Sciencemadness Discussion Board

reduce double bond with Aluminum amalgam?

Filemon - 25-8-2008 at 10:31

Does Aluminum amalgam reduce double bond?

fuming_nitric_acid - 8-9-2008 at 06:29

Which double bond are you talking about? C=C ? But which allylic aromatic??? AFAIK even Na in liquid NH3 can't reduce alkenes (allylic double bonds) so I dont think that Al Amalgam would do the job!

Sandmeyer - 8-9-2008 at 17:29

Alkenes are saturated upon reaction with Al/Hg. Compounds with C=C bonds activated by electron withdrawing substituents are easier to reduce. See for instance: JACS 1957, 79, 4487 and JOC 1991, 56, 5472. There are also a number of examples of practical procedures on the web-pages and forums, dealing mostly with reduction of nitrostyrenes into amines.

DNA - 11-9-2008 at 23:57

It will indeed reduce double bonds so will nitro groups be reduced to amines as sandmeyer mentioned

[Edited on 12-9-2008 by DNA]

Nicodem - 12-9-2008 at 00:38

But in both references a highly conjugated, electron poor double bond is reduced. Are there examples where aluminium amalgam under any conditions reduces nonconjugated or electron rich alkenes?

DNA, that aluminium amalgam can reduce conjugated nitroalkenes to amines is no proof that it can reduce all double bonds in general, neither is proof that it can reduce all conjugated alkenes. Conjugated nitroalkenes can also be reduced without involving the actual C=C double reduction by going trough the enamine stage (C=C-NO2 => C=C-NH2 => C-C=NH => C-CH-NH2).

PS: The benzyl and allyl ethers of phenols are not cleaved by aluminium amalgam.

fuming_nitric_acid - 13-9-2008 at 08:29

Yes Nicodem! I would mention the same thing! Electron poor double bonds can be easily reduced as Al/Hg can reduce NitroAlkenes but can he reduce for example Allyl Benzene or Allyl Alcohol? I doubt it. That's why I asked "which double bond?" at the first place.

[Edited on 13-9-2008 by fuming_nitric_acid]