Die metallionenkatalytische Decarboxylierung der Oxalessigsäure (OES)

Abstract

Abb. 6. Relative Bildung der OES(Eno1)-Metallchelate (a) bzw. Decarboxylierunge-Geschwindigkeit der OES(Keton)-Metallchelate (b) in Abhiingigkeit von der Ordnungs-Rurve a: Bei der Chelatbildung maximal erreichbare Extinktion (60-90 Sek.), gemeesen Kurve b : Decarboxylierungs-Geschwindigkeitskonstanten k, ber. aus der Halkwertsaeit der C0,-Entwicklung bei 30,1° und p H = 1,SO. Im Warburg-GefiiS befmden sich:

Photofragmentation of Α‐oxocarboxylic Acids in Aqueous Solution. An Epr Study. Formation of Semidione Radicals by Decarboxylative Substitution of Α‐oxocarboxylic Acids by Acyl Radicals–ii. Oxaloacetic Acid (Oxosuccinic Acid)*

“…Taking account of the isomeric distribution, the ratio of the light absorbed at 280 nm by the enol and by the keto compound, respectively, is thus calculated to be 33.2: 1. Experiments with OAA are further complicated by its spontaneous decarboxylation in solution to pyruvic acid, especially when present in the monoanion form of the keto isomer (Tsai, 1967;Bamann et al, 1968;Duc and Thomas, 1972).…”

“…Reaction (3) can therefore be identified as the source of 2. 4 must be produced by reduction of pyruvic acid [reaction (4)] formed (Tsai, 1967;Bamann et al, 1968;Duc and Thomas, 1972) by thermal decarboxylation of OAA. 6 is derived from the keto isomer of OAA by H-abstraction.…”