Enhanced Diffusion of Molecular Catalysts Is Due to Convection

Intriguing reports of enhanced diffusion in enzymes and molecular catalysts have spurred significant interest in experimental and theoretical investigations of this phenomenon, with mechanistic understanding the subject of ongoing and lively debate. Here we use time-resolved diffusion NMR methods to measure the diffusion coefficients of small molecule species involved in chemical reactions with high temporal resolution. We show the enhanced diffusion of small molecules cannot be explained by reaction velocity, and that apparent measurements of enhanced diffusion by small molecules appear to be caused by bulk fluid flow processes such as convection.