Digital Hepatitis - 19-11-2012 at 09:38
Mandelic acid can be easily had as it is the chief constitutent of certain over-the-counter facial peels sold by beauty supply companies. One "25%
Mandelic Acid Peel" was found to have the following ingredients:
Purified water, mandelic acid, SD alcohol, witch hazel distillate, propylene glycol, malic acid, butylene glycol, hydropropylcellulose, green tea
extract, hops, horsetail plant, lemongrass, goldenseal.
It was surmised that most of these constituents would evaporate and leave only the mandelic acid and botanical (junk) ingredients remaining.
After several days, the liquid peel had indeed evaporated to leave a cakey, thick white mush (as it turns out, mandelic acid gets mushy in warmer
temperatures, so don't mistake said "mushiness" for the lingering presence of water. Upon cooling, the white "mush" solidified into a hard mass in
the freezer in a healthy white color but still obviously tainted by botanicals, fragrance ingredients, etc. that left the purity much to be desired.
After consulting the available data on mandelic acid solubility here...
http://lxsrv7.oru.edu/~alang/onsc/solubility/allsolvents.php...
...it was decided that diethyl ether was the choice solvent for mandelic acid extraction and cleanup. ~55 g was dissolved in ~400 ml of diethyl ether
and washed with 2 * 30 ml portions of water (which took on a nice green botanical color that provided visceral satisfaction as far as how efficient it
was at removing the impurities.) Upon evaporation of the ether, ~53g of nice, white (a little brighter than "eggshell white" but not quite "blinding
snow white") mandelic acid remained. In hindsight, an additional wash (with a greater volume of water) would have been used as the mandelic acid
definitely likes the ether. It would also be interesting to try extracting with methyl-tert butyl ether, which is much more handy to work with than
the indispensable (but smelly, overly volatile, and dangerous) diethyl ether.
smaerd - 19-11-2012 at 15:02
couldn't you have added a base rinse in there to form the water soluble carboxylate separating it from the other non-polars?
mr.crow - 19-11-2012 at 18:54
Cool, mandelic acid looks like an easy way to store and prepare benzaldehyde.
If you search for patents this is one way to make vanillin and similar aldehydes.