十二烷基硫酸鈉(SDS)，是一種廣為人知的介面活性劑及賦形劑，被廣泛地應用於洗髮精、洗衣粉、化妝品中的發泡劑亦或作為電泳實驗的試劑。在結晶領域，根據文獻的報導，已被解析過的SDS晶相共有4種，分別為1/8水∙SDS、1/2水∙SDS、1水∙SDS及無水SDS，但大部分對於SDS晶相的研究大多僅注重於結晶本身的探討而並未考慮化學合成，因此本研究之目的在於結合化學反應與常見的反溶劑結晶及冷卻結晶法去設計一個從合成到分離純化SDS結晶的穩定製程。由文獻得知，十二烷醇加硫酸進行酯化反應生成硫酸十二烷酯，再引入氫氧化鈉水溶液使其反應為SDS及副產物硫酸鈉，接著添加的反溶劑(加入丙酮，該丙酮的添加量是原始水溶液中所含水量的4倍)將溶液中的副產物硫酸鈉逼出並進行抽氣過濾，並將母液保留的SDS以冷卻結晶法(攝氏25度冷卻至攝氏5度)進行分離及純化後可得到高結晶度的SDS晶體。然而以本實驗之製程所製得的產物在X射線衍射圖譜(XRD)上無法與上述任一文獻結果相符，但在經過傅里葉變換紅外光譜（FTIR）及拉曼光譜儀(Raman)之定性分析證明了產物確實為SDS，故猜測SDS擁有尚未被發現的水合物晶相。而此水合物晶相在另外設計的反溶劑結晶實驗中成功地以單晶的形式被分離，並經X-射線單晶繞射儀(SXRD)分析為「4水∙SDS」。以本研究之製程所得之產物經由傅里葉變換紅外光譜(FTIR)、熱重分析(TGA)、差示掃描量熱法(DSC)和粉末X射線衍射(PXRD)鑑定後均觀察到和購買的1/8水∙SDS有顯著的差異，且產物PXRD圖譜和4水∙SDS之SXRD圖譜的特徵峰相吻合。;Sodium dodecyl sulfate (SDS) is a well-known surfactant and excipient. It is widely used as shampoos, washing powders, foaming agents in cosmetics, or as reagents for electrophoresis experiments. According to the literature, SDS had four crystal hydrate forms: SDS∙1/8 hydrate, hemihydrate, monohydrate, and dihydrate. Although the crystallization process is generally followed by chemical synthesis, most of the researches only focus on different crystallization methods or conditions for preparing different crystal polymorphs and hydrates/solvates. Therefore, the purpose of this study is to develop a robust process connecting chemical synthesis and crystallization for producing a novel SDS tetrahydrate form. Esterification of dodecanol with concentrated sulfuric acid gives dodecyl sulfate, which then reacts with sodium hydroxide to produce SDS as a product and sodium sulfate as a by-product. Two crystallization methods, including antisolvent addition (i.e. adding acetone which was 4 times than the volume of the water contained in the original aqueous solution) and cooling (i.e. cooling the temperature of the co-solvent system from 25 °C to 5 °C), were combined produce highly crystalline SDS tetrahydrate crystals, as opposed to the commercial form or SDS∙1/8 hydrate. X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) and Raman spectroscopy were used to characterize our products. A separate experiment was carried out to grow a single crystal of the novel SDS tetrahydrate form for its structural determination and confirmation by single-crystal X-ray diffraction (SXD).
