Is an experiment with an air sensitive catalyst an appropriate way to gauge experimental skill and technique to handle a pyrophoric reagent? That appeared to be one of the arguments that the defense attorney of University of California, Los Angeles, chemistry professor Patrick G. Harran was setting up last month in a court hearing.
Harran faces felony charges of labor code violations relating to the death of researcher Sheharbano (Sheri) Sangji. Sangji died from injuries sustained in a 2008 fire in Harran’s lab that started when she was handling tert-butyllithium.
C&EN and the Safety Zone covered the preliminary hearing in Harran’s case. One of the charges centers on failing to provide chemical safety training. In cross-examination of prosecution witnesses, Harran’s defense attorney, Thomas O’Brien, seemed to be building the assertion that Harran had provided sufficient training and oversight by watching Sangji do an earlier experiment involving a Grubbs II catalyst. From Sangji’s lab notebook, here are the experimental details:
Oct. 14, 2008, experiment that Harran observed
- Air-sensitive reagent was a Grubbs II catalyst, which loses potency on exposure to air
- Working in a glove bag, Sangji added 63 mg of the catalyst to a 50-mL flask. She then added 2.5 mL of
1,2-dichloromethane1,2-dichloroethane to the flask, followed by 250 mg of vinyl glycine dissolved in 2.5 mL of 1,2-dichloromethane1,2-dichloroethane and 256 mg of undecen-1-ol simultaneously over 20 minutes. She lowered the flask into an 80 ºC oil bath and stirred it under reflux for 20 hours. She sampled the reaction solution to run thin-layer chromatography at 16 and 20 hours. She filtered the solution and then purified it on a silica gel column.
- Sangji’s notes aren’t clear whether this entire process was done in a glove bag or just the step of weighing the catalyst.
Dec. 28, 2008, experiment that started the fire
- Air-sensitive reagent was tert-butyllithium (tBuLi), which ignites spontaneously in air
- Sangji was scaling up an Oct. 17, 2008 experiment to produce 4-hydroxy-4-vinyl decane. The first step of the synthesis was to generate vinyllithium. In October, she added 28 mL anhydrous ether and 3.0 mL vinyl bromide to a 200-mL flask. After stirring the mixture for 15 min at -78 ºC, she added 54 mL of 1.67 M tBuLi. She stirred the mixture for two hours, moved it to a 0 ºC bath for 30 minutes, and took it back to -78 ºC. She then used a double-tipped needle to transfer 3.90 mL of 4-undecanone in 6 mL ether to the vinyllithium solution. She stirred the solution for two hours, then quenched it with sodium bicarbonate. She put the quenched mixture in a separatory funnel, collected the organic phase, dried it to remove residual water, and rotovapped it to remove the solvent from the product.
- Sangji doesn’t say it in her notebook, but she was probably not working in a glove bag to do this reaction. Going by what she did in December, she was more likely working in a hood, running nitrogen lines to the tBuLi bottle and reagent flask, and using a syringe to transfer tBuLi from one to the other.
- Sangji scaled up this experiment three-fold in December and used a 60-mL syringe for the tBuLi transfer. We know that she did not clamp the bottle, and so was likely holding it upside down in one hand while manipulating the syringe in the other. She was probably on her second or third transfer, reusing the needle and syringe, when the syringe plunger came out of the barrel, exposing the tBuLi to air and starting the fire. Sangji’s clothes caught fire and she was burned on her thighs, torso, arms, and neck.
What say you, Safety Zone readers? Was a 63-mg Grubbs II experiment an appropriate one by which to gauge Sangji’s skills and technique to handle tBuLi at the 54- or 160-mL scale?