Chapter 3: Q47E (page 88)

Draw the most stable conformation of 1,4-dichlorobutane, using wedges and dashes to represent bonds coming out of the paper and going behind the paper respectively.

Short Answer

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Wedge and Dash Representation

Wedge and dash projection is a way of representing a molecule in 3-D in which three types of lines are used to represent the structure in 3-D.

Solid lines are used to represent the bonds that are in the plane of the paper.

Dashed lines are used to represent the bonds that extend away from the viewer (behind the paper)

Wedge shaped lines are used to represent the bonds that are oriented towards the viewer ( coming out of the paper plane)

For example: Wedge and dash representation of methyl alcohol is-

Methyl alcohol

Newmann projection of 1,4-dichlorobutane

We know that the most stable conformation of a molecule is the one wherein the bulky groups of molecule lie as far apart as possible i.e., staggered conformation. While drawing the Newman projections we get three staggered conformations for 1,4-dichloro butane.

Among the three conformations, the first conformation where, both the CH2Cl groups are lying anti periplaner to each other( i.e., at dihedral angle of 180) is the most stable, because, being in staggered conformation it has least torsional strain and bulky groups being far apart it has least steric strain.