Paving the way for greener solvents
The production of many everyday essentials, from shampoo to plastic and pharmaceuticals, requires chemical reactions. These ‘organic syntheses’ need solvents, which are traditionally derived from fossil fuels such as oil and gas. A greener pathway is coming. New plant-based solvents could further reduce our dependence on fossil fuels, yet a lack of reaction studies is slowing their adoption. “The knowledge gap exists mainly because bio-based solvents are relatively new and have not yet been systematically studied using quantitative physical-organic methods,” says Armin R. Ofial, research group leader at LMU Munich(opens in new window). Through the ResolveByBio project, which was supported by the Marie Skłodowska-Curie Actions(opens in new window) programme, Ofial and his team sought to fill this gap by providing data on electrophile-nucleophile reactions in bio-based solvents. These reactions involve the construction of new molecules by connecting two reaction partners through a new chemical bond. The electron-rich nucleophile shares one electron pair with the electron-poor electrophile, which accepts it to form a new bond. “A key aspect of the project is that it bridges fundamental physical organic chemistry with real-world sustainability challenges,” adds Ofial. “By combining kinetic analysis, spectroscopy and computational insights, the work not only advances scientific understanding but also provides actionable tools for greener chemical synthesis.”
Examining electrophile-nucleophile reactions
The reactivity of nucleophiles depends on the solvent in which the reactions are carried out. ResolveByBio focused on quantifying the reactivity of nucleophiles in bio-renewable solvents, using time-resolved spectroscopy. “This involved monitoring the decay rates of coloured, electrophilic reaction partners under controlled conditions,” explains Ofial. The researchers ran experiments to find out the rate at which reactions happened in plant-based solvents. Then they mathematically analysed the results to calculate scores of how reactive each nucleophile was. “In this way, new data for the reactivity of important classes of nucleophiles, such as phosphines and enamines, in bio-renewable solvents could be embedded in the currently most comprehensive reactivity scale for polar reactions,” notes Ofial. This scale, known as the Mayr scale, previously held only entries for the reactivity of nucleophiles in conventional fossil-based solvents or aqueous solutions.
Expanding our knowledge of plant-based solvents
In one recent study, for example, vinyl azides(opens in new window) reacted faster in the bio-renewable solvent Cyrene™(opens in new window) than in the fossil-fuel-derived solvent dichloromethane. “This result highlights that bio-renewable solvents are advantageous because they not only simply replace existing fossil-based solvents, but sometimes even bring an extra bonus with them by shortening reaction times,” notes Ofial.
Driving sustainable transformation in the EU chemical sector
The project contributes fundamental data needed to replace hazardous, fossil-based solvents by sustainable alternatives, and enables researchers to forecast reaction times in bio-based solvents. “This removes a major hurdle to their industrial adoption,” remarks Ofial. “It contributes directly to the EU’s ‘sustainable-by-design’ strategy and supports the transition to safer, low-carbon chemical processes and overall less industrial waste.” The researchers plan to expand their research studies to include a broader range of reactions and solvent systems, which could help develop new products in more environmentally friendly ways. “Ultimately, the goal is to use these fundamental insights as tools to facilitate practical applications, including the synthesis of functional molecules using environmentally benign solvents,” concludes Ofial.