The Relationship Between the Infra-Red Absorption Spectra of Some 5:5′-Substituted Barbituric Acids and Their Pharmacological Activity

Summary

1. The infra-red spectra of a number of barbiturates classified according to the duration of their activity in depressing the central nervous system have been recorded in the range of the carbonyl frequencies.

2. An analysis of the bands obtained has been made and their relation to the bonds derived.

3. It is found that the longer acting drugs tend to have a band system at slightly higher frequencies.

4. This indicates slightly lower polarities and greater fat-solubility, which is suggested as being a possible contributory cause to the duration of their activity.