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This question is about spectroscopy - AQA - A-Level Chemistry - Question 7 - 2021 - Paper 2
Question 7
This question is about spectroscopy. Compound K has molecular formula C4H8O Figure 5 shows the infrared spectrum of K. Which functional group does K contain? Tick ... show full transcript
Worked Solution & Example Answer:This question is about spectroscopy - AQA - A-Level Chemistry - Question 7 - 2021 - Paper 2
Step 1
Step 2
Suggest three ways in which the infrared spectrum of M is different from the infrared spectrum of L.
Answer
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The peak at 2220-2260 cm⁻¹ (for C≡N) disappears in the spectrum of M, indicating that the nitrile group is no longer present.
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A new peak around 3300-3500 cm⁻¹ appears in M's spectrum, which is characteristic of the NH group from the hydrogenation process.
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The fingerprint region of the spectrum is different, showing unique absorption peaks that are distinct to the new compound M.
Step 3
Deduce the structure of Q.
Answer
The structure of Q is CH3-CH2-O-CH2Cl.
This is deduced from the integration values that indicate ratios of hydrogen atoms connected to different groups. The integration ratio of 2:2:3 matches with two CH2 groups and one CH3 group.
The chemical shifts in the NMR provide additional confirmation that suggests an ether or alcohol structure, thus supporting the deduction of the ethoxy and chloromethyl groups.