First, I am wondering about naming conventions for cyclic ethers. I have found [tex]C_2O[/tex] : Ethylene oxide [tex]C_4O[/tex] : Tetrahydrofuran But (I think) these are trivial names. I think I found a system where for example a cycle of three O-atoms and three C-atoms in C-O-C-O... fashion becomes 1,3,5-trioxycyclohexane. Also, in compounds, we count from the O-atom closest to the bond between the compounds, like in 2,3-benzo-1,3-dioxycycloheptane? Can anyone confirm this, eventually contribute additional useful rules related to this? Thanks in advance.