Functionalization at the double‐bond region of jojoba oil. 9. solid‐state nuclear magnetic resonance characterization of substituted jojoba wax chemically bonded to a polystyrene matrix

Abstract

Solid extractants for metal ions have been prepared by chemical bonding of jojoba wax to a polystyrene backbone, followed by phosphonation or sulfur-chlorination of the jojoba moiety. In this study, the intermediates and final solid products of the reactions were characterized by solid-state 13 C and 31 P nuclear magnetic resonance spectroscopy. The spectra showed the expected chemical shifts of the atoms involved in the chemical reactions, as well as other parts of the reacting molecules. Thus, the carbonyl carbon of the jojoba chain appears at 175 ppm, the methyl carbons at 15 ppm, the polystyrene backbone at 40-42 ppm (aliphatic carbons) and 128, 137, 143-147 (aromatic carbons). Carbons adjacent to N, S, and P appear at 45-55, 60, and 48 ppm, respectively. JAOCS 75, 521-525 (1998). KEY WORDS:Chemically bonded oil to polystyrene, jojoba oil, phosphonated jojoba oil, solid-state NMR, sulfur-chlorinated jojoba oil.Solid extractants for metal ions from aqueous solutions have the dual advantage that they can be recycled without loss of material or extraction activity (1,2). Thus, small quantities of such solid matrices can be used to purify large volumes of contaminated aqueous wastes, either to remove the toxic elements or to recover the precious metals. Solid supports of this type were recently prepared by chemical bonding of jojoba wax, a long-chain liquid ester, to a polystyrene backbone, either directly by C-C bond or via a "spacer," such as polyamine, by C-N bonds. The double bonds in the jojoba wax molecule were subsequently phosphonated or sulfurchlorinated to produce the solid extractant for metal ions (3,4). These jojoba-based extractants were found to be efficient and selective for specific ions (5).Because these new extractants are rich in polystyrene, conventional methods of chemical analysis are not suitable for characterization of the intermediates or the final products. We therefore used solid-state 13 C nuclear magnetic resonance (NMR) spectroscopy as a characterization tool and found that this informative technique lent support to the proposed synthetic pathways outlined in Schemes 1 and 2. We also obtained the 31 P NMR spectrum of the phosphonated final product as independent confirmation of the chemical identification of the product. EXPERIMENTAL PROCEDURESThe solid products were obtained as described in our preceding papers (3,4). 13 C NMR and 31 P NMR spectra in CDCl 3 solution were obtained on a Bruker DMX-500 MHz instrument (Karlsruhe, Germany). Solid-state 13 C NMR spectra were obtained with a Bruker DSX-300 MHz spectrometer and a 4-mm MAS probe. All 13 C spectra were run on samples spinning at 10,000 ± 2 Hz. The variable amplitude cross polarization-magic angle spinning (VACP-MAS) 13 C and 31 P spectra were recorded with a proton decoupling power of 85 kHz, a mixing time of 4 ms, and a repetition time of 2 s; 800 scans were accumulated before Fourier transformation. The 31 P spectra were measured at a spinning speed of 6,000 ± 2 Hz. RESULTS AND DISCUSSION13 C NMR of jojoba oil (illustrate...