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Stereo Model Study: Ethane

1. Aim

To use a stereo model to compare rotation about the carbon-carbon single bond of ethane and identify staggered and eclipsed conformations. Ethane is the second named PCI section III model topic. The actual model and observations must be recorded here. [1]

2. Requirements

An instructor-approved model kit or preassembled ethane model, an angle guide or viewing card if supplied, observation sheet, safe work surface, and teaching supervisor are needed. No chemicals are needed. Kit-piece identity, angle guide, and course assessment criteria are specified in your college lab manual and instructor's method sheet. [2]

3. Theory

Ethane contains two tetrahedral carbons joined by a single bond. The groups on one carbon can rotate relative to those on the other without breaking that bond. In an eclipsed view, bonds on the rear carbon line up with bonds on the front; in a staggered view they are offset. The approximate dihedral angles used for the idealized comparison are 0 degrees and 60 degrees respectively. A model can show this change of conformation, but it does not measure the true motion or energy distribution of the gas. Rotation changes conformation rather than bond connectivity. [2]

4. Procedure

1. Identify the two carbon centres and their single-bond connection in the approved kit.
2. Build or inspect the ethane model with three terminal pieces on each carbon.
3. Hold one carbon group fixed while rotating the other around their connecting axis.
4. Stop at a view where front and rear directions align and label this eclipsed.
5. Rotate to an offset view and label this staggered; compare with the instructor angle guide.
6. Record whether any bond had to be disconnected to move between the two views.
7. Explain why the two views are conformations of one compound and return the kit.

5. Calculation, graph, or images as appropriate

Pre-assumed observations for explanation only: rotating the rear group moves an aligned view into an offset view without disconnecting the carbon-carbon bond. This supports the distinction between eclipsed and staggered conformations. Actual model handling must be recorded here. This section records shape or orientation rather than a synthesis yield. No reagent-volume or product-mass calculation is required.

6. Result

Report the named geometry or stereochemical relationship only after comparing the actual model with the cited reference and the instructor's labels. The submitted model result must be recorded here. Safety note: Use the model under teaching supervision and do not force connectors or point small parts toward anyone.

7. References

1. Pharmacy Council of India, Pharm.D. Regulations, 2008.
2. OpenStax, Carbon and Molecular Geometry.
3. Widener University, Molecular Models.
4. Shasta College, Conformations of Ethane.

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