Ligands Go Chiral!

Scientists, specifically Baihua Ye and Nicolai Cramer added biotin to a cyclopentadienyl ring, functionalized it with rhodium, and attached it to the protein streptavidin. What does this all do? This complex allows them to perform rhodium catalyzed reactions to make single-enantiomer products, or products with a single conformation. This is very important to scientists since it allows them to get products that they desire, as as we all know, a little change in structure results in a big change. Here is a link of an image of what is being described

 

You can see in the picture that a ring is attached to Rhodium--that is the catalyst. Furthermore, the Rh is connected to Streptavidin which is then connected to biotin. This may seem very complicated, which it is, the point is that the conformation in this picture is what makes the complex useful. It works like an enzyme, a lock and key like structure. Once again, this we see the connection of transmetal catalysts to biology and specifically enzymes. One may think that since enzymes are catalysts, that it isn't out of the ordinary for there to be such a connection between enzymes and transition metal catalysts. However, it is very hard to join these things together, as seen in our previous posts about the rhodium catalyst as well. So don't take this as a walk in the park. The emergence of organocatalysts are no minor thing in the timeline of chemistry.

Bang for Your Biofuel Buck?

Metal catalysts are being used to prepare new biofuels that would improve the environment as well as producing a fuel that could be used in place of gasoline. The catalytic metals help assist in the fermentation technique once used to make cordite, the explosive propellant that replaced gunpowder in bullets and artillery shells. With the addition of the metal catalyst, researchers at the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have shown that the production of acetone, butanol and ethanol from lignocellulosic biomass could be selectively upgraded to the high volume production of gasoline, diesel or jet fuel.

This connects claerly to the environment, as biofuels can prove to be a great extra source of...fuel. However, are biofuels really a solution? Although the article mentions how making biofuels is great, it doesn't address the fact that biofuels still need to be burneed to be used. Its a combustion reaction...which is not good for the environment! Here it is, the combustion of ethanol and methanol (yes we are too lazy to actually type it)

As we know, the burning is exothermic so change in Enthalpy is negative (this may seem obvious but bear with me). Thus, we get energy from this reaction. However...the Carbon dioxide biproduct is not favorable. So biofuels just give us more oil, they do not solve the environmental problems. So even though the scientists use catalytic metals to produce biofuels, I would not glorify their process too much not only to show we are not biased towards all transition metal catalytic processes, but also to show that making biofuels only postpones the environmental problem.

The Haber Process: Why Transition Metal Catalysts are Responsible for Half of the World's Population

That's right, you heard (or read) us correctly. Transition metal catalysts are responsible for half of the world's population or more! The reason for this is its integral role in the Haber process, arguably the most significant chemical process made by man.

First, an intro into the Haber Process. The Haber process was discovered by Fritz Haber in 1909. He found out a way to synthetically make ammonia. The chemical Equation for the process is as follows:
N2 + 3H2 --> 2NH3
However, this equation does not tell the whole story. The process is actually very slow, and requires a catalyst, which in this case is Iron. Thus, a more accurate representation of the process is below:

The Haber Process uses reactants that can be relatively easily gathered, Nitrogen and Hydrogen, and reacts it with an Iron oxide catalyst to make Ammonia. The unreacted gas is also recycled to make the process more efficient.

Thus, without the iron catalyst, the Haber process (also called Haber-Bosch process since Carl Bosch industrialized the process)  would be useless.

Now, that begs the question--why is this process so important? Well MIT Press says that The Haber-Bosch process "has been of greater fundamental importance to the modern world than ... the airplane, nuclear energy, space flight, or television. The expansion of the world's population from 1.6 billion people in 1900 to today's six billion [in 2000] would not have been possible without the [industrial] synthesis of ammonia." What the Haber process does is that it produces a fixed form of nitrogen, which is essential to all living beings. Essentially, the Haber process makes fertilizer. Before the haber process, nitrogen could only be fixed naturally thorugh bacteria or lightning. In fact, only 140 million tons of nitrogen could be fixed per year by the entire world without the Haber Process. However, with the Haber Process, today, an additional 100 million tons of nitrogen is fixed per year, which is an astounding number. To add to that, Professor Vaclav Smil of the University of Manitoba, estimates that "only about half of the population of the late 1990s could be fed at the generally inadequate per capita level of 1900 diets without nitrogen fertilizer." In other words, half of the world's population would not be here withouth the Haber process! Here is a graph of the increasing nitrogen fertilizer consumption over the years, taken from Hub Pages.

