Uncatalyzed and Amine Catalyzed Decarboxylation of Acetoacetic Acid: An Examination in Terms of No Barrier Theory

Guthrie, J. Peter

doi:10.1006/bioo.2001.1231

Cited by 39 publications

(51 citation statements)

References 77 publications

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“…The Arrhenius parameters: E a,D = 22.8 kJ mol −1 , A D = 12.1 s −1 , associated with k D , the pseudo first‐order rate constant for the decomposition of D in ice, are much smaller than those typical of the thermal decarboxylation of β ‐oxocarboxylic acids in aqueous solution ( E a ∼ 95 kJ mol −1 , A‐factor ∼ 10 12 –10 13 s −1 ) [ Guthrie , 2002]. A D = 12.1 s −1 represents an impossibly large negative activation entropy for an elementary reaction: Δ S ∼ −230 J K −1 mol −1 [ Andraos , 2000; Benson , 1976].…”

Section: Resultsmentioning

confidence: 99%

Photolysis of pyruvic acid in ice: Possible relevance to CO and CO₂ ice core record anomalies

2007

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The abnormal spikes detected in some CO and CO2 polar ice core records indicate persistent chemical activity in glacial ice. Since CO and CO2 spikes are correlated, and their amplitudes scale with reported CO/CO2 yields for the photolysis of dissolved natural organic matter, a common photochemical source is implicated. Given that sufficient actinic radiation is constantly generated throughout ice by cosmic muons (Colussi and Hoffmann, 2003), it remains to be shown that the photolyses of typical organic contaminants proceed by similar mechanisms in water and ice. Here we report that the photodecarboxylation of pyruvic acid (PA, an ubiquitous ice contaminant) indeed leads to the same products nearly as efficiently in both media. CO2 is promptly released from frozen PA/H2O films upon illumination and continues to evolve after photolysis. By analogy with our studies in water (Guzmán et al., 2006b), we infer that 3PA* reacts with PA in ice producing CH3C(O)C(O)O· and (CH3 (OH)C(O)OH) radicals. The barrierless decarboxylation, CH3C(O)C(O)O· → CH3C(O)· + CO2, accounts for prompt CO2 emissions down to ∼140 K. Bimolecular radical reactions subsequently ensue in fluid molecular environments, both in water and ice, leading to metastable intermediates that decarboxylate immediately in water, but protractedly in ice. The overall quantum yield of CO2 production in the λ ~313 nm photolysis of PA in ice at 250 K is ∼60% of that in water at 293 K. The in situ photolysis of natural organic matter is, therefore, a plausible explanation of CO and CO2 ice core record anomalies.

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Section: Resultsmentioning

confidence: 99%

Photolysis of pyruvic acid in ice: Possible relevance to CO and CO₂ ice core record anomalies

2007

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“…Here, we found that 3-aminobutyric acid is also a promising amino donor for the asymmetric synthesis of chiral amine compounds using transaminases, as this molecule is changed into acetoacetic acid (compound d in Fig. 5) which is decomposed spontaneously into acetone and carbon dioxide (20), leading to easy removal from the reaction mixture at the end of the reaction (Fig. 5).…”

Section: Discussionmentioning

confidence: 96%

Cloning and Characterization of a Novel β-Transaminase fromMesorhizobiumsp. Strain LUK: a New Biocatalyst for the Synthesis of Enantiomerically Pure β-Amino Acids

