# Stability of pyridine derivatives

Arrange the following pyridine derivatives in the order of increasing stability of adduct formed with $$\ce{BBr3}.$$ Explain briefly.

I'm pretty confused about which structure is the most stable. I'd say structure III is the most stable as it has two methyl groups to donate electrons to nitrogen and increase its Lewis basicity.

However, I think III may not be the most stable because of steric hindrance. In fact, structure II could be the most stable as the methyl group is closer to nitrogen and there's no steric hindrance. Therefore, the answer should be III < I < II.

Is my reasoning correct? Are there any factors to consider for stability?