Org Prep Daily

November 21, 2007

a young chemist = plague

Filed under: lab destruction — milkshake @ 10:45 pm

koshak123.jpg 

I started reading about chemistry around the age of 8 -  searching the compendiums and textbooks for ways of making  explosives. The next Christmas I got a Young Chemist set made in Bulgaria with its awfully mistranslated manual. The set was a great disappointment – very dull and didactic experiments: calcium carbonate plus diluted HCl, copper sulphate and iron wire, and so on.  I sweet-talked my mom into buying some additional chemicals for my set. The photo-supply shop had few interesting things I wanted. Soon after I was oxidizing acidified KI solution with hydrogen peroxide…

I was hoping to make NI3.NH3 but the recipe I  knew called for using solid iodine. (My dad once mentioned the compound  as we were gleefully “disposing” old firecrackers, gunpowder and nitrocellulose which he stashed away as a teenager, then many years later re-discovered in a shed.) I was getting only iodine solution from KI - it would not precipitate; probably an excess of HCl and KI kept I2 dissolved as triiodide. My mom worked in administration of the Academy of Science. As I accompanied her on a 1st May parade I was introduced to a chemist from some institute. (I think mom was bragging a little about my “advanced” interests). I shared my frustration about my attempts at preparing solid iodine.  “But you won’t need solid iodine for nitrogen triiodide - add ammonia to your iodine solution, NI3 should crash out” the helpful man suggested. Two weeks later I was already in a hospital with burned face and eyes. I accidentaly detonated  a spoonfull of dried NI3 few inches from my face, with no glasses. The explosion blew the window and my eardrums; I was back from the hospital in a week and I could see again – but the iodine-stained corneas made my eyes extremely sensitive and I wore dark glasses for months afterwards. I also lost the sense of smell for a long time - it came back eventually but even now my nose is not that discriminating. (Probably a good thing, for a chemist.)

There was a ban on experiments after the explosion: It took me months to talk my parents back into letting me grow some colorful crystals of chromium salts. Soon I was playing with calcium carbide and silver acetylide (we cracked an expensive garden window pane, by igniting a plastic bag filled with acetylene+oxygen mix) and I was making flash powders with permanganate and Al powder that was sold in drugstores as a silver paint pigment. As not to alarm my folks I covered up a badly scorched hand (the mishap also painted my face in Halloween style with the Mn + Al flashbang ashes). But then I got my parents really furious and for such a simple mistake:  A solid mix of urea peroxide and sodium dithionite self-ignites when moistened and as it burns rapidly it produces a stinky smoke-bomb- all kids in Prague in 80s knew this, it was the Menthos-and-soda of our generation. Dithionite was sold as a textile-dye remover, the urea peroxide tablets were available in hair color treatment kits. I left a bag of the dithionite powder in my shirt pocket, mom put the shirt together with the rest of the laundry to soak in a tub. The entire load of our family shirts (and mom’s undies) got bleached into funky splotchy pattens 

I was also making a bromoacetone tear-gas on the balcony on a 100g scale - by a procedure that I figured out by myself - it used acetone mixed with solid KBr to which was added a pre-mixed 30% hydrogen peroxide solution with 40% battery-grade sulfuric acid, very gradually through the reflux condenser. (I had no 3-neck flask or addition funnel and the cooling water was fed into the condenser by gravity, from a tubing dipped into a bucket) The bromine was generated and consumed in situ, the mix heated itself to reflux, the exothermic reaction was controlled by the rate of acid+peroxide addition and there was no induction period (unlike with Br2 + acetone) . When all Br2 color disapeared the mix cooled down and the product layer separated in the fridge as gorgeously refractive pale yellow heavy blobs…  

As this was going on in the 7th grade I naturally had to bring a sample of my bromoacetone to the school, to share the excitement of discovery. I was sitting way in the back on a math class and I did not know the bottle was leaking – the fumes must have been spreading away, to the front of the class - I did not understand why the other kids were getting antsy and reaching for hankies; eventually the tear front made it all the way to the teacher and she figured something was up - she evacuated the class and I “explained” that it was a glue for the scale-model plane building club that I attended after the school. I also isolated few mL of neat essence of cinnamon and of cloves by steam distillation, from about half a pound of the spices. My schoolmates put the oil eagerly all over themselves, undiluted – and complained when the cinammon oil burned their skin. And the concentrated cinnamon reek is very tiresome - our class was like a potpoury shop for days. 

