Innovative Preparation and Characterization of Zinc Ricinoleate through alkali catalysis

Zinc ricinoleate, the zinc salt of ricinoleic acid, was prepared via an innovative two-step synthesis. First, an intermediate compound, methyl ricinoleate, was prepared through the transesterification of castor oil with methanol and catalyzed by sodium hydroxide. Then, methyl ricinoleate underwent an alkali-catalyzed saponification in the presence of zinc oxide (ZnO) particles, following by an ultrasonication step which resulted in the formation of zinc ricinoleate. The resulting white-like paste was characterized by FTIR, NMR and X-ray diffraction and the morphology was analyzed by HR-SEM and AFM. The change in the ZnO particle volume influenced the zinc ion coordination geometry in the resulting carboxylate-zinc complexes, yielding PZR1 with a combination of both bridging and chelating arrangement, and PZR2 possessing a combination of both chelating and monodentate arrangement. 1H and 13C NMR spectroscopy enabled to confirm the successful preparation of zinc ricinoleate with the presence of characteristic peaks of alkyl chain of the fatty acid anion. XRD patterns also confirm the zinc ricinoleate preparation with the presence of crystalline and amorphous regions. The presence of the following peaks at 2θ= 31.72°, 34.38° and 36.21°, indicates the existence of the Wurtzite ZnO structure and the apparition of amorphous regions in the 2θ range 19°–23° indicates the presence of disordered alkyl chains in the ZnO-carboxylate complexes.

蓖麻酸锌（Zinc ricinoleate）作为蓖麻酸的锌盐，通过创新性两步合成法制备得到。首先，以氢氧化钠为催化剂，将蓖麻油与甲醇进行酯交换反应，制备得到中间体化合物蓖麻酸甲酯。随后，在氧化锌（ZnO）颗粒存在下，蓖麻酸甲酯经碱催化皂化反应，再辅以超声处理步骤，最终生成蓖麻酸锌。所得类白色膏体采用傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy，FTIR）、核磁共振波谱（Nuclear Magnetic Resonance，NMR）及X射线衍射（X-ray Diffraction，XRD）进行表征，并通过高分辨扫描电子显微镜（High Resolution Scanning Electron Microscopy，HR-SEM）与原子力显微镜（Atomic Force Microscopy，AFM）分析其微观形貌。氧化锌颗粒的体积变化会影响所得羧酸锌配合物中锌离子的配位几何构型：其中PZR1同时兼具桥联与螯合两种配位模式，而PZR2则同时存在螯合与单齿配位模式。氢谱（¹H NMR）与碳谱（¹³C NMR）波谱分析证实了蓖麻酸锌的成功合成，产物中可观测到脂肪酸阴离子烷基链的特征峰。X射线衍射图谱同样验证了蓖麻酸锌的成功制备，产物同时包含晶态与无定形区域：2θ=31.72°、34.38°及36.21°处的特征峰表明存在纤锌矿型氧化锌结构，而2θ在19°~23°范围内出现的无定形衍射峰则说明羧酸锌-氧化锌复合物中存在无序烷基链。