A dithiane is a compound whose molecule has a six-membered ring containing two sulfur atoms.  Dithianes are classified into three classes.

1.  1,2-dithianes

Dithiane 1 and its derivates are called 1,2-dithianes.

2.  1,3-dithianes

Dithiane 2 and its derivates are called 1,3-dithianes.

3.  1,4-dithianes

Dithiane 3 and its derivatives are called 1,4-dithianes.

The three classes of dithianes are different from one another functionally.  A 1,2-dithiane is a disulfide.  A 1,3-dithiane is either a cyclic thioacetal or a cyclic thioketal (see acyl anion equivalent).  The molecule of a 1,4-dithiane contains two thioether groups.