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Blog Profile / Org Prep Daily


URL :http://orgprepdaily.wordpress.com/
Filed Under:Academics / Chemistry
Posts on Regator:69
Posts / Week:0.2
Archived Since:July 23, 2009

Blog Post Archive

Pleasures of Process Development

Refluxed in 12 molar HCl Carefully watched for a frothing Painstakingly drained from the reactor To strip down and scrub off that gross thing My bosses, I tried please believe me I’m doing my best as you insist I’m ashamed of the material I burned through I’m ashamed of the deadlines I missed But if […]

Pleasures of Process Development

I refluxed six liters of HCl, 12M And fought a terrible foaming Now I can filter that mud, Then take the reactor apart To clean the whole damn thing

A kilo-scale hydrogenation reactor?

I have been running some kilo-scale hydrogenations of our polymers, at atmospheric pressure, under balloons, and it is a bit of a chore. It would be nice to have something akin to a giant-sized Parr shaker and run the hydrogenation at few bars, to reduce the catalyst loading and shorten the reaction time. I wanted […]

O-acetyl L-tyrosine

1. HTyr(Ac)OH.MsOH: In a 2L round flask with a wide 29/42 joint and a large egg-shaped stir bar, neat methanesulfonic acid 80mL (1.2 mol) was added to a slurry of L-tyrosine 181.2g (1.0 mol) in acetic acid 0.5L and the resulting warm mixture was stirred vigorously without cooling until complete tyrosine dissolution. The flask walls […]

nitrilotriacetic acid anhydride; 4-(carboxymethyl)-morpholine-2,6-dione

30 mL of acetanhydride (317 mmol) was added to a slurry of nitrilotriacetic acid N(CH2CO2H)3 50.0g (261.5 mmol) in DMF 100mL. N-methylimidazole 0.21mL (1 mol%) was added and the mixture was stirred and heated on a 60 C oil bath for 6 hours under Ar – the mixture gradually became homogenous. Neat allyl bromide 0.5mL […]

Happy 4th!

                                              Credit: Jiri Sliva

Oil pump desanguination – brilliant!

I just had the fastest pump oil change of my career, thanks to invention of my colleague. We use giant Welsh belt-driven pumps installed in steel cabinets under the hoods and these beasts are reliable – but so heavy: they take just over 3 liters of oil to fill, and the whole thing weights about […]

Blood curdles if you don’t stir it

Trityl group on sulfur is unstable to LiAlH4 reduction. It falls off as triphenylmethyl anion – that’s where the gorgeous red color is coming from. (Unlike trityl cation, which is canary yellow). I did not know about this S-trityl instability – my Greene book (3rd edition) for example mentions only the electrochemical reduction at highly [...]

Uroboros

I have been making water-soluble polymers with biomedical applications for the last 16 months and it is quite satisfying: Our macromolecules are usually well behaved – they extract into organic phase. They precipitate as a snow-white fluffy crystalline solid, on a kilo scale. They even have beautiful NMR spectra. Unfortunately, such was not the case [...]

Shake and pray

There is a pop-chem procedure on YouTube that I find astonishing – it beats the Diet Coke and Mentos trick hands down: A guy loads NaOH dry solid pellets, about 1 inch high, into a plastic bottle, and adds about 2-3 inch thick layer of dry ammonium nitrate granules. Then he fills the bottle with [...]

Uroboros

. So I have been making water-soluble polymers with biomedical applications for the last 16 months and its quite satisfying. Some macromolecules are nicely behaved – they extract into organic phase if you want them to and they even precipitate as a snow-white crystalline solid, on a pound scale. Unfortunately the frothy solution in the [...]

S-tritylthioacetic acid

Neat mercaptoacetic acid 24.0g (260 mmol, about 18 mL) was added in one portion to a solution of trityl chloride 58.0g (208.0 mmol) in benzene 200mL (non-anhydrous, ACS grade). The flask was equipped with a gas outlet Drierite tube and the mixture was stirred for 17 hours: The HCl gas evolution ceased at this point [...]

Shake and pray

There is a popular synthetic organic chemistry procedure on YouTube that I find absolutely astonishing. It beats the Diet Coke and Mentos trick hands down. It goes like this: A masked dude – or a gal – takes an empty plastic bottle with a cap (preferably a wide mouth bottle – i.e. from a large [...]

Potassium hydride self-ignition

I had a rather bad fire last Friday. I was washing a large jacketed glass reaction vessel used for polymer scale-ups, after pouring the reaction mixture out, and a tiny particle of potassium hydride (from this poorly quenched reaction) that was adhering to the bottom of the reaction flask ignited just as I was giving [...]

Potassium hydride self-ignition

I had a rather bad fire last Friday, probably the most serious lab mishap in 15+ years. As I was washing a large jacketed glass reaction vessel used for polymer scale-ups, a tiny particle of potassium hydride from a poorly quenched reaction – a particle that was adhering to the bottom of an empty flask [...]

Replacement process solvents

A recent Organic Process R&D editorial (thanks Chemjobber for pointing it out) publicizes Pfizer Process green solvent replacement chart that discourages chemists from using solvents that are either known to be toxic or are expensive to dispose as waste. OPR&D makes it now a submission policy too, and if you submit a paper that uses a [...]

Fighting Pd colloids with salt

I have been running some debenzylations of a macromolecule with the Pearlman catalyst  in water. The hydrogenation often results in reaction mixtures with persistant dark colloids. I have seen this kind of problem before, with small molecule-hydrogenations on Pd/C though it was never quite as bad. I suppose this polymer loves to stabilize Pd nanoparticles [...]

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