| ¹³C NMR (500 MHz Bruker without cryoprobe; 300 µL mixture and 200 µL D₂O; 0.2 M stock solutions mixed in 0.1 M H₂SO₄, 1:1; exponential window function before phase and baseline correction; TopSpin 4.5.0) | A clear peak at the characteristic molecular shifts of GAOxime; image data were not transcribed |
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Hanqing Yin, Gustav Stausbøll Hedemark, María Escudero-Escribano, Soren B. Scott, Alexander Bagger. “C–N coupling in electrochemical amino acid synthesis occurs in solution, not on the catalyst surface.” ChemRxiv (). https://doi.org/10.26434/chemrxiv.15008005/v1
The main paper refers to supporting information, but no separate supporting information file was available on the ChemRxiv article page
| ¹H NMR (500 MHz Bruker with cryoprobe; water suppression, 64 scans, 30 s delay; 300 µL electrolyte, 200 µL D₂O locking solvent, 25 µL 0.1 M maleic acid internal standard; no window functions; phase and baseline correction; TopSpin 4.5.0) | The purple circle denotes the singlet corresponding to glycine; a single new singlet peak has appeared at a chemical shift consistent with glycine; the ¹H NMR spectrum also shows several small peaks of very low intensity; due to the minimal integrals, we could not assign these resonance peaks; in addition, we also observe two peaks at 7.1 ppm and 8.2 ppm, respectively, where the former is attributed to a less abundant stereoisomeric form of glyoxylic acid oxime; the singlet of moderate intensity observed near 8.2 ppm could not be unambiguously assigned, but it is tentatively attributed to a minor species, whose chemical shift appears to be pH-dependent, reflecting a protonation or tautomerisation equilibrium; notably, this peak shifts downfield following bulk electrolysis; image data were not transcribed |
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| ¹³C NMR reference spectra of product and reactant (500 MHz Bruker without cryoprobe; 300 µL mixture and 200 µL D₂O; 0.2 M stock solutions mixed in 0.1 M H₂SO₄, 1:1; exponential window function before phase and baseline correction; TopSpin 4.5.0) | These spectra provide experimental evidence that oxime formation also occurs for a range of carbonyl-containing precursors; image data were not transcribed |
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