Question

Draw structural formulas for the cis and trans isomers of 1,2 -dimethylcyclopropane.

Short answer

Answer: The main difference between the structural formulas of cis and trans isomers of 1,2-dimethylcyclopropane is the orientation of the two methyl groups. In the cis isomer, both methyl groups are on the same side of the molecule, while in the trans isomer, they are on opposite sides.

Step-by-step solution

Draw the cyclopropane ring structure

Start by drawing the simple cyclopropane ring structure, which is a triangle-shaped molecule with a carbon atom at each vertex.

Add Hydrogen atoms to the carbon atoms

Each carbon atom in the cyclopropane ring should have two hydrogen atoms bonded to it. For now, add them to the vertices, making the molecule appear flat.

Identify the first and second carbon atoms

In the 1,2-dimethylcyclopropane, the two substituents (methyl groups) will be placed at adjacent carbon atoms. Choose any two adjacent carbon atoms and label them as the first and second carbon atoms.

Place the methyl groups for the cis isomer

In the cis isomer, the two methyl groups are on the same side of the molecule. Place the methyl groups (\(\textrm{-CH}_3\)) on the same side of the first and second carbon atoms. Replace one hydrogen atom at each carbon atom with a methyl group, making sure they are on the same side (either both coming towards you or both going away from you).

Draw the structural formula for the cis isomer

Draw a wedge or a dashed line to indicate the orientation of the methyl group. If the methyl group is coming towards you, use a wedge, and if it's going away from you, use a dashed line. This will help represent the three-dimensional structure of the cis isomer.

Place the methyl groups for the trans isomer

In the trans isomer, the two methyl groups are on opposite sides of the molecule. Place the methyl groups (\(\textrm{-CH}_3\)) on opposite sides of the first and second carbon atoms. Replace one hydrogen atom at each carbon atom with a methyl group, making sure one is coming towards you and the other one is going away from you.

Draw the structural formula for the trans isomer

Again, use a wedge or a dashed line to indicate the orientation of the methyl group. If the methyl group is coming towards you, use a wedge, and if it's going away from you, use a dashed line. This will help represent the three-dimensional structure of the trans isomer. Now you have the structural formulas for both the cis and trans isomers of 1,2-dimethylcyclopropane.