Educational Materials for Organic Chemistry

Monosubstituted Cycloalkanes

While manipulating the structures in the tables below, try to make comparisons between different conformations of the same molecule (eg: in methylcyclohexane, which conformation has closer interections between hydrogens on the methyl group and hydrogens in the ring?). Making comparisons will help you understand why stereoisomeric conformations have different energies.

Learning Exercises to accompany these Models

View each molecule as a wirefram model and practice drawing different orientations of the model. Decide which one is usually represented on paper. Practice this until you can look at the pictures on paper (in the book and on exams) and imagine a three-dimensional molecule.
View each molecule as a spacefilling model - compare the two conformations of each molecule and determine which is least stable due to "bumps" between hydrogen atoms. Make sure the conformation you chose as least stable has the highest strain energy.
Find the axial/equitorial/flagpole/eclipsing hydrogens on appropriate molecules before highlighting them. This may be easier to do with the wireframe models.
Find all 1,3-diaxial interactions before highlighting them.

Methylcyclohexane - Chair Conformations

Axial Methyl Group		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)	Strain Energy = 2.6952 kcal/mol
Equitorial Methyl Group		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)	Strain Energy = 1.2998 kcal/mol

Methylcyclopentane - Envelope Conformations

Pseudo-axial Methyl Group		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight pseudo-equitorial hydrogen Highlight methyl group hydrogens Highlight interaction between methyl hydrogens and vicinal ring hydrogens (methyl group hydrogens are red, vicinal ring hydrogens are blue) Highlight interaction between methyl hydrogens and cross-ring hydrogens (methyl group hydrogens are red, cross-ring hydrogens are blue)	Strain Energy = 11.6553 kcal/mol
Pseudo-equitorial Methyl Group		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight pseudo-axial hydrogen Highlight methyl group hydrogens Highlight interaction between methyl hydrogens and vicinal ring hydrogens (methyl group hydrogens are red, vicinal ring hydrogens are blue) Highlight interaction between methyl hydrogens and cross-ring hydrogens (methyl group hydrogens are red, cross-ring hydrogens are blue)	Strain Energy = 11.1629 kcal/mol

Methylcyclobutane - Bent Conformations

Pseudo-axial Methyl Group		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight pseudo-equitorial hydrogen Highlight methyl group hydrogens Highlight interaction between methyl hydrogens and vicinal ring hydrogens (methyl group hydrogens are red, vicinal ring hydrogens are blue) Highlight interaction between methyl hydrogens and cross-ring hydrogens (methyl group hydrogens are red, cross-ring hydrogens are blue)	Strain Energy = 33.9530 kcal/mol
Pseudo-equitorial Methyl Group		Push button to view spacefilling model Push button to view wireframe model Highlight carbons Highlight pseudo-axial hydrogen Highlight methyl group hydrogens Highlight interaction between methyl hydrogens and vicinal ring hydrogens (methyl group hydrogens are red, vicinal ring hydrogens are blue) Highlight interaction between methyl hydrogens and cross-ring hydrogens (methyl group hydrogens are red, cross-ring hydrogens are blue)	Strain Energy = 33.7202 kcal/mol

Return to cycloalkane conformation index
Return to main index

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 besent toparrill@argus.cem.msu.edu.