Formation of 3‐Methylfuran from the gas‐phase reaction of OH radicals with isoprene and the rate constant for its reaction with the OH radical

3‐Methylfuran has been identified as a product of the gas‐phase reaction of the OH radical with isoprene, and under simulated atmospheric conditions a formation yield of 0.044 ± 0.006 was determined. In an analogous manner, the OH radical reaction with 1,3‐butadiene formed furan with a yield of 0.039 ± 0.011. Using a relative rate method, a rate constant for the reaction of the OH radical with 3‐methylfuran of 9.35 × 10 −11 cm 3 molecule −1 s −1 (with an estimated overall uncertainty of ±20%) at 296 ± 2 K was also determined. These data show that 3‐methylfuran is a reactive compound which will be present in the troposphere at concentrations ⩽5% of those of its isoprene precursor.