A long‐chain dibasic acid with six‐membered ring, C₂₁ dibasic acid (C₂₁‐DA), was synthesized with mixed fatty acid, acrylic acid as starting materials, and iodine as the catalyst and quinol as polymerization inhibitor. The product was purified by distillation under reduced pressure and characterized using mass spectroscopy (MS) and nuclear magnetic resonance spectroscopy (¹H NMR). An anionic surfactant, C₂₁ dibasic acid potassium (C₂₁‐DAP), was synthesized with KOH via neutralization reaction. The synergistic effect was investigated by mixing C₂₁‐DAP with fatty alcohol polyoxyethylene ether with 7 ethoxy groups (AEO₇), dodecyl trimethyl ammonium chloride (DTAC) and octadecyl dimethyl betaine (BS‐18), respectively, to evaluate the surface activity. The results showed that the mixed system of C₂₁‐DAP/DTAC possessed the best synergistic effect among all studied systems, where a minimum surface tension at the critical micelle concentration (γ_CMC) of 28.28 mN m⁻¹ was obtained. Because of the electrostatic attraction between C₂₁‐DAP and DTAC, the repulsive force between the same kind of molecules and micelle molecules in the surface adsorption layer was indirectly reduced.

中文翻译：

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C21二元酸钾的合成及配合性能研究

合成了具有六元环的长链二元酸C ₂₁二元酸（C ₂₁ -DA），以混合脂肪酸，丙烯酸为起始原料，碘为催化剂，喹啉为阻聚剂。通过减压蒸馏将产物纯化，并使用质谱（MS）和核磁共振谱（¹ H NMR）表征。通过中和反应与KOH合成了阴离子表面活性剂C ₂₁二元酸钾（C ₂₁ -DAP）。通过将C ₂₁ ‐DAP与具有7个乙氧基的脂肪醇聚氧乙烯醚（AEO ₇），十二烷基三甲基氯化铵（DTAC）和十八烷基二甲基甜菜碱（BS-18）来评估表面活性。结果表明，C的混合系统₂₁ -DAP / DTAC拥有所有研究的系统，其中，在临界胶束浓度的最小表面张力（γ之间的最佳协同作用_CMC 28.28 MN米）^-1得到。由于C ₂₁ -DAP和DTAC之间的静电吸引，表面吸附层中相同种类的分子与胶束分子之间的排斥力间接降低。