temperature and then acidified with dilute HC1 while cooling. The initial red color turned to yellow and then white. After the mixture was cooled in ice, a solid precipitate was collected, washed with H20, and dried under vacuum (0.1 mm). Taken up in 2 L of boiling CH3CN containing Norit, filtered, concentrated to 1 L, and cooled, it gave a first crop, and after concentration to 250 mL, a second was obtained for a total yield of tetranitrile 2 amounting to 3.15 g (81%): mp 325-330 °C dec (lit.2 mp >360 °C);
The kinetics of bromination of the 1,2-dihydro-1,3-dimethyl-2-oxopyrimidinium cation (Q+) in aqueous media (pH 0–5) have been studied using the stopped-flow method. At the higher acidities (pH < 2) the results are consistent with rate determining attack by bromine upon the pseudobase (QOH), whereas at low acidities (pH > 4) it appears that pseudobase formation is rate determining. The change occurs because at high acidity the reversal of the pseudobase QOH to the cation is fast relative to bromine attack, whereas at low acidity the converse is true. Results obtained at intermediate acidities (pH 2–4) are consistent with this interpretation.A separate kinetic study of pseudobase formation (and decomposition) yielded rate constants in good agreement with those derived from the bromination study.
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