kaoutar
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Need help for the interpretation of an IR spectra
Hello,
I'll need your help for the interpretation of an IR spectra. It's my first time using such analysis. The sample studied is a copper paste removed from
copper drawing machine. I'll be greatful if u could tell me wich molecule as represented by these spectra attached as PDF document, and what's the
difference between the four spectra.
Attachment: IR spectra.pdf (265kB)
This file has been downloaded 640 times
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gdflp
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This very much seems like a homework problem, in which case you will not get a direct answer. Questions such as these belong in
Beginnings.
Show us what(if any) effort you have put into solving this problem. Look up IR correlation tables online, such as this one, this will help you to identify the different functional groups in those spectra. Finally, infrared spectroscopy is not a quantitative
analytical technique unlike others such as mass spectroscopy or nuclear magnetic resonance spectroscopy which allow you to determine the mass of the
molecule and it's fragments, and the number of protons(H1) respectively. Thus it is very difficult, if not impossible, to determine the
structure of a molecule with only an IR spectrum. IR spectroscopy is best for determining the presence of various functional groups and patterns and,
to a lesser extent, the purity of a compound with respect to known contaminants.
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fluorescence
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I wasn't good at IR-Interpretation but there are some things you can look for if it's your first time.
The area from 600 to about 1500 is not really usefull. It's characteristic but you can't read much out of it. Some say you can see Aromatic systems in
there but that is more or less the case if nothing else is present. So don't focus too much on that area. Important is that huge peak at 3372. That
can possibly only 2 functional groups where one seems more logic due to the intesity and size.
I tend to look at around 1600-1800 usually for Keto Groups or other funtional groups.
But as gdflp said, you can find pretty much in charts. And there are some really good ones.
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aga
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Huh ?
So with IR there's nothing useful in the 600-1500 range ?
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gdflp
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I disagree. There is quite a lot of useful information that region such as C-O single bonds from alcohols, phenols, carboxylic acids, etc.; C-X bonds
in alkyl and aryl halides, nitroaromatics, and substitution patterns of aromatics.
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kaoutar
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Thank you very much for your interest to this post. I already tried to use the tables but it didn't help much. All i need to know is the nature of the
organic molecule. During this project I made the hypothesis that the copper paste may contain a calcium soap, and I made those analysis to find out if
it's true or not. A previous analysis using the spectrophotometre sowed the presence of ions of calcium, chlore.
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Metacelsus
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Here's my reading of the spectrum, with no preconceptions of what the compound is:
Large, broad peak at 3372: O-H stretch
Peaks at 2922 and 2852: C-H (sp3) stretch
Peak at 1740: C=O stretch, possibly an (unconjugated) ester
Peak at 1641: C=C stretch
Peak at 1457: C-H bend
Peak at 1168: C-O ester stretch?
Broad peak at 719: C-H (sp3) rock? (unclear)
My guess would be that it's some sort of fatty acid/ester, mostly saturated but with a few double bonds here and there. There's also a fair bit of
water in there.
Can you help narrow down the list of possible compounds? Is this just some unknown residue you found in your machine? How did you prepare the sample
for spectroscopy?
[Edited on 19-8-2015 by Cheddite Cheese]
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kaoutar
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Thank you very much for your help. The paste has been removed from the dies and cabestans of drawing machines that uses an emulsion of 92-94% water
and 6-8% drawing oil containing:
- A base oil : mineral ( naphthene , paraffin , Aromatic ) and synthetic ( polyalphaolefin )
- Lubricant additives : polyglycoles , polyether ,
- Surfactants : emulsifying , wetting and detergent (soap and alkaline amino , sulfonate, based polyethylenoxide and fatty alcohol with EO / PO)
- A defoamer
- An anticorrosion
- A bactericide and fungicide ...
During my studies of the project i made 2 hypothesis about the organic component of the copper paste: it may be a complex of Calcium and detergent, or
it may be a fatty acid from the drawing oil used as u said.
I'd like to thank you again for your help 
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