Some questions about naming conventions for ethers

[espen180]

First, I am wondering about naming conventions for cyclic ethers.

I have found
C_2O : Ethylene oxide
C_4O : 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.

[pzona]

Names like THF are like calling H2O water instead of hydrogen hydroxide (pretty much). These aren't IUPAC names, so you're right, they're trivial. I'm not great with cyclical naming, so I'll leave the second part to someone who's a little more experienced in organic chemistry.