Wikipedia
Hemithioacetal
Hemithioacetal is an organic functional group with the general formula RCH(OH)SR. They are also called thiohemiacetal. With four substituents on carbon, hemithioacetals are chiral. A related functional group are dithiohemiacetal, with the formula RCH(SH)SR. Although they can be important intermediates, hemithioacetals are usually not isolated since they exist in equilibrium with the thiol and aldehyde: