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Offline IUPACNamingHelp

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IUPAC Naming Help
« on: May 08, 2018, 11:18:09 PM »
I am currently trying to figure out how IUPAC nomenclature works for more complex molecules such as LSD. Currently, I have only found 2 IUPAC names for LSD: 9,10-didehydro-N,N-diethyl-6-methylergoline-8β-carboxamide, which is easy to follow but doesn't offer much with the naming of complex polycyclic/aromatic compounds because the cores structure is simplified to -ergoline; and (6aR,9R)-N,N-diethyl-7-methyl-4,6,6a,7,8,9-hexahydroindolo[4,3-fg]quinoline-9-carboxamide from the Wikipedia page which is very confusing and could use come clarification. What I take from this name is this:
- (6aR, 9R) is referring to the isomerism expressed by the hydrogens at carbons 6a and 9.
- N,N-diethyl is referring to the 2 ethyl groups on the amine (Am I using that word properly?)/nitrogen
- 7-methyl is referring to the methyl group attached to the 7th atom, which happens to be a nitrogen.
- 4,6,6a,7,8,9-hexahydro is very confusing to me. This implies that there are extra hydrogens where the normally wouldn't be on the 4,6,6a,7,8,9 atoms. What I don't understand is where these atoms are actually located. From looking at it, I can see only 4 atoms that are able to hold hydrogens, the rest are filled by double bonds with other carbons. My understanding is that -hexahydro implies that there are six extra hydrogens at each of the locants (Is that the right words to use for the numbers?) but there are only 4 atoms not taken up by carbon=carbon carbon-nitrogen bonds. Of these 4 atoms, 2 can only hold one hydrogen each but two can hold 2, so 2+(2*2) does add up to 6 but each of the locants is unique and there are no repeating ones so I feel like this part may be incorrect. Also the inclusion of 7 is even more confusing because I thought 7 refers to the nitrogen with the methyl group and this nitrogen has all 3 available bonds (without being ionized) taken up already and so there isn't a place for a hydrogen atom. Some clarification here would be nice. Maybe the IUPAC name is incorrect, it was from Wikipedia after all :P
- indolo[4,3-fg]quinoline makes some sense to me. The -indolo refers to the indole structure. The -quinoline refers to the quinoline structure. [4,3-fg] refers to the shared carbon atoms. Although I was confused as to how these numbers where given to the atoms, I think I figure it out. I think that indole structures and other common structures have separately numbered carbons from the compound they are found in, and the [4,3-fg] means that the 4 and 3 carbons of the indole structure are shared with the quinoline structure. The structures share 3 carbons but listing the 3a carbon is redundant, right? What does the -fg after the 3 mean? Additionally, how is the configuration of the quinoline found if it's shared carbons aren't listed? Shouldn't this be somewhere to make the IUPAC name unambiguous?
- 9-carboxamide refers to the carboxamide group bound to the 9 carbon.

That is all that I could understand from the IUPAC name. If someone could explain how this molecule's atoms are numbered that would also help a ton.

Lastly, here are two random molecules I've made. Could someone walk me through how each one would be named?

I learned SMILES while writing this post so I could make those. Took forever, but I'm proud to say I did it :)

Offline Borek

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Re: IUPAC Naming Help
« Reply #1 on: May 09, 2018, 02:40:53 AM »
My knowledge about naming is next to nothing, but ACD/ChemSketch (which has a freeware version) does the naming - perhaps you will be able to learn details by modifying the molecules and seeing how the modifications relate to the generated name.
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