ABSTRACT
This chapter provides a discussion of the physicochemical properties, synthesis, and structure-activity-relationships of the barbiturates, 1, 3-propanodiols, and benzodiazepines. Barbituric acid, like the monoureides, may be synthesized by a condensation of urea with malonic acid. The sodium salts of these barbiturates which are present in the lactam moiety are relatively soluble and unstable in aqueous and alcoholic solutions. Barbiturates in physical solution exist in both the unionized and ionized state. The extent of ionization of these weak acids is not only dependent on their pKa, but the pH of their solution. The newer minor tranquilizers, such as the propanediol and benzodiazepine derivatives, were primarily introduced into clinical medicine in the 1950’s to replace the barbiturates for their anxiolytic and sedative effects. The dose of this agent that is anticonvulsant produces a drug-induced sleep, while an agent like pheno-barbital terminates convulsions at a dose that is approximately 1/3 the hypnotic dose.
