Trouble Identifying this Organic Unknown

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Discussion Overview

The discussion revolves around identifying an unknown organic compound based on physical data and an IR spectrum. Participants explore the implications of the provided boiling point, refractive index, and spectral data, considering various potential compounds.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant notes the physical characteristics of the unknown, including its clear, yellowish liquid form and fruity smell, suggesting it may be an ester.
  • Another participant questions the accuracy of the boiling point measurement, implying it could affect the identification process.
  • Based on the IR spectrum, a participant suggests that many compounds on the list can be eliminated, emphasizing the importance of spectral data over olfactory cues.
  • Concerns are raised about the possibility of contamination affecting the IR spectrum, with suggestions that the unknown might not be a single compound.
  • A later reply reiterates the contamination concern and proposes obtaining a melting point to assess purity.
  • One participant recommends using boiling point data to further narrow down the list of potential compounds.

Areas of Agreement / Disagreement

Participants express differing views on the reliability of the boiling point and the potential for contamination, indicating that multiple competing perspectives remain regarding the identification of the unknown compound.

Contextual Notes

Participants mention the need for careful consideration of the purity of the sample and the limitations of relying solely on smell or boiling point for identification.

Who May Find This Useful

This discussion may be useful for chemistry students, organic chemists, or anyone involved in compound identification and analysis.

stuartischees
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Alright, I've got a bunch of physical data and an IR Spectrum, but somehow it doesn't seem to match up with any compound I find through google. Even worse, I have a list of compounds it should be and there's still no obvious winner. Any help is dearly appreciated.

Clear, yellowish liquid. Fruity smell.

BP ~ 165.5C
Refractive index ~ 1.55 @ 20C

IR Specrtum:
Obvious OH shoulder, looks like a carboxylic acid
C=O band at 1703
Presumed C-O bond at 1204
Small band at 3064
Moderate bands at 2820 and 2850

Possible Unknowns:
Cyclohexanone
Bromobenzene
1-Bromobutane
2-Chloroethanol
Phenylacetylene
1-Octanol
Ethyl Benzoate
Propionic Acid
Benzaldehyde
1-Octene

Again, all help is appreciated!
 
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Smell suggests ester, are you sure about BP?

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Well based on your IR readings you should be able to eliminate at least half the compounds on your list. I wouldn't go just on smell, but like Borek said, a sweet/fruity smell suggests an ester.
 
Are you sure this is a single compound, and isn't contaminated by anything else that would appear in the IR spectrum? (i.e. ester contaminated with alcohol or acid left over from synthesis)
 
PhaseShifter said:
Are you sure this is a single compound, and isn't contaminated by anything else that would appear in the IR spectrum? (i.e. ester contaminated with alcohol or acid left over from synthesis)

This is a good point; I hadn't thought of this. Depending on the equipment you have available, you might want to cool it down enough to get a melting point, which can give you a general idea of the purity.
 
Handbook of Chemistry and Physics. You should be able to eliminate a ton of those from BP alone.