Hypothiocyanite is the anion [OSCN] and the conjugate base of hypothiocyanous acid (HOSCN). It is an organic compound part of the thiocyanates as it contains the functional group SCN. It is formed when an oxygen is singly bonded to the thiocyanate group. Hypothiocyanous acid is a fairly weak acid; its acid dissociation constant (pK) is 5.3.
Hypothiocyanite is formed by peroxidase catalysis of hydrogen peroxide and thiocyanate:
: HO + SCN → OSCN + HO