Table 7.
Comparison of 13C NMR chemical shifts in purine incubated in concentrated sulfuric acid for two different time periods. All NMR data were obtained at room temperature.
| Purine | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 13C | ||||||||||
| Solvent | C2 (ppm) | C4 (ppm) | C5 (ppm) | C6 (ppm) | C8 (ppm) | |||||
| 11 October 2022 | 7 November 2023 | 11 October 2022 | 7 November 2023 | 11 October 2022 | 7 November 2023 | 11 October 2022 | 7 November 2023 | 11 October 2022 | 7 November 2023 | |
| 81% D2SO4/19% D2O 1 | 149.28 | 149.27 | 151.44 | 151.44 | 121.09 | 121.09 | 140.49 | 140.48 | 150.14 | 150.14 |
| 88% D2SO4/12% D2O | 149.36 | 149.34 | 151.30 | 151.30 | 120.92 | 120.93 | 140.57 | 140.55 | 150.12 | 150.11 |
| 94% D2SO4/6% D2O | 149.39 | 149.39 | 151.16 | 151.18 | 120.78 | 120.79 | 140.61 | 140.61 | 150.06 | 150.07 |
| 98% D2SO4, 2% D2O | 149.39 | 149.39 | 151.04 | 151.04 | 120.66 | 120.68 | 140.66 | 140.65 | 150.00 | 150.01 |
1 After the one-year-long incubation of purine in 81% w/w sulfuric acid, one new peak emerges at 167.66 ppm. The new peak likely corresponds to an unknown reactive contaminant in the reaction mixture and does not indicate the instability of a purine ring, as all chemical shifts of the purine ring remain unchanged. See also https://zenodo.org/records/10793625 (accessed on 7 March 2024).