Trouble Identifying this Organic Unknown

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In summary, the conversation is discussing a clear, yellowish liquid with a fruity smell and physical data including a boiling point and refractive index. The IR spectrum shows an OH shoulder, C=O band, presumed C-O bond, and various other bands. The possible unknown compounds include cyclohexanone, bromobenzene, 1-bromobutane, 2-chloroethanol, phenylacetylene, 1-octanol, ethyl benzoate, propionic acid, benzaldehyde, and 1-octene. It is suggested to eliminate compounds based on the IR readings and to consider potential contamination in the sample. Additionally, cooling the sample to obtain a melting point can provide
  • #1
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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  • #2
Smell suggests ester, are you sure about BP?

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  • #3
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.
 
  • #4
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)
 
  • #5
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.
 
  • #6
Handbook of Chemistry and Physics. You should be able to eliminate a ton of those from BP alone.
 

FAQ: Trouble Identifying this Organic Unknown

What is an organic unknown?

An organic unknown is a substance that has not yet been identified or characterized as a specific organic compound. It may have been isolated from a natural source or synthesized in a lab, but its chemical composition is not known.

Why is it important to identify organic unknowns?

Identifying organic unknowns is important for several reasons. It can help to determine the properties and potential uses of the substance, as well as its potential hazards and risks. It can also aid in the development of new drugs, materials, and other products.

What are the common methods used for identifying organic unknowns?

The most common methods for identifying organic unknowns include spectroscopy techniques such as infrared (IR), nuclear magnetic resonance (NMR), and mass spectrometry (MS). Other techniques such as elemental analysis and chromatography may also be used.

What are the challenges in identifying organic unknowns?

Identifying organic unknowns can be challenging due to the vast number of possible compounds, as well as the potential for impurities or mixtures in the sample. The lack of reference materials or databases for certain compounds can also make identification difficult.

What steps should be taken when identifying an organic unknown?

The first step is to collect as much information as possible about the unknown, such as its physical properties, possible sources, and any known reactions or reactions it may undergo. Then, various analytical techniques can be used to obtain data on the unknown's structure and properties, which can be compared to reference materials and databases to make an identification.

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