Multiple Choice
In the context of NMR spectroscopy, into how many peaks will each proton shown in red be split if it has two equivalent neighboring protons?
185
views
15. Analytical Techniques: IR, NMR, Mass Spect
NMR Practice
Multiple Choice
A 1H NMR spectrum contains a quartet at 4.1 ppm integrating to 2H and triplet at 0.9 ppm integrating to 3H, among other signals. What fragment is likely part of this molecule?
A
An ethyl group
B
A methyl group
C
An isopropyl group.
D
A t-butyl group
Verified step by step guidance1
Identify the splitting pattern of the signals: A quartet indicates a CH2 group adjacent to a CH3 group, and a triplet indicates a CH3 group adjacent to a CH2 group.
Consider the integration values: The quartet integrates to 2H, suggesting it corresponds to a CH2 group, and the triplet integrates to 3H, suggesting it corresponds to a CH3 group.
Recognize the chemical shift values: The quartet at 4.1 ppm is downfield, indicating the CH2 group is likely near an electronegative atom or group, while the triplet at 0.9 ppm is upfield, typical for a CH3 group in an alkyl chain.
Combine the splitting pattern, integration, and chemical shift information: The combination of a CH2 group (quartet) and a CH3 group (triplet) with the given chemical shifts is characteristic of an ethyl group.
Conclude that the fragment is an ethyl group, as it matches the observed NMR data with a CH2-CH3 structure, where the CH2 is deshielded, causing the downfield shift.
Related Practice
