malvaxman (Hive Bee)
02-25-02 22:06
No 273406
      Preparation of DL-Amphetamine Phosphate  Bookmark   


1 mol of phenyl-2-nitropropene, C6H5CH=C(CH3)NO2, is dissolved with a solvent prepared by mixing 1000ml of ethanol with 500ml of acetic acid and 500ml of 12 N sulfuric acid. The resultant solution is placed in the cathode compartment of a divided electrolytic cell containing a metallic cathode of mercury, copper, or other metal of similar nature. Current is passed, using a current density of ~0.2 amp/cm2 of cathode surface. The temperature is kept at about 40C during the electrolysis which is continued until at least eight Faradays of electricity have been passed.

When the reduction is completed, the amphetamine may be separated from the solution. A convenient way of doing this is by removing the ethanol and ethyl acetate present by evaporation and then making the residual solution strongly alkaline by addition of caustic alkali. The basic layer thus formed is separated from the aqueous solution and contains the desired amphetamine freebase.

135 g (1 mol) of amphetamine freebase were stirred into 300ml of acetone in a 1000ml erlenmeyer flask. To the resultant solution there were slowly added under constant agitation 115.3 g of 85% phosphoric acid (containing 1 mol of H3PO4), care being taken to avoid any sudden rise in temperature or local overheating due to the considerable amount of heat that is evolved. During the addition of the phosphoric acid a fine, white, flocculent precipitate appears which becomes more and more dense and abundant, as the quantity of added acid increases.

When the entire quantity of the phosphoric acid has thus been added, agitation of the mixture is continued for about a half-hour or more to insure complete conversion. The precipitate is then allowed to settle, the supernatant liquid is drawn off, and the residue is filtered. The precipitate thus separated is washed with acetone and is then dried by evaporation to constant weight. It forms a fine, white, impalpable powder consisting of pure monobasic amphetamine phosphate.

Reference: Pharmaceutical Manufaturing encyclopedia (1988)
(../rhodium/chemistry /amphetamine.phosphate.html)

What yeld could be expected ???
(Hive Bee)
02-26-02 09:45
No 273678
      Re: Preparation of DL-Amphetamine Phosphate  Bookmark   

What yeld could be expected ???

1 mole
(Hive Bee)
02-27-02 05:38
No 274078
      Re: Preparation of DL-Amphetamine Phosphate  Bookmark   

Would Pb not be better for the cathode (as it has a similar hydrogen overvoltage, isn't as toxic as Hg and less reactive than Cu)?

Also what was the purpose of the acetic acid??

I wouldn't do that if I were you.....
(Chief Bee)
02-28-02 01:31
No 274532
      Re: Preparation of DL-Amphetamine Phosphate  Bookmark   

The acetic acid is probably there as a co-solvent. The H2SO4 is to act as a proton donor and to reduce side reactions.
(Hive Bee)
03-03-02 00:48
No 275949
      Re: Preparation of DL-Amphetamine Phosphate  Bookmark   

Could someone please help me to finaly understand this..

How should the cell look like? Should it be divided by some membrane or what???
After all the current is passed how much of the PNPropen is turned to amine? Could it realy be 100%?