Oct 24, 2009

Fantastic scenery in organic chemistry

Contrary to the media's portrayal of chemistry, in organic chemistry, the only colours a chemist comes across are yellow, black, or colourless (which is of course not a colour). Unlike its inorganic counterpart, organic chemistry is typically visually boring. There are notable exceptions though.

For me, it is so pleasing to the eye when you load a flash column with a solution of brown crude product from a reaction, and the brown junk gets stuck at the top. Of course, that joy is short lived if you find out that you failed to achieve good separation, or that the brown junk accounted for most of the weight of your starting material...

More visually spectacular however is the colour of a sodium benzophenone still. For those not familiar with this, the sodium and benzophenone system is used to dry (remove trace amounts of water from) a range of organic solvents, such as diethyl ether, benzene, tetrahydrofuran (THF). Thinly rolled (or drawn) sodium is added to the solvent along with benzophenone. When water is still present in the solvent, the solvent/benzophenone mixture is yellow. However, once the solvent is completely dry, the colour turns to a deep deep blue colour. The sight of a deep blue solution of THF with bits of metallic silver sodium bobbing up and down as the solvent refluxes brings tears to my eyes. Well not really, but it's a pretty awesome sight.

My all time favourite (for now) is in distillation of reagents. I had to distill TMSOTf the other day. Actually you'd think it shouldn't be yellow considering it was stored in an ampule. In any case, I distilled the stuff across into a Schlenk flask nice and clear, leaving the yellow residue behind. Beautiful!


  1. This post brings tears to my eyes. Not the good kind, but not the bad kind either. Just the kind you have when you really pity someone for finding such joy in a completely joyless area.

  2. KH + Water = Tears in eyes + No eyebrows

  3. LIES! there are plenty of awesome colors in organic chemistry. you just picked a subfield that doesn't appreciate them (switch to organic semiconductors, you'll see what i mean)...

    by the way, your blog is awesome, and i wish i'd discovered it sooner :)

  4. @Ψ*Ψ Thanks :) Yeah, in our subfield we certainly don't see a lot of colours, unless we're working in a natural product synthesis with a lot of conjugation. Just put on a reaction, and unsurprisingly, the colour is... yellow.

  5. try a refluxing ether still without a pressure-outlet.

    you'll have a lovely blue fountain in no time.

    but do stand back a bit, as the flame is quite hot :)

  6. Its a valuable content shared,would like to know more about it.

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