IR, NMR, and mass spectrometry interpretation concepts for determining organic molecule structure, tested on the MCAT.
40 cards · basic cards · AI-written, checked twice. Edit anything.
- What molecular motions does IR spectroscopy detect?
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Bond stretching and bending vibrations- What is the characteristic IR range for an O-H stretch in alcohols?
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3200-3550 cm-1, broad- How does an amine N-H stretch differ in appearance from an alcohol O-H stretch in IR?
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N-H is sharper and less broad than O-H- What is the typical IR range for a carbonyl (C=O) stretch?
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1650-1750 cm-1, strong- What is the typical IR range for sp3 C-H stretches in alkanes?
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2850-2960 cm-1- What is the characteristic IR range for a terminal alkyne C-H stretch?
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About 3300 cm-1, sharp- What is the typical IR range for a C=C stretch in alkenes?
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1620-1680 cm-1, weak to medium- What is the typical IR range for a C triple bond C stretch in alkynes?
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2100-2260 cm-1, weak- What is the typical IR range for a nitrile C triple bond N stretch?
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2200-2260 cm-1- Why does a carboxylic acid O-H stretch look different from an alcohol O-H stretch in IR?
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It is much broader, spanning roughly 2500-3300 cm-1, due to strong hydrogen bonding- How does an ester C=O stretch frequency compare to a ketone C=O stretch?
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Ester C=O appears at higher wavenumber, about 1735-1750 cm-1, than a ketone- Why does an amide C=O stretch appear at lower wavenumber than a ketone?
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Resonance delocalization of the nitrogen lone pair lowers the C=O bond order- What is the fingerprint region of an IR spectrum?
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The 1500-400 cm-1 region, unique to each molecule- What two peaks near 2720 and 2820 cm-1 are diagnostic for an aldehyde in IR?
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A pair of weak C-H stretch bands from the aldehyde proton- What molecular property must change during a vibration for it to produce an IR absorption?
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The dipole moment of the bond
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