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Highlights in Chemical Technology

Chemical technology news from across RSC Publishing.

Organic synthesis goes supercritical

07 September 2007

Swiss chemists have developed a greener and more efficient way of making an industrially important aldehyde.

The catalysed reaction of but-2-enal producing 2-ethylhexanal

2-Ethylhexanal is a key compound in the manufacture of perfumes and paints. Until now, its large-scale synthesis was dogged by the need for several consecutive reaction steps, poor yields or the need for large excesses of certain reagents.

Alfons Baiker and his colleagues at the Swiss Federal Institute of Technology (ETH) in Zürich have now developed a way of making it in a highly selective way and in a single step from crotonaldehyde (but-2-enal) using only a small excess of hydrogen.

"The catalyst exhibits high activity, selectivity and a long lifetime"
- Alfons Baiker of the Swiss Federal Institute of Technology
Supercritical carbon dioxide (where it is in a fluid state that is mid-way in character between a gas and a liquid) at 60 °C and 16 MPa pressure is used as the reaction medium for the starting materials, and the reaction takes place by passing it over a palladium catalyst at a constant flow rate.

According to Baiker, 'the catalyst exhibits high activity, selectivity and a long lifetime', adding that the only by-product, butyraldehyde, is also industrially useful and easily separated by distillation.

'The.method.may provide a promising alternative for the industrial production of [these] two important aldehydes,' he said.

Martyn Poliakoff, a fellow of clean technology at the University of Nottingham and chair of Green Chemistry's editorial board, considers Baiker's work an 'interesting development'. He added that he saw 'considerable potential for [the development of] sustainable chemical processes'.

David Parker

Link to journal article

Continuous catalytic one-pot multi-step synthesis of 2-ethylhexanal from crotonaldehyde
Tsunetake Seki, Jan-Dierk Grunwaldt and Alfons Baiker, Chem. Commun., 2007, 3562
DOI: 10.1039/b710129e

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