As you can see, nitrogen fertilizer consumption has DRAMATICALLY increased due over the years due to the Haber process



The Haber Process even changed the crops it was helping grow--because earlier crops did not respond as expected to the added nutrients, new high-yeald varieties (HYV) were made. Today HYV crops are used all over the world, once again showing the far-reaching consequences of the Haber Process.

To sum it all up, without the Haber Process, the world would consist of much fewer people, and without the iron catlyst, the Haber Process would be useless. Thus, using simple logic, the iron catalyst played a huge part in the Earth's population today. This connects perfectly with what we are learning since it shows how catalysts are an integral part of industry, and that if the kinetics of a reaction are not taken care off, the reaction will be of no societal use.

Catalysts in Nature

The good part about transition metal catalysts is that they are found everywhere. Metal can be hidden underground in the form of ore, or it may be found in rocks as well. Interestingly, these metals can be found in the same sedimentary rocks that contain natural gas. So, why not use the metals in the rock to catalyze a reaction that results in some hydrocarbons and natural gas? That's exactly what Frank D. Mango and his researchers did, with successful results.

So what does the reaction comprise of? The researchers react hydrogen with n-alkenes (alkenes are unsaturate hydrocarbons, look here for more info). This reaction is indeed catalytic, as the researchers showed that without the metals in the sedimentary rock, the reaction does not occur as quickly.
The positives of the reaction are that normally, for thermal cracking, environments of 500 degrees Celcius are required, while catalytic reactions require 200 degrees Celcius. Furthermore, thermal cracking does not bring out the true composition of natural gas, which is usually 90% Methane (CH4). Catalytic reactions, however, bring out mostly methane, thus using the natural gas to its full potential.  In relatively moderate conditions, Mango shows that a catalytic approach to extracting natural gas from sedimentary rocks is also possible, and is a viable alternative to thermal cracking, the method normally used.

Thus, the above experiment connects perfectly with what we are learning in chemistry today. There are two approaches to everything--thermodynamic and kinetic. In this case, the kinetic approach is shown over the thermodynamic approach. Rather than using temperature and heat to do the job, catalysts are used. The Catalysts make the reaction faster, and does not require as much heat for completion.

We're More than Engineers!

Recently, Colorado State University has made a transition metal catalyst that reacts with unactivated carbon hydrogen bonds, which gives scientists something to manipulate since all organic compounds have carbon and hydrogen bonds. Yes, as learned from our last blog post, unactivated means that the carbon hydrogen bonds are in their lowest, non-reactive state. The unactivated bonds  are thermodynamically and kinetically stable. Thus, as you can see, the catalyst is very useful if it can allow scientists to manipulate these bonds. Specifically, the rhodium catalyst allows scientists to shorten the time it takes to change natural compounds into ones that they want for making certain drugs. The diseases that these drugs treat do include cancer, which is a huge deal. Experiments have shown what would take scientists months to make, the rhodium catalyst cut down to a day! The head researcher, Tomislav Rovis, got his work published in Science, so you know that this research is quite legitimate. We know this description is a bit too general, but the paper is not out yet on the internet. But you can be that as soon as it is out, its gonna be on this blog! 

The philosophical part of this catalyst above, and many other transition metal catalysts, is that it is made of organic and inorganic parts, as in a metal and organic matter. As the article states, these things are not really meant to be together, but the catalyst brings them together, and thus achieves success. This idea comments on the nature of chemists. Chemists do not just make compounds by putting lifeless pieces of matter together; chemists are mediators they bring two or more opposing sides together. Chemists are not lego builders, the pieces do not just go together. Chemists sometimes have to fit, in a figurative sense, a box into a circular hole. Usually, chemists are called "molecular engineers"--but really, they are more than just engineers. Chemists have to deal with more than just structural problems when making molecules. Thus, this idea of calling a chemist a "molecular engineer" is not apt, but rather, it is inadequate, and will not be followed by this blog.

