Determination of the Rate Constants of the Reactions CO2+ OH– → HCO3— and Barbituric Acid → Barbiturate Anion +H+ Using the Pulse Radiolysis Technique

Schuchmann, Man Nien; Sonntag, Clemens von

doi:10.1515/znb-1982-0917

Cited by 16 publications

(5 citation statements)

References 6 publications

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“…This was expected, since the reportedL5] value of k , = 1.6 x lo4 dm3mol-'s-' is close to that of the reaction of OH-with CO, [k(OH-+ CO, -+ HCO;) = 6.9 x l o 3 dm3 s -1]. [14] The conductivity in the present experiments was evalu-k , = 9 S K I . ated by fitting only the first (Faster) part of the conductivity change to a first-order reaction.…”

Section: A Kinetic Study Of the Hydrolysis Of Phosgene In Aqueous Solsupporting

confidence: 78%

“…'CC12-CCI,0H f 'CC12-C(0)C1 + H + + C1- (14) As can be seen from Figure 2 there is a third conductivity increase in the 100-ms time range. This increase is equivalent to 2.2 x l o -' mol J-', and its half-life is independent of the dose rate (dose per pulse).…”

Section: A Kinetic Study Of the Hydrolysis Of Phosgene In Aqueous Solmentioning

confidence: 86%

“…A geminal chlorohydrin similar to trichloromethanol (albeit with an unpaired electron in the position) is formed when the OH radical reacts with tetrachloroethene [reaction (13)]. In this case HCl is liberated within 3 vs [reaction (14)],['31 which implies k,, 2 7 x 10's-I. We thus conclude that phosgene is produced in situ at times 2 50 ps.…”

Section: A Kinetic Study Of the Hydrolysis Of Phosgene In Aqueous Solmentioning

confidence: 96%

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A Kinetic Study of the Hydrolysis of Phosgene in Aqueous Solution by Pulse Radiolysis

Mertens

Sonntag

Lind

et al. 1994

Angew. Chem. Int. Ed. Engl.

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COMMUNICATIONS i J 1 I I 10349 rellections]. wR2 = 0.141 ; Enraf-NoniusCAD4 four-circle diffractometer: 173 K : Cu,,, radiation: 11 =l.OOmm-'; 2.85 < 0 < 69 : empirical ahsorption correction (DIFABS [18]); structure solution with SHELX-86 [16], refinement with SHELXL-93 [17]: the torsion angles were refined for all the methyl groups. the remaining H atoms were calculated in ideal positions and treated iis "riding" in further refinements. 1 crystallizes with two formula units per unit cell in the triclinic space group PT. The asymmetric unit contains two cations. one anion. and one and a half molecules of benzene. Further details of thc ci-)\kil structiii-e investigation iimy be obtained from the Fachinformationszentrum Karlsruhe. D-76344 Eggenstein-Leopoldshafen (FRG) on quoting the depository number CSD-57976.

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Section: A Kinetic Study Of the Hydrolysis Of Phosgene In Aqueous Solsupporting

confidence: 78%

Section: A Kinetic Study Of the Hydrolysis Of Phosgene In Aqueous Solmentioning

confidence: 86%

Section: A Kinetic Study Of the Hydrolysis Of Phosgene In Aqueous Solmentioning

confidence: 96%

See 1 more Smart Citation

A Kinetic Study of the Hydrolysis of Phosgene in Aqueous Solution by Pulse Radiolysis

Mertens

Sonntag

Lind

et al. 1994

Angew. Chem. Int. Ed. Engl.

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“…In any case, dissolved CO 2 should be considered a final product in our LIOAS experiments, because the time for the reaction of CO 2 in aqueous medium exceeds by far the upper limit of integration time in our LIOAS experiment, i.e. at pH Ͼ 10 the reaction CO 2 ϩ OH Ϫ → HCO 3 Ϫ occurs with a bimolecular rate constant of 6900 M Ϫ1 /s at 21ЊC (20), and at pH Ͻ 8 the predominant reaction is CO 2 ϩ H 2 O → H 2 CO 3 , occurring with a pseudo-first order rate constant of 0.03 s Ϫ1 (21).…”

