Wolff Kishner Reaction – conversion of ketones/aldehydes to alkanes

by James

Description: The Wolff-Kishner is a reaction for converting carbonyls (such as ketones and aldehydes) into alkanes.
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{ 12 comments… read them below or add one }

bazla siddiqui January 14, 2012 at 4:51 pm

i think it is a very good way of representing this method.i like it

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Nima Omid-Fard March 11, 2012 at 11:23 pm

does this reduce alcohols to alkanes too?

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james March 12, 2012 at 12:14 am

no, just ketones and aldehydes

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Casey April 20, 2012 at 3:51 am

Yes, but for a Wolff-Kishner reaction that does not imply the use of a strong base (i.e. hydroxide), would water be able to deprotonate that amine in step one to give the N-N double bond? I ask because in the synthesis of the drug Amiodarone, they do not specify basic conditions. Rather, they allude that they use hydrazine hydrate only.

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james April 20, 2012 at 2:43 pm

Water isn’t basic enough to deprotonate. The pKa of the hydrazone hydrogens is about 22, whereas that of H3O(+) is -2. The equilibrium would be 24 orders of magnitude in opposition to the desired reaction.
I found a publicly available reference to the synthesis here: : http://bit.ly/J2TCRA
Although they don’t specifiy basic conditions in the reaction scheme, it’s not uncommon to leave out details such as base, solvent and heat. The Wolff Kishner is generally a very unfavorable reaction as it is – it requires heating at 180 degrees C or more – so I am nearly 100% certain that they merely omitted writing base in the scheme here.

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Casey April 26, 2012 at 7:12 pm

Great! Thank you.

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Aleksandra May 3, 2012 at 6:25 am

And what is a role of ethylene glycol in this reaction?
The site is really great.

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james May 3, 2012 at 8:28 pm

Ethylene glycol serves as a solvent here. It has a very high boiling point (~200 degrees C); the fact that the reaction needs to be heated so much is why this solven tis used.

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james May 3, 2012 at 1:00 pm

Good question. One reason I’ve read is the greater strength of the C-O (pi) bond as opposed to the C-C (pi) bond. I’m not sure this is the whole picture but it is at least a component.

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Aleksandra June 15, 2012 at 1:04 pm

Thanks for answer.

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shashikumar k.paknikar September 7, 2012 at 7:51 am

nice presentation. Can we use potassium carbonate and ethylene glycol and temperature ~200 degree C?

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james September 8, 2012 at 7:11 pm

I suppose you could use potassium carbonate but it will not deprotonate ethylene glycol irreversibly; at 200 degrees C, however, the reaction should still proceed well.

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