New life of old molecules: calcium carbide

Scientists from St.Petersburg University and Zelinsky Institute, Russia investigated chemical applications of calcium carbide. The project advances the idea of diverse acetylene chemistry on the basis of carbide technology. Cheap carbide raw material has been transformed into valuable products for material science and organic synthesis.

Unremarkable gray "pebbles" of calcium carbide -- valuable material for science and industry.

Over the last few decades, researchers have focused their attention on very large molecules and molecular systems. Scientists from all over the world study proteomics, genomics, construct complex proteins, nucleic acids, decode the genomes of entire organisms, and design new sub-cellular structures. Outstanding enthusiasm for these important and essential areas of science has become so widespread that the question arose: "Is there a place for small organic molecules in modern science?" It might seem that old and well-known small organic molecules, as well as some areas of classical organic chemistry, have been forgotten.

Remarkably, despite the above mentioned trend of mega-molecules, state-of-the-art research anticipates re-investigation of tiny molecules. Indeed, small molecules carry a huge and previously unrevealed potential for science and industry. Renaissance in this area of science initiated an enlightenment of the well-known small molecules. An example of a small molecule is acetylene and derivative of acetylene - CaC2 or calcium carbide.

Friedrich Wohler first introduced the prominent calcium carbide in 1862. As a matter of fact, this breakthrough revolutionized the lighting in the 20th century Europe and US. The manufacture of carbide reached thousands of tons by the middle of the last century. Such an increase was caused by the fact that carbide was mainly used for the production of acetylene. Nevertheless, the end of carbide lamps era came with the advent of safer electric light sources. The development of catalysis and petrochemistry introduced cheaper acetylene sources, so calcium carbide was left behind.

An innovative method, proposed by a group of researchers led by Professor Ananikov, investigates the synthesis of valuable organic molecules directly from calcium carbide, without separation and storage of acetylene gas. As an example, thiovinylation reaction occured directly in the reaction mixture. Firstly, acetylene is allocated from calcium carbide and water, and secondly, thiol molecules get attached to the acetylene molecules. Both processes take place one-pot and do not require sophisticated equipment. The use of calcium carbide not only fundamentally simplifies and reduces the cost of synthesis, but also avoids the problems associated with transporting, storing, and handling of acetylene gas.

The developed process gives a vivid example of successful replacement of dangerous and difficult to handle acetylene gas by a simple and inexpensive calcium carbide. If the further research manages to carry out the chemistry of acetylene utilizing carbide-based technologies, the proposed method will open a new direction in organic chemistry. Without a doubt, the "little" calcium carbide will find its a place in modern chemistry, which acknowledges the ideas of safety, sustainability, and simplification.

The article ┬źEfficient Metal-Free Pathway to Vinyl Thioesters with Calcium Carbide as the Acetylene Source┬╗ by Konstantin Rodygin and Valentine P. Ananikov was published in Green Chemistry journal by the Royal Society of Chemistry.

Reference: Green Chemistry, 2015; DOI: 10.1039/C5GC01552A
On-line link: http://dx.doi.org/10.1039/C5GC01552A