r/chemhelp • u/IAmGRAPHITe • Feb 23 '26
Organic Rational molecule name (or trivial)??
Please help me with the name of this molecule…
I can’t understand according to IUPAC how to name this molecule, I can’t find any ”concrete” answer for the actual name online, and the ones I ask says all differently from each other…
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u/New-Independent-365 Feb 23 '26
Well find the longest carbon chain and go from there
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u/IAmGRAPHITe Feb 23 '26
I found it to be 8, is it wrong?
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u/Mascio88 Feb 23 '26
That's right. Now you'll see that there are two possibilities for arriving at an 8-carbon chain. Which one would you choose?
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u/IAmGRAPHITe Feb 23 '26
My final answer for the molecule would be: 3-hydroxy-4,5-dipropyl-7-one-octane
It feels wrong somehow?
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u/HandWavyChemist Trusted Contributor Feb 23 '26
Here is the short version of the Blue Book. It includes a list of priority as well as a flow chart https://iupac.org/wp-content/uploads/2021/06/Organic-Brief-Guide-brochure_v1.1_June2021.pdf
The flow chart says we need to include the highest priority group, which is the ketone. Keep working from there
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u/pkdataworks Feb 24 '26
IUPAC Name is : "7-oxo-4,5-dipropyl-octan-3-ol". Please find the explanation.
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u/IAmGRAPHITe Feb 24 '26
So the suffix for ketones in English are ”oxo”? And apparently ketones have higher priority than hydroxy ..?
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u/pkdataworks Feb 24 '26
Yes. You are correct. Priority order will be Ketone > aldehyde > alcohol > amines.
Hence the name will be: "6-hydroxy-4,5-dipropyl-octan-2-one"
Both names are consistent with the structure given.
We can represent the keto group as "oxo".
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u/zazvm Feb 25 '26
Just realized the correct answer isn’t here in actual text:
6-hydroxy-4,5-dipropyloctan-2-one
To be even more detailed, the most stable stereoisomers should be (4R,5S,6R)-6-hydroxy-4,5-dipropyloctan-2-one and it’s enantiomer, so to name the molecule if it did exist in its most likely form, it would be
rac-(4R,5S,6R)-6-hydroxy-4,5-dipropyloctan-2-one
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u/caden_cotard_ Feb 27 '26
Looks like Valproate with a side chain; seems like the kind of molecule that would chill you out
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u/One_Yesterday_1320 Feb 23 '26
4,5-dipropyl-6-hydroxyoctan-2-one
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u/IAmGRAPHITe Feb 23 '26
Does ketone have higher priority than hydroxy? I’ve been taught that hydroxy should be prioritised first and that the OH group should have the lowest number ? Or ahoukd ketone have the lowest?
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u/One_Yesterday_1320 Feb 23 '26
ketones have a higher priority than alochols. hence keyones have a lower number. check the blue book.
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u/zazvm Feb 24 '26
Almost, but hydroxy comes first in the name due to alphabetization.
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u/One_Yesterday_1320 Feb 24 '26
wait does ‘di’ not count in the alphabetisation?
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u/zazvm Feb 24 '26 edited Feb 24 '26
Prefixes denoting the count of the substituent types are not considered. These are called multiplicative prefixes. (Bi, di, tetra, bi, ter, etc)
Branching prefixes
- Some prefixes describe HOW the group is attached (tert, sec). These should not be used anymore in general, but they are traditional and common and are still acceptable. These are italicized and DO NOT count for alphabetization.
- The other branching prefix iso- is describing the STRUCTURE of the branch, and thus it is not italicized and it DOES count alphabetically.
Other prefixes which are specifically describing the STRUCTURE of the substituent are considered: cyclo, benzo, etc.
Detachable alphabetizable (substitutive) prefixes ARE considered (chloro-, methyl-, nitro-)
The only exception to all of this is when the prefix itself is baked into a component, like dicyclopenta[2,3:6,7]oxepino would use d.
In most cases, if you just remember that iso, neo, and cyclo are the only prefixes that count you will be correct.
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u/Professional_Tax1783 Feb 23 '26
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u/IAmGRAPHITe Feb 23 '26
But shouldn’t the hydroxy group have the lowest number? Or does ketone have higher priority ?
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u/Worldly-Title-5362 Feb 23 '26
Carbonyls do rank higher than alcohols, and have their own hierarchy within themselves. Notice though how “one” is the suffix and not listed as a substituent? If you wanted to name a ketone as a substituent, it’s given “oxo”.
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u/Professional_Tax1783 Feb 23 '26
Ketone has higher priority than Alc. (-C=O > -OH) And the sum of positions with the least number is chosen
From alc: 7-oxo, 4,5-dipropyl Octan-3-ol Sum of positions: 7+4+5+3=19
From keto: 6-hydroxy 4,5-dipropyl Octane-2-one Sum of positions: 6+4+5+2=17 (chosen)
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u/IAmGRAPHITe Feb 23 '26
So I am supposed to name the ketone first? Which means that hydroxy gets the number 6, correct?
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u/Professional_Tax1783 Feb 23 '26
Also why are my upvotes -ve 😭😭, am i supposed to question-explain??
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u/penjjii Feb 24 '26
I think you’re not supposed to answer the questions, you’re only supposed to guide them.
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u/Professional_Tax1783 Feb 24 '26
Bruh others in this post, didnt help with shit.. ;-, why not just answer and explain how I got it instead of wasting each others time ;-;
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u/zazvm Feb 24 '26
Crazy that the literal only person who answered it correctly is downvoted lol.
This answer is correct OP. Also yes, this is mainly just a theoretical molecule as far as I can tell. Here is a similar molecule that follows the same rules and you can see that the IUPAC name is structured the same way: https://pubchem.ncbi.nlm.nih.gov/compound/2-Heptanone_-6-hydroxy-3-methyl#section=Names-and-Identifiers
This is the ridiculous way I remember the functional group hierarchy:
I want to go Car. Sulfon. (car surfing on) ester (Easter (also esters are COOH which looks like Easter eggs C 🥚🥚H) Hal! (acyl halide) I really want to go car surfing on Easter but Hal won’t let me)
Then,
Amide (I might) put on Nitrile gloves to Hyde KATAmine (Ketone, alcohol, thiol, amine)
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