Figure 6 | Scientific Reports

Figure 6

From: Nature-Guided Synthesis of Advanced Bio-Lubricants

Figure 6

Complete 500-MHz proton NMR spectrum for unfractionated Ov estolide oil in CDCl3 at 28 °C. Full spectrum (bottom) shows estolide, glycerol methylene, and hydroxy-bearing methine resonances within the region from δ 5.24 – 3.5 ppm, as well as other signals corresponding to the acyl chains. (ad) Show an expansion of the methine on the carboxyl side of an estolide ester (δ~4.9) and the doublet of doublet (dd) resonances for the methylene hydrogens of the glycerol backbone at approximately δ 4.1 and 4.3 ppm. (a) Expansion for Ov oil with the estolide signal at δ 4.86. Spectral data is shown for benzoylated castor oil (b), where the homoallylic estolide methine at C-12 is further downfield at δ 5.15 but the glycerol resonances are unperturbed. In benzoylated Ov oil (c), both naturally occurring and benzoyl estolides linkages are observed. Of note, signals from the glycerol backbone are more complex, altered by the proximate benzoyl ester at C-7, possibly stemming from magnetic anisotropy. In panel (d), the smaller, downfield multiplet for the methine of the free C-18 alcohol and the prominent broad methine resonance at C-7 for the free hydroxyl group in Ov oil are observed, consistent with the estolides primarily occurring at C-18 on wuhanic/nebraskanic chains.

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