Dealing With Unstable Compounds: Part 4

http://en.wikipedia.org/wiki/Thiazyl

This stuff was a hoot. The synthesis was something out of alchemy and gave a wicked smelling residue from the filtered reaction mixture that had at least four different crystalline compounds in it. Pasteur separation of the products and repeated recrystallisation gave a binary mixture of sulphur and S4N4. This is where it becomes interesting. S4N4 is a contact explosive and the sulphur moderates the explosiveness (remove the sulphur and it becomes treacherously unstable). My first research job as an undergraduate was to recrystallize S4N4 until "it crackles when you grind it" (that was what I was told). Not a lie. The crackling was the result of tiny explosions between the mortar and the pestle and indicated that the S4N4 was pure enough to use. Later I would go to work at a lab in Durham England where an amazing chemist from Czechoslovakia prepared very pure S4N4 and purified it further by sublimation. One night a small beaker of the stuff just spontaneously exploded and destroyed a lab bench (one end was wrecked and the bench was split its entire length. What was ominous was that the explosion occurred without any initiation. That was new and we all started to find ways to do our chemistry without S4N4. When I taught this section in my inorganic chemistry courses I would bring in some S4N4 crystals and grind them before the students and then tap the powder and get a small bang like a gunpowder cap. Then the students could smell the sulphur containing decomposition products in the air above the mortar. That was until I had a larger class and used more crystals than usual. I was using my large, very expensive agate mortar and pestle and the explosion was a bit more exciting than usual. The explosion jumped the pestle out of my hand and it shot across the classroom leaving my hand numb and the mortar itself was split in two. Best ... classroom .... demo ... ever.

Dealing With Unstable Compounds: Part 3

Ah yes, metal azides. Most excellent and unpredictable explosions.

My first job in a research group was to act as the “hands” for a graduate student that had been preparing a new Tellurium azide. He had prepared a small amount (about 50 mg) in a Monel can and was in the drybox working up the reaction when it exploded in the bottom of the can. Unfortunately, the metal can served to focus the explosion and neatly sheared off the ends of two of his fingers thus creating a job opening for me. My first job was to repeat the chemistry that the graduate student had been doing. They said that it would be safer because I would do it in a glass vessel so the explosions would not be as extreme (the bursting pressure of a well made glass vessel was about 10 atmosheres according the group elders). Thankfully the grad student was so close to completion that they decided he would not need the reaction to graduate and I was moved over to the sulphur-nitrogen work.

Dealing With Unstable Compounds: Part 2

Preparing the post below brought up some great old memories. There was a point in my research career that I really, really wanted to get into phosphaalkene and phosphaalkyne chemistry. The problem was that the entry compound was tris(trimethyl silyl)phosphine [P(TMS)3] which one could buy at that time for $100 per gram. The only option was to make it. The best preparation was refined by Manfred Regitz and his glorious mitarbeiters in Germany. Get this the reaction involved taking pyrophoric white phosphorus (horrifyingly toxic) and heating it in explosively sensitive thf to reflux while slowly dropping liquid Na/K alloy (the liquid metal reduction fire from God) from a pressure equalized dropping funnel (PEDF) all under a dynamic bed of Argon. Once the addition of Na/K was complete you then opened a second PEDF that contained lashing of trimethyl silyl chloride. After the screaming and weeping you then fractionally distill the product to collect the P(TMS)3. I had to hire a post-doc for the one task of developing this reaction in our lab. I later learned that Regitz was so concerned about th potential for disaster in this preparation that he actually had a concrete bunker built in the chemistry department parking lot where his students could do the reaction and if something happened they wouldn't take the chemistry department building out. I had a hard time convincing my post-doc to wear safety glasses.

Anyway the product was air sensitive and would spontaneously catch fire in air and if it came in contact with anything such as cloth or tissue a fire would quickly occur. Needless to say we handled it with the greatest of care.

One day I decided to go to a conference. It was my habit to call back to my lab at dinner time to get caught up on what was going on in my research group. On this one day I was in a phone booth and I called the lab to have my post-doc answer the phone and say the words all supervisors dread ...

"Oh Professor H. it's good that you called ... the firemen have just left."

It turns out that, despite a strict cleaning protocol concerning the glassware used in the P(TMS)3 preparation, a PEDF with a teeny tiny speck of Na/K had somehow made it into our huge rubbermaid ethanol/KOH bath. Hilarity ensued as the teeny tiny speck of Na/K set fire to the ethanol and we immediately had a huge serving of glassware flambe. The column of fire roared up to the ceiling and my post-doc and a graduate student (net cost to me per year ~ $ 46,000) wasted three CO2 fire extinguishers trying to put the fire out. No luck. By now the sides of the rubbermaid container was starting to melt and the contents drip out onto the floor in a scene reminiscent of the movie "Volcano". It was my undergraduate summer student (net cost to me per year ~ $ 0) who understood the situation and found a dry powder fire extinguisher and put out the fire in seconds.

Yes, the fire was out but now every surface in the lab was contaminated with the powder and we would be weeks cleaning the lab. I have no doubt that there are surfaces in that lab that are still contaminated.

The Clock Resets to 505 Days

As of today, Tuesday, April 17, 2007
There are 0 days left in the lecture schedule, only the exams remain.

AND

There are 505 days until the next day that I have to lecture here again (the first day of classes in the fall semester 2008).

Teach us to number our days that we may apply our hearts unto wisdom Psalm 90 : 12

Where will Professor Honeydew go on sabbatical you ask?

May 2007 Preparation for conference presentation on research at National Chemistry Conference of the Chemical Institute of Canada in Winnipeg.

May – August 2007 Travel to the Chemistry Department of UNB (at the invitation of Professor P.) to initiate a new study on the unusual equilibrium between the cations in the reaction of SNS+ with alkenes.




September – December 2007 Travel to the Chemistry Department of MtAU (at the invitation of Professor B.) to work on a project involving low valent phosphides from tris(trimethylsilyl)phosphine



January – May 2008 Manuscript preparation and submission (at home in Moncton) on the two projects listed above and preparation of conference presentations for both projects in May 2008 at National Chemistry Conference of the Chemical Institute of Canada in Edmonton

June – July 2008 Travel to the Chemistry Department of Dalhousie University (at the invitation of Professor B.) to investigate reactive strained rings incorporating phosphorus.




August 2008 Vacation and preparation for the fall semester 2008

There are other projects I am thinking about including:

Learning how to make DSC measurements on air-sensitive compounds.
Conducting a survey of the first year chemistry courses in our region.
Initiating a project with Professor C. at SMU just for the fun of it.