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Locating a Labeled Oxygen in a Model Ester 4 questions
Locating a Labeled Oxygen in a Model Ester
Base your answers on the information provided and your knowledge of chemistry. Use the 2025 Chemistry Reference Tables as needed.
A display represents methyl acetate as CH3–C(=O)–O–CH3. It tracks one signal for stretching the C=O bond and a second signal for the central carbon’s single bond to oxygen. In this simplified detector, replacing an oxygen with a heavier isotope shifts only the signal for the bond from that oxygen to the central carbon.
| Molecule | C=O signal (model units) | Central C–O signal (model units) |
|---|---|---|
| All oxygen unlabeled | 80 | 50 |
| Unknown U | 77 | 50 |
Question 1
Where is the heavy oxygen in unknown U under the stated detector model?
- Only at the oxygen double-bonded to the central carbon
- Only at the oxygen single-bonded to the central carbon
- At both oxygens
- At neither oxygen
Question 2
Explain why U still has the same number of oxygen atoms as the unlabeled molecule.
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A second molecule, V, keeps the C=O signal at 80 units but shifts the central C–O signal from 50 to 48 units.
Question 3
Copy the given structural formula with the same connections. Mark the heavy oxygen in V with a star and show the double bond to the central carbon.
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Question 4
Both U and V have one heavy oxygen atom. Explain why measuring only their molecular masses would not distinguish the two positions.
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