OH proton NMR

[docmayer]

I was always taught in university that OH bonds do not show a signal in proton NMR, but I did AAMC 10 and the answer included that they do? Whaaaaaaaaaaaaaa!!

Ohh, and fractional distillation is used to seperate 2 compounds based on their b.p's if they are within 25 degrees of each other, and this was an answer for 2 compounds that differed by 100 degrees...stupid stupid stupid!!!! yes rant

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[salim271]

I was always taught in university that OH bonds do not show a signal in proton NMR, but I did AAMC 10 and the answer included that they do? Whaaaaaaaaaaaaaa!!

Ohh, and fractional distillation is used to seperate 2 compounds based on their b.p's if they are within 25 degrees of each other, and this was an answer for 2 compounds that differed by 100 degrees...stupid stupid stupid!!!! yes rant

OH bonds do show up on NMR. I forgot what it was for alcohols, but carboxylic acids show up at about 12 ppm. H NMR will always show a peak if there is a hydrogen, no questions about it.

As for your second question, was distillation also a choice? If it was, then i would agree with you about it being a bad question, especially since fractional takes longer and doesnt yield as much product as a normal distillation would.

 

[plzNOCarribbean]

OH bonds do show up on NMR. I forgot what it was for alcohols, but carboxylic acids show up at about 12 ppm. H NMR will always show a peak if there is a hydrogen, no questions about it.

As for your second question, was distillation also a choice? If it was, then i would agree with you about it being a bad question, especially since fractional takes longer and doesnt yield as much product as a normal distillation would.

I think the OH proton shows up at around 3.5-4 ppm. Some universities say that the OH proton does not show up, because in some instances it reacts with the solvent, so that there is a proton transfer occurring while the NMR is being taken. I know, it's stupid and I wish it were more straightforward but for the MCAT I would assume that if you see an proton anywhere on any functional group, to assume that it will show up on the spectrum

 

[justhanging]

I think the OH proton shows up at around 3.5-4 ppm. Some universities say that the OH proton does not show up, because in some instances it reacts with the solvent, so that there is a proton transfer occurring while the NMR is being taken. I know, it's stupid and I wish it were more straightforward but for the MCAT I would assume that if you see an proton anywhere on any functional group, to assume that it will show up on the spectrum

I think what your talking about is the exchanging of Hydrogen for Deuterium, which doesn't have a nuclear spin so it doesn't show up on NMR. This usually happens if the solvent is made up of Deuterium and if the analyte or solute has acidic protons.