Which of the following compounds does not show tautomerism?
The correct answer is (a), and I'm curious if this is because to show tautomerism, there can't be any net charge.
For instance, ketones can tautomerize to enols, and more importantly, enamines can tautomerize to imines. In (a), we would get an imine-like thing, but the nitrogen would be positively charged. Does this still count as tautomerization?
EDIT: Thank you everyone for your helpful clarifications, but I'm still a bit confused as to why, mechanistically, we need a hydrogen on the nitrogen.
When I Google the mechanism for imine tautomerization, what if find is this:
Where the nitrogen lone pair pushes down and the double bond reaches out to pick up a proton. There isn't a transfer of hydrogen from the nitrogen to the solvent in the case shown below, yet the molecule still tautomerizes.