Every IUPAC Systematic name I have come across, I have understood up until now. This is Carminic Acid ($\ce{C22H20O13}$):
(source: chemspider.com)
This is the IUPAC Systematic Name for Carminic Acid:
(1S)-1,5-Anhydro-1-(7-carboxy-1,3,4,6-tetrahydroxy-8-methyl-9,10-dioxo-9,10-dihydro-2-anthracenyl)-D-glucitol
I have 3 main questions:
- I do not understand the numbering system inside the brackets. The numbering system implies that the numbers assigned to the carbon atoms is the following:
I would have thought the numbers assigned to the carbon atoms would be the following:
Why is the numbering system the way it is? (Why does the numbering system not go around the molecule, in a normal cycle, counting off each carbon?, Why is the number 10 carbon opposite the number 9 carbon?, Why are 4 carbons [circled in the picture below] left out in the numbering system?)
- I also do not understand why Carbons 9 and 10 in the anthracene group are referred to as '9,10-dioxo-9,10-dihydro'. Surely, they only need to be referred to as '9,10-dioxo'? And what is a '-hydro' group?
- Doesn't '1,5-Anhydro...-D-Glucitol' imply the following: Hexan-2,3,4,6-tetrahydroxy-1-yl, a chain, and NOT a ring structure of: Oxan-3,4,5-trihydroxy-6-hydroxymethyl-2-yl, considering D-Glucitol (shown below). Also, as well as '1,5-Anhydro...-D-Glucitol' not accounting for the ring structure of that section of the molecule, it also doesn't account for the Oxygen.