How do chemists make imines?
1 Answer
Easily, if the amine is alkyl and the carbonyl is an aldehyde. Not so easily in other circumstances.
Explanation:
Imine formation is a condensation reaction, and the reaction proceeds with the elimination of water:
If electron rich (alkyl) reagents are used, sometimes these reactions may be performed WITHOUT a solvent, and the water product may be removed with a Pasteur pipette. Such imines (formally aldimines) tend to be a little unstable, and should be used directly.
With ketones, the reaction tends to be a little bit more sluggish, and often the reaction is performed at reflux under Dean Stark conditions, so that the water is progresively removed:
Dean Stark conditions are a classic technique in which the reactants are heated at reflux, and the condensate is collected over a glass bridge in a trap. Because water is denser than say benzene or toluene, the typical solvents, the water produced in the reaction collects in the trap. Other methods of imine formation use dehydrating agents.
