Submitted to: American Chemical Society (ACS) Catalysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2014
Publication Date: 9/23/2014
Publication URL: https://handle.nal.usda.gov/10113/60433
Citation: Murray, R.E., Walter, E.L., Doll, K.M. 2014. Tandem isomerization-decarboxylation for converting alkenoic fatty acids into alkenes. American Chemical Society (ACS) Catalysis. 4:3517-3520.
Interpretive Summary: Transforming a bio-oil based material into a drop-in replacement for petroleum is a complicated, yet worthy process. Materials called alkenes are used in the plastic materials that Americans use every day. In order to make these materials from bio-oils, there are a couple of different approaches. Some of them only work at extreme temperatures and other methods require expensive reagents in order to proceed. These reactions can also produce undesirable side products such as the poisonous carbon monoxide, or large amounts of sulfates. The method reported here uses only a very small amount of catalyst. The only by-product of the reaction is harmless carbon dioxide. This technology is a small step in the direction in which the alkenes may find their way into your plastic mug, and could be based on American agriculture.
Technical Abstract: We report a facile Ru-catalyzed route to alkenes from alkenoic fatty acids via a readily accessible pre-catalyst [Ru(CO)2RCO2]n. The catalyst apparently functions in a tandem mode by dynamically isomerizing the positions of double bonds in an aliphatic chain and, subsequently, decarboxylating specific isomers with lower activation barriers. Substrates capable of tandem isomerization-decarboxylation processes (oleic acid, undecylenic acid) are readily converted to mixtures of alkenes. A catalytic cycle is proposed that relies on isomerization positioning double bonds proximate to the acid function to enable facile decarboxylation. To elucidate the proposed mechanistic pathway, substrates capable of only isomerization (methyl oleate) or decarboxylation (cinnamic acid), but not both, were shown to be operational under these catalytic reaction conditions. Another illustrative comparison shows that the saturated octadecanoic acid is 28 times less reactive than the unsaturated counterpart when reacted using this precatalyst.