Final answer:
The oxidation state of sulfur in a disulfide bond is +2. In a disulfide bond, sulfur loses a bond to a hydrogen and gains one to another sulfur atom.
Step-by-step explanation:
The oxidation state of sulfur in a disulfide bond is +2. In a disulfide bond, sulfur loses a bond to a hydrogen and gains one to another sulfur atom, which leads to the oxidation of thiols. This can be seen in the reaction of two thiol groups (R-SH) oxidizing to form a disulfide bond (RS-SR) with the release of water (H2O).