According a theory, an electric field can sometimes replace catalysts, speeding up the rate at which chemical reactions occur, has been verified.
Biology and industrial chemistry both depend on catalysts, materials that induce or accelerate chemical reactions without being changed in the process.
“Nature uses enzymes as the ultimate catalyst, which can vary reaction rates by 14 orders of magnitude,” said Professor Michelle Coote of the Australian National University in a statement. However, finding a suitable catalyst for a specific reaction is often hard – and where catalysts do exist, they can be enormously expensive.
Coote noted that one of the ways catalysts work is to create localized electric fields. By placing reagents, raw materials for the reaction, in the appropriate alignment within the field, the catalyst can stimulate the reaction. She made a prediction that if reagents could be orientated appropriately within an electric field, faster reactions would occur even without catalysts.
In Nature, Coote and colleagues have announced the first successful demonstration of her prediction. Normally, reactions do not benefit from the presence of electric fields because the polarity of molecules are randomly aligned. Consequently, the process required the research team to make sure both reagents were in the right orientation.
“In the experiment, we attached one molecule to a surface with a chemical bond,” Coote told, “and the other to the tip of a scanning tunneling microscope.” A powerful electric field was then generated. A Diels-Alder reaction, part of a well-known class of organic reactions used to form molecules with six carbon atoms, occurred five times as fast as would normally happen without catalysis.
However, making useful quantities of anything in this way will be a challenge. “You couldn’t apply a battery to a giant chemical reaction,” Coote said. “The field strength will be too low for one thing.” In limited circumstances, where tiny quantities are needed and reactions are currently very slow, Coote said it might be possible to “tether reagents to a surface with a chemical bond that could be cleaved later.” If only one reagent needed to be tethered, rather than both as in the Nature paper, the cost would become more realistic.
In the meantime, Coote hopes that the use of electric fields to accelerate reactions could prove a useful research tool. She is particularly interested in the potential for applying fields to self-healing polymers instead of heat or light, as is currently done.
“Without having proof, I would say that if an electric field is strong enough, it would influence all chemical reactions,” Coote said. “Even a reasonable field will probably influence most, based on the modeling we have done of charged groups of free radicals.” The challenge is to find ways to position the reagents appropriately.