Reaction models for cooperative catalysis between metal ions and acids or bases: hydration and enolization of oxalacetate

Tsai, Suh Jen; Leussing, D. L.

doi:10.1021/ic00263a015

Cited by 9 publications

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“…In suitable cases, divalent metal ions may also afford electrophilic catalysis of ester hydrolysis (15), as distinct from cases where the catalysts function by delivering a metalbound OH-to the ester (or amide) carbonyl(7c, 16) or in some other way (17). 13 The present results emphasize that any reaction that produces a salicylate-type dianion in its rate-limiting step has the potentiality for electrophilic catalysis by metal ions, as well as by the proton. ow ever, the extent to which a significant amount of metal ion catalysis actually occurs depends primarily on whether it can compete with proton catalysis.…”

Section: --Tmentioning

confidence: 51%

Metal ion catalysis of the decomposition of transient 2-carboxy-2,5-cyclohexadienones in aqueous solution

Tee¹,

Iyengar²

1988

Can. J. Chem.

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OSWALD S. TEE and N. RANI IYENGAR. Can. J. Chem. 66, 1 194 (1988).Bromide ion induced debromination of the anion of 4-bromo-4-methyl-2,5-cyclohexadienone-2-carboxylic acid (1) is catalyzed by cupric ions and ferric ions. Similarly, the enolization of the anion of the benzocyclohexadienone 3, which is formed during the bromination of 1-naphthol-2-carboxylic acid, is catalyzed by some metal ions. The origin of the catalysis in these reactions is strong metal ion binding to the incipient dianion products that are of the salicylate type. Evidence for this is that the efficiency of the metal (and hydrogen) ion catalysis parallels the stability of the analogous complexes with the salicylate dianion.OSWALD S. TEE et N. RANI IYENGAR. Can. J. Chem. 66, 1194 (1988.La dkbromation, induite par l'ion bromure, de l'anion de l'acide bromo-4 mCthyl-4 cyclohexadiene-2,5 one-2 carboxylique (1) est catalysCe par les ions cuivrique et ferrique. De la m&me manikre, l'tnolisation de l'anion de la benzacyclohexadienone 3, qui se forme lors de la bromation de l'acide naphtol-1 carboxylique-2, est catalyste par quelques ions mttalliques. La catalyse dans ces rkactions est due B la forte liaison des ions mCtalliques avec les produits dianioniques qui se foment et qui sont du type salicylate. Le fait que I'efficacitC de la catalyse par les ions mttalliques (ou I'hydrogtne) soit parallele B la stabilitt des complexes analogues avec le dianion salicylate est en accord avec la conclusion prkctdente.[Traduit par la revue]Labile cyclohexadienones can be observed during the aqueous bromination of phenols lacking electron-withdrawing groups (1-4). Two types of dienone are formed and they decompose by different reactions, depending on the phenol. Where the starting phenol has nopara substituent a transient 4-bromo-2,5-cyclo-hexadienone is formed, which enolizes to the 4-bromo product (1-3). On the other hand, withp-alkylphenols, part of the initial fast bromine attack occurs ipso to the alkyl group, leading to a 4-alkyl-4-bromo-2,5-cyclohexadienone, an "ipsodienone" (4,5), which cannot enolize and which decomposes by debromination ( l , 4 ) .Two particularly interesting examples of the above types of intermediates that we have found are the cyclohexadienones 1 and 3, derived from bromine attack on certain salicylic acids. The bromide ion induced debromination of the ipso-dienone 1 (--, 2-, eq. [I]) is greatly facilitated by the 2-carboxyl group (4, 6). Similarly, the enolization of the benzocyclohexadienone 3 (+ 4-, eq. [2]) is catalyzed by its internal carboxyl group and by Br-Br 0 external bases (3). We hereby report that the debromination of 1 and the enolization of 3 are also catalyzed by some metal ions.We were prompted to look for such behaviour by the ongoing interest in enzymic and non-enzymic metal ion catalyzed reac-'Author to whom correspondence may be addressed. tions (7,8) and by the knowledge that salicylate dianions form weak to strong complexes with various metal ions (9). It was anticipated that the binding of metal ions to the a...

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Section: --Tmentioning

confidence: 51%

Metal ion catalysis of the decomposition of transient 2-carboxy-2,5-cyclohexadienones in aqueous solution

Tee¹,

Iyengar²

1988

Can. J. Chem.

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“…Evidence of this could be found in Larson and Lister, where at pH below p K CuA(1968) = 3.81 (p K [Cu(H2A)] in this study), rates of decarboxylation in (acetonedicarboxylato)copper solutions were only 20% higher than those in acetonedicarboxylate solutions without copper, indicating a marginal increase in reactivity . Competition between H + and Cu II ions for ligands and catalyzed enolization reactions at acidic pH has also been found in studies on oxalacetate, 2-oxalopropionic acid, and acetylacetone metal-enol(ate)s. − ,, An inflection point over the pH range 3.0–4.0 of the pH-dependent bell-shaped copper-catalyzed decarboxylation rate constant profile in Hay and Leong happened to coincide with p K [Cu(H2A)] , which falls between those two pH values. This inflection point may therefore provide a previously overlooked hint toward the underlying reaction mechanism.…”

