Multi-technique structural analysis of zinc carboxylates (soaps)

A series of medium- and long-chain zinc carboxylates (zinc octanoate, zinc nonanoate, zinc decanoate, zinc undecanoate, zinc dodecanoate, zinc pivalate, zinc stearate, zinc palmitate, zinc oleate, and zinc azelate) was analyzed by ultra-high-field Zn-67 NMR spectroscopy up to 35.2 T, as well as C-13 NMR and FTIR spectroscopy. We also report the single-crystal X-ray diffraction structures of zinc nonanoate, zinc decanoate, and zinc oleate-the first long-chain carboxylate single-crystals to be reported for zinc. The NMR and X-ray diffraction data suggest that the carboxylates exist in three distinct geometric groups, based on structural and spectroscopic parameters. The ssNMR results presented here present a future for dynamic nuclear polarization (DNP)-NMR-based minimally invasive methods for testing artwork for the presence of zinc carboxylates.

Automated summary

A series of medium- and long-chain zinc carboxylates were analyzed using ultra-high-field Zn-67 NMR, C-13 NMR, and FTIR spectroscopy. The single-crystal X-ray diffraction structures of zinc nonanoate, zinc decanoate, and zinc oleate were also reported for the first time. The NMR and X-ray diffraction data suggest the existence of three distinct geometric groups for the carboxylates. This study provides a future direction for the use of dynamic nuclear polarization (DNP)-NMR-based minimally invasive methods to test artwork for the presence of zinc carboxylates.