Count the signals in the proton NMR spectrum of each compound, counting each set of equivalent…
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Count the signals in the proton NMR spectrum of each compound, counting each set of equivalent hydrogen atoms once. Do this for 2-methylpropan-2-ol, for butan-2-ol and for methoxypropane. Then count the signals of butan-2-ol after the sample is shaken with heavy water and the OH hydrogen exchanges for deuterium.
Need a reminder? The key ideaShow
Degree of unsaturation . Each group of equivalent hydrogens gives one NMR signal. The OH signal disappears with . The molecular ion has . Zeisel: one AgI for each OCH group, .
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Three compounds.
Step 1. 2-Methylpropan-2-ol. Nine equivalent hydrogens of three methyl groups, and the OH: 2 signals.
Step 2. Butan-2-ol, . The CH next to CH, the CH, the CH, the other CH, and the OH: 5 signals.
Step 3. Methoxypropane, . The OCH, the OCH, the middle CH and the end CH: 4 signals.
Step 4. With . The OH hydrogen is replaced by deuterium and its signal disappears: signals.
Check. Total hydrogens: butan-2-ol has , as in .
Answer: 2, 5, 4 and 4.
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