Molecules: You'd better learn to live with them.
The previous entry on cyclohexadiene reminded me of another important piece in some hydrogenations - Raney nickel.
If you have an alloy of nickel and aluminum, and put a chunk of it into a sodium hydroxide solution, you'll end up dissolving the aluminum selectively (generating some hydrogen gas along the way). You'll end up with a little aluminum, mostly nickel, with a high surface area and quite a bit of hydrogen gas adsorbed to the nickel - true to periodic theory, Ni acts much like Pd and Pt with respect to hydrogen.
Raney nickel comes as a slurry in water - if you let it get dry in air, it will quickly catalyze the oxidation of the adsorbed hydrogen and even start on fire! It's an unusual experience having a metal reagent you're supposed to keep in water - so much of this stuff is supposed to be far, far away.
See Derek Lowe's entries on hydrogenation.
Physical Science
Comments
We had a rainey nickel fire in our lab a few months ago. Student was filtering the reaction, and let the solvent get a bit too low. Pretty large fireball ensued. Probably 3 feet tall flame which spread to some cloth towels and tubing draped outside his hood. Those were thrown into the sink to self burn out. We had to empty a full fire extenguisher for that one, and the student singed an eyebrow.
Curiously the fire alarm never went off... We cleaned up, got a new extinguisher and went on with our chemistry.
Posted by: azmanam | September 21, 2007 2:59 PM
I made a really terrible pun about Raney nickel a while ago.
Posted by: Adam Engelhart | September 21, 2007 8:49 PM