Betaines

Ketones and Aldehydes - Rutgers University

Betaines are unusual since they have a negatively charged oxygen and a positively charged phosphorus. Phosphorus and oxygen always form strong bonds, and these groups therefore combine to generate a four membered ring - an oxaphosphetane ring. This 4 membered ring quickly collapses to generate an alkene and (very stable) triphenyl phosphine oxide.

  Ketone, Aldehydes and ketones, Aldehydes, Betaine