Tips and Tricks on Purification Characterization Organic Compounds


A technique used in reaction and separation includes:
heating under reflux (NOT just 'reflux')
distillation and fractional distillation
recrystallisation and filtrationsolvent extraction

Techniques used in analysis:
melting temperature and mixed melting temperature
elemental analysis (empirical formula)
relative molecular mass determination and mass spectra
other spectra: ultraviolet, infrared, nuclear magnetic resonance

Qualitative Analysis of Organic Compounds
There is no definite set procedure that can be applied overall to organic qualitative analysis.
A. Preliminary Test
Note physical characteristics: solid, liquid, color, and odor. Compounds that are yellow to red in color are often highly conjugated. Amines often have a fish-like odor, while esters usually have a pleasant fruity or floral smell. Acids have a sharp, biting odor. Odors can illicit information about your unknown; it is wise to sniff them with caution. Some compounds can have corrosive vapors or make you feel nauseous.
B. Physical Constants
Determine the boiling point or melting point. Distillation is recommended in case of liquids. It serves the dual purpose of determining the boiling point as well as purifying the liquid for subsequent tests.
C. Solubility Tests
The solubility of the unknown in the following reagents provides very useful information. In general, about 1 mL of the solvent is used with approximately 0.1 g or 0.2 mL (2-3 drops) of the unknown compound.
Assistance in analyzing the results from your solubility tests can be found in the solubility flowchart.
D. Group Classification Tests
After analysis of the previous tests and the compound's IR spectrum, if needed, further information can be deduced by performing carefully selected functional group classification tests.

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Alkanes, Alkenes and Alkynes
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