Tag Archives: CO2

What to Do with All That CO2 Stuff?

CO2_carpetThe Scripps Institution of Oceanography at UC–San Diego reported the past April 2014 a terrifying new milestone of 400 ppm of CO2 in the atmosphere. The accumulation of CO2 into the atmosphere is causing a growing reinforcement of the natural green house effect and is thus “extremely likely” causing the increase of average temperature in our planet. In other words, if we continue denying the evidence of a strong relationship between CO2 emissions and climate change we may reach a “no-return point”.

Let’s not be apocalyptic YET. There is a real concern about CO2 in the scientific community, research institutions and funding agencies are promoting a change of mentality towards bigger efforts on CO2 research. And here it comes the question, What to do with all the CO2? It is a tricky question with no easy answer as unfortunately there are many international conflicts of interests in terms of CO2 emission and climate change. From a scientific perspective there are a few strategies that can be followed to reduce, avoid and make a smart use of CO2.

-Smarter use of energy: an indirect way to reduce CO2 emissions. Invest and research in more efficient use of energy, insulation of buildings, fuel-efficient vehicles. For a higher effectiveness, all this must come along with educating people about a more conscious personal attitude toward energy use.

-Fuel shift from coal to gas: another way to reduce CO2 emissions. As simple as the amount of CO2 produced by burning gas is sensibly lower than by burning coal.

-Renewable sources of energy: such as sun, wind or geothermal. A field in continuous growing and development with the major drawback of reliability of supply as renewable energy often relies on weather and geographical location.

-Carbon  capture and storage: This technology with the focus of capturing and storing CO2 in huge amounts attracted the attention and enthusiasm of many. But there are also certain doubts as it can be seen as sweeping the CO2 under the carpet due to the uncertainty about the time permanence of stored CO2 and the possible impact on natural systems.

-And last but not least, Transform CO2 into chemicals. This is, no doubt, my favourite strategy, what did you expect? I’m a chemist. Transforming CO2 into chemicals is an indirect way to trap CO2 in a productive way and thus reducing the carbon footprint. CO2 has its most important application in the synthesis of urea for the industry of fertilizers and urea-formaldehyde resins, it is used in the synthesis of salicylic acid (the precursor of aspirin), the production of carbonates through direct reaction with epoxides and has many prospective applications in the area of polycarbonates and fuel production.

uses CO2

Production of chemicals with CO2 will pay off if two main objectives are accomplished. The first is that the amount of CO2 produced burning fuels for energy for a process must be lower than the CO2 transformed into a chemical. And the second is that the time CO2 stays as a chemical must be long enough to have an impact in the accumulation of CO2 into the atmosphere.

Do you want to know more? Here you are a couple of interesting reviews:

– Martina Peter, Burkhard Köhler1, Wilhelm Kuckshinrichs, Walter Leitner, Peter Markewitz, Thomas E. Müller. Chemical Technologies for Exploiting and Recycling Carbon Dioxide into the Value Chain. Chem. Sus. Chem. 2011, 9, 1216–1240.

– Michele Aresta, Angela Dibenedetto, Antonella Angelini. Catalysis for the Valorization of Exhaust Carbon: from CO2 to Chemicals, Materials, and Fuels. Technological Use of CO2. Chem. Rev., 2014, 114, 1709–1742.

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A Trace-less Directing Group for Meta-Selective Arylation of Phenols.

The methodology developed by Larrosa and co-workers towards the meta-selective arylation of phenols is a  great example of combination of knowledge and creativity. Ortho-carboxylation of phenols with CO2  (Kolbe-Schmitt reaction) is a well known process that is used to synthesise salycilic acid, the precursor of aspirin. In addition, CO2 is a smart choice as directing group as it is abundant, inexpensive, non-toxic and non-flammable.

Traceless directing group

The direct meta-functionalization of phenols is quite a challenge due to the ortho/para directing ability of the hydroxyl group. Previous methodologies to achieve meta-functionalization require the use of protection-deprotection strategies with the consequent additional synthetic and purification steps.

Larrosa an co-workers approach the problem by in-situ introducing an ortho carboxyl group through direct reaction of phenol with CO2. The carboxyl function acts as a transient ortho-directing group that facilitates a palladium mediated metha-selective (to the hydroxyl group) cross coupling before being removed. An important drawback of the methodology is the requirement of high temperatures which could be a limitation for its scope in synthesis.

Do you want to know more? Go directly to the source:

Junfei Luo , Sara Preciado , and Igor Larrosa. Overriding Ortho–Para Selectivity via a Traceless Directing Group Relay Strategy: The Meta-Selective Arylation of Phenols. J. Am. Chem. Soc., 2014, 136, 4109–4112.