NMR, IR, Mass Spectroscowhatsitsthingie

[An Yong]

How important is it to have the ability to interpret spectroscopy results on the mcat? I noticed its on the list of topics announced by aamc. Do I have to memorize what group lies in what wavelengths etc, or will that be given to us?

Thanks in advance!

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[MUN2005]

If you are asked, it would be very basic. Just know major IR stretches, like acids and alcohols etc. You should know how to distinguish between certain functional groups. Same thing for nmr.

 

[usmaple]

IR - you can probably get away with knowing the carbonyl stretch at 1800 and the broad -OH peak at ~3500

H NMR - know about splitting due to protons on adjacent carbons, relative areas under peaks, and some major landmarks (e.g. aldehyde protons at ~10, aromatics at ~7-8, and for the rest closer to electronegative atoms = higher relative values).

There may be some more in depth questions, but the above info will get you by in a pinch. I had an NMR question on the April test, so this stuff is definitely fair game.

 

[jdpharmd?]

Originally posted by usmaple
IR - you can probably get away with knowing the carbonyl stretch at 1800 and the broad -OH peak at ~3500

H NMR - know about splitting due to protons on adjacent carbons, relative areas under peaks, and some major landmarks (e.g. aldehyde protons at ~10, aromatics at ~7-8, and for the rest closer to electronegative atoms = higher relative values).

There may be some more in depth questions, but the above info will get you by in a pinch. I had an NMR question on the April test, so this stuff is definitely fair game.

That -OH peak is REALLY broad, so remeber that, and I think it's frequently a little lower (~3200-3300)

 

[premedi-kid]

also, if you exchange with D20 (deterium water), the OH peak disappears as all alcohols do. Thought you might like to know...

 

[Bones99]

the carbonyl stretch is not usually at 1800 cm^-1. Generally it is around 1700 wavenumbers, if it is conjugated it will be lower at about 1625-1650 cm^-1. If I remember correctly the MCAT does not go that in depth and you should only need to remember 1700 for C=O stretches.

I didn't have any MS stuff on my test, but I would make sure I knew some common fragmentation patterns (i.e. CO loss is the a difference of 28, etc)

The NMR stuff I had was very easy. Just lok at the answers and see what the compound could be.

I wouldnt;t stress too much about the NMR, MS, IR stuff. It wasnt't a large proportion of my test and from what I heard about previous exams there wasn't much on those either.

Best of luck to you on the MCAT. Study hard and I'm sure you'll do fine.

-Bones

 

[BobbyDylanFan]

I actually had about 4 questions on my april mcat about nmr, I was quite suprised to say the least! But as the above poster said, they aren't terribley difficult. Just understand the basics of it very well and you should be fine.

BDF