The sulfur atom in 1,4-oxathiane can undergo reaction as other substituted sulfides can.
It can be oxidised to a sulfoxide with calcium hypochlorite or sodium periodate, or continuing to a sulfone.

It can react with ammonia to form diimines.

With elemental chlorine below 0 °C, 3-chloro-1,4-oxathiane is formed.
Above 0 °C, 2,3-dichloro-1,4-oxathiane results and further chlorination yields 2,3,5,6-tetrachloro-1,4-oxathiane.

With hydrofluoric acid, 1,4-oxathiane is undergoes electrophilic fluorination to yield perfluoro-1,4-oxathiane: all eight hydrogen atoms are replaced with fluorine substituents, and also four fluorine atoms are attached to the sulfur atom.

With elemental bromine in ether, an oxathianium salt is formed.
In this an extra bromine atom bonds to the sulfur atom which gets a positive charge.
To balance this, a bromide ion forms to make up a salt.
Similarly iodine in acetic acid reacts to make 4-iodo-1,4-oxathianium iodide.
Heating 1,4-oxathiane with ethyl iodide yields 4-ethyl-1,4-oxathianium iodide.
The sulfur atom in 1,4-oxathiane can undergo reaction as other substituted sulfides can. It can be oxidised to a sulfoxide with calcium hypochlorite or sodium periodate, or continuing to a sulfone.
It can react with ammonia to form diimines.
With elemental chlorine below 0 °C, 3-chloro-1,4-oxathiane is formed. Above 0 °C, 2,3-dichloro-1,4-oxathiane results and further chlorination yields 2,3,5,6-tetrachloro-1,4-oxathiane.
With hydrofluoric acid, 1,4-oxathiane is undergoes electrophilic fluorination to yield perfluoro-1,4-oxathiane: all eight hydrogen atoms are replaced with fluorine substituents, and also four fluorine atoms are attached to the sulfur atom.
With elemental bromine in ether, an oxathianium salt is formed. In this an extra bromine atom bonds to the sulfur atom which gets a positive charge. To balance this, a bromide ion forms to make up a salt. Similarly iodine in acetic acid reacts to make 4-iodo-1,4-oxathianium iodide. Heating 1,4-oxathiane with ethyl iodide yields 4-ethyl-1,4-oxathianium iodide.
1,4-Oxathiane