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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Plumbum on July 06, 2015, 11:42:44 AM

Title: Unknown mixture 2
Post by: Plumbum on July 06, 2015, 11:42:44 AM

hi

So I solved the old one and got a new one. Thanks so much to everyone who helped me. I now have my final analysis. Three substances are in it. I already know one for sure : citronellol.

I can't quite tell what functional groups I might have.

It looks like I might have an aromate, Not quite sure about a carbonyle peak is it one ?


I didn't Do any tests yet, the solution is neutral. The solution doesn't dissolve in water but it does in diethylether.
What functional groups might I have?

Thx

Title: Re: Unknown mixture 2
Post by: Arkcon on July 06, 2015, 12:49:44 PM

The IR might be the first thing to do, unless you want to fractionally distill, under vac, and isolate your 3 first.  I wouldn't do wet chem for functional groups first, is what I'm saying.

Title: Re: Unknown mixture 2
Post by: Plumbum on July 06, 2015, 01:39:41 PM

I totally forgot to upload my IR ! Here it goes :)

Title: Re: Unknown mixture 2
Post by: Plumbum on July 07, 2015, 12:08:01 PM

Can anyone help me? I'm pretty clueless.

I know one substance for sure which is an aldehyde. I have no halides because there was no precipitates with agno3. I have an aromate though. Maybe alcohol ? Because the test with Ceric ammonium nitrate seems to be positive. Some kind of gas appeared when I was heating it. Something might have react.

I tried to vacuum destilatte it. The ir doesn't looks very differently any ideas what I might have or what I should do next ?

THANK U

Title: Re: Unknown mixture 2
Post by: Plumbum on July 07, 2015, 12:17:30 PM

Those are the irs of my two fractions when I destilated.

Title: Re: Unknown mixture 2
Post by: Plumbum on July 07, 2015, 03:35:42 PM

No Advise ?

Title: Re: Unknown mixture 2
Post by: phth on July 07, 2015, 06:31:42 PM

#2 thing I thought was that it could be an aldehyde with an overtone frequency around (2870 is not, its below 2830cm-1).   The 1512 is phenyl group, 1671 could be benzaldehyde(C=O), but it has to have a strong hydrogen bonding conjugating effect for example 2-hydroxybenzaldehyde(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fwww.chemicalbook.com%2FSpectrum%2F90-02-8_IR2.gif&hash=1aebbe6ab4ca70e34a0d645a3ba449a62c270764)<--C=O @ 1665.  We should see line broadening of the aldehyde CO and there are no OH peak.  I see conflicting results with your OH test.

Title: Re: Unknown mixture 2
Post by: Plumbum on July 08, 2015, 01:47:21 AM

yeah i thought so top i cant have an oh group.

i do have an aldehyde and thst one is citrale i aoready know that. i also have an aromate..

what do you think are nitriles or acetale possibl

Title: Re: Unknown mixture 2
Post by: Plumbum on July 08, 2015, 08:26:59 AM

@phth why do you think benzaldehyde though. the carbonyl peak could be from my citrale

Title: Re: Unknown mixture 2
Post by: phth on July 08, 2015, 03:10:47 PM

i dont understand whats pure and whats not.  conjugated aldehyde is possible, i was saying somthing similar to the picture i posted

Title: Re: Unknown mixture 2
Post by: Plumbum on July 08, 2015, 03:52:49 PM

oh okay. I do have citrale, thats the aldehyde...

I am not sure about the other substances though =(

Title: Re: Unknown mixture 2
Post by: Plumbum on July 08, 2015, 04:10:44 PM

due to th boiling point ( I had one at 134 and one at 178) and the index of refraction i thought i might have
Ethylbenzene and/or p-cymene

Title: Re: Unknown mixture 2
Post by: phth on July 09, 2015, 02:56:39 PM

para makes sense

Title: Re: Unknown mixture 2
Post by: Plumbum on July 10, 2015, 01:45:12 AM

I'm still pretty clueless. So I distilated and that's my first fraction. I distilated with vacuum/ 1,5 mbar

I don't think the fractions are absolutely pure but at least they are different.

So here is what I see:


3019-2870: ch stretch in Alkanen
1514: n-o stretch from nitro compounds  ?
1020: c-n stretch from amine  (my test with ninhydrin though was negative)
720: ch stretch from alkanes
541: c-Br (there was no precipitate with agno3 though)
Und 813: c-cl

All contradictory :((

Title: Re: Unknown mixture 2
Post by: Plumbum on July 10, 2015, 01:49:25 AM

Here is the second fraction about 100 Grad/ 1.5 mbar.

What I see :

3421: Alcohol oder Amin, solution wasn't basic that's why I think alcohol
2966/2913: ch in Alkane
2174:alkine
1670: carbonyl
1449/1432: ch in Alkane
1195/1150/1121: CN bei aliphatic amine, solution not basic though.

I also have the refraction index  : 1,501

Please help me out i am so desperate


---------

To sum all up I have :
Solution does dissolve in water not in ether though
I have an aromate
Not basic,ph 4
Compounds are lighter than water

Title: Re: Unknown mixture 2
Post by: Plumbum on July 10, 2015, 01:55:40 AM

Sorry double post

Title: Re: Unknown mixture 2
Post by: phth on July 10, 2015, 03:25:08 AM

nitro has two, not one, stretches asymmetric and symmetric stretching: 2 N-O bonds vibrating in phase or not.

Title: Re: Unknown mixture 2
Post by: Plumbum on July 10, 2015, 04:49:13 AM

Okay then I do not have a nitro compound.

Do you agree with me that in my first ir I have an alcohol with a carbonyle

And my second ir I have an aromate bound to an alkane?

Title: Re: Unknown mixture 2
Post by: Plumbum on July 10, 2015, 08:44:39 AM

I found my 2. substance !! Now i only need to finde the substance with the peak in 3440