Dissociation

Noun

1. The act of dissociating or disuniting; a state of separation; disunion.
2. The process by which a compound body breaks up into simpler constituents; said particularly of the action of heat on gaseous or volatile substances.

   "the dissociation of the sulphur molecules"

3. A defence mechanism where certain thoughts or mental processes are compartmentalised in order to avoid emotional stress to the conscious mind.