Calcium carbide replaces explosive acetylene in organic synthesis

Scientists have replaced explosive acetylene with cheap and benign calcium carbide to make common small organic molecules in a safer, cheaper and more atom-economical way, and at scale.

The small organic molecules they synthesised, vinyl thioesters, are ‘important building blocks for synthesising sulfur-functionalised polymers, which can be applied in many types of new materials such as optoelectronics and nanoparticles,’ explains synthetic chemistry expert Masaichi Saito from Saitama University, Japan. They are usually synthesised from acetylene using complicated high-pressure equipment under highly basic hazardous conditions and at high cost.

Now, Valentine Ananikov and Konstantin Rodygina from the Russian Academy of Sciences have developed a safer, greener and cheaper process using widely available and stable calcium carbide as the starting material. ‘Calcium carbide reacts with a carefully dosed amount of water and produces acetylene directly inside a flask resulting in the formation of vinyl thioesters,’ explains Ananikov. The reaction proceeds under mild conditions using a standard laboratory setup and has already been scaled up to synthesise grams of sulfides with the potential to scale up further.

‘Discovered in 1888, calcium carbide is an old molecule now experiencing a renaissance thanks to the achievements obtained by Ananikov and his team,’ says green chemist Evelina Colacino from University of Montpellier, France. ‘This less hazardous form of chemistry is achieved with higher atom-economy than previous reports and has the advantage of scalability and the generation of non-hazardous, eventually recyclable, waste.’