Section: Resultsmentioning

confidence: 99%

“…Naturally occurring 1,3- and 1,3,5-β-keto(carboxylic) acids rely on β-carbonyl/α-carbon CH 2 resonance to form keto-enol tautomers and enolates with transition metals and have remained as an area of continued research due to their wide importance across chemical disciplines . Although fundamental research studies, such as the metal-ion-catalyzed decarboxylation of oxaloacetate, − have provided detailed information on reaction mechanisms, other studies seek to broaden our understanding of the biochemical significance of metal-enol(ate)s. For example, in active sites of enolases, Serratia endopeptidase, dioxygenase, and in β-keto acid cleavage enzymes, transition metals have been shown or postulated to induce enolization and stabilize reactive enolates, which otherwise do not exist at significant concentration at circumnetural pH. − At physiological pH, deprotonation of β-keto acid α-carbon CH 2 is generally unfavorable in the absence of metal ions or metalloenzymes, but in their presence, pathways for enol and enolate formation open up .…”

Section: Introductionmentioning

confidence: 99%

“…[2][3][4][5]7,37 An inflection point over the pH range 3.0− 4.0 of the pH-dependent bell-shaped copper-catalyzed decarboxylation rate constant profile in Hay and Leong happened to coincide with pK [Cu(H2A)] , which falls between those two pH values. This inflection point may therefore provide a previously overlooked hint toward the underlying reaction mechanism.…”

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confidence: 99%

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New Insight into and Characterization of the Aqueous Metal-Enol(ate) Complexes of (Acetonedicarboxylato)copper

Jefferson

Song

et al. 2017

ACS Omega

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Nearly 50 years have passed since the classic studies by Larson and Lister [ Larson D. W. Lister M. W. Larson D. W. Lister M. W. Can. J. Chem. 1968 , 46 823 and Hay and Leong [ Hay R. W. Leong K. N. Hay R. W. Leong K. N. J. Chem. Soc. A 1971 0 3639 on the copper-catalyzed decarboxylation of acetonedicarboxylic acid (H 3 Acdica). Although the authors laid the foundations for what we know about this reaction; still very little information exists regarding the underlying aqueous metal-enol(ate)s of (acetonedicarboxylato)copper. In this study, UV–visible titrations revealed three p K values, p K [Cu(H2A)] , p K [Cu(HA)] , and p K [Cu(A)] . We associated the first two with ionization of α-carbon CH 2 groups in [Cu II (H 2 Acdica) keto ] 1+ and [Cu II (HAcdica) keto ] 0 to form unstable metal-enolates, {[Cu II (HAcdica) enolate ]} and {[Cu II (Acdica) enolate ]}, which through β-carbonyl oxygen protonation can form metal-enols [Cu II (H 2 Acdica) enol ] 1+ and [Cu II (HAcdica) enol ] 0 . The square-planar Cu II center (electron paramagnetic resonance results) plays a dual role of stabilizing negative electron density at the β-carbonyl oxygen and as an electron sink in [[Cu I (HAcdica) enolate ] 0 ] ‡ and [[Cu I (Acdica) enolate ] 1– ] ‡ (confirmed through cyclic voltammetry as two single 1 e – transfers). The π → π* transition associated with [Cu II (HAcdica) enol ] 0 was used to determine p K [Cu(A)] (deprotonation of enol OH) and enolization rate constant (stopped-flow spectroscopy) but also exhibited a time-dependent decrease in absorbance (on the order of min –1 ), suggesting a new method to possibly obtain experimental values for the estimated “ k CuL ...

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“…For [Zn(II)] >1 mM, k −2 drops to the unaugmented value. This inhibition results from the formation of unreactive dinuclear enolate metal ion complexes (Covey & Leussing 1974; Tsai & Leussing 1987). The results shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Oxaloacetate-to-malate conversion by mineral photoelectrochemistry: implications for the viability of the reductive tricarboxylic acid cycle in prebiotic chemistry

Guzmán

Martin

2008

International Journal of Astrobiology

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The carboxylic acids produced by the reductive tricarboxylic acid (rTCA) cycle are possibly a biosynthetic core of initial life, although several steps such as the reductive kinetics of oxaloacetate (OAA) to malate (MA) are problematic by conventional chemical routes. In this context, we studied the kinetics of this reaction as promoted by ZnS mineral photoelectrochemistry. The quantum efficiency w MA of MA production from the photoelectrochemical reduction of OAA followed w MA =0.13 [OAA] (2.1r10 x3 +[OAA]) x1 and was independent of temperature (5 to 50 xC). To evaluate the importance of this forward rate under a prebiotic scenario, we also studied the temperature-dependent rate of the backward thermal decarboxylation of OAA to pyruvate (PA), which followed an Arrhenius behavior as log (k x2 )=11.74-4956/T, where k x2 is in units of s x1 . These measured rates were employed in conjunction with the indirectly estimated carboxylation rate of PA to OAA to assess the possible importance of mineral photoelectrochemistry in the conversion of OAA to MA under several scenarios of prebiotic conditions on early Earth. As an example, our analysis shows that there is 90 % efficiency with a forward velocity of 3 yr/cycle for the OAApMA step of the rTCA cycle at 280 K. Efficiency and velocity both decrease for increasing temperature. These results suggest high viability for mineral photoelectrochemistry as an enzyme-free engine to drive the rTCA cycle through the early aeons of early Earth, at least for the investigated OAApMA step.

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Reaction models for cooperative catalysis between metal ions and acids or bases: hydration and enolization of oxalacetate

Abstract: Cage Complex Formation: 25 °C, I = 0.275, d = 6 Á

Cited by 9 publications

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Metal ion catalysis of the decomposition of transient 2-carboxy-2,5-cyclohexadienones in aqueous solution

Metal ion catalysis of the decomposition of transient 2-carboxy-2,5-cyclohexadienones in aqueous solution

New Insight into and Characterization of the Aqueous Metal-Enol(ate) Complexes of (Acetonedicarboxylato)copper

Oxaloacetate-to-malate conversion by mineral photoelectrochemistry: implications for the viability of the reductive tricarboxylic acid cycle in prebiotic chemistry

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