The Kinetics and Mechanism of the Reaction between Barbituric Acid and Glycidol, Part I: The Products Analysis

Abstract

The hydroxyalkyl derivatives of barbituric acid (BA) were formed in the reaction between BA and glycidol (GL). The reaction was performed at BA:GL 1:1, 1:2, and 1:4 molar ratios in DMF or without solvent. The progress of reaction was monitored by determination of the epoxide number and IR and NMR spectroscopy. It was found that primary reactive site of BA was C5 and further nitrogen ring atoms. BA was always involved in keto‐enol equilibrium, the latter form being less reactive. The isolated hydroxyalkyl derivatives are useful precursors of oligoetherols with the pyrimidine ring.

The Kinetics and Mechanism of the Reaction between Barbituric Acid and Glycidol, Part II: Glycidol Reacts with Imide and Methylene Groups

“…DEBA and GL were reagent-grade products supplied by Sigma-Aldrich (Steinheim, Germany) and DMBA (grade) was purchased from Alfa Aesar (Germany). Substrates and solvent (DMF) were purified before use as described in Part I [2].…”

“…Kinetics of DEBA and DMBA reaction with GL was studied as described in Part I [2], namely by determination of epoxide number (EN) and acidic number (AN). The temperature dependence on the rate of reaction was studied at constant concentration of DEBA or DMBA (1.00 mol kg −1 solvent) and fixed initial concentration of GL (2.00 or 1.00 mol kg −1 solvent, respectively) within the 90-120°C temperature range at 10°C intervals.…”

“…Barbituric acid (BA) undergoes enolization upon heating in glycidol (GL) [1,2]. It also reacts with GL to give hydroxyalkyl derivatives of BA.…”

“…It suggested that an keto-enol equilibrium of BA is reached and influenced the kinetic behavior of the system. Despite the complicated pattern of reaction, it has been found that a primary reaction site of BA was the methylene group at C 5 , and then upon prolonged time of reaction and GL availability the secondary reactive site became the imide group [2]. To further clarify the relative reactivity of these two different groups of BA, we have used the model compounds of BA with blocked C 5 : 5,5diethylbarbituric acid (DEBA) or with the blocked both imide groups: 1,3-dimethylbarbituric acid (DMBA).…”

Kinetics and Mechanism of the Reaction between Barbituric Acid and Glycidol, Part III: Methylene Group Reaction with Glycidol at High Concentration

“…The rate law was formulated based on substituting b versus time, t . The acidic number (AN) was determined by titration with KOH in the presence of phenolphthalein .…”