Can magnetic fields affect a chemical reaction?
Here is a nice review paper on the subject: Rodgers, C. T. Magnetic field effects in chemical systems. Pure Appl. Chem. 2009, 81 (1), 19–43. DOI: 10.1351/PAC-CON-08-10-18.

From the abstract:


  Chemical reactions that involve radical intermediates can be influenced by magnetic
  fields, which act to alter their rate, yield, or product distribution. These effects have
  been studied extensively in liquids, solids, and constrained media such as micelles. They  may be interpreted using the radical pair mechanism (RPM). Such effects are central to the field
  of spin chemistry of which there have been several detailed and extensive reviews.