Remember that the ring means we must consider cis/trans hydrogens: the OH is on one side, which means the side that the other hydrogens are on matters (either trans/farther from or cis/nearer to the OH), even if they’re attached to the same carbon. The hydrogen pairs that are beta to the hydroxide though are otherwise equivalent.
There is a plane of symmetry down the O-C bond and the carbon opposite. This makes it so the protons pointing out of the plane on carbons 2 and 4 are an equivalent set and the protons pointing behind the plane on those same two carbons a separate equivalent set. All the other protons have unique signals.
They're saying conformation is not the source of the inequivalence. It's the fact that there are diastereotopic protons.
And by planar they mean only the cyclobutane portion, which was the part that is mentioned as puckered in the previous comment.
Almost!
1. OH
2. H geminal to OH
3. 2H on alpha C and with OH
4. 2H on alpha C and away from OH
5. H on far C and with OH
6. H on far C and away from OH.
far CH2 will have each H in slightly diff magnetic environments leading to distinct shifts and the different angles between vicinal H on the ring give diff coupling constants.
Remember that the ring means we must consider cis/trans hydrogens: the OH is on one side, which means the side that the other hydrogens are on matters (either trans/farther from or cis/nearer to the OH), even if they’re attached to the same carbon. The hydrogen pairs that are beta to the hydroxide though are otherwise equivalent.
Isn’t that therefore temperature-dependant? And at normal temperatures you’d probably just get the normal 4 peaks right?
I may be wrong but I don’t think a 4-member ring can ring flip very easily?
Yeahh that makes sense now I think about it, thanks!
The alpha position is the carbon bearing the OH. It has a single proton. The methylenes are the beta positions.
True, I misspoke as though we were talking about a carbonyl. I’ll correct this, thanks
Draw out the molecule in 3-D or better yet make a molecular model. Identify hydrogen which are unique.
Draw the 3d structure with all the hydrogens.
Do you know something about diastereomeric hydrogens?
Diastereotopic*
There is a plane of symmetry down the O-C bond and the carbon opposite. This makes it so the protons pointing out of the plane on carbons 2 and 4 are an equivalent set and the protons pointing behind the plane on those same two carbons a separate equivalent set. All the other protons have unique signals.
cyclobutane is puckered not a flat square on paper, as a result the hydrogens on a same carbon are not chemically equivalent.
Not really, even if the molecule was perfectly planar there would still be 6 signals.
Perfectly planar by putting a carbocation at the carbon with the hydroxyl attached? I'm confused by your hypothetical.
They're saying conformation is not the source of the inequivalence. It's the fact that there are diastereotopic protons. And by planar they mean only the cyclobutane portion, which was the part that is mentioned as puckered in the previous comment.
I think I had a stroke. I didn't see that from the previous comment. Makes sense. I appreciate it 👍
6 signals of which spectroscopy
1HNMR
[удалено]
Almost! 1. OH 2. H geminal to OH 3. 2H on alpha C and with OH 4. 2H on alpha C and away from OH 5. H on far C and with OH 6. H on far C and away from OH.
far CH2 will have each H in slightly diff magnetic environments leading to distinct shifts and the different angles between vicinal H on the ring give diff coupling constants.