Unknown Chemical compound identification using IR spectroscopy??

[N2Microbes]

Hello,

 

I am trying to determine the identification of an unknown. My boiling point is some where between 129- 134.7 Celsius. My Refractive index was 1.392 after being corrected for room temperature. It was not soluble and water and was less dense.

 

MY IR spectroscopy is attached below please help I have been unable to identify this compound for about 4.5 hours now.

Best regards,

N2Microbes

 

 

also on another note it smells like bananas

Edited October 14, 2015 by N2Microbes

[DrP]

At first glance - the peek at around 3000 usually represents an aromatic ring iirc.. that will let you know there is a benzene/aromatic ring in there at least.

 

Can't help much more than that as it has been a very long time. ;-)

 

Check the peak at 1750 - that one might tell you something too.

1750 might be a C=O of some kind.. Maybe a carboxylic acid? Benzoic acid even?

Yea - the peaks at 1100 can depict a C-O bond too - so looking like it could be a carboxylic acid of benzene.

Not sure about the big peak at 1250 though... :-/ let us know what you come up with.

OK after more reading, if it is aromatic then the peaks that are at 3000 would be the sp2 CH stretches and they will also need to show a C=C aromatic stretch somewhere between 1400 to 1600.

[DrP]

Doing a bit of reading, that peak at 3000 is probably O-H as it goes.. and the one at 1250 is probably also O-H.

 

The peak at 1100 could be the aromatic?

 

So with the O-H's and the C=O and an aromatic I still reckon something similar to benzoic acid.

Here is some info - the spectra at the bottom of the page is benzoic acid - it looks quite similar with peaks at the same places. The proportions of the peaks are a little different, but that is probably because the y axis is shorter/aquashed. http://www.4college.co.uk/a/wm/infrared.php

 

it says, for benzoic acid:

1. An O-H group is present in the molecule (identified by the region between 2500-3300 cm^-1)
2. Absorption between 1680-1750 shows that a C=O is present.
3. Absorption around 1300 cm^-1 again shows the presence of an OH group.
4. Absorption around 900-1100 cm^-1 could be due to the benzene ring or to the carbon-oxygen bond of the acid grouping.

...all of which, seems to be going on in your spectra - except - the BP of benzoic acid is 249.2... So maybe another carboxylic acid of some kind.

OK then, how about Isoamyl acetate. It is supposed to smell like bananas and it has a boiling point just over what you described. It has a similar IR spectra too:

 

http://orgchem.colorado.edu/Spectroscopy/specttutor/ex5.html

 

"Carbonyls show up in the region 1760-1665, and specifically, saturated aliphatic esters from 1750-1735. Sure enough, there is a band at 1743 indicating a saturated aliphatic ester. There is a possibility that the compound is has both a ketone and an ether group instead of an ester, however, the band at 1743 indicates an ester instead of a saturated aliphatic ketone. You can also see bands in the region 1300-1000 which can indicate the C-O stretch."

Sorry it's all a bit late for your lab now. Let us know what it was when you find out.

Edited October 14, 2015 by DrP

[BabcockHall]

The peak is too narrow to be OH. C-H sp³ is less than 3000 wave numbers; C-H sp² is > 3000 wave numbers. The peaks near 1750 and 1200 are the only other ones that are helpful here. The smell is also useful.

[imatfaal]

If your BP is a little out then Isobutyl Acetate fits the fruity (pears, bananas, roses, raspberries) smell and refractive index

[hypervalent_iodine]

If your BP is a little out then Isobutyl Acetate fits the fruity (pears, bananas, roses, raspberries) smell and refractive index

This seems about right. Easiest way to check these assignments is with SDBS. For known organics, anyway.

 

http://sdbs.db.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi

 

If you search by CAS number (110-19-0), you can view the recorded spectra for isobutyl acetate. The important thing to match is the fingerprint region below 1500 cm^-1. It looks pretty similar to me.

[Sensei]

DrP voted for Isoamyl acetate,

Imatfaal and hypervalent iodine for Isobutyl Acetate.

There is easy way to check which is true: by its melting point.

 

Isoamyl acetate has −78 °C,

and Isobutyl Acetate has -99 °C.

Using dry ice will make one of them solid?

Or liquid nitrogen will be needed?

 

ps. N2Microbes, you need to use IR spectroscopy, or you can do whatever you like to identify compound?

I would burn it in controlled environment, to produce CO2 and H2O, and measure amount of gas produced..

 

Butyl acetate has BP at 126.1 °C, and RI 1.3941, closer to measured values.

https://en.wikipedia.org/wiki/Butyl_acetate

Edited October 17, 2015 by Sensei

[John Cuthber]

There is easy way to check which is true: by its melting point.

 

Using dry ice will make one of them solid?

 

Butyl acetate has BP at 126.1 °C, and RI 1.3941, closer to measured values.

https://en.wikipedia.org/wiki/Butyl_acetate

"Using dry ice will make one of them solid?"

Or not, dpending on the weather etc. Any impurities present will lower the melting point.

The sublimation temperature of CO2 is affected by atmospheric pressure.

​So, you can use the melting point, but you might need something rather colder than dry ice.

 

Also, the measured BPt of the material will depend on pressure.

N2Microbes,

What altitude are you at?