organic chemistry reactivity of carbon dioxide

'That amount is still too high for industrial use and needs further improvement,' says Duong. The reaction also needed relatively large amounts of catalyst – roughly one catalyst molecule for every 10 to 20 molecules of the starting material. The reaction generally produced good yields of products when run at just 70 ✬ and atmospheric pressure, although it was less successful in those cases where particularly large chemical groups were attached to one end of the starting material. 'These are highly versatile building blocks for organic synthesis,' explains Duong. The products of the reaction contain a carbon–carbon double bond and a carboxylic acid group, arranged in a very predictable pattern. They assumed that the copper catalyst works by knocking the boron group off the molecule and briefly taking its place so that it can shepherd carbon dioxide into the right position to bond with the molecule. The researchers tested a range of molecules that feature a carbon–carbon double bond close to a boron-containing chemical group. Milder starting materials that contain tin tend to be highly toxic, 'so we looked at the use of more environmentally benign organoborons,' says Duong. However, these metals often destroy other sensitive chemical groups in the molecule during the reaction.

Some reactions involving carbon dioxide require high-energy starting materials that contain reactive metals such as lithium or magnesium. The commercially available catalyst consists of a copper atom joined to a bulky ligand called 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr). Hung Duong of the A*STAR Institute of Chemical and Engineering Sciences in Singapore and co-workers have shown that a copper catalyst can incorporate carbon dioxide into organic molecules under much milder conditions. For example, to synthesize salicylic acid, a precursor of aspirin, carbon dioxide must be squeezed to 100 times atmospheric pressure and the reaction mixture heated to 125 ✬. Only a few industrial processes currently use carbon dioxide as a reagent because it takes a lot of energy to break its strong chemical bonds.

Organic chemistry reactivity of carbon dioxide