An Infrared Study of the Reaction of Barbiturates with p-Nitrobenzyl Chloride

Abstract

In alkaline media barbiturates of the general formula HNCONHCOCR'R“CO react with p-nitrobenzyl chloride to sive derivatives of the composition NCONCOCH₂ C₆HNO₂CR'R”COCH₂-C₄HNO₂. It is postulated that the process of complex formation proceeds via the interaction of a negatively charged enolized barbituric acid ion with a positively charged p-nitrobenzyl ion. The infrared absorption spectra of the derivatives are in accord with this mechanism and suggest that in the complex the barbiturate is bonded to the p-nitrobenzyl moiety through the carbonyl oxygens in the 4 and 6 positions The compounds show unique features throughout the region studied, 4000–650 cm⁻¹, and hence the method affords a high degree of specificity for detecting and characterizing these sedative drugs

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