A quick post to share my experience with this reagent, as it was really a joy to work with.
Firstly, diphenyl ether is a solid at room temperature, melting at 25-26 C. I was using it as a solvent for a high temperature reaction – it seems like a primary use for it is to enable quite high temperature reactions, as its reflux is 258 C. It also demonstrated that I need a thermometer that goes over 250 C. Let me also add that this is notably higher than I like to work at, but when the procedure calls for it, I stand ready.
Anyway, this was supposed to be the solvent but fortunately you can get essentially the same thing as Dowtherm A and that is actually a pourable liquid.
The procedure was one in which a solid was added to the heated Dowtherm A then heated at reflux to give a cyclization reaction. Adding solid to a reaction vessel at above 200 C is not among my favorite procedure methods.
Getting rid of such a high boiling solvent was, surprisingly, not so bad as my product was a solid and it was just a matter of washing the pad with a more friendly solvent. However, getting rid of it off the glassware was somehow more tricky and all the more annoying because of its peculiar smell, which seems to linger for quite some time on anything it is spilled on.
The best part was how I got to do it again as it worked so well. And how I am penciled it to run it when we ever need some more of that material.