Question detail
In a carbon-13 NMR spectrum, a peak appears at 75 ppm. What type of carbon environment does this peak most likely represent?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
Question
Type
exam_style
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Topic
Nuclear magnetic resonance spectroscopy (A-level only)
Question
In a carbon-13 NMR spectrum, a peak appears at 75 ppm. What type of carbon environment does this peak most likely represent?
Answer
The peak at 75 ppm indicates a carbon atom that is part of a carbonyl group (C=O) or a carbon atom adjacent to electronegative atoms. This answer is anchored to NMR spectroscopy (A-level only).
Explanation
The peak at 75 ppm indicates a carbon atom that is part of a carbonyl group (C=O) or a carbon atom adjacent to electronegative atoms. is the best answer because it directly supports the AQA A-Level Chemistry objective to use carbon-13 NMR spectra to identify carbon environments. This reasoning is anchored to NMR spectroscopy (A-level only) in Nuclear magnetic resonance spectroscopy (A-level only), and it separates NMR from similar A-Level ideas rather than relying on a vague recall statement. Other options are weaker if they use the wrong evidence, calculation, mechanism, observation, unit, or conclusion for this subtopic.
Common mistake
Misidentifying Carbon Environments
Students often confuse the chemical shifts of different carbon environments, leading to incorrect identification of carbon types in a molecule.
To fix this, refer to a reliable table of carbon-13 NMR chemical shifts. Identify the environment by matching the chemical shift value to the corresponding carbon type, ensuring to consider the molecular structure.
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