[PoetryInMotion]

Problem. I need to qualitatively compare the dipole moments of imidazole and the imidazolium cation.

My thoughts. The dipole moment is a vector. Thus, it has both direction and magnitude. Let's start with the direction. Imidazole has to two nitrogens on the same of the molecule.

Since nitrogen is more electronegative than carbon and hydrogen, this should mean that the side with the nitrogens is more (partially) negatively charged and that the dipole moment points towards the nitrogen-end of the molecule.

In the imidazolium ion, the nitrogen shares one positive charge. This makes me confused. Are the nitrogens still more negatively charged than the rest of the molecule? Or does protonation make the nitrogens so positively charged that the dipole moment is reversed?

When it comes to the magnitude of the two dipole moments, I must say that I have no clue. A wild guess is that it's smaller in the case of the imidazolium ion, due to the competing effects of the electromagnetically and formal charges.

I know these thoughts are pretty messy, but I hope you understand enough to give me some guidance forward.