Author Topic: LSA ---> Lysergic acid  (Read 2959 times)

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LSA ---> Lysergic acid
« on: February 25, 2002, 06:04:00 AM »
A solution of 6.7 g KOH in 100 mL H2O, under an inert atmosphere and magnetically stirred, was brought to 75 °C, and 10 g ergotamine tartrate (ET) added. The reaction mixture turned yellow as the ergotamine went into solution over the course of 1 h. The stirring was continued for an additional 3 h. The reaction mixture was cooled to about 10 °C with an external ice bath, and acidified to a pH of about 3.0 by the dropwise addition of 2.5 N H2SO4. White solids started to appear early in the neutralization; approximately 60 mL of sulfuric acid was required.

i'm somewhat confused by the above procedure...

Shouldn't adding ET to a basic solution form ergotamine freebase? If so, then why was a precipitate formed when the acid was added? Or does ET not act like a good alkaloid should? Also, i'm guessing that the acidification casues the below reaction...

RCONH2 + H+ + H2O ---> RCOOH + NH4
RCONH2 + OH- + H20 ---> RCOO- + NH3 + H20
apply to LSA? I would imagine it would, but i have very little formal background in chemistry, so maybe i'm missing something...

- nevry.

p.s. if the above reactions apply to LSA, then shouldn't an a/b extraction convert LSA to Lysergic acid???

- nevry.


  • Guest
Re: LSA ---> Lysergic acid
« Reply #1 on: February 25, 2002, 07:19:00 AM »
Ergotamine is an amide of lysergic acid. The ergotamine is reacted with hot, strong alkali to hydrolyze the amide linkage and liberate the lysergic acid as per the equation that you give:
RCONH2 + OH- + H20 ---> RCOO- + NH3 + H20

While lysergic acid is a base due to an amine nitrogen it also has a carboxylic acid group. This makes its solubility in water at various pH values different from what you would expect with a simpler amine such as amphetamine. Lysergic acid is only slightly soluble in water and much more soluble in solutions of alkali hydroxide.


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Yes, you're partly right.
« Reply #2 on: May 20, 2002, 12:06:00 AM »

i'm guessing that the acidification casues the below reaction...

RCONH2 + H+ + H2O ---> RCOOH + NH4

Yes it would if the reaction was done with a concentrated acid in a hot reflux. But
1) the acid is pH 3 which is weak
2) the solutions are cooled
3) don't leave the amide in contact with acid for very long.

Making sure that the amide stays OK.

Happy now?

The basic hydrolysis of the amide? I'd be worried about that too but I'd have to trust the source of my information (Shulgin?). Make sure you monitor the temperature to keep it from rising too high.