Educational Materials for Organic Chemistry

Disubstituted Cycloalkanes

Placing substituents at more than one position on a cycloalkane gives rise to two stereoisomers (molecules differing by the arrangment of atoms in space, but having the same connectivity). Placing two methyl groups on the same side (cis) of a ring is not exactly the same as placing the two methyl groups on opposite sides (trans) of the ring. (The resulting molecules are not superposable) The molecules on this page should help you to be able to identify cis and trans cycloalkane isomers - you should also try working with a tutorial on this subject.

Exercises to Try with These Models

View the molecules as wireframe models and try to draw them from different angles. Try to build a mental correlation between the three-dimensional model and the pictures drawn in the textbook.
View the molecules as spacefilling models and compare the two chair conformations of each compound. Try to decide which is more stable based on overlaps between the spheres. Then switch to wireframe models and try to count the number of 1,3-diaxial interactions in each. Use the number of 1,3-diaxial interactions to determine stability and make sure you've chosen the same conformation by each method.
Identify the axial and equitorial hydrogens on the wireframe model, then check your assignment by highlighting these hydrogens with the buttons.
Set all the molecules to wireframe models, cover up the Cis and Trans identifications at the left side, and randomly page around trying to identify which molecules are cis and which are trans.

Dimethylcyclohexane - Chair Conformations

1,2-Dimethylcyclohexane

Cis		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight equatorial hydrogens Highlight axial hydrogens Highlight methyl group hydrogens Highlight 1,3-diaxial interactions with axial methyl group (methyl group hydrogens are blue, axial ring hydrogens are red)
Cis		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight equatorial hydrogens Highlight axial hydrogens Highlight methyl group hydrogens Highlight 1,3-diaxial interactions with axial methyl group (methyl group hydrogens are blue, axial ring hydrogens are red)
Trans		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight equatorial hydrogens Highlight axial hydrogens Highlight methyl group hydrogens Highlight 1,3-diaxial interactions with axial methyl group (methyl group hydrogens are blue, axial ring hydrogens are red)
Trans		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight equatorial hydrogens Highlight axial hydrogens Highlight methyl group hydrogens Highlight 1,3-diaxial interactions with axial methyl group (methyl group hydrogens are blue, axial ring hydrogens are red)

1,3-Dimethylcyclohexane

Cis		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Number hydrogens Highlight equatorial hydrogens Highlight axial hydrogens Highlight methyl group hydrogens Highlight hydrogens nearest to the methyl group (methyl group hydrogens are blue, ring hydrogens are red)
Cis		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight equatorial hydrogens Highlight axial hydrogens Highlight methyl group hydrogens Highlight hydrogens nearest to the methyl group (methyl group hydrogens are blue, ring hydrogens are red)
Trans		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight equitorial hydrogens Highlight axial hydrogens Highlight methyl group hydrogens Highlight hydrogens nearest to the methyl group (methyl group hydrogens are blue, ring hydrogens are red)
Trans		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight equitorial hydrogens Highlight axial hydrogens Highlight methyl group hydrogens Highlight hydrogens nearest to the methyl group (methyl group hydrogens are blue, ring hydrogens are red)

1,4-Dimethylcyclohexane

Cis		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight equitorial hydrogens Highlight axial hydrogens Highlight methyl group hydrogens Highlight hydrogens nearest to the methyl group (methyl group hydrogens are blue, ring hydrogens are red)
Cis		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight equatorial hydrogens Highlight axial hydrogens Highlight methyl group hydrogens Highlight hydrogens nearest to the methyl group (methyl group hydrogens are blue, ring hydrogens are red)
Trans		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight equitorial hydrogens Highlight axial hydrogens Highlight methyl group hydrogens Highlight hydrogens nearest to the methyl group (methyl group hydrogens are blue, ring hydrogens are red)
Trans		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Number hydrogens Highlight equitorial hydrogens Highlight axial hydrogens Highlight methyl group hydrogens Highlight hydrogens nearest to the methyl group (methyl group hydrogens are blue, ring hydrogens are red)

Return to cycloalkane conformation index
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Last modified 9/11/96

Abby Parrill
Department of Chemistry
Michigan State University

These pages may be downloaded and linked from other pages freely for academic and educational purposes. Questions, problems, and errors should be sent to parrill@argus.cem.msu.edu.