Deprotonation processes of ellagic acid in solution and solid states

被引:40
作者
Hasegawa, M [1 ]
Terauchil, M
Kikuchi, Y
Nakao, A
Okubo, J
Yoshinaga, T
Hiratsuka, H
Kobayashi, M
Hoshi, T
机构
[1] Aoyama Gakuin Univ, Dept Chem, Coll Sci & Engn, Setagaya Ku, Tokyo 1578572, Japan
[2] Mac Sci Co Ltd, Kanagawa 2220033, Japan
[3] Tokyo Denki Univ, Inzai, Chiba 2701382M, Japan
[4] Kyushu Inst Technol, Dept Appl Chem, Fac Engn, Kitakyushu, Fukuoka 8048550, Japan
[5] Gunma Univ, Dept Chem, Fac Engn, Gunma 3768515, Japan
来源
MONATSHEFTE FUR CHEMIE | 2003年 / 134卷 / 06期
关键词
ellagic acid; X-ray structure analysis; electronic absorption spectra; pyridine complex; thermal analysis;
D O I
10.1007/s00706-002-0552-1
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The electronic absorption and polarized absorption spectra were measured at various pH conditions for ellagic acid. Comparison of these spectral data with MO calculations shows that ellagic acid exists in a 7:3 mixture of ethanol and water as free in the pH region less than 0.5, as a mixture of free and singly deprotonated species in the pH region 0.5-5.6, and as doubly deprotonated form in the pH region larger than 5.6, being deprotonated from hydroxyl group at position 8 (and/or 8'). In the pH region beyond 12.4, one lactone ring of the doubly deprotonated species opens to give a carboxyl derivative. Thermal and single crystal X-ray analyses show that ellagic acid forms a 1:4 complex with pyridine in the solid state. The endothermic energies indicate that the hydrogen bond energy between ellagic acid and pyridine is estimated to be ca. 11.4 kJ mol(-1) per pyridine. Ellagic acid molecules stack almost face-to-face with the intermolecular distance of ca. 4.8 Angstrom, and take column structure along the a-axis, inclining toward the a-axis. The columns of ellagic acid molecules are stabilized through pyridine-pyridine intermolecular interactions.
引用
收藏
页码:811 / 821
页数:11
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