Bozakium
(Hive Addict)
07-30-04 12:06
No 522724
Decant the supernatant liquid! You forgot to decant the supernatant liquid! Fools! Fools!
Here's the original synth, with all the details as it appeared in the Journal Bibliothek fur chemie von der Fremdenverkersburo:
(Proper German-English translation by Bozakium)
To a 25 litre crock nestled in a dry ice/acetone bath is introduced 4 litres of liquid(substituted) BzCN dimer. Dropwise with stirring 8 litres of
equimolar (25.223%) sodium methylate in anhydrous acetone is added. The stirring is continued until all the emulsion disappears into solution.Allow
to stand until no more emulsion forms, stirring each time to disperse it. Add 4 litres of cooled ethyl acetate as a co-solvent. Remove from the
dry-ice bath and allow to warm to room temperature. At room temp(20C), the solution will be seen to separate ito two separate, but hard to see layers.
Decant the supernatant liquid and discard it. This will pollute the product if allowed to remain,as it contains many Bz2 moieties which will thrust
their way into the crystal lattices; however the small amount (<50mL) left behind actually helps catalyze the crystallization. This is why we
decant.
Warm slowly (10-15C/Hr), with stirring to 60C. Crystallization will commence at 55-58C and cease before 62C. Any wider a range indicates a
polluted product or improper stoichiometry.Collect accordingly. Be sure to use the BzCn dimer, as even with adjusted stoichiometry, the momomer is
unstable and will cause polymerization in the end product (sticky goo). Gillmann /Blatt (1903) used (monoisobutyl)ether to assist forcing
crystallization, but diglyme is found to be better as it does not tend to force dirty crystals against their will as does ether. Vacuum filter through
a #69(really)Buchner funnel with 120-bore or smaller escrima paper. Drying may be done at STP, but is aided by a combination infrared/ultraviolet heat
lamp. Do not use a regular light bulb, as excessive photons in the 589 to 589.4 nM wavelength range(yellow) excite the electrons on the androgyne
carbon of the alpha-acetyl group and can cause explosive decomposition. Keep this intermediate out of direct sunlight for the same reason. Failing to
decant the supernatant liquid in the earlier step GREATLY exacerbates this danger! The white, needle-like prisms(other crystals indicate failure, an
incorrect product)are the sodium salt of n-acetylacetonitrile. Bung the salt at a rate of 450g /500mL of 40%(by wt. not vol.) sulfuric acid in a large
beaker with rapid stirring. "Bung" translates best into "refresh, with shooshing", this is done in practice as one would spread
rock salt on an icy sidewalk out of a scoop, with sweeping horizontal motion. I believe it is to allow the reaction with the sulfuric to proceed upon
maximum unimpeded surface area, to prevent diphenylacetone formation. Stir rapidly during bunging to break up the effervescence(or beaker will
overflow), until all effervescence(you should see the German word for that!) ceases. Proto- and final hydrolysis as well as the subsequent
decarboxylation should now be complete. Check by TLC eluted with 60/40 tin/lead dichromate(at 2% wt/vol dilution in deionized, distilled dihydrogen
oxide. Develop the plates with iodine vapour to visualize. If not complete, a SMALL amount of concentrated acid may be added dropwise wit very fast
strring, rechecking TLC after every .22 drops/mole of crystals used. Heat on an electric mantle(NO flame), with rapid stirring to 75C for one hour to
allow deracemization.
Add water to an acidity of 20%, checking with pH paper. The organic layer containing the product will float. Extract with light
petroleum(pentanes), wash 3x with a 10% sodium bicarbonate solution. Eveporate the solvent in vacuo. Yield should be 80-90%. Mp should be +/- 2 deg.
of reference product. Total synthesis time(minus workup) is ca. 2 Hr. This is a pretty small-caliber synthesis and should be easy for anyone to
compleat sucessfully. |
i would greatfully appreciate it. seems the n-but is hard to come buy here, nobody
want to sell it ....