Sunday, August 1, 2010

Carbon Tetrachloride

Who could not feel sorry for this much maligned molecule. Simple in its structure but so complex in its properties. It is a nonpolar solvent that is still the best for bromination chemistry. Sure it has its environmental issues and has largely been replaced but it will never go away completely. More about the history of carbon tet in a minute. Let's talk about this blog for a moment. Many people think I named this blog after tetrachloromethane. I suppose that was one aspect of the name that appealed to me but it really was much more than that. There is more to Carbon Tet than the halomethane. I thought the name could also connote 'Tetrahedral Carbon' which would play right into the topics of asymmetric synthesis and catalysis. And, besides, I just like saying 'Carbon Tet! Carbon Tet!'.

But this is a chemistry blog, so let's talk a bit more about the molecule. Carbon tet was first prepared way back in 1839. The French chemist Henri Victor Regnault reacted chloroform with chlorine producing carbon tet and HCl. Now it is made from methane but before the 1950s it was prepared by chlorination of carbon disulfide.

As a halocarbon it is not flammable. In the early part of the 20th century carbon tetrachloride was used to extinguish fires. It was placed into brass bottles with a pump which was used to spray carbon tet onto a fire. If you tour some of the mansions of Newport, RI you may find some of the historic homes had vessels of carbon tet mounted near the ceiling. In the case of a fire the contents would spill out into the room to help douse the fire. It was also used as a dry cleaning solvent as it is particularly good at dissolving nonpolar grease.

Since the 1980s production of carbon tetrachloride has dropped precipitously due to its role in the destruction of the ozone layer. Industry has all but abandoned its use though it is still used in small quantities for research purposes. Once a cheap solvent, carbon tet now costs more than gold. If you have any, hang on to it! It could be your hedge against inflation.

1 comment:

Taitauwai said...

Hi! Welcome back. What have you been up to? Really miss reading your blog.