How count the carbons in 2,3,7,8-Tetrachlorodibenzo-p-dioxin?

[arabianights]

hi guys,

I did some reading into dioxin in light of recent incident in Ohio.
I'm not sure how to count the carbon in this compound, if i start counting from top left or top right, I comes with carbon 2, 3, 8, 9 that bounds with Chlorine atom.

https://www.epa.gov/dioxin/learn-about-dioxin

 

[mjc123]

Interesting; I would have called it 2,3,6,7 by analogy with anthracene, but apparently the O atoms are numbered 5 and 10 (not 9 and 10). See https://en.wikipedia.org/wiki/Dioxins_and_dioxin-like_compounds