Fig. 1
a Expanded 6.50–8.50 ppm region of 600 MHz 1H NMR profiles acquired on Products 4 (top) and 3 (bottom), showing the unusual, very broad resonance detectable in that of Product 4 only; b Expanded 6.50–8.50 ppm region of the 600 MHz 1H NMR spectrum of Product 4 in C2HCl3 solution before (top) and after (bottom) treatment with a 10 µL volume of 2H2O. HQ and BQ, singlet resonances assignable to the aromatic ring protons of 2,5-di-tert-butylhydroquinone (DTBHQ) and its benzoquinone oxidation product respectively, the latter arising from the former’s ability to block peroxidation of CLO UFAs during periods of laboratory storage and sample preparation (the intensity ratio of these two signals therefore serves as a measure of such artefactual peroxidation taking place during such periods). Inset abbreviations: 2-PE and Tyr, aromatic ring protons of 2-phenylethylamine and tyramine respectively; 1 and 2, 13C satellites of the residual CHCl3 solvent and 1,3,5-trichlorobenzene standard 1H NMR resonances respectively