Hello nice people!
Many syntheses use a metal
to bind two reactants, cyclize or bridge a reactant... This is usually done in a solvent, which introduces drawbacks like its own reactivity, and can take hours or days. So I wonder if a metal vapour
can do the task, when the reactant can be gaseous.
The vapourized metal being atomized, it becomes much more reactive, which shall address the speed concern
but the obvious consequence is that the metal loses selectivity, so the process isn't expected to fit every subtle reaction; I hope that the careful control of dilutions and residence times can keep some simple reactions
To begin, here under are the vapour pressure versus temperature
for some metals. Figures are fromhttp://en.wikipedia.org/wiki/Vapor_pressures_of_the_elements_(data_page)
which I just put in shape. More curves are inhttp://yorkamo.phys.yorku.ca/general_stuff/2012/09/post.html
and some metals achieve a notable vapour pressure at temperatures bearable by organic compounds
- by some simple ones.
Among monovalent metals
, lithium looks too hot, but sodium and potassium could fit. Rubidium and caesium are more volatile but more bulky. (You may have to log in and click on the images for full size)
, magnesium seems difficult, zinc and cadmium better - since atomic metals must react very quickly, a low pressure can still be productive, and the compounds can leave the hot zone quickly. I've put the volatile mercury as well, though its two valences won't help. Other metals like calcium, strontium, barium are less volatile.Trivalent metals
are little volatile. Thallium is the least bad I saw.
Most metals will be liquid at the operating temperature.
Halides of these metals use to have a high boiling point: at least 1171°C at 1atm for I-VII salts. II-VII salts are less refractory, but oxides of most bivalent metals are. This means that the salt by-products will fall away from the reactants and products.
An example of a reactor is to come.
Marc Schaefer, aka Enthalpy