Synthesis, Characterization and Analysis of Water Solubility of Resorcinol Calix4arenes Modified by Chiral Alanine

Taking resorcinol as raw material, three kinds of resorcinol calix4aromatic compounds of C−ethyl resorcinol calix4arene (1a), C−n−propyl resorcinol calix4arene (1b) and C−iso−butyl resorcinol calix4arene (1c) were synthesized. With three raw materials as the substrates, water-soluble alanine was introduced at the position of C−2, and three kinds of water-soluble compounds of C−ethyl tetramethylene L−alanine resorcinol calix4arene (2a), C−n−propyl−tetramethylene L−alanine resorcinol calix4arene (2b) and C−iso−butyl tetramethylene L−alanine resorcinol calix4arene (2c) were successively synthesized. The structures of six kinds of compounds were characterized and analyzed through FT−IR, ¹H NMR and elemental analysis, and the water solubility of two types of compounds was compared and analyzed. The results show that the characteristic infrared peak signal and nuclear magnetic resonance peak signal are consistent with the molecular structures of six kinds of compounds. The pH of calixarene compounds in pure water at room temperature and 40 ℃ basically unchanged, maintaining about 6.50. Compared to this, the pH of water-soluble compounds shows a significant downward trend, and the water solubility gradually increaseswith the shortening of the bridging alkyl substituent chain. The pH of water-soluble compound 2a can reach 5.35 at room temperature and 4.50 at 40 ℃, the concentration of hydrogen ions in aqueous solution increases by nearly two orders of magnitude, and the introduction of alanine can greatly the water solubility of calixarene.