The purpose of this experiment was to isolate a solid and liquid unknown from an
ether solution, recrystallize the solid, and identify both the solid and liquid based on
boiling point, melting point, IR, H-NMR, and C-NMR spectra.
Extraction is a way of separating two immiscible compounds through their
differences in polarity.
Polarity is a measure of how electrons in a bond are shared.
more electronegative and atom is, the more the electrons are attracted to that atom.
on atom in a molecule is more electronegative than the other, the electrons spend more
time close to that atom than the other.
This results in dipoles, which are partial charges.
The more electronegative atom obtains a partial negative charge and the less
electronegative atom obtains a partial positive charge.
Unequal sharing of electrons
creates a polar molecule.
If two atoms in a molecule have similar electronegativities,
there is an equal sharing of the electrons which means there are no dipoles, and the
molecule is non-polar.
In extraction, the two immiscible substances are mixed together.
When the solution settles, two layers form, one contains the polar molecules (the aqueous
layer), and one contains the non polar molecules (the organic layer).
They do not
combine however, because polar substances cannot dissolve non polar substances and
One of the layers can then be drained off, separating the polar and non polar
Kd is the distribution coefficient.
It is the ratio of the solubilities of the
compound being extracted in the two layers.
The higher the Kd, the more organic the
Kd = [organic] / [aqueous].
Another important concept in this experiment is acid base reactions.
An acid is a
substance that donates and proton, and a base is a substance that accepts a proton.
an acid and base are mixed, the acid donates a proton to the base.
The products of an
acid base reaction are a salt and water.
Recrystallization is a way of purifying non-volatile organic substances.
of dissolving the substance to be purified in an appropriate hot solvent.
solvent will dissolve the substance when it is hot, but not when it is cool.
Also, when the
mixture of the solvent and substance are cooled, the crystals should reform quickly and
It must also dissolve impurities readily so that they do not become trapped in the
purified substance when it is cooling and recrystallizing.
The solvent cannot react with
the solute by breaking bonds.
It cannot chemically alter the solute, only dissolve it, by
breaking the intermolecular forces.
Its boiling point must be lower than the solute’s
melting point so that the solute does not melt and oil out in the solvent.
Lastly, it should
be volatile so that it can be easily evaporated off of the newly formed crystals.
solvent is chosen, it is slowly added to the solvent until it has completely dissolved.