This paper describes a new chloroperoxidase oxidative activity, namely, propargylic oxidations. Under appropriate conditions, chloroperoxidase catalyzes the oxidation of a variety of 2-alkynes to aldehydes via alcohol intermediates. Both hydrogen peroxide and t-butyl hydroperoxide can serve as terminal oxidants. The triple bond in the substrate is usually untouched. A free radical mechanism is proposed for the initial hydroxylation step in the overall reaction. (C) 1998 Academic Press.