Welcome to the Quiz!
This quiz contains 18 questions from a mix of 1 subtopics.
What is the main purpose of NMR spectroscopy?
to measure the melting point of a substance
to determine the molecular weight of compounds
to understand the structure of molecules
to identify the functional groups present in a molecule
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What characteristic do atomic nuclei with an odd total number of protons and electrons exhibit?
nuclear decay
nuclear spin
nuclear fusion
nuclear fission
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Which alignment of nuclei corresponds to a state of lower energy?
independent of the external magnetic field
perpendicular to the external magnetic field
parallel to the external magnetic field
anti-parallel to the external magnetic field
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What does the term chemical environment refer to in NMR spectroscopy?
the external magnetic field applied to the sample
the temperature of the sample during analysis
all atoms, functional groups, and bonds directly connected to the nucleus
the solvent used to dissolve the sample
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What is the common reference standard used in NMR spectroscopy?
dimethyl sulfoxide (DMSO)
chloroform (CHCl3)
tetramethylsilane (TMS)
benzene (C6H6)
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What does the chemical shift (δ) represent in NMR spectroscopy?
the intensity of the NMR signal
the difference in absorption frequency relative to the TMS peak
the width of the NMR peaks
the number of peaks in the NMR spectrum
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What do chemical shift values towards higher frequencies indicate?
(Select all that apply).
peaks corresponding to nuclei with increased shielding by surrounding electrons
peaks corresponding to nuclei with decreased shielding by surrounding electrons
peaks moving towards the right on the NMR spectrum
peaks moving towards the left on the NMR spectrum
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Nuclei situated in different chemical environments will be to varying degrees, leading them to absorb waves at slightly different frequencies and energies.
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In NMR spectroscopy, the chemical shift is expressed in units of {A}.
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Spin-spin coupling occurs between...
hydrogens on alternate carbon atoms
hydrogens on neighbouring carbon atoms
all hydrogen atoms in the molecule
hydrogens on the same carbon atom
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According to the n+1 rule, a triplet peak in a 1H NMR spectrum indicates the presence of how many neighbouring hydrogen atoms?
3
0
1
2
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In the 1H NMR spectrum of chloroethane (CH3CH2Cl), the signal from the CH3 hydrogens will appear as a with an integral area of , while the signal from the CH2 hydrogens will appear as a with an integral area of .
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Why are deuterated solvents used in 1H NMR spectroscopy?
they reduce the cost of the analysis
they enhance the signal-to-noise ratio
they produce signals outside the range observed in 1H NMR
they increase the solubility of the sample
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Which of the following statements about the chemical shift scale in 1H NMR spectroscopy is correct?
it is measured in parts per billion (ppb)
it helps identify the type of hydrogen atom present based on the peak position
it is used to determine the number of hydrogen atoms in each environment
it is not affected by the strength of the applied magnetic field
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The disappearance of an -OH peak in a 1H NMR spectrum upon the addition of D2O confirms...
the presence of a methyl group adjacent to a CH2 group
the presence of an aldehyde proton
the occurrence of proton exchange between the O-H and D2O
the presence of an alkene proton
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In a 1H NMR spectrum, the peak is proportional to the number of hydrogen atoms in that environment.
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In the 1H NMR spectrum of propanone (CH3COCH3), how many peaks are present?
3
2
4
1
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In the 1H NMR spectrum of bromopropane, CH3CH2CH2Br, how many separate peaks are present?
2
4
3
1
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