I also distilled a crude mix containing ethyl mercaptan, made from a solution of EtBr and KHS. EtSH is best described as the essence of ass, and it has an incredibly low odor treshold. We gased a public transport bus with it: the driver was yelling, everybody running out - a great fun we thought at the time. Then my junior highschool buddies spilled the mercaptan in the school basement - they said they wanted to re-create a KGB gas torture chamber there. The heating gas pipe main control valve was in the basemet and soon the fire trucks were converging on the school with sirens blaring. We were evacuated for a suspected gas leak and no classes for us that afternoon. (I was very frightened we get nailed for this stunt).

While doing all this I managed to have some glass splinters taken out from my corneas for the second time as my home-made ignition cord short-ignited and a glass tube stuffed with acetoneperoxide blew into my face. I was making this material at home in multigram quantities - and I used a heat gun to dry it (the vapors had a pleasant minty smell…) As the powder was too fluffy I melted it on the kitchen stove, using a long cocktail spoon and toaster hotplate – and I melt-casted the liquid; the operation resulted in a loud bang and bent spoon whenever a drop spilled on the hotplate. (The neighbors soon came and asked if I was discharging a gun at home…) I was also buying half-kilo chunks of sulfur and I milled it in our fancy electric coffee-grinder. My “burritos” made from permanganate, sulfur and aluminum foil produced giant white fireworks, with burning metal flying into every direction.  

Eventually I got pretty close to getting expelled in the junior high: I liked to put a powdered acetonperoxide on my palm and I would ignite it: From a tiny heap of fluffy powder the deflagration produced an enormous gasoline-like fireball. (They still use benzoyl peroxide in Holywood for their exploding-car special effects). It was a rather cold flame and it was shooting upwards from the palm so it did not burn me. A stunning effect – and I was completely oblivious to what could have happen if the deflagration turned into detonation- until the day when I brought a hard pellet that I made by gluing the powder together with a collodium solution. To showcase it to my classmates, I intended to lit it on my palm but then I had a second thought and did it on the bench instead - in the classrom during a break. The pellet went off with a bang like a shotgun blast. I found myself explaining to our principal that it was a mere blank signal cartridge - a less involved story than the one about home-made materials… 

My moronity was gathering momentum: One day a large roll of home-made ignition cord (made from a twine soaked in a NaClO3 weed-killer solution) self-ignited in my pocket as it got into contact with red phosphorus on a matchbox strip. I actually stuffed the ignition cord roll into my jacket breast pocket and I put a box from jumbo-sized fireplace matches on top. The box had no matches in - it was filled with ten polyethylene tube bombletts packed with acetonperoxide. I put this all into the breast pocket of my jacket, the cord and the box with the charges – and I zipped the jacket up (it was difficult - the jacket was rather tight and the breast pocket overstuffed). My parents were already doing checks on me - I was trying to sneak out my stuff. Suddenly the whole roll of the ignition cord caught on fire on me, with a tremendous hiss. Before I could even unzip and throw the jacket off the roll burned itself down and  through the jacket, it rolled under the bed leaving a 4-inch wide scorched carpet trail behind. I looked at the paper match box with the explosive charges still in my pocket - it was charred but it did not burn through; the ignited roll of cord burrowed itself down so fast… I was finally shaken enough to quit: it was obvious even to me that if I put that cord roll into my breast pocket ontop of the box with charges, I would surely become a suicide bomber.  I paid for the carpet and jacket, I destroyed the acetonperoxide and never tempted my luck with explosives again. 

_______________________________________________________________ 

Shortly after the last incident with explosives I got access to a decent laboratory owned by a youth center - and I started doing a real chemistry, namely I was trying to synthesize papaverine. I soon found that making  bangs and fires was dull - compared to the excitement of synthetic chemistry. With the free run of the cabinets stocked with NaN3, picric acid and nitromethane there was no challenge in making things go off.  I was almost unsupervised and I  had several bad accidents in that lab - the nitrations and brominations that I mixed up on a grand scale tended to erupt into volcanoes; from then on I was busy trying not to produce the bangs and fires.

I continued to be an exceptionally bad experimental chemist ever since  and I got fired from five labs in three institutions in Prague within few years there. The mishaps I had in these labs were bot grotesque and scary and I ruined a staggering amount of expensive glassware also. I earned a nick “Bořivoj” -  it translates as “the man who tears down the places”.

