Carolina Scientific Building Hydrocarbon Chains and Future Work With this two-step system, after each subsequent cycle, the alkane becomes longer and longer by utilizing short alkane molecules. The catalysts are able to link the short hydrocarbons onto each other Figure 2: Dehydrogenation Reaction (where R is a as an alternate synthesis of gasoline and other types hydrocarbon chain and M is the Ir-catalyst) of fuels. But why isn’t this method more popular? Step 2: Olefin Metathesis After the olefins are formed from the iridium-based Unfortunately, the reactions proceed extremely catalyst, the second catalyst actually joins the two slowly, which is suspected to be caused by the demolecules. This union of the olefins is a specific reac- composition of the olefin metathesis catalysts [3], tion called olefin metathesis. Specifically, metathesis so the groups are working on developing better refers to the breaking and rearrangement of double catalysts that will withstand decomposition. Nonebonds between two molecules to form new mole- theless, this system is an extremely novel, creative, cules; it is extremely useful because it causes groups and a green technique, and thanks to the Brookhart to switch positions with each other (see Figure 3) [7]. and Goldman group, it will hopefully inspire similar techniques to help solve today’s fuel problem.
~Ann Liu ‘11 is a Biochemistry and Business double major.
Figure 3: Metathesis Reaction (where R is a hydrocarbon chain)
~Special thanks to Dr. Brookhart for his help in the editing process.
*Note: for full mechanism, see ref. 8
The products of the metathesis is ethene (C2H4, a gas) and an olefin that has nearly doubled in length and now just needs to be reduced back to its alkane form. This is where the iridium-based catalyst from step 1 comes back in; at this point, the catalyst still has two extra hydrogen atoms attached to it. Now, the catalyst reattaches one hydrogen atom to each carbon of the double bond, restoring it back to an alkane (see Figure 4) [3].
Figure 4: Final Step
The catalyst is also now back in its original state and can be used again in another cycle.
5
References:
1. Krauss, Clifford. 2007. Venture Capitalists Want to Put Some Algae in Your Tank. The New York Times. 16 Oct 2008. <http://www.nytimes.com/2007/03/07/business/07algae.htm>. 2. Rostrup-Nielsen, J.R. Science. 2005. 308(5727):1421-1422. 3. Goldman, Alan S. et al. Science. 2006. 312(5771): 257-261. 4. “Cracking.” 2008. In Encyclopædia Britannica. Retrieved October 16, 2008, from Encyclopædia Britannica Online: http://www.britannica.com/EBchecked/topic/141550/cracking 5. “Gasoline.” 2008. In Encyclopædia Britannica. Retrieved October 16, 2008, from Encyclopædia Britannica Online: http://www.britannica.com/EBchecked/topic/226565/gasoline 6. Service, Robert F. Science. 2006. 312(5771): 175. 7. “Robert H. Grubbs.” 2008. In Encyclopædia Britannica. Retrieved October 16, 2008, from Encyclopædia Britannica Online: http://www.britannica.com/EBchecked/topic/1090691/Robert-H-Grubbs. 8. Ahlberg, Per. 2005. Development of the metathesis method in organic synthesis. Advanced Information on the Nobel Prize in Chemistry. http://nobelprize.org/nobel_prizes/chemistry/laureates/2005/adv.html
Spring 2009, Volume I Issue II