On the Surprising Kinetic Stability of Carbonic Acid (H2CO3)

Loerting, Thomas; Tautermann, Christofer S.; Kroemer, Romano T.; Kohl, Ingrid; Hallbrucker, Andreas; Mayer, Erwin; Liedl, Klaus R.

doi:10.1002/(sici)1521-3773(20000303)39:5<891::aid-anie891>3.0.co;2-e

Cited by 165 publications

(225 citation statements)

References 23 publications

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“…In order for such exchange to occur, C-O bonds in the carbonic acid would have to break and reform. We regard this as unlikely given the kinetic stability of carbonic acid under anhydrous environments (Loerting et al, 2000;Hage et al, 1998 and reference therein). For these reasons, we focus on step 2-the dissociation of carbonic acid.…”

Section: Transition State Theory Of Reaction Ratesmentioning

confidence: 54%

Isotopic fractionations associated with phosphoric acid digestion of carbonate minerals: Insights from first-principles theoretical modeling and clumped isotope measurements

Guo

Mosenfelder

Goddard

et al. 2009

Geochimica et Cosmochimica Acta

230

374

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Section: Transition State Theory Of Reaction Ratesmentioning

confidence: 54%

Isotopic fractionations associated with phosphoric acid digestion of carbonate minerals: Insights from first-principles theoretical modeling and clumped isotope measurements

Guo

Mosenfelder

Goddard

et al. 2009

Geochimica et Cosmochimica Acta

230

374

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“…Further corroboration for this proposal comes from an analysis that demonstrates the surprising kinetic stability of carbonic acid in the absence of water. [35] The zinc ± nitrogen distance with optimized hydrogen bonds has been computed to be 6.9 , while the experimental value is 7.5 . [36] Considering the possibly nonoptimal hydrogen-bonding distances in the actual pocket of the enzyme (due to other restraints), this correspondence with the experimentally determined distance appears to be excellent.…”

Section: The H 2 O/hco 3 à Replacement Stepmentioning

confidence: 68%

New Insights into the Mechanistic Details of the Carbonic Anhydrase Cycle as Derived from the Model System [(NH3)3Zn(OH)]+/CO2: How does the H2O/HCO3− Replacement Step Occur?

Mauksch¹,

Bräuer

Weston

et al. 2001

ChemBioChem

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The full reaction path for the conversion of carbon dioxide to hydrogencarbonate has been computed at the B3LYP/6-311+G** level, employing a [(NH(3))(3)Zn(OH)](+) model catalyst to mimic the active center of the enzyme. We paid special attention to the question of how the catalytic cycle might be closed by retrieval of the catalyst. The nucleophilic attack of the catalyst on CO(2) has a barrier of 5.7 kcal mol(-1) with inclusion of thermodynamic corrections and solvent effects and is probably the rate-determining step. This barrier corresponds well with prior experiments. The intermediate result is a Lindskog-type structure that prefers to stabilize itself via a rotation-like transition state to give a Lipscomb-type product, which is a monodentate hydrogencarbonate complex. By addition of a water molecule, a pentacoordinated adduct with pseudo-trigonal-bipyramidal geometry is formed. The water molecule occupies an equatorial position, whereas the hydrogencarbonate ion is axial. In this complex, proton transfer from the Zn-bound water molecule to the hydrogencarbonate ion is extremely facile (barrier 0.8 kcal mol(-1)), and yields the trans,trans-conformer of carbonic acid rather than hydrogencarbonate as the leaving group. The carbonic acid molecule is bound by a short O...H-O hydrogen bond to the catalyst [(NH(3))(3)Zn(OH)](+), in which the OH group is already replaced by that of an entering water molecule. After deprotonation of the carbonic acid through a proton relay to histidine 64, modeled here by ammonia, hydrogencarbonate might undergo an ion pair return to the catalyst prior to its final dissociation from the complex into the surrounding medium.

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“…The first proton is transferred before reaching the TS and the second one after having passed the TS, which yields a hydronium ion (H 3 O ϩ ) character of the transition state. Recently, we found that a similar mechanism applies to the hydration of carbon dioxide (85). In contrast to this mechanism, the tautomerization of the 7-azaindole dimer, which is also facilitated by the addition of water molecules, is likely to occur stepwisely (86,87).…”

Section: Resultsmentioning

confidence: 99%

Toward elimination of discrepancies between theory and experiment: The rate constant of the atmospheric conversion of SO ₃ to H ₂ SO ₄

Loerting

Liedl

2000

Proc. Natl. Acad. Sci. U.S.A.

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On the Surprising Kinetic Stability of Carbonic Acid (H2CO3)

Cited by 165 publications

References 23 publications

Isotopic fractionations associated with phosphoric acid digestion of carbonate minerals: Insights from first-principles theoretical modeling and clumped isotope measurements

Isotopic fractionations associated with phosphoric acid digestion of carbonate minerals: Insights from first-principles theoretical modeling and clumped isotope measurements

New Insights into the Mechanistic Details of the Carbonic Anhydrase Cycle as Derived from the Model System [(NH3)3Zn(OH)]+/CO2: How does the H2O/HCO3− Replacement Step Occur?

Toward elimination of discrepancies between theory and experiment: The rate constant of the atmospheric conversion of SO ₃ to H ₂ SO ₄

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On the Surprising Kinetic Stability of Carbonic Acid (H2CO3)

Cited by 165 publications

References 23 publications

Isotopic fractionations associated with phosphoric acid digestion of carbonate minerals: Insights from first-principles theoretical modeling and clumped isotope measurements

Isotopic fractionations associated with phosphoric acid digestion of carbonate minerals: Insights from first-principles theoretical modeling and clumped isotope measurements

New Insights into the Mechanistic Details of the Carbonic Anhydrase Cycle as Derived from the Model System [(NH3)3Zn(OH)]+/CO2: How does the H2O/HCO3− Replacement Step Occur?

Toward elimination of discrepancies between theory and experiment: The rate constant of the atmospheric conversion of SO 3 to H 2 SO 4

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Toward elimination of discrepancies between theory and experiment: The rate constant of the atmospheric conversion of SO ₃ to H ₂ SO ₄