Distillation of Benzene and Workup of “Orange Stuff”

On Christmas I decided to make some more benzene because I was running low. I followed Nile Red’s video, as I had in the past, and got a 67% yield, which is a little low, but not bad.img_2777The distillation apparatus used to distill benzene from a mixture of sodium benzoate and sodium hydroxide.

The reactants probably could have been ground up more finely, and my sodium hydroxide was quite old and slightly damp.

After the first distillation, I realized that the orange impurity in the benzene is very fluorescent.img_2783
Fluorescence of crude benzene. Solid particles in the flask are calcium chloride prills used to dry it.

After the second distillation, I extracted the remaining orange solid with toluene and allowed this to evaporate to recrystallize. After nearly all the toluene had evaporated, I scraped the thick, orange paste into a small round bottom flask and pulled a vacuum on it for several hours. Then I broke up the lumps, and vacuumed the flask again for several hours, leaving me with 1.36 grams of dry orange powder. The fluorescence is very intense, but unfortunately my phone’s camera can not capture it very well.

sidebysideThe recrystallized byproduct in visible light and UV. The fluorescence is much brighter than it appears in the picture. In person, it is similar to the fluorescence of an orange highlighter.

The main component of the orange byproduct is probably tetracene, but there are likely smaller amounts of other mid weight polycyclic aromatic hydrocarbons present, such as anthracene, chrysene, phenanthrene, and pyrene. I plan to send a small amount to a friend to test using GC/MS.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s