<P> In chemistry, a disulfide refers to a functional group with the structure R--S--S--R' . The linkage is also called an SS - bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups . The connection is a persulfide, in analogy to its congener, peroxide (R--O--O--R'), but this terminology is rarely used, except in reference to hydrodisulfides (R--S--S--H or H--S--S--H compounds). </P> <P> In inorganic chemistry disulfide usually refers to the corresponding anion S2 − 2 (S--S), for example in disulfur dichloride . </P>

The conversion of a thiol into a disulfide occurs by what type of chemical reaction