So if you are just starting your chemistry career and if you think you are clumsy and inadequate, don’t feel that way. Everybody has a personal quota to fill – of dumb things to do, of fume hoods to set on fire and the labs to flood.  But remeber to wear the protective glasses.  Never make acetonperoxide or iodonitride and never load up mol-scale preparations on the first run.

November 12, 2007

Only under Communism

Filed under: Uncategorized — milkshake @ 10:05 pm

chaos.jpg Credit: Jiri Sliva

When I was doing my thesis work in Prague I was stubborn about working on my own project and for that I needed a lab. A great man, docent Karel Capek took me in. He was a carbohydrate chemist, and he also had a fine reputation as a pharma process chemist. He once said that all his research papers would perhaps amount to a footnote in some monograph but he was proud of the projects he did for the industry – like developing a new Tamoxifen manufacturing route which made it available to the patients in Czechoslovakia. (The drug would be too expensive to import. For his patent-busting synthetic process he got dragged into a litigation by ICI – but he prevailed). Docent Capek had his hand in a number of useful chemical processes, mostly manufacturing drugs and food additives. And probably his weirdest industry experience was the project of recycling chloramphenicol base. I think the story is quite illustrative of the chemistry done under the ‘real socialism’.

Chloramphenicol used to be an important antibiotic and the Spofa plant was the main producer in the Eastern Bloc. One enantiomer of the drug is active, the other one is only toxic and the amine precursor (sans dichloroacetyl) can be resolved by fractional crystallization. This separation was done in Spofa on a ton scale and they had a problem with the unwanted enantiomer – for years they have been putting this sideproduct into barrels. When they eventually run out of the storage space they took the barrels to a landfill… Capek was told that a great reward awaited the man who finds a way of recycling the unwanted enantiomer. (“You build yourself a villa with the money you get for solving this thing.”)

And Capek promptly solved the problem – an oxidation of the benzylic OH produced an easy-to-racemize aminoketone intermediate that was one step back on the synthetic scheme. The chemistry was nice and simple, just one step (the oxidation was done on the unprotected amino-diol with 2 chiral centers – and the used oxidant was aqueous KBrO3) . But under the ‘real socialism’ even the simplest things could never be quite as simple – everything was very political and red-tape ridden and management did not care about the profitability because every silly detail was planed out centrally. Then there was a resistance on the plant floor – against any changes in the established manufacturing route. A headache-producing innovation was best to be avoided. And this oxidation procedure was a radical chain reaction that was initiated by visible light – it needed a dedicated glass-top reactor equipped with floodlights and there were no funds allocated for such pilot project in the production plan, etc.

One day a reactor with 2,4,5-trichlorophenol in Seveso plant in Italy overheated and bursted. The accident released a kilo quantity of the TCDD dioxin and contaminated wide area in a spectacular fashion; there were hundreds of cases of serious poisoning. The Seveso plant was shut down and like in Chernobyl, the center zone remained off limits for years until extensive decontamination could be completed. The Seveso plant was also the world’s main producer of p-nitroacetophenone – the starting material in the Spofa synthesis of chloramphenicol.

Since no other supplier could suddenly provide Spofa with the starting material in the sufficient quantity, the Spofa management was getting desperate. So they built the illuminated reactor. They sent bulldozers on an excavation mission. And in the end there was so much of the “undesired” enantiomer dug out from the landfill that for a year all chloramphenicol in Czechoslovakia was manufactured from those recovered barrels.

Docent Capek never got the money to build a mansion – but the brightly-lit oxidation reactor became a showpiece impressing the visitors in the Spofa plant…

November 8, 2007

Dioxins Are Us

Filed under: industry life — milkshake @ 2:18 am

mile-deti.jpg

The main dioxin-cotaminated active component of Agent Orange, 2,4,5-trichlorophenoxyacetic acid, was manufactured in Czechoslovakia from 1965 to 1968, for US military use, and supplied directly to South Vietnam. There were other suppliers but the Czech-made 2,4,5-T was the cheapest- and it also had an exceptionally high dioxin content.

