クロラムフェニコール長鎖状エステルのPolymorphism (第1報)

転移について

抄録

It was found that chloramphenicol palmitate, myristate, and caprylate come in two kinds of crystalline form and one amorphous form. These compounds were prepared and their transition conditions were examined.
1) When the crystals is dissolved in a solvent and crystallized out, optional form of crystals can be obtained by controlling crystallization rate and this form is not affected by polarity or pH of the solvent. Crystals of α-form is obtained by rapid crystallization while the β-form is obtained by gradual crystallization. When a small amount is fused and cooled rapidly in a refrigerator, a vitrious substance is obtained.
2) Transition between the solids occur only in the direction of amorphous to α-form to β-form, and there is no reverse progress. The transition rate is faster, the nearer the melting point. The mechanism of such a transition is thought to be the transition to a stable form by the heat motion of the molecule itself. The transition rate becomes suddenly rapid after formation of β-form crystal and this is considered to be due to added effect of catalytic transition.