A dithiane is a heterocyclic compound composed of a cyclohexane core structure wherein two methylene bridges (-- units) are replaced by sulfur. The three isomeric parent heterocycles are 1,2-dithiane, 1,3-dithiane and 1,4-dithiane. They are all colorless solids.

1,2-Dithianes

1,2-Dithiane is an organosulfur compound with the formula S2C4H8. It is one of three isomers of the formula (CH2)4S2. The 1,2-isomer, a disulfide, arises by the oxidation of 1,4-butanedithiol.

1,3-Dithianes

1,3-Dithiane is an organosulfur compound with the formula CH2S2C3H6. It is one of three isomers of the formula (CH2)4S2. The 1,3-isomer arises by the reaction of 1,3-propanedithiol with formaldehyde. 1,3-Dithianes are sometimes used as protecting group of carbonyl-containing compounds. They form by treatment of the carbonyl compound with 1,3-propanedithiol under conditions that remove water from the system. The protecting group can be removed with mercuric reagents, a process that exploits the high affinity of Hg(II) for thiolates. 1,3-Dithianes are more importantly employed in umpolung reactions, such as the Corey–Seebach reaction:

1,4-Dithianes

1,4-Dithiane is an organosulfur compound with the formula (SC2H4)2. It is one of three isomers of the formula (CH2)4S2. The 1,4-isomer, a bisthioether, arises by the alkylation of 1,2-ethanedithiol with 1,2-dibromoethane. It has no applications but traces occur as a product of degradations, e.g., cooking coal pyrolysis.