Write the correct stability order of the following compounds:
I don't have any concern with estimating stability of (1), only (2), (3) and (4). Our teacher said that unless the carbocation has three isopropyl groups, it won't be as stable as the quasi-aromatic compound — in this case, the tropylium cation.
My friends claim the isopropylmethylium cation should be more stable than the tropylium cation.
Is there any experimental data saying which one is more stable? How many cyclopropyl rings are needed to “dominate” over a tropylium cation?
Previously, I reviewed the following questions about triisopropylmethylium carbocation: