Detection of the formyl radical by EPR spin-trapping and mass spectrometry

Abstract

For the first time we here present the unambiguous identification of the formyl radical (CHO) by EPR (Electron Paramagnetic Resonance) spectroscopy and mass spectrometry (MS) using DMPO (5,5-dimethyl-1-pyrroline N-oxide) as spin trap at ambient temperature without using any catalyst(s). The CHO was continuously generated by UV photolysis in closed anoxic environment from pure formaldehyde (HCHO) in aqueous solution. The isotropic hyperfine structure constants ofCHO were determined as a = 15.72G and a = 21.27G. The signals were deconvoluted and split by simulation in their single adduct components: DMPO-CHO, DMPO-H and DMPO-OH. We verified our results at first using MNP (2-methyl-2-nitroso-propane) as spin trap with known literature data and then mass spectrometry. Similarly the MNP adduct components MNP-CHO, MNP-H as well as its own adduct, the MNP-2-methyl-2-propyl (MNP-MP) were deconvoluted. Due to the low signal intensities, we had to accumulate single measurements for both spin traps. Using MS we got the exact mass of the reduced CHO adduct independently confirming the result of EPR detection of formyl radical.

Proton-assisted electron transfer and hydrogen-atom diffusion in a model system for photocatalytic hydrogen production

“…4b). In addition, the hyperfine coupling constants (hfcc) for nitrogen (a N ) and hydrogen (a H ) atoms are shown in Table 1, and the hfcc values are well consistent with reported values, further confirming the formation of •H radical 54,55 . Moreover, the •H radical signal strengths of the samples were also compared (the peak area in Table 1).…”

Electrocatalytic Deuteration of Halides with D2O as the Deuterium Source over a Copper Nanowire Arrays Cathode

“…Then, the carbon radicals coupled with the deuterium radicals produced via electrocatalytic D 2 O splitting to form the desired products. Both the carbon and hydrogen radicals were confirmed by the electron paramagnetic resonance (EPR) measurements using 5,5‐dimethyl‐1‐pyrroline‐ N ‐oxide (DMPO) as the trapping agent (Figure f) . A decreased conversion of the product after adding tertiary butanol ( t ‐BuOH), which could scavenge the hydrogen atoms, was observed, identifying the role of hydrogen radicals in this electrocatalytic reduction reaction (Supporting Information, Figure S7).…”

Electrocatalytic Deuteration of Halides with D2O as the Deuterium Source over a Copper Nanowire Arrays Cathode

“…Then, the carbon radicals coupled with the deuterium radicals produced via electrocatalytic D 2 O splitting to form the desired products. Both the carbon and hydrogen radicals were confirmed by the electron paramagnetic resonance (EPR) measurements using 5,5‐dimethyl‐1‐pyrroline‐ N ‐oxide (DMPO) as the trapping agent (Figure f) . A decreased conversion of the product after adding tertiary butanol ( t ‐BuOH), which could scavenge the hydrogen atoms, was observed, identifying the role of hydrogen radicals in this electrocatalytic reduction reaction (Supporting Information, Figure S7).…”