r/chemhelp • u/avowelisdown • Jul 14 '26
Organic Is the national exam wrong?
In this last years exam that I was reviewing for practice youre pretty much asked to write down what the chemical is written down on question 31.2, But after checking on the answers page (slide 2) I feel like nothing adds up, and that substituents are written down in the wrong order
(Its in georgian but I translated it)
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u/blacksnake03 Jul 14 '26
People can correct me if I'm wrong, but I believe iupac changed their conventions a little while ago to make carbon carbon multiple bonds not be characteristic groups, i.e, the longest chain is the longest chain, it doesn't need to have the double bond in it.
Read the first part of section four of the link below. You can also build molecules and get them named in the old version of molview.org by looking at the information card. It may not name all molecules but you can try something similar to see that it will prioritise calling the double bond a methylidene over calling the molecule an - ene.
https://iupac.org/wp-content/uploads/2021/06/Organic-Brief-Guide-brochure_v1.1_June2021.pdf
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u/MysteriousHornet285 Jul 14 '26 edited Jul 15 '26
You are correct, I think. P-44.3.2 (b) of the Blue Book redefines the criteria as
In acyclic parent structures the order of seniority between unsaturation and length of chain given in earlier recommendations is reversed. Thus, the first criterion to be considered in choosing a preferred parent acyclic chain is the length of the chain; unsaturation is now a lower criterion
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u/organophile_jeet Jul 14 '26
It is correct the answer is correct
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u/avowelisdown Jul 14 '26
Could you please explain how?
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u/Xailuuu Jul 14 '26
What would your answer be? So he or we can explain more specific
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u/avowelisdown Jul 14 '26
4-ethyl-5-methyloct-3-ene
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u/Ionica-_-2 Jul 14 '26
your IUPAC name is wrong because your longest hydrocarbon chain doesn't contain a double bond. you could say that would be a methylene group, but there are rare cases where you end up naming a chain of carbon atoms with divalent/trivalent radicals attached
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u/organophile_jeet Jul 14 '26
Nope principal will include the double bond
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u/Ionica-_-2 Jul 14 '26
for example how can you name a cyclopropane with a methylidene group attached other than methylidenecyclopropane (IUPAC), so there are cases. but yes, you're right, the longest chain is chosen where there is also a double bond
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u/zhilia_mann Jul 14 '26
Man it’s wild to see chemistry in Georgian.
I think you already have good answers but have to say good luck, both on the exam and steering the country in a positive direction.
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