37,35Cl isotope effects on19F and13C chemical shifts of chlorofluoro- and hydrochlorofluorocarbons

Rapid Interfacial Exchange of Li Ions Dictates High Coulombic Efficiency in Li Metal Anodes

“…In addition to rapid interfacial exchange, solution NMR analyses of the liquid electrolyte post-mortem indicate that TFSI – decomposition produces more-soluble salt fragments upon cycling in pure LiTFSI electrolytes than in LiTFSI/LiNO 3 electrolytes. 19 F solution NMR spectra of the pristine samples (Figure , bottom spectra) show large peaks at −79.4 ppm consistent with TFSI – , as well as small resonances at −79.1 ppm and −80 ppm that are assigned to 13 C/ 12 C isotope effects (i.e., 13 C F 3 SO 2 NSO 2 12 CF 3 , 12 C F 3 SO 2 NSO 2 13 CF 3 , and 12 C F 3 SO 2 NSO 2 12 CF 3 will all exhibit different chemical shifts) . Upon cycling, resonances at −78.3 ppm, −78.4 ppm (0.2% of the sample), and −79.3 ppm (1.7% of the sample) appear (Figure , top spectra), which represent RCF 3 fragmentation.…”

“…19 F solution NMR spectra of the pristine samples (Figure 6, bottom spectra) show large peaks at −79.4 ppm consistent with TFSI − , 53 as well as small resonances at −79.1 ppm and −80 ppm that are assigned to 13 C/ 12 C isotope effects (i.e., 13 CF 3 SO 2 NSO 2 12 CF 3 , 12 CF 3 SO 2 NSO 2 13 CF 3 , and 12 CF 3 SO 2 NSO 2 12 CF 3 will all exhibit different chemical shifts). 54 Upon cycling, resonances at −78.3 ppm, −78.4 ppm (0.2% of the sample), and −79.3 ppm (1.7% of the sample) appear (Figure 6, top spectra), which represent RCF 3 fragmentation. These RCF 3 fragments are present in the cycled Taking these results together, we find that the transition to smooth Li deposition morphologies and enhanced CE shown in Figure 1 is correlated with fast Li exchange across the electrode/SEI interface in LiNO 3 -based electrolytes.…”

Ultra‐high resolution band‐selective HSQC for nanomole‐scale identification of chlorine‐substituted 13C in natural products drug discovery

“…We sought to expand a potential solution to this problem that relies on the isotope shift (Δδ) observed for 13 C NMR signals substituted by 35 Cl- 37 Cl at natural abundance (3:1). While this isotope effect has been long known, 12 it was first exploited for natural product assignments by Suzuki [13] and Braddock. [14] Under high digital resolution acquisition conditions, a Cl-substituted 13 C NMR signal sometimes separates into a split peak due to the 35 Cl/ 37 Cl induced isotopic shift (Δν ~0–0.9 Hz).…”

Conformational and substituent effects in the 19F spectra of C7–C10 straight‐chain chlorofluoroalkanes

“…In some of the compounds, the exact magnitudes of J were obscured by multiplicities resulting from the presence of chlorine isotopes. 11 In 2, the resonance of CF 3 in position 1, assigned as we have described above, consists not of small triplets but instead of small doublets, obviously resulting from coupling to the single fluorine in position 4. The CF 3 at the other end of the chain, in contrast, shows the usual small triplet.…”