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Topic: Li, NH3, NH4Cl  (Read 14716 times)

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Offline g-bones

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Li, NH3, NH4Cl
« on: April 07, 2008, 12:05:58 AM »
Li, NH3, NH4Cl

these reagents are one step in a total synthesis problem so i do not know the end product because there are several steps before the intermediate is shown.  there is an enone in the starting material if that helps, but i could use some general reactivity of these reagents together or any help possible.  thank you.

Offline Dan

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Re: Li, NH3, NH4Cl
« Reply #1 on: April 07, 2008, 03:11:29 AM »
Post the full question, ChemSketch is free

http://www.acdlabs.com/download/chemsk.html

You are probably looking at reduction. The ammonium chloride is probably added at the end of the reaction to quench it.
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Offline g-bones

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Re: Li, NH3, NH4Cl
« Reply #2 on: April 07, 2008, 04:27:53 AM »
here is a picture of what i believe are the reactivity areas

Offline Dan

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Re: Li, NH3, NH4Cl
« Reply #3 on: April 08, 2008, 10:53:38 AM »
Yes, you're looking at a reduction here. Metal-ammonia systems generate solvated electrons, and can be used to reduce CC multiple bonds.

In the case of a,b-unsaturated carbonyls you will get reduction to the enolate. Then addition of ammonium chloride quenches any excess reagent, and your enolate is protonated and equilibrates back to the ketone.

Another notable use of such systems is the reduction of alkynes to trans alkenes (whereas hydrogenation would give the cis alkene).
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Offline g-bones

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Re: Li, NH3, NH4Cl
« Reply #4 on: April 26, 2008, 06:20:06 PM »
thanks dan, that helped!

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