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Topic: Unknown mixture  (Read 12409 times)

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Offline Plumbum

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Re: Unknown mixture
« Reply #15 on: July 02, 2015, 01:59:15 PM »
I am not allowed to do mass spectrum or NMR unfortanely.

I suppose one of the substances is glycerol.
-The IR is similar
-its a colorless liqour and viscous
-it odorless
-it dissolves in water
-boiling point is very high ( does anyone know when glycerol boils at 50 bar?)

what do you think?
There might be some language misunderstandings - I'm from Germany

Offline phth

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Re: Unknown mixture
« Reply #16 on: July 02, 2015, 03:55:36 PM »
What you can conclude abbout the OH peak, it is likely that it is intermolecularly bonded because the peak is more <-- than usual.  There are 2 C-O stretches.  Saturated primary should be higher than secondary and more intesne 1054 ∆t
 = 0.00012 (760 - p) (t + 273) t in kelvin, p in bar.

Offline Plumbum

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Re: Unknown mixture
« Reply #17 on: July 02, 2015, 04:16:43 PM »
So...you think I might have a double bond?

( Sorry- my english is not so good)
There might be some language misunderstandings - I'm from Germany

Offline pgk

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Re: Unknown mixture
« Reply #18 on: July 02, 2015, 06:52:04 PM »
Double bond appears at ≈1550-1600cm-1. So, you do not have a double bond in the first IR spectrum.
According both IR spectra, your product is probably glycerol that decomposes during fast distillation to acrolein which remains as an impurity. Thermal decomposition occurs through a dehydration mechanism, followed by enol-aldheyde tautomerism.
Acrolein (bp = 53oC): carbonyl at 1704 cm-1 and double bond at 1473 cm-1 in the new IR spectrum.
Note: Under normal conditions, glycerol decomposes to acrolein at 280oC. However, decomposition may starts near 50oC in small scale, fast distillation. In practice, distillation of glycerol without any decomposition is very difficult, in the lab. Besides, vacuum boosts the dehydrative decomposition, during distillation.
.
« Last Edit: July 02, 2015, 07:07:57 PM by pgk »

Offline Plumbum

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Re: Unknown mixture
« Reply #19 on: July 03, 2015, 08:57:44 AM »
so im starting to think thst my second Substance is methanole due to the perfect fitting IR. what do you think
There might be some language misunderstandings - I'm from Germany

Offline Dan

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Re: Unknown mixture
« Reply #20 on: July 03, 2015, 09:50:54 AM »
Methanol boils at 65 °C and it smells.
My research: Google Scholar and Researchgate

Offline pgk

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Re: Unknown mixture
« Reply #21 on: July 03, 2015, 12:16:15 PM »
Try to compare the first IR spectrum with the one of glycerol. Are there any differences, in regards of peaks or peak intensities?
Hint: Comparing IR spectra in absorbance scale instead of transmittance one, is more spectacular.

Offline Plumbum

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Re: Unknown mixture
« Reply #22 on: July 04, 2015, 01:48:20 PM »
So thats my current plan :

the following functional groups could be in my mixture:

-Ketone
-aldehyde
-acetale
-carboxylic acid
-ester
-Carboxamide
-Organic acid anhydride
-Acyl chloride
-nitrile
-Hydrocarbons
-alkylchloride/bromide/iodide/halide
-Polyhalides
-alcohole
-phenole
-ether
-primary und secunday amine
-tert amine
-Nitro compound
-sulfurous compounds

I can exlude al of them expect : Acetale, Nitrie, hydrocarbons, alkylchloride/bromide/iodide/halide, polyhalide compounds,alcohol or ether  ( right??)

So I need to test for those functional groups.

Im pretty sure my first compound is glycerol but whats the second? I thought maybe another alcohol.
The following alochols can be in my mixture.

- 2-methyl 1 propanol
-methanol
-ethanol
-2-propanol
-2-methyl-2-propanol
-allyl alkohol
-1-propanol
-2-butanol
-2 methyl 2 butanol
-2 methyl 1 propanol
-3 methyl 2 butanol
-3 pentanol
-1 butanol
-2 pentanol
-trans 2 buten 1 ol (crotylalkohol)
-ethylen glycol monomethyl ether
-2-chlorethanol
-4-methyl 2 pentanol
-2 dimethylaminoethanol
-3 methyl 1 butanol
-3 methyl 2 pentanol
-2 ethoyalkohol
-1 pentanol
-cylopentanol
-2 ethyl 1 butanol
-2.2.2 trichlorethanol
-milchsäurethylester
-hexyl alcohol
-cyclohexanol
-4 hydroxy 4 methyl 2 pentanon
-furfuryl alkohol
-2-aminoethanol
-1 heptanol
-tetrahydrofurfuryl alcohl
-2-octanol
-2.3 butanediol
-1.2propanediol
-3.6 dioxa 1 heptanol
-1 octanol
-1.2 ethanediol
-3.3.5 trimethylcylohexanol
-1-phenylethanol
-benzyl alcohol
-1.3 propanediol
-1-nonaol
-phenethyl alcohol
-citronellol
-geraniol
-1-decaniol
-1.4 butanrdiol
-1.5 pentanediol
-2.2'-oxydiethanol
-1,3-glycerindiacetat
-4 methoxybenzylalkohol
-2.2' iminodiethanol
-glycerol
-3 hydroxypropionitrile
-lactic acid

pls help
There might be some language misunderstandings - I'm from Germany

Offline pgk

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Re: Unknown mixture
« Reply #23 on: July 04, 2015, 02:37:09 PM »
Please, read my replies more carefully.

Offline Plumbum

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Re: Unknown mixture
« Reply #24 on: July 04, 2015, 03:27:57 PM »
Sorry!

I only have an IR In transmittace, the IR Looks quite similar to the one from Glycerol, what do you think about my further approach ?
There might be some language misunderstandings - I'm from Germany

Offline pgk

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Re: Unknown mixture
« Reply #25 on: July 04, 2015, 03:55:03 PM »
There are not still enough data from IR, only. However, if there is no much difference in the IR spectra, think about another alcohol or a diol that does not smell. If an alcohol, it does not boils due to formation acrolein acetal during fast distillation and therfore, boiling point is not a safe criterion.

Offline Plumbum

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Re: Unknown mixture
« Reply #26 on: July 04, 2015, 05:45:28 PM »
Can I exclude  Acetals, nitriles , hydrocarbons, alkylchloride/bromide/iodide/halide, polyhalide compounds, or ether  ,though?
There might be some language misunderstandings - I'm from Germany

Offline pgk

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Re: Unknown mixture
« Reply #27 on: July 05, 2015, 03:50:58 AM »
No, because their peaks might be covered, if being in small amounts. As mentioned earlier, the IR only is not an absolute criterion for structural identification of mixtures.

Offline Plumbum

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Re: Unknown mixture
« Reply #28 on: July 05, 2015, 06:22:27 AM »
okay so I need to test for them. But I was told I can exclude the carbonyls they are very strong.
There might be some language misunderstandings - I'm from Germany

Offline pgk

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Re: Unknown mixture
« Reply #29 on: July 05, 2015, 07:20:37 AM »
Yes

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