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Stereo Model Study: Cis Alkene

1. Aim

To construct or inspect a substituted cis alkene model and identify the same-side relationship of a specified pair of comparable substituents. This is the fifth named PCI section III model topic. The selected example and observations are specified in your college lab manual and instructor's method sheet. [1]

2. Requirements

Approved substituted-alkene model pieces or a preassembled pair of geometric isomer models, two distinct substituent labels at each double-bond carbon, reference card, observation sheet, and teaching supervisor. No reaction chemicals are required. Exact substituent identity and kit assessment criteria are specified in your college lab manual and instructor's method sheet. [2]

3. Theory

Cis-trans description is possible for a suitable alkene only when each double-bond carbon has two different substituents. In a cis example, the chosen comparable groups lie on the same side of the double-bond framework. The double bond restricts rotation, so the same-side arrangement cannot be changed into the opposite-side arrangement by simple rotation while keeping bonding intact. In more complex substituted alkenes, E/Z nomenclature may be required instead of a simple cis-trans label. The model exercise must state which two groups are being compared before assigning cis. [2]

4. Procedure

1. Confirm that both double-bond carbons have two different substituent labels.
2. Identify the pair of comparable groups to be used for the cis-trans comparison.
3. Assemble or inspect the assigned substituted alkene without changing its connections.
4. View the double-bond framework from a consistent orientation and place a reference card beside it.
5. Record whether the two compared groups lie on the same side.
6. Try only permitted whole-model rotation and observe that this does not switch the same-side relationship.
7. Label the arrangement cis only if the stated comparison is valid; record any need for E/Z nomenclature.

5. Calculation, graph, or images as appropriate

Pre-assumed observations for explanation only: two matching labelled groups are on the same side of a model with two different groups on each double-bond carbon. The specified pair meets the cis description; the actual assigned example 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: This is a physical-model task under teaching supervision. Do not force double-bond connectors or lose small labelled pieces.

7. References

1. Pharmacy Council of India, Pharm.D. Regulations, 2008.
2. Lewis-Clark State College, Geometric Isomers.
3. OpenStax, Carbon and Molecular Geometry.

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