CHEM 313 Lecture Notes - Conjugate Acid, Methionine, Lysine
Document Summary
Imine formation and hydrolysis come up many times in this course, so it is worthwhile looking at their reactions in some detail. A primary amine can react with an aldehyde or ketone to give an imine. The reaction usually requires removal of water, as it is reversible and the amine/carbonyl are thermodynamically favored over water/imine. There are two main steps, addition and collapse of the tetrahedral intermediate (ti). Collapse of the ti is the rate-determining step (rds) under neutral and basic conditions because hydroxide is a poor leaving group and the protonated alcohol (needed for water to leave) is in low concentration. Since amines are pretty good nucleophiles, addition if relatively fast. Under acidic conditions, the concentration of amine is low, as it is mostly ammonium, so addition is the rds. Imine hydrolysis: generally, protonated aldehydes are more electrophilic than iminiums, but imines are more basic aldehydes, so the concentration of iminiums is usually higher than the protonated alcohol.