A Step Back

Hi all,

Today we're focusing on the basics, and less on transition metal catalysts specifically. We noticed that this blog is on catalysis, but no specific background is given on catalysts itself. Many of our viewers may understand that catalysts help a reaction get over the "hump" known as activation energy, but they may not really know what  activation energy is, and what causes it to be there. Why is there that hump in that potential energy diagram? What is the meaning of an activated complex versus a inactivated complex? These fundamentals are imperative to understanding the beauty of catalysis. This video, taken from the meteorically rising education phenomenon called Khan Academy, really clears up some important information on catalysis. However, some of the video is too basic, so it is recommended to watch the video at around the 3 minute mark on. The content before that is really on the "easy" side. Nevertheless, here is the video:


First an important Summary, and then there will be some cool discussion. What he says that is most significant is that the reason there is activation energy is that for the bonds of the two reactants to break, the reactants actually have to go to a higher energy state. At this state, the system is called an activated complex. Then the bonds break and they reach their lowest energy state, where they are inactivated. Thus, the moving of the reactants into that higher energy state before actually breaking bonds is the cause of the activation energy, and that is where catalysts come in since they allow us to bypass the activation energy, making the reaction occur quickly. The other information about surface area, concentration etc. is all important, but the emphasis remains on what is the cause of the activation energy.

Now, some may ask why we put this here? As alluded to above, the fundamentals are necessary to appreciate any field. Even in art, for example, unless you understand how difficult it is to even draw a straight line without a ruler,  you won't truly appreciate artists who draw freehand. In another perspective, in catalysis, the activation energy can be considered the basic problem we catalyst makers need to overcome.  Unless we understand the problem, we cannot begin to appreciate the solutions, which in our case are transition metal catalysts.

The next reason we wanted to put this video is that it is a quintessential example of how education using technology can be beneficial. Khan Academy, which has been in the spotlight for quite some time now, has revolutionized how students can learn. Salman Khan, an American, single-handedly uploaded over 3000 videos, which quite aptly describe every topic they cover. The videos range from math to physics, chemistry and biology, epitomizing the power of the internet. This connects to the goal of this blog as well. Metalysis is not just a place for "nerds" to gather, but rather, it is a forum for anyone who needs information on the catalysis that we deal with. This may be someone who really enjoys speaking about transition metal catalysts, but also a could be as student who has a project due the next day and needs some information. We want to help anyone in anyway we can, no matter what the intent our information is being used for (except for extreme cases of course!).

alCHEMISTS

Chemists at Princeton are taking an approach to chemistry that seems a little similar to the age old art of Alchemy. No, they are not turning lead to gold, but they are using iron instead of platinum for the same catalytic processes. 

Catalysts, such as platinum, are used in reactions to speed them up without loosing any of the catalyst in the process; unfortunately this is not always the case. As the reaction occurs trace amounts of the catalyst are lost, which is problematic for a chemical as rare as platinum, as its price is very high. Thus, recently, synthetic forms of the catalyst have been produced by using iron. Iron is much less precious than platinum and loosing iron in a reaction is not as cost worthy. This "synthetic form of Platinum" may result in the discovery of new types catalysts that work even better than ones that are being used today and might also cost less. This process of using cheaper catalysts could help companies all over stay away from the scarce elements. Beer, denim, fuel cells, makeup, pharmaceuticals, cookware, glue and many other products all currently use rare transition materials in manufacturing. So if cheaper metal catalysts could be mass produced, they would have an instant and direct impact on the market.

Here is a picture of the platinum and iron catalyst developed by Princeton University Professor Paul Chirik:

As you can see, the bottom catalyst only requires one iron molecule, while the above catalyst requires two platinum molecules. The iron catalyst presents a combination of economy, beauty, and effectiveness that cannot be beaten by the platinum catalyst. Thus, the price reduction begins at the molecular level, which brings up an interesting connection between chemistry and the economy--every single atom and molecule can be thought of as money spent, and if the structure of the molecule is not as efficient and parsimonious as possible, the greater money spent.