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Topic: Trouble Determining the Structure of the Compound  (Read 4977 times)

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Offline aram2189

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Trouble Determining the Structure of the Compound
« on: November 18, 2013, 08:46:30 PM »
From the Mass Spec data given I've formulated the molecular formula to be C4H8O2.  My IHD calculations indicate the presence of one double bond.

From my IR I've determined a carbonyl stretch at  1728.44. There is no broad peak between 3500 to 3200 indicating the absence of an alcohol and there is no broad peak from 3200 to 2500 indicating the absence of a carboxylic acid. 

From C13 NMR I have a carbon at 160 ppm indicating a carbon from a carboxylic acid derivative, most likely an ester.  The peak at roughly 65 ppm is most likely the carbon attached to the oxygen and not the carbon of the ester. 

From my HNMR I have what looks to be a propyl group that is attached to the oxygen of the ester. 
Triplet (2H) 4.1 ppm
"Quartet" (2H) 1.7 ppm
Triplet (3H) 0.9 ppm

Putting this information together I get my compound that I've attached as a picture.  Is this the correct answer? Is this compound even possible? I've tried to name the compound using IUPAC nomenclature so I can search it online but I can't seem to name it. Any help would be much appreciated.

(This image was taken from "Spectra Problems Set 1" 2nd edition by Dr. Richard A. Tomasi)

Offline Archer

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Re: Trouble Determining the Structure of the Compound
« Reply #1 on: November 18, 2013, 11:50:13 PM »
From the Mass Spec data given I've formulated the molecular formula to be C4H8O2.  My IHD calculations indicate the presence of one double bond.

From my IR I've determined a carbonyl stretch at  1728.44. There is no broad peak between 3500 to 3200 indicating the absence of an alcohol and there is no broad peak from 3200 to 2500 indicating the absence of a carboxylic acid. 

From C13 NMR I have a carbon at 160 ppm indicating a carbon from a carboxylic acid derivative, most likely an ester.  The peak at roughly 65 ppm is most likely the carbon attached to the oxygen and not the carbon of the ester. 

From my HNMR I have what looks to be a propyl group that is attached to the oxygen of the ester. 
Triplet (2H) 4.1 ppm
"Quartet" (2H) 1.7 ppm
Triplet (3H) 0.9 ppm

Putting this information together I get my compound that I've attached as a picture.  Is this the correct answer? Is this compound even possible? I've tried to name the compound using IUPAC nomenclature so I can search it online but I can't seem to name it. Any help would be much appreciated.

(This image was taken from "Spectra Problems Set 1" 2nd edition by Dr. Richard A. Tomasi)


This looks okay to me, you don't have a quartet though (look closer and bear in mind this is a low res spectra) as this is between a CH2 and a CH3. Logic would suggest a sextet, which is how it appears (N+1 rule, 5+1=6) but as these are non equivalent protons on either side you actually have a triplet of quarters which is overlapping to give a pseudo-sextet.

If you want to check your work on these then go look at the Spectral Database for Organic Compounds (SDBS) website.
 http://sdbs.db.aist.go.jp/sdbs/cgi-bin/ENTRANCE.cgi

Remember though, this is a tool to check your work. I have come across incorrectly assigned spectra on here more than once but you appear to know what you are doing so you will spot these mistakes.
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