rannyfash
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creating anhydrides with complex carboxylic acids
how would i create an anhydride of lysergic acid (fairly complex) without destroying the structure of the molecule via side reactions, can i react
lysergic acid with phthalic or maleic anhydride, is there any dehydrating agent that will not undergo side reactions, no physical applications
involving me, i was just interested why i cant find documentation of this route to lsd
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Hohenheim
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I think you need to clarify... Do you mean anhydrous lysergic acid? What end do you have in mind? You mention LSD, but I don't quite get it.
Layout your thought process, or route in mind, on LSD from lysergic acid... I might be able to help. (I promise not to flame for drug stigma.)
Let no man belong to another that can belong to himself.
-Paracelsus Von Hohenheim
Quote from Turd:
"And what is Stugartt supposed to be? Are you sure you don't mean Stuttgart, or is this supposed to be a transcription of some crazy high German
dialect?"
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fledarmus
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I'm not sure exactly what route you are talking about. Phthalic anhydride and maleic anhydride are typically used to react with primary amines,
forming imides - they are already very stable anhydrides and there is no driving force for them to form a mixed anhydride with another carboxylic
acid. Lysergic acid has no primary amine.
Anhydrides are typically made by preparing an activated carboxylic acid derivative (an acid chloride or activated ester) and then adding a second
carboxylic acid. The dehydrating agents that can also be used tend to be highly active, like phosphorus pentoxide. If you are already making an
activated carboxylic acid, it is easier to go straight to the amide from the activated acid derivative than to go through an anhydride.
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rannyfash
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thanks fledarmus, how am i able to tell what acids will form mixed anhydrides with lysergic acid (and generally with other acids), on an offnote can
sodium diethylamide exist? sodamide is made by passing ammonia over metallic sodium, would the extra ethyl groups make it unstable?
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rannyfash
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i also found the method, it used trifluoroacetic anhydride, what makes it so special at being able to form a mixed anhydride?
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ScienceSquirrel
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The trifluoroacetate anion is a very good leaving group.
So acid that you want to make a derivative of plus trifluoroacetic anhydride gives the mixed anhydride plus trifluoroacetic acid or it's salt.
Add your nucleophile and end up with the amide, ester that you want plus a trifluoroacetic acid salt.
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rannyfash
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cool, im guessing other anhydrides will form mixed anhydrides with lysergic acid, what makes it a good leaving group? im currently halfway through my
a-level course, in my understanding from what ive being taught, surely a molecule with halogen atoms causes the chiral carbon to have a partial
positive charge, and with flurines high electronegativity surely it would react by nucleophillic substitution with the nitrogens lone pair? any other
examples of 'good' leaving groups? im not trying to be obnoxious and know there are exceptions at a-level which we are not taught so please do not
rage at me 
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rannyfash
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am i right in thinking the pka is a good representation of how 'good' a leaving group is?
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Nicodem
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Thread Moved
25-2-2012 at 13:44 |
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