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Topic: Unknown Alcohol  (Read 19058 times)

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Offline chrisbb

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Unknown Alcohol
« on: April 03, 2008, 06:30:39 PM »
OK, just done an experiment today.
The alochol has a smell like Almonds, or nuts.

Any ideas/hints what this may be.
I'll post again when i've cleared up my final results, like BP, Desnity etc :)

Offline Arkcon

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Re: Unknown Alcohol
« Reply #1 on: April 03, 2008, 07:52:40 PM »
IIRC, lots of things I made in organic chem class smelled like that, also with kinda acrid smell accompanying.  You will need the other physical data to really know what you have.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline agrobert

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Re: Unknown Alcohol
« Reply #2 on: April 03, 2008, 09:36:27 PM »
Many nitriles and benzaldehyde are known for this smell but as Arkcon said smell alone is not enough.
In the realm of scientific observation, luck is only granted to those who are prepared. -Louis Pasteur

Offline chrisbb

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Re: Unknown Alcohol
« Reply #3 on: April 11, 2008, 05:31:32 PM »
OK, so here is the updated info:

Alcohol:
Observations = smells like nuts (maybe almonds), clear, kind of viscous
BP = 121.7oC
Refractive Index = 1.4022
Density = 0.71g/ml
I also did a Jones reagent test, and it reacted immdeiately (turning from orange to green in seconds) this indicates either a 1 or 2o alcohol.

I was asked to run the OH through an esterfication set-up, and it yielded:
Ester:
Observations = smells like nuts (maybe almonds), yellow/clear, kind of viscous
BP = 110.5oC
Refractive Index = 1.3955
Density = 0.67g/ml



Right, here is a list of esters that are possible. I'll only lsit the more "relavant ones";
* Fragrance, Ester name, BP760mm, Refractive Index, Density*

- Pear, n-propyl acetate, 102, 1.3842, 0.8878
- Solvent, s-butyl acetate, 112, 1.3877, 0.8758
- Fruity, isobutyl acetate, 117, 1.3902, 0.8712
- Pineappple, Ethyl Butyrate, 122, 1.4000, 0.8785

Before corrections on the BP and RI, this is my guess for the ester, but the IR is kinda hard to pick out the peaks. I have to know the alcohol, working backwards is the "key" i was told.
The peak cirlced on the OH scan is supposed to be a big hint whether it is a 1/2/3o OH, so any ideas, and I will take many :)
« Last Edit: April 13, 2008, 07:36:18 PM by chrisbb »

Offline chrisbb

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Re: Unknown Alcohol
« Reply #4 on: April 13, 2008, 03:50:08 PM »
Anyone have any other ideas for the IR scans?

Offline english

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Re: Unknown Alcohol
« Reply #5 on: April 13, 2008, 03:55:52 PM »
You can't do any NMR spectra on it? 

 ;)

Offline agrobert

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Re: Unknown Alcohol
« Reply #6 on: April 13, 2008, 04:14:26 PM »
You should know which ester in general you made because you should have recorded the acid that you esterified.  Did you esterify acetic acid?

Also your IR for your "ester" is almost useless because your alcohol and or acid is still present and is overlaying whatever ester you made.  Sure there are some C=O peaks but this is really unclear.

As for telling if the alcohol is 1º or 2º this is usually difficult and interpreted more clearly with H NMR.
In the realm of scientific observation, luck is only granted to those who are prepared. -Louis Pasteur

Offline nj_bartel

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Re: Unknown Alcohol
« Reply #7 on: April 13, 2008, 05:58:11 PM »
Just fyi, cyanide gas has a smell of almonds, so if there's the slightest chance that's what you're producing, you might want to be careful.

Offline chrisbb

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Re: Unknown Alcohol
« Reply #8 on: April 13, 2008, 06:08:10 PM »
hi all.
thanks so far :)

I dont have access to NMR :( No, I didn't esterfy acetic acid. I had to esterfy the unknown alochol.
Any idea what the cirlced peak on the RHS of the OH IR scan is?

I'm going to run another recov. ester scan in a few days.... so we'll what we've got then.
Thanks,

Chris :)

Offline agrobert

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Re: Unknown Alcohol
« Reply #9 on: April 13, 2008, 06:42:37 PM »
What acid did you esterify?
In the realm of scientific observation, luck is only granted to those who are prepared. -Louis Pasteur

Offline chrisbb

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Re: Unknown Alcohol
« Reply #10 on: April 13, 2008, 07:25:03 PM »
Please forgive me being like a snail (was the first time for esterfication)

I added 11ml acetic anhydride, 3 drops of conc. H2SO4.
Then 10ml of the unknown alcohol :)

Offline agrobert

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Re: Unknown Alcohol
« Reply #11 on: April 13, 2008, 07:33:40 PM »
Ok so you acylated your unknown alcohol.  Then your ester derivative must be one of the acetic derivatives(acetate).  This cancels Ethyl Butyrate.  When you post your new IR maybe I can be of more help.  Don't too much, in general the purpose of identification labs is to get you to think and problem solve (which you are clearly doing).  As you get better at this you will appreciate the hard work you put in for this experiment.  A clear C=O peak in your new IR should help you so make sure your sample is clean (no alcohol or water).
In the realm of scientific observation, luck is only granted to those who are prepared. -Louis Pasteur

Offline chrisbb

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Re: Unknown Alcohol
« Reply #12 on: April 13, 2008, 07:37:31 PM »
OK, well that is one off the list :)
Thanks!

I'll post again soon when I've got the new IR :D

Offline chrisbb

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Re: Unknown Alcohol
« Reply #13 on: April 17, 2008, 07:39:33 AM »
OK!
I searched the web for IR's of 4 clostest possible esters, and then worked backwards to gain the alochol. I have determined that it could possibly be THIS!

n-propyl alochol!
LMK what you all think about the choice.

But there is one thing, the BP and RI do not match 100%, and suggestions to why that could be?!  :-\
Thanks again,

Chris

Offline AWK

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Re: Unknown Alcohol
« Reply #14 on: April 17, 2008, 07:52:50 AM »
Nor smell nor IR nor esterification is devoted for identification of alcohols. Of course, sometimes you can guess the alcohol on this basis. Much more helpful is NMR or MS
AWK

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