Atom Economy – Green Chemistry Principle #2


Welcome back and thanks for tuning in. Today we’re going to tell you about the second principle of green chemistry, atom economy, which describes an important concept for chemists to consider when they are making molecules. In essence, this principle is very similar to
principle number one, prevention, but in this case we are preventing waste at the atomic scale maximizing the incorporation of atoms in the final product from all the molecules that are part of the reaction. Today my colleague Melanie and I will demonstrate how this works. We will each make the same molecule, the common over-the-counter painkiller ibuprofen. We have chosen two industrial processes that have been used to make ibuprofen and will complete the processes using coins instead of atoms so we can see exactly how economical
each reaction really is. We have arbitrarily assigned the
following values to the coins for this reaction. What do you think Brian? Ready
to get started? Let’s do it! Alright. Okay. Now that we’re both finished, let’s take a look at the two processes and do some atom economy calculations. You know Ryan, it looks like your reaction might have been a bit more wasteful than mine. Yeah it’s looking like yours is just a little, no, uh, a lot of more efficient than mine. Let’s just um, no that’s a lot of money. Let’s calculate the percent atom economy of each reaction and see how they stack up. So, to do the calculation we take the molar mass of the product and divide that by the molar
mass of all of the reactants used. The atom economy from my reaction is only… 40 percent, um, yeah… and uh what’s yours? That, that’s seventy seven percent. That’s just a little bit better. Yes it is. This is because significantly more atoms are incorporated into the final product in
Mel’s reaction. Actually Brian, the company that made my reactions also figured out a way to capture the leftover acetic acid by-product from the
reaction and market it. So the actual atom economy of my reaction is a hundred percent and the waste that they produced is zero. Brian’s six step process was developed in the 1960’s and was the original way to make ibuprofen. In the 1980’s the synthesis was overhauled into a three step process that was significantly more efficient and atom economical, which is the process that I demonstrated. All ibuprofen today is made by the new three step process. That’s more than 30 million pounds of ibuprofen per year. If we still used the old six step method, that would be over thirty five million pounds of waste produced each year to make the world’s use of ibuprofen. So in summary atom economy is a measure of the reaction efficiency. It is a way to help chemists quantify how well they’re using all of the atoms in their flask. Just like we discussed in our last video on waste prevention, through careful planning we can prevent ending up with excess materials that will end up going to waste. Today we have illustrated this can have a huge impact on how expensive a process is as well as the overall environmental impact of the process. So the next time you have a headache and reach for some ibuprofen, remember how green chemistry brought it to you in a more efficient, cost effective, and environmentally-friendly process. Thanks for watching! Make sure you like this video, comment ,and subscribe to see the rest of our series on the principles of green chemistry. If you want to learn more about the Green
Chemistry Initiative, check us out on our website or Twitter or Facebook