Thesis (M.Sc.)--Chulalongkorn University, 2003

This thesis presents the first successful crystal structure determination of anhydrobarakol and anhydrobarakol hydrochloride. Anhydrobarakol and anhydrobarakol hydrochloride were crystallized in a monoclinic system, space group P21/c and P21/n, Z = 4 with unit cell parameters a = 13.2280(7), b= 6.8738(2) , c = 19.7879(9) A, [beta] = 127.013(2) and a = 12.2547(2), b = 8.051(2) , c = 12.8133(2) A, [beta] = 99.514(1), respectively. The novel 1:1 molecular complexes of barakol and carboxylic acid (phthalic acid and 3-hydroxybenzoic acid) were synthesized and charactherized by spectroscopic and X-ray crystallographic techniques. Electrostatic effects, electron delocalization, and intermolecular interactions in the barakol ring system were investigated. The X-ray crystallographic studies revealed that the barakol-phthalate complex exists in an ion-pair complex. The formation of barakol-phthalate ion-pair complex is stabilized by the complementary of ion-ioninteraction, [pi-pi] interaction and hydrogen bonding. The barakol-3-hydroxybenzoic acid complex is a [pi-pi] molecular complex. The co-crystallization of barakol-3-hydroxybenzoic acid complex is solely stabilized by [pi-pi] interactions. The spectroscopic studies including IR, 1H-NMR and UV-visible are consistent with the results from the X-ray analysis. The 1H-NMR spectrum of the barakol and phthalic acid complex in a mixture of CDCl3-CD3OD showed a dramatic spectral changes with downfield shifts of the ortho-protons of phthalic acid ([triangle][delta]H(ppm) = 0.37), and the proton resonances of barakol ([triangle][delta](ppm) = 0.31 for proton H3, 0.53 for proton H4, 0.57 for proton H6 and 0.33 for proton H9).