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Greener Chemistry Stirs Up Debate

University of Cincinnati
James Mack is doing solvent-free chemistry and is the only American speaking at an international conference about it this week.

First, an elementary lesson in solvents. They are used in a lot of things including drugs, tires, plastics and more. Most people believe solvents are necessary to mix certain chemical elements together.

James Mack is an associate professor of chemistry at the University of Cincinnati. “So let’s suppose if you wanted to mix together salt. So, you had salt. Salt is a polar molecule that is going to be soluble in another polar molecule like water. So you see, salt dissolves in water and you can get chemical reactions to occur.”

Then Mack explains if you wanted to make aspirin and you had molecules that were non-polar, a molecule or solvent that you could use is something like benzene. Benzene is a carcinogen that comes from the petroleum industry.

He says, “So all the things that you hear about from the petroleum industry that you want to get rid of and try not to pollute the environment are all the things typically used in the pharmaceutical industry as well as products used to make things we use everyday.”

Credit Ann Thompson / WVXU
UC undergrad chemistry major Mica Cunningham and doctoral student Heather Hopgood prepare a vial in the ball mill which shakes the molecules.

When it comes to drugs, Mack says the federal government requires that all solvents be removed from pharmaceuticals before they are sold. It’s expensive to do. But what if solvents weren’t needed? Mack and his students are doing chemistry without solvents.

A loud machine, called a ball mill, breaks up the molecules by shaking them. Using a custom-made stainless steel vial and a stainless steel ball, the molecules bash into one another over a 16 hour period.

Heather Hopgood is using the machine, nicknamed T-Rex, Dual Mill, Betty Spaghetti and Beast. She’ll get her PhD next spring. “Organic chemists, they dissolve everything so you can get down to that molecular and atomic level so they are able to interact. The problem if you don’t dissolve then is you really only have the outside surface. If you think about the salt cube, you only have the outside surface of the salt that can interact with something else.”

But the ball mill that shakes the molecules in a figure eight pattern apparently solves that problem. This kind of chemistry is called mechanochemistry, or solvent-free chemistry. James Mack is trying to determine the rules of this system as he converts thermal energy to mechanical energy.

Mack says there is always going to be a push to use petroleum in everyday life because it’s a booming business. He says there is a 22 percent waste in the pharmaceutical industry and much of that waste is hazardous. “If you could see the volatile organic compounds in the environment - if it was color coded in some way - then I think people would have a much different viewpoint of how dangerous these things are and how important it is to limit their use.”

The pharmaceutical industry is looking for ways to cut its hazardous waste.

Mack’s research is funded by the National Science Foundation. He leaves this week for China as the only American to speak at the International Symposium on Mechanochemistry. Solvent-free chemistry is already big in Europe and Asia. It’s something UC chemistry major Mica Cunningham hopes catches on in the U.S.

She says, “I love saving the environment and stuff and you don’t think about these things when you do chemistry. You literally just throw everything away and to have that idea, just to use the ball mill, not using solvents, that saves so much of the planet so why not do it?”

Mack believes it could take 10 to 15 years to implement this greener type of chemistry.