conformations.
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Barrier to rotation: Energy difference between the lowest and highest energy conformations.
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Zigzag skeletal structures: Representation of alkanes with staggered conformations and all large groups anti.
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Description
Test your knowledge on the conformations of acyclic alkanes, specifically focusing on ethane and butane. Explore key concepts such as staggered and eclipsed conformations, dihedral angles, and torsional energy. This quiz will help reinforce your understanding of molecular arrangements and their stability.
