Emde degradation
The Emde degradation is a method for the reduction of a quaternary ammonium cation to a tertiary amine with sodium amalgam:
Image:Emderxn.png|center|500px|Emde-degradation
This organic reaction was first described in 1909 by the German chemist Hermann Emde. It was for a long time of great importance in structure elucidation of many alkaloids, for example that of ephedrine.
Alternative reducing agents exist for this reaction; for instance, lithium aluminium hydride.