2,2,6,6-Tetramethylpiperidine - Brønsted Basicity I understand that this molecule can only act as a Brønsted base because it is sterically hindered by its multiple methyl groups. 



However, isn't the proton bound up in solution? Doesn't that increase the effective size of the proton? How then exactly is a proton expected to reach the site of basicity if it's tied up with multiple water molecules? Or is the size of the hydrated proton still quite small? Or does the proton separate from the water molecules once the proton is sufficiently close to the site of basicity (the lone pair on the nitrogen)?
I don't see much hinderance[note that they all have been optimised to stable configurations]
Blue: nitrogen,White: Hydrogen,Grey: Carbon

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