PRECIPITATION BEHAVIOR OF 1,1,DI-(PARA-HYDROXYPHENYL)CYCLOHEXANE CLATHRATE CRYSTALS FROM ACETONE SOLUTIONS CONTAINING D-LIMONENE

The precipitation behavior of 1,1-di(p-hydroxyphenyl)cyclohexane (DHC) from acetone solutions containing d-limonene (1-methyl-4-(1-methylethenyl)cyclohexene) was studied. From the pure acetone solution or the solutions containing a small amount of d-limonene crystals (B) precipitated, which clathrate only acetone with a guest/host (G/H) molar ratio of 1.0. However, when the d-limonene concentration is increased to more than ca. 2 mol L. crystals (A) precipitated which had a different habit from the B crystals. In the A crystals d-limonene is clathrated together with a large amount of acetone and the G/H value of d-limonene increases with the concentration in the solution up to the maximum value of 0.2. As the diffraction patterns of the A and B crystals are similar, it is assumed that a part of the acetone molecules in the B crystals are replaced by d-limonene molecules. The acetone in the A crystals escapes rapidly, but the d-limonene remains for a long time. This may indicate that the large molecule of d-limonene cannot diffuse rapidly within the host lattice owing to three-dimensional hindrance. It was clear that the solubility of the A crystals is higher than that of the B crystals and the transformation from the metastable A to the stable B crystals proceeds during the crystallization of A crystals.