Synthesis, Crystal Structure and Application of Maleopimaric Acid Mono-Ethyl Ester

Abstract

The compound maleopimaric acid mono-ethyl ester (MAMEE) was synthesized by Diles-Alder, acyl chlorination and esterification reaction between rosin and maleic anhydride, SOCl2 and anhydrous enthanol. It was characterized by single crystal X-ray diffraction. The white crystals crystallized in the orthorhombic system, space group P2₁₂₁₂₁ with cell dimensions: a = 7.3830 (15) Å, b = 17.877 (4) Å, c = 19.601 (4) Å, a = 90°, b = 90 °, g = 90°, V = 2587.1 (9) ų and R1 = 0.0568, wR₂ = 0.1407. The two fused and unbridged cyclohexane rings adopt approximate chair conformations while other six-membered rings have boat conformations and the two methyl groups in axis positions. Crystal water existed in the molecular and stabilized the structure through intermolecular hydrogen bonds. The soldering flux prepared by using maleopimaric acid monoethyl ester achieves a high wetting ability and is excellent in spreading rate and storage stability.