Light so excites crystals of cinnamic acid that they can unite rapidly and undamaged without the need for potentially harmful solvents, report physical chemists who are trying to understand reactions that could lead to cleaner chemicals processing.

Samantha Atkinson and her team at the University of Reading chose cinnamic acid because its reactions are well documented and 'may be taken as a paradigm of single crystal organic reactions'.

And the technique need not be limited to solids, adds Matthew Almond, a member of Atkinson's team, noting that the team plans to probe similar solvent-free reactions of gases and liquids.

Katharine Sanderson