Sciencemadness Discussion Board

ketone reduction

rannyfash - 22-4-2012 at 15:12

will Zn + HCl or Fe + CH3COOH reduce ketones? what reagents will reduce a nitro group and not a ketone?

weiming1998 - 22-4-2012 at 16:54

Quote: Originally posted by rannyfash  
will Zn + HCl or Fe + CH3COOH reduce ketones? what reagents will reduce a nitro group and not a ketone?


What? Both hydrated zinc chloride and iron(II) acetate aren't strong reducing agents. You will need a fairly strong oxidizing agent to oxidize Fe(II) to Fe(III) so that's not a reducing agent, and even in the presence of a strong oxidizing agent, you cannot oxidize ZnCl2.

Ketones need very strong reducing agents, like sodium borohydride or lithium aluminum hydride, to reduce. See here for the reducing agents that can reduce ketones http://en.wikipedia.org/wiki/Ketone_reduction#Aldehyde_and_k...

Because nitro groups are strongly oxidizing, probably only a weak reducing agent is needed. But what are you going to reduce the nitro group into? You need to answer that question first.

[Edited on 23-4-2012 by weiming1998]

bbartlog - 22-4-2012 at 17:14

He's not talking about ZnCl2 or iron acetate. Both the zinc and iron would be starting with zero valence.
Glucose can reduce some nitro groups and will not as far as I know reduce ketones. But you would need to research your specific case to know whether it would be likely to work - I know that glucose is certainly far from being a *general* reducing agent for such groups.

barley81 - 22-4-2012 at 17:15

No, zinc and HCl will probably readily reduce nitro groups (Fe does, so zinc probably does). It isn't the zinc chloride/iron acetate that does the reducing. It's the nascent hydrogen generated by the reaction of zinc with HCl or iron with acetic acid (if they both work). Zinc itself might also do the reducing, I'm not sure.

weiming1998 - 22-4-2012 at 18:41

Well, on the Wikipedia article, it says that hydrogen, paired with a platinum/ruthenium catalyst, can reduce ketones/aldehydes. As atomic hydrogen is a stronger reducing agent than normal H2, it might be able to reduce the ketone without a catalyst, although I am not exactly sure. How about bubbling hydrogen generated from zinc+acid through a ketone, then pour a dilute KMnO4 solution in and add a bit of sulfuric acid as a catalyst. If any of the ketone are reduced at all, the solution should turn from purple to opaque brown.

barley81 - 22-4-2012 at 19:04

Zinc amalgam and HCl will reduce ketones and aldehydes, but all the way to alkanes. See here:
http://en.wikipedia.org/wiki/Clemmensen_reduction

rannyfash - 23-4-2012 at 07:00

in essence i want to change a nitro group to an amine without reducing an adjacent ketone group, does anyone have any citations for zn + cl being unable to reduce ketones (i already know they can reduce nitro groups) or any other reagents that can reduce nitro groups while leaving a ketone untouched?

bbartlog - 23-4-2012 at 07:20

Oh, now you want citations but don't care to even tell us what compound you are trying to reduce? Regardless, would suggest this paper as a starting point: http://www.avantium.com/downloads/accelerated-process-develo... , especially since your coyness about your substrate suggests you have some pharmaceutical compound in mind.

Nicodem - 23-4-2012 at 08:34

Quote: Originally posted by barley81  
It's the nascent hydrogen generated by the reaction of zinc with HCl or iron with acetic acid (if they both work). Zinc itself might also do the reducing, I'm not sure.

Nascent hydrogen? You must have been reading articles from the 19th century. That hypothesis has been rendered totally obsolete long since. Dissolving metal reductions work by the reduction at the metal surface. The reduction is affected by the electrons that form from the M -> M<sup>+</sup> + e<sup>-</sup> oxidation reaction. In essence, the reactions are related to the electroreductions. In fact, the less hydrogen forms during the metal dissolution, the better the reduction.
Quote: Originally posted by rannyfash  
in essence i want to change a nitro group to an amine without reducing an adjacent ketone group, does anyone have any citations for zn + cl being unable to reduce ketones (i already know they can reduce nitro groups) or any other reagents that can reduce nitro groups while leaving a ketone untouched?

Sounds like some kind of a tasteless joke? How can anybody answer such a vague question if you don't even provide the very minimum information needed. You didn't even bother giving the structure of the nitroketone! Besides, you should open unanswerable and/or referenceless threads only in the Beginnings section. Make sure you read the forum posting guidelines.

barley81 - 23-4-2012 at 15:16

Quote: Originally posted by Nicodem  

Nascent hydrogen? You must have been reading articles from the 19th century. That hypothesis has been rendered totally obsolete long since. Dissolving metal reductions work by the reduction at the metal surface. The reduction is affected by the electrons that form from the M -> M<sup>+</sup> + e<sup>-</sup> oxidation reaction. In essence, the reactions are related to the electroreductions. In fact, the less hydrogen forms during the metal dissolution, the better the reduction.


Sorry. I think the article I was reading was derived from information from the 19th century indeed. I'll post references next time.