Kim

Kyung

Yun

et al. 2007

Appl Environ Microbiol

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A novel ␤-transaminase gene was cloned from Mesorhizobium sp. strain LUK. By using N-terminal sequence and an internal protein sequence, a digoxigenin-labeled probe was made for nonradioactive hybridization, and a 2.5-kb gene fragment was obtained by colony hybridization of a cosmid library. Through Southern blotting and sequence analysis of the selected cosmid clone, the structural gene of the enzyme (1,335 bp) was identified, which encodes a protein of 47,244 Da with a theoretical pI of 6.2. The deduced amino acid sequence of the ␤-transaminase showed the highest sequence similarity with glutamate-1-semialdehyde aminomutase of transaminase subgroup II. The ␤-transaminase showed higher activities toward D-␤-aminocarboxylic acids such as 3-aminobutyric acid, 3-amino-5-methylhexanoic acid, and 3-amino-3-phenylpropionic acid. The ␤-transaminase has an unusually broad specificity for amino acceptors such as pyruvate and ␣-ketoglutarate/ oxaloacetate. The enantioselectivity of the enzyme suggested that the recognition mode of ␤-aminocarboxylic acids in the active site is reversed relative to that of ␣-amino acids. After comparison of its primary structure with transaminase subgroup II enzymes, it was proposed that R43 interacts with the carboxylate group of the ␤-aminocarboxylic acids and the carboxylate group on the side chain of dicarboxylic ␣-keto acids such as ␣-ketoglutarate and oxaloacetate. R404 is another conserved residue, which interacts with the ␣-carboxylate group of the ␣-amino acids and ␣-keto acids. The ␤-transaminase was used for the asymmetric synthesis of enantiomerically pure ␤-aminocarboxylic acids. (3S)-Amino-3-phenylpropionic acid was produced from the ketocarboxylic acid ester substrate by coupled reaction with a lipase using 3-aminobutyric acid as amino donor.

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“…The mechanism has been studied extensively by classical means. 5,6,7,8 A topic of debate stretching over 70 years concerned whether the decarboxylation was a concerted process in which the intramolecular proton transfer and carbon-carbon bond cleavage occurred in a single step (eq 1) or involved an initial proton transfer to afford an intermediate followed by a separate decarboxylation (eq 2). …”

Section: Introductionmentioning

confidence: 99%

“…A qualitative theoretical study by Guthrie applying no-barrier theory favored a stepwise pathway for the decarboxylation. 8 A gas-phase study of simple decarboxylations by Bach in 1996 found concerted TSs. 9 For the current study, it was particularly interesting that Bach’s TSs involved “essentially complete proton transfer.” This places the TS near the bottom edge of Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Concert along the Edge: Dynamics and the Nature of the Border between General and Specific Acid–Base Catalysis

Aziz

Singleton

2017

J. Am. Chem. Soc.

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Reactions that involve a combination of proton transfer and heavy-atom bonding changes are normally categorized by whether the proton transfer is occurring during the rate-limiting step, as in the distinction between general and specific acid-base catalysis. The experimental and computational study here of a β-ketoacid decarboxylation shows how the distinction between the two mechanisms breaks down near its border due to the differing time scales for proton versus heavy-atom motion. Isotope effects in the decarboxylation of benzoylacetic acid support a transition state in which the proton transfer is complete. In quasiclassical trajectories passing through this transition state, the new O–H bond after proton transfer undergoes several vibrations before heavy-atom motion completes the reaction. The bonding changes are thus temporally separated at a “dynamic intermediate” structure that acts equivalently to an ordinary intermediate in the trajectories, including the reversal of trajectories at the intermediate when the second “step” fails, but the structure is not an energy minimum. The results define a border between mechanisms where the usual energetic definition of intermediates is not meaningful.

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Uncatalyzed and Amine Catalyzed Decarboxylation of Acetoacetic Acid: An Examination in Terms of No Barrier Theory

Cited by 39 publications

References 77 publications

Photolysis of pyruvic acid in ice: Possible relevance to CO and CO₂ ice core record anomalies

Photolysis of pyruvic acid in ice: Possible relevance to CO and CO₂ ice core record anomalies

Cloning and Characterization of a Novel β-Transaminase fromMesorhizobiumsp. Strain LUK: a New Biocatalyst for the Synthesis of Enantiomerically Pure β-Amino Acids

Concert along the Edge: Dynamics and the Nature of the Border between General and Specific Acid–Base Catalysis

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Uncatalyzed and Amine Catalyzed Decarboxylation of Acetoacetic Acid: An Examination in Terms of No Barrier Theory

Cited by 39 publications

References 77 publications

Photolysis of pyruvic acid in ice: Possible relevance to CO and CO2 ice core record anomalies

Photolysis of pyruvic acid in ice: Possible relevance to CO and CO2 ice core record anomalies

Cloning and Characterization of a Novel β-Transaminase fromMesorhizobiumsp. Strain LUK: a New Biocatalyst for the Synthesis of Enantiomerically Pure β-Amino Acids

Concert along the Edge: Dynamics and the Nature of the Border between General and Specific Acid–Base Catalysis

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Photolysis of pyruvic acid in ice: Possible relevance to CO and CO₂ ice core record anomalies

Photolysis of pyruvic acid in ice: Possible relevance to CO and CO₂ ice core record anomalies