April 13, 2014
Texas A&M University at Galveston, Galveston, Texas
When determining unknown compounds, performing a qualitative organic analysis can establish the physical, chemical, and spectral properties of chemical. This data can then be used to name the functional groups of each unknown. Each functional group has a specific atomic structure and specific chemical behavior that determines the chemistry for all known organic molecules1. The possible functional groups for the compounds in the experiment are the alkenes, alkanes, alkyl halides, alcohols, esters, and aldehydes.
By establishing the unknown's boiling point during distillation, insight can be gained as to the strength of the molecular bonds of the compound. Stronger hydrogen bonds will have higher boiling points, followed by dipole-dipole interactions, and atoms held together by van der Waals forces will have the lowest boiling point2.
Density will provide information on the molecular weight of the atoms divided by the molecular volume.
This will indicate if "heavier" organic elements, such as Nitrogen or Chlorine, are involved and a possible estimate as to the number of such atoms present3.
Solubility level differs depending on whether the compound is of the same polarity as the solvent or if it can form hydrogen bonds with it. This affects the degree of which the compound will dissolve into the solvent, and ringed or branched structures are typically more soluble than straight chain structure3.
Infrared (IR) Spectroscopy provides frequencies of the vibrations that occur when covalent bonds absorb infrared light. High energy frequencies display "peaks" relative to the number of bonds and if the vibrations are causing them to stretch or bend. Specific bonds register "fingerprint peaks" which are used to identify the composite functional groups of the tested compound and generate possible molecular structures4.
Purification and Physical Properties.