Spolana Neratovice is a large organochlorine plant that manufactures bulk chemicals and vinyl plastics. For a long time it also served as the main producer of insecticides in the Eastern Bloc. A popular insecticide  hexachlorocyclohexane is made by photochlorination of benzene; HCH has several stereoisomers and only one of them, gamma-HCH aka Lindane, has the useful activity/toxicity profile - the undesired isomers are removed by crystallization. As the purified Lindane constitutes only a fraction of the crude chlorinated mixture, the Lindane manufacture generates a huge waste stream. The chemists in Neratovice were offered bonuses and other incentives to find ways of using the HCH waste for anything of value. One solution of the problem was to treat the undesired HCH isomers with alkali at high temperatures to bring about elimination+hydrolysis. This was done chiefly because one of the products, 2,4,5-trichlorophenol, was the key intermediate for production of a potent herbicide used in agriculture, 2,4,5-T. And  suddenly there was a growing demand for 2,4,5-T and the Czechs were eager to earn some hard currency…

2,4,5-trichlorophenol when heated under strongly basic conditions readily cyclizes to TCDD - the most dangerous dioxin, as we know now. But at the time, long before Seveso and Yuschenko, dioxin formation was considered just a nuisance -one of many yield/purity-affecting side-reactions. (The US military was not picky about the product purity.) 

The communist government of Czechoslovakia never acknowledged its part in the dioxin disaster -  we were told that Agent Orange was an especially terrible poison invented by the imperialists… There has been a substantial direct economic aid to Vietnam over many years though, this included also visitor-worker jobs and student visas (so there is now a substantial Vietnamese community in the cities). I wondered why Vietnam was the recipient of Czech help - but not Cuba, Angola, Syria, North Korea or any other friendly totalitarian regime. Now I think it was quite likely the bad conscience about the Spolana war legacy - and that’s how we got our great & fun-loving Vietnamese students in the Charles Uni organic chemistry class.

Credit: Drugs and Poisons for bringing up the subject of the Rainbow Herbicides

Addendum: A massive Seveso-like poisoning of about 60 workers from 2,4,5-T reactor explosion in Spolana in 1968 ended the production of this material there. The Spolana plant used to have a huge site contaminatition problem; some dioxin-and-mercury buildings were closed off but the cleanup got undeway only after the summer of 2002 when a record flood washed everything into Elbe river. The rising water in 2002 floods also lifted the massive storage tanks for liquified chlorine.  The connecting pipes tore off and about 100 tons of chlorine got out. The yellow cloud fortunately missed the nearby towns. (The slow rate of the underwater release also helped.) The typical inventory at the plant used to be 1000 tonns of liquified chlorine. The main process using chlorine - vinyl chloride production - was taken down some time before the flood because the hydrocarbon cracking unit that provided ethylene for the process blew up. Workers ignited heating gas in the furnaces – a gas that was already mixed with air – and they landed away in some distance but alive. To repair the damage the production got delayed and the electrolysis was halted also. And so by enormous luck the chlorine tanks stood near-empty when the flood ripped them from the pipes.

November 3, 2007

High temperatures

Filed under: procedures — milkshake @ 10:58 am

I was recently attempting cyclizations that are best done thermally but they did not work at 250C (unlike the literature precedent) so I investigated them after the Russian manner; in diphenyl ether and under pressure at 290 - 340C they confessed everything.

The temperatures needed were outside the range of a Biotage microwave reactor and oil bath. I did not have an alloy bath and I was looking for some cheap high-temperature bath liquid (I needed temperature reproducibility and the sand bath/solid metal block temperature readings are notoriously unreliable). I found that molten sodium nitrite worked well for the purpose: A 60mL beaker was filled with solid NaNO2 and buried in sand bath obtained by filling a heating mantle with sand (the mantle was controlled via Variac transformer). This setup was placed on top of a stirplate. When NaNO2 melted a magnetic stirbar rod was added (a common stirbar from which the Teflon coating was shaved off) and bath behaved nicely in range 280-340C. I also found out that I could extend the range downwards a little, approximately to 260C-340, by adding few spoons of KNO3. The bath starts bubbling a bit at 360C because NaNO2 begins to decompose slowly above 320C but a 20 min heating to 340 was without problems. My main worry was what might have happened if my reaction vial had ruptured and the organics got into the bath: molten NaNO2 is a pretty strong oxidant and tiny bits of paper burst into flames when fed into the bath…

If you have run high-temperature reactions like this – please what kind of bath did you use?

Addendum: A 2:1 (by weight) fused mixture of KNO3 and LiNO3 melts around 140-160C and solidifies at 125C. It should be far more heat resistant than the NaNO2-based mixtures and thus it should be applicable even for very high temperatures (>300C). LiNO3 is not expensive – but it is somewhat hygroscopic. Of course spilling a reaction mixture into the bath would still backfire :) Thanks Kai for the reference.

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