Molecular size was inferred from direct measurements of self-diffusion for species resolved by 1H DOSY NMR (table 2 ). Often the sizes of oil oxidation products are estimated using size exclusion chromatography in THF solvent, with polystyrene standards. In contrast, DOSY provides self-diffusion coefficients (D) of multiple species in solution resolved by 1H NMR.
DOSY measures the measured by mean-squared displacement (D), in one direction (z), of a molecule undergoing Brownian motion, over time (t) as z2 = 2Dt. D (in units of m2/s) is obtained for multiple species simultaneously, replacing laborious measurements with tracer reagents. Application of a linear magnetic field gradient (G) allows detection of molecular translations (over micrometers), see Figure S1 . D is used to reveal changes in size. More massive molecules (oligomers) diffuse more slowly. DOSY plots are expanded in the D dimension, leaving out the 1H signal (at 7.25 ppm) from residual CHCl3 (in CDCl3), with fast D = ca. 30 x 10-10 m2/s.