Osmium
(Stoni's sexual toy)
02-13-02 05:49
Post 269032 (https://www.thevespiary.org/talk/index.php?topic=7427.msg26903200#msg26903200)
(Osmium: "Re: Hg Amalgamation rates", Chemistry Discourse)
An amalgam is an alloy containing Hg having the interesting property of overvoltage. This means the Al wants to react and dissolve badly with alcohols and water producing H2 in the process, but this reaction is greatly hindered (NOT completely stopped, just slowed down a lot!) since H2 doesn't like to be produced on Hg surfaces.
When there is anything reducable around, like a nitro compound or an imine the Al can dissolve without having to produce H2 gas, and it readily will do so.
This reaction involves electron transfers between the reaction partners, which is just another way of saying the Al is dissolving and gives up its electrons to the Hg which in turn transfers them to the organic reactand to be reduced. It's not the Hg salt that breaks up the Al. If there is nothing around to be reduced then the Al can't get rid of those electrons, and it will not dissolve. Al/Hg in an inert solvent like hexane or toluene should be quite stable for a while. Al/hg will react with oxygen because Al is a very reactive metal which is only protected by its oxide coating (passivation), once that coating is removed it will oxidise in air, but that is usually not an option when covered by a solvent since O2 solubility is very low.
The solvolysis reaction with an alcohol will be very slow with thick Al because it has a much higher Hg loading on its surface and a much lower exposed surface area than foil.
Al/Hg in a pure alcohol: only very slow dissolving via solvolysis. Greatly enhanced by water presence (since Al2O3 formation is very exothermic and the driving force) and change to basic pH
Al/Hg in water: exothermic, will heat up considerably and might eventually react violently
Al/hg with nitro in alcohol: very exothermic reaction due to water formation, and since nitro is hot stuff
Al/Hg with nitro in alcohol containing considerable amounts of water and a base: let's not go there, runaway reaction with foil, very exothermic with sheet
Al/Hg with an imine in alcohol with a littlewater: rather slow and gentle reaction
Foil reacts much faster than sheet!
Don't try to tweak the reaction too much and reinvent the wheel! Al/hg works, in up to 90% according to the literature and some bees experience. And when done without haste and with thick Al it can even be very volume efficient.
This is perhaps the best explanation I have found of the properties of the reaction. It seems to suggest, and please correct me if I am wrong, that the Al/Hg does not by itself break up into slush because H2, the product of the reaction, does not like to be produced on Hg surfaces, and that simply the prescence of the reducable compound and the presence of oxygen(proton source) allow the reaction to take place, ultimately with water as a byproduct of imine formation. Osmium does however state that water is a initiator as well. I think the main function of water is to make absolutley sure you have availiable oxygen to start the reaction, but if for some reason it was present anyway in the solvent I believe that would substantiate Chromic's statement about water's neccessity. I think this would be correct anyway, but i've been up 38 hours.
Or perhaps the solvent alone, rate depending on how strong of a proton donor the alcohol is?
No, Seriously, Chromic, Man, would this interpretation be correct?
Or do I need to read up on redox?
BTW For those of you who didn't know Osmium is obviously a genius. ;) My hat is off to you. Keep the wisdom coming.
Flip