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Topic: Mystery Alcohol  (Read 1916 times)

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Offline MajoraGuy

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Mystery Alcohol
« on: July 25, 2019, 12:43:17 AM »
Hi everyone, I'm in a bit of a bind and really need some advice.

I was given a mystery compound, and told it was either a carbonyl compound or an alcohol, and was given an IR/NMR Spectroscopy Sheet with it (attached). I was immediately sure that my compound was an alcohol, but we were then told we needed to identify the exact compound. I measured a boiling point (~90 C), found that it was water insoluble, and that it was a tertiary alcohol (via the Lucas Test). However, I have exhausted my options in finding a tertiary alcohol that both fits the boiling point and the NMR. My closest guess would be 2-Methyl-2-butanol, but I don't think that's correct. Does anyone know the exact compound? If not, is there somewhere obvious that I went wrong?

Offline Babcock_Hall

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Re: Mystery Alcohol
« Reply #1 on: July 25, 2019, 10:04:41 AM »
Are there integrals with the 1H-NMR spectrum?  Can you explain why you think that it is not 2-methyl-2-butanol?
« Last Edit: July 25, 2019, 01:12:52 PM by Babcock_Hall »

Offline MajoraGuy

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Re: Mystery Alcohol
« Reply #2 on: July 25, 2019, 11:33:37 AM »
Thanks for your clarification question.

We were not given any integrals with the H-NMR, unfortunately. Or rather, I wasn't, some people did get them. The peaks in the .6 - 1.6 ppm region look very similar to those from 2-methyl-2-butanol, but I don't have anywhere else to go from here.

Offline Babcock_Hall

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Re: Mystery Alcohol
« Reply #3 on: July 25, 2019, 01:14:39 PM »
I might work with the splitting pattern that is expected for 2-methyl-2-butanol, and see whether or not your pattern is similar.

Offline MajoraGuy

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Re: Mystery Alcohol
« Reply #4 on: July 25, 2019, 01:33:43 PM »
It is quite similar, but lacks the distinct singlet and OH peak. The reason I was drawn to that particular compound was because the alkane splits looked very similar. For reference, here is the NMR I was using as a reference point:

http://www.hmdb.ca/spectra/nmr_one_d/3974

Offline rolnor

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Re: Mystery Alcohol
« Reply #5 on: July 25, 2019, 03:26:16 PM »
Is it not a carbonyl compound? Maybe a ketone?

Offline MajoraGuy

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Re: Mystery Alcohol
« Reply #6 on: July 25, 2019, 03:35:37 PM »
There is no carbonyl peak on the attached IR, only alkane stretches and a strong OH stretch

Offline rolnor

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Re: Mystery Alcohol
« Reply #7 on: July 25, 2019, 04:04:54 PM »
Sorry, missed that!

Offline MajoraGuy

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Re: Mystery Alcohol
« Reply #8 on: July 25, 2019, 04:35:11 PM »
No worries

Offline rolnor

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Re: Mystery Alcohol
« Reply #9 on: July 25, 2019, 05:48:44 PM »
Can the peak at 2,5 be the OH-proton? These are generally a broad peak and lower downfield but if its a alcohol it must be this peak, or is the OH invisible?

Offline rolnor

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Re: Mystery Alcohol
« Reply #10 on: July 25, 2019, 06:38:48 PM »
Sorry again, I focused in a tertiary alcohol and thats where it went wrong. I see now what it is.

Offline hollytara

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Re: Mystery Alcohol
« Reply #11 on: July 25, 2019, 07:30:24 PM »
That sharp peak at 3600 is unusual.  Usually a hydroxyl WITHOUT hydrogen bonding.  But you also have the broad peak that has hydrogen bonding. 

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