Characterization of hydrogen bonding between selected barbiturates and polyethylene glycol 4000 by IR spectral...

Several barbiturates and primidone were equilibrated with polyethylene glycol 4000 in pyridine. IR spectral properties of these samples indicate that seven disubstituted barbiturates complex with polyethylene glycol 4000 while five disubstituted barbiturates and two trisubstituted barbiturates as well as primidone do not. Forces responsible for complexation of barbiturates with polyethylene glycol 4000, as inferred from spectral data, consist of hydrogen bonds formed between N1 and N3 hydrogens of the barbiturate ring and two oxygen atoms of the --O--CH2CH2--O--moiety. Also, there appear to be three configurations of intermolecular hydrogen bonding sites between disubstituted barbiturates. Several factors affect the barbiturate-polyethylene glycol 4000 interaction, including the nature of the solvent, C5 substituents, the number of hydrogen bonds formed between reactants, and the 2-carbonyl group of the barbiturate ring. Complexes of polyethylene glycol 4000 with phenobarbital, butabarbital, and cyclobarbital are stable in water at 26 degrees or below, but complexes of polyethylene glycol 4000 with butethal, cyclopentenyl allylbarbituric acid, pentobarbital, and probarbital are not.