Effect of β-cyclodextrin on mucochloric acid and 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone

Abstract

Cyclodextrins form inclusion complexes with a wide range of guest molecules which wholly, or in part, fit into their hydrophobic cavity. Since no covalent bonds are formed in this complexation, the guests can subsequently be eluted. The possibility of such complexation was envisioned as a means of removing chlorinated furanones from drinking water. Using a combination of infrared and ultraviolet techniques, evidence is presented for inclusion complex formation between mucochloric acid and β-cyclodextrin in acidic aqueous solutions. Ultraviolet evidence supports the conclusion that under these acidic conditions, mucochloric acid exists in its cyclic form. Solid samples of the mucochloric acid-β-cyclodextrin complex could be isolated by recrystallization of a 1∶1 mole ratio of the above compounds from water at pH ∼2. Solid sample infrared (potassium bromide or Nujol) showed a carbonyl shift of ∼20 cm⁻¹ when mucochloric acid was compared to the mucochloric acid-β-cyclodextrin complex. No such shift was found upon simply grinding together the above components. Thus the carbonyl shift is ascribed to inclusion complexation of mucochloric acid into the β-cyclodextrin cavity.

Melting point and thin-layer Chromatographic analyses also yielded supporting evidence for the formation of solid mucochloric acid-β-cyclodextrin complexes. Pilot studies with 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), suggest a similar β-cyclodextrin-complex formation in acidic solutions.