[msk034]

Consider amine addition to the carbon of carbonyl bond with subsequent water detachment to form imine. What is the mechanism of water detachment - monomolecular, with hydrogen intramoleular migration, or base-mediated? I can guess it may be both. Are there any examples when the reaction like intramolecular proton shift betwteen an acid and a base sites occurs through unmediated proton migration at a distance of 2-3 (or more) Angstrems ?

[orgopete]

I wrote the mechanism as stepwise. I don't think the pH gradient is too large to form an aminal and have it extrude hydroxide.

I have searched for bona fide examples of proton transfers with four atoms. If anyone has one, I am interested.

Six, beta-ketoacids or acetate pyrolysis.
Five, sulfoxide, selenoxide, or amine oxide eliminations.

As I had thought about it was whether the attacking and leaving electrons could both bond to a proton. That is, how acute of an angle can one still have a hydrogen bond?