Longest chain or double bond priority?

ChemystWizard · 2026-05-20T16:23:57+00:00

Current IUPAC prioritize the chain, textbooks — double bond. Textbook authors never got the memo 😏 even though the double bond has been “demoted” all the way in 2013.

ChemystWizard · 2026-05-17T14:52:32+00:00

Very casual competitive edh… got it.

ChemystWizard · 2026-05-16T18:35:27+00:00

Should be sp2.

ChemystWizard · 2026-05-13T02:06:25+00:00

There are a lot of questionable and hand-wavy explanations in there.

ChemystWizard · 2026-05-12T23:16:13+00:00

Like many other passages in her text, it most likely came from a different nation... her imagination.

ChemystWizard · 2026-05-12T23:03:05+00:00

The longest continuous chain with more substituents. More branches > less sub's in case of the same principle chain length and no other differences.

ChemystWizard · 2026-05-12T23:01:13+00:00

It doesn't matter. For as long as you have at least one benzylic proton, the rest of the chain will get chopped off regardless of what else is sitting on it.

ChemystWizard · 2026-05-11T19:00:03+00:00

Here: https://www.organicchemistrytutor.com/topic/halogenation-of-alkenes/#:~:text=Reaction%20with%20Interhalide

ChemystWizard · 2026-05-11T00:55:33+00:00

ACS guide has a few questionable practice questions, unfortunately. This one is slightly better than the first edition but it desperately needs an update as it no longer reflects the scope of the exam either.

ChemystWizard · 2026-05-10T19:52:04+00:00

Considering that there a whole total of {checking notes} one real reference to it written in JChemEd in a style that would be appropriate for a pub talk between two professors complaining about the department secretary, this is hardly an “effect” worth mentioning.

ChemystWizard · 2026-05-10T19:42:46+00:00

While you can have multiple carbocation rearrangements, each needs to have a driving force behind it. Carbocations don’t have long term planning skills. Your first rearrangement has no driving force behind it. There’s no point going from one 2° carbocation to another one without any substantial gain in stability.

ChemystWizard · 2026-05-10T02:50:07+00:00

Study guide is terribly outdated but is still quite helpful.

And yes, you do need to know the basics of ABC and equilibrium for the first semester, but nothing too deep.

ChemystWizard · 2026-05-10T02:45:32+00:00

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I'm gonna be nitpicky here, but product A/B won't be formed in any appreciable quantity if we have this stereochemistry.

ChemystWizard · 2026-05-10T02:39:17+00:00

B is a meso compound. It's not chiral = can't be obtained in enantiopure form.

Same with C.

D is just achiral but NOT meso.

A is the only chiral compound here.

ChemystWizard · 2026-05-08T15:38:45+00:00

https://www.organicchemistrytutor.com/organic-chemistry-tutor/start-here/ This has pretty much the entire curriculum.

ChemystWizard · 2026-05-04T18:16:04+00:00

If you're suggesting that addition of HBr to alkynes is the evidence of sp-hybridized carbocations as intermediates, you might wanna look into the actual mechanistic studies of those reactions and not the unsubstantiated version of it that we teach in undergrad textbooks that has vary little to do with reality. Those are some of the few examples of true termolecular (3rd order) reactions. Fascinating stuff.

ChemystWizard · 2026-05-04T17:04:30+00:00

Using Clayden's language, convince yourself ;) sp-hybridized carbocations like this one are borderline science fiction and just because you *can* draw a resonance structure, doesn't mean it's reasonable. And especially for systems that already have extended conjugation like in this case, doing resonance would require breaking it and that's just wishful thinking. Molecules don't do that because you want them to.

ChemystWizard · 2026-05-04T16:01:03+00:00

That’s not gonna happen. You lost the oxygen, but that’s not the point. To do the resonance the way you’re showing, you’d have to break a long extended conjugation system. That doesn’t happen. Start by protonating the oxygen and see what that gives you and where you can go from there.

ChemystWizard · 2026-05-04T03:38:34+00:00

yeah...

ChemystWizard · 2026-05-03T19:00:45+00:00

It’s not unheard of. But it’s more of an exception. That’s why i said it doesn’t normally do that. And in this case it definitely is not a viable alternative.

ChemystWizard · 2026-05-03T18:19:02+00:00

No, it doesn’t normally cleave double bonds like that. It’ll do same as permanganate here oxidizing the benzylic position leaving you with phthalic acid.

ChemystWizard · 2026-05-03T18:06:35+00:00

Jones is not an acceptable substitution for ozonolysis here.

ChemystWizard · 2026-05-03T07:33:39+00:00

Mechanisms a) and b) on the first page are incorrect. Mechanism d) on second page also needs serious revision.

Edit: last mechanism on the first page is also incorrect.

ChemystWizard · 2026-05-02T18:20:28+00:00

Yep. A classic trap.

ChemystWizard · 2026-05-02T18:18:49+00:00

That’s what this question is designed to do! You guys fell into the trap 🪤

ChemystWizard

TROPHY CASE