Pictures of the Day 3-28-08

 

Once Again, A Movie Ripping Off Chemistry

Enamines ("Mini me") Do you believe me now?
Enamines ("mini me") are molecules derived from ketones and secondary amines, generally pyrrolidine. They react as nucleophiles analogous to enolates ("Dr. Evil"). Note how there is considerable partial negatve charge (red color) on the beta-carbon atom. This is because of the minor resonance contributor that places negative charge at that position. This partial negative charge makes this carbon nucleophilic, exactly analogous to an enolate. Note that the nitrogen atom is also red, even though the minor contributing structure has a positive charge on the nitrogen. This is not a contradiction because the major resonance contributor has partial negative charge on the nitrogen (due to the lone pair of electrons on nitrogen), and this partial negative charge more than compensates for the small amount of positive charge indicated in the minor contributor. The nitrogen atom does not react as a nucleophile because that would create a less stable product (no motive) compared to reaction at carbon. Complex arguments aside, the important things to remember about enamines are 1) they are formed under mild conditions (it is just a simple Schiff base formation), 2) they react as nucleophiles analgous to enolates woth both alkyl halides and acid chlorides and 3) they are reversibly formed and can be taken off by H3O+ after the reaction. Yea baby!!!