Suppose that you carried out the following synthesis of octyl salicylate:
cat. H2SO4
salicylic acid + 1-octanol (large excess) ------------> 1-octyl salicylate + H2O
The structures of salicylic acid and 1-octanol can readily be found.
1-Octyl salicylate is the octyl ester of salicylic acid (you can look up
the way esters are named and how this implies their structure).
Now for the question:
This reaction is an equilibrium reaction, so it is expected that not all
of the starting materials will be consumed. The equilibrium should lie
quite far to the right, however (but not completely), due to the excess
1-octanol.
Explain how you would go about isolating 1-octyl salicylate from the
reaction mixture in as pure a form as possible. Assume you need to make
use of the physical properties of the compounds present, including their
solubility in various solvents, acid-base reactivity (and solubility after
acid-base reaction), and boiling point/melting point. You can use water,
diethyl ether (a solvent that is immiscible with water and also serves as
a good solvent for neutral organic compounds), 5% aqueous NaOH, 5% aqueous
NaHCO3, and 5% aqueous HCl. Note that most neutral organic compounds of 6
carbons or greater are not soluble in water unless they are significantly
polar. Also, as you contemplate the acid-base reactions you might employ
to influence solubility, consider the pKa's of the functional groups
involved and the strength of the acids and bases that you have available
(especially the bases).
In order to break the problem up into subsections, you might first
consider the acid-base properties of each compound involved in the
reaction above and the potential of each to react with the acidic and
basic solutions provided (based on relative acidity and basicity and pKa's
of acids and the conjugate
That's all folks!
CBF
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Craig B. Fryhle, Ph.D. Office 206-535-8314 FAX 206-536-5055
Associate Professor Email fryhle@u.washington.edu
Department of Chemistry URL http://rainier.chem.plu.edu/fryhle.html
Pacific Lutheran University
Tacoma, Washington 98447 ^ ^ ^ ^ ^ ^
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