Org Prep Daily

August 19, 2015

How to destroy eighteen teflon Schlenk stopcocks in one go

Filed under: lab destruction — milkshake @ 11:04 am

It turns out that the teflon air-free stopcocks used in Schlenk-ware aren’t all teflon, they have little viton O-rings hidden under two teflon sleeve rings (=the green bits that provide the actual seal contact surface). And viton swells in acetone like a sponge…

After finishing a year-long scaleup project done with boiling conc. HCl, I had to overhaul my hood, because of all the corrosion. Long story short, the vacuum manifold glass parts went into a base bath, the O-rings and air-free stopcocks sat in a bucket with acetone. About an hour later, I noticed that the O-rings from manifold joints were already up to double in size. Those old swollen O-rings may eventually return close to their original size when they dry up. But all stopcocks from a long double bank manifold got ruined – the green teflon parts, stretched and lifted by the bulging viton from inside, are going to stay out of shape for good.

It is nice to learn that these teflon air free stopcocks used for all kinds of harsh chemistry actually won’t tolerate immersion in a solvent like acetone, DCM, THF. The ones I just killed cost $500 plus one week of wait-time to replace.



  1. I hear you are the expert on phenylacetic acid. We have a horrible smell in the lab and we are pretty sure that is the cause. How do you get rid of the smell?

    Comment by Rachelle — September 15, 2015 @ 11:06 am

    • I would first try to identify the source of stench – did someone spill it on the floor, or pour it over the waste drum, spilled it around the balances? I would wash the area thoroughly with iPrOH or ethanol, maybe afterwards also use some ammonia diluted with iPrOH on it, to neutralize. When it is vinyl flooring that was soaked with the stuff, just cut out the vinyl flooring and re-do the flooring in the area. Otherwise it will never go away.

      At my previous job, we had a less than brilliant Romanian dude who dropped half a kilo of phenacetyl chloride on the floor and did lousy cleanup job, that just smeared the stuff everywhere. Fortunately it was not my lab, just my neighbors. (Everyone in that lab smelled like sweet stale urine for the next year, the stuff really gets into your clothes and you smell like you have a little incontinence problem.)

      Comment by milkshake — September 15, 2015 @ 12:00 pm

      • Thanks for the info. The biggest problem is we don’t know where it was spilled. We’ve been cleaning everything

        Comment by R — September 16, 2015 @ 11:40 am

        • You need to do some more sniffing around. If you don’t identify the source it will never stop – as you know a little bit carries a long way, and it has low volatility so it stays stinky practically indefinitely. Only when you take out the source it makes sense to pour a bottle of ammonia in a large tray on the floor (before a long holiday weekend) and shut the door and post the “Do not enter” signs/

          Comment by milkshake — September 16, 2015 @ 2:19 pm

  2. I have a compound that is the sulfate salt or a pharmaceutical I need to remove the salt bit the compound also bears a phenol. I fear that passing it over basic alumina to remove the salt will remove my compound any tips

    Comment by sam — September 22, 2015 @ 9:06 am

    • I would take some quaternary ammonium Amberlyst, of the structure Polymer-NMe3+ Cl- the kind that swells in MeOH. I would swell it in hot de-ionized water (few re-slurries/decantations), then I would re-slurry it couple times with half-saturated NaHCO3, then wash thoroughly with water and then methanol. I would pass your sulfate salt in methanol through the bicarbonate column, and I would TLC check the eluates to make sure all your material is already washed out from the column, then just evaporate. You want to use at least ten times the theoretic ammount of ion exchanger (20 meq. for 1 mmol of your sulfate)

      Comment by milkshake — September 22, 2015 @ 1:45 pm

      • any tips if the compound does not appear to be methanol soluble? It is soluble in water can I try DMF then add methanol before adding to the amberlyst?

        Comment by Sam — September 24, 2015 @ 6:09 pm

        • you can use water equally well – it is even better for ion exchange resins than methanol. Only the evaporation of solutions on rotavap is going to be more painful. (Maybe you could freeze and lyophilize your eluates, if you are not in hurry. That way you can get a much nicer solid product.)

          Comment by milkshake — September 24, 2015 @ 6:37 pm

  3. Do you have a published protocol for the use of trifliroethanol as a solvent to react amines and epoxides

    Comment by sam — October 2, 2015 @ 3:06 pm

    • I could not find the exact patent procedure that I was doing, but I remember using a concentrated solution of the epoxide (about 1:3 by volume) in trifluoroethanol, cooling the epoxide-TFE solution on ice, adding morpholine (1.1eq.) and letting the cooling bath expire to R.T. overnight, then evaporating to dryness and drying on highvac.

      A quick Scifinder search gives these three references, but I did not use them (the work was done about 2001-2002):

      Journal of Fluorine Chemistry (2010), 131(1), 106-110
      Organic & Biomolecular Chemistry (2009), 7(10), 2026-8
      Chemistry – A European Journal (2008), 14(5), 1638-1647

      Comment by milkshake — October 2, 2015 @ 3:58 pm

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