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Reading the Two Sides of a Double Bond 4 questions

Reading the Two Sides of a Double Bond

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A molecular display shows two models of butene. Each CH3 label represents one carbon and three hydrogens. Each C at the center has one H and one CH3 attached. The central double bond prevents the two ends from turning independently in this model.

Model P has both CH₃ groups above the central carbon-carbon double bond and both H labels below. Model Q has its left CH₃ group above and right CH₃ group below, with each H opposite the CH₃ on its carbon.
Two models of the groups attached to a double bond.
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Question 1

Which statement distinguishes the two models?

  1. P has more carbon atoms than Q.
  2. Q has a single central bond.
  3. The CH₃ groups are on the same side in P and opposite sides in Q.
  4. Only P has an H attached to each central carbon.

Question 2

Find the molecular formula of each model. Show how the CH₃ groups and separate H labels are counted.

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Question 3

A student turns the entire P drawing 180° in the plane of the page. Explain whether this can make the two CH₃ groups appear on opposite sides of the double bond.

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A student builds a different model in which the central bond is single and one additional H is attached to each central carbon. The two ends can now turn relative to one another.

Question 4

Explain why an observation of the CH₃ groups on opposite sides in the single-bond model does not require a different fixed arrangement of the atoms.

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