Question

Predict what changes, if any, would you expect in the 1H NMR spectrum if trimethylazulene in CDCl3 were treated with D2O and a small amount of D2SO4. Any changes in the 13C NMR? What changes, if any, would you expect in the 1H NMR spectrum if trimethylazulene were treated with D2O and a small amount of KOtBu? Any changes in the 13C NMR?

Answer 1

In case of trimethylazulene when treated with CDCl3 containing D2O under acidic D2SO4 conditions, all of aromatic protons will eventually get deuterated and signals due to aromatic protons will be lost and only CH3 siglet will be seen. In the 13C spectrum the carbon siggnals for the aromatic will be shifted upfield. On the other hand when trimethylazulene is treated with D2O and a small amount of base KOtBu, the CH3 protons will be deuterated and in the 13C spectrum the aromatic carbon will be intact at its position, whereas, the CH3 carbon signal will shift upfield. In the 1H spectrum the CH3 signal will now be not seen.