Column shield jacket

A solution of 9-diazo-9f/-fluorene (200 mg, 1.0 mmol) in styrene (20 mL, 18.2 g, 0.17 mol) was placed in a Pyrex outer jacket surrounding a quartz immersion well. After being purged with a dry N2 gas stream for 2 h, the solution was irradiated for 24 h with a Hanovia 450-W medium-pressure Hg lamp placed within the water-cooled immersion well and shielded by a cylindrical uranium glass filter to remove all wavelengths below 330 nm. After removal of excess styrene in vacuo, yellow crystals were observed. Purification by chromatography on a column of silica gel (230-400 mesh) with 20% benzene in hexane as eluant gave 246 mg (92%) of product mp 127 C. 

Another potential danger is the implosion of the outer vacuum jacket. For safety, we wrap strips of transparent tape in a grid around the column and place a Plexiglas shield in front of it when in use. 

The glass jacket shields the column from drafts and minimizes temperature variations from run to run. Air is blown through the annular space between the column and glass jacket to cool the column at the end of each analysis. 

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