Comment on “The chemical reactions in electrosprays of water do not always correspond to those at the pristine air–water interface” by A. Gallo Jr, A. S. F. Farinha, M. Dinis, A.-H. Emwas, A. Santana, R. J. Nielsen, W. A. Goddard III and H. Mishra, Chem. Sci., 2019, 10, 2566

Recently, Gallo et al. (Chem. Sci., 2019, 10, 2566) investigated whether the previously reported oligomerization of isoprene vapor on the surface of pH < 4 water in an electrospray ionization (ESI) mass spectrometer (J. Phys. Chem. A, 2012, 116, 6027 and Phys. Chem. Chem. Phys., 2018, 20, 15400) would also proceed in liquid isoprene–acidic water emulsions. Gallo et al. hypothesized that emulsified liquid isoprene would oligomerize on the surface of acidic water because, after all, isoprene, liquid or vapor, is always a hydrophobe. In their emulsion experiments, isoprene oligomers were to be detected by ex situ proton magnetic resonance ((1)H-NMR) spectrometry.