Section: Discussionmentioning

confidence: 99%

“…The second species cannot be attributed to the reaction of the detached CO 2 with the solvent, because this reaction occurs in a longer time scale than the upper time resolution of the LIOAS experiment (see above) (20,21). Thus, a reaction of carbanion 1 with the solvent should take place.…”

Section: Ph Effect On the Transient Speciesmentioning

confidence: 99%

Photodecarboxylation of Ketoprofen in Aqueous Solution. A Time-resolved Laser-induced Optoacoustic Study¶

Borsarelli

Braslavsky²,

Sortino

et al. 2000

Photochem Photobiol

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The photodecarboxylation reaction of 2-(3-benzoylphenyl)propionate (ketoprofen anion, KP-) was studied in water and in 0.1 M phosphate buffer solutions in the pH range 5.7-11.0 by laser-induced optoacoustic spectroscopy (LIOAS, T range 9.5-31.6 degrees C). Upon exciting KP- with 355 nm laser pulses under anaerobic conditions, two components in the LIOAS signals with well-separated lifetimes were found (tau 1 < 20 ns; 250 < tau 2 < 500 ns) in the whole pH range, whereas a long-lived third component (4 < tau 3 < 10 microseconds) was only detected at pH < or = 6.1. The heat and structural volume changes accompanying the first step did not depend on pH or on the presence of buffer. The carbanion resulting from prompt decarboxylation within the nanosecond pulse (< 10 ns) drastically reduces its molar volume ([-18.9 +/- 2.0] cm3/mol) with respect to KP- and its enthalpy content is (256 +/- 10) kJ/mol. At acid pH (ca 6), a species is formed with a lifetime in the hundreds of ns. The enthalpy and structural volume change for this species with respect to KP- are (181 +/- 15) kJ/mol and (+0.6 +/- 2.0) cm3/mol, respectively. This species is most likely a neutral biradical formed by protonation of the decarboxylated carbanion, and decays to the final product 3-ethylbenzophenone in several microsecond. At basic pH (ca 11), direct formation of 3-ethylbenzophenone occurs in hundreds of ns involving a reaction with the solvent. The global decarboxylation reaction is endothermic ([45 +/- 15] kJ/mol) and shows an expansion of (+14.5 +/- 0.5) cm3/mol with respect to KP-. At low pH, the presence of buffer strongly affects the magnitude of the structural volume changes associated with intermolecular proton-transfer processes of the long-lived species due to reactions of the buffer anion with the decarboxylated ketoprofen anion.

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Aufklärung von Peroxyl‐Radikalreaktionen in wäßriger Lösung mit strahlenchemischen Techniken

Sonntag

Schuchmann

1991

Angewandte Chemie

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Immer wenn es zur Bildung von Radikalen kommt, sei es thermisch, durch UV‐ und ionisierende Strahlen oder in Redoxreaktionen, werden sie in Gegenwart von Sauerstoff rasch in die entsprechenden Peroxyl‐Radikale überführt. Nicht nur in aquatischen Systemen wie den Flüssen, Seen und Meeren, sondern auch in der lebenden Zelle sowie in der Atmosphäre in beträchtlichem Ausmaß (in Wassertröpfchen) laufen Peroxyl‐Radikalreaktionen in wäßriger Umgebung ab. Die Peroxyl‐Radikalchemie in diesem Medium unterscheidet sich häufig sehr von der in der Gasphase oder in organischen Lösungsmitteln. Trotz der großen Bedeutung dieser Reaktionen auch in der Medizin, beispielsweise bei der Strahlentherapie des Krebses und der Ischämie, liegen vergleichsweise wenige Untersuchungen über Peroxyl‐Radikalreaktionen in wäßrigem Medium vor. Für derartige Untersuchungen liefern uns jedoch strahlenchemische Techniken, z. B. die Pulsradiolyse, die besten Handwerkszeuge. So überrascht es nicht, daß der überwiegende Teil der Kenntnisse auf diesem Gebiet mit strahlenchemischen Methoden gewonnen wurde. Die Strahlenchemie des Wassers kann so gelenkt werden, daß im wesentlichen ·OH‐Radikale entstehen (Ausbeute ca. 90%), die mit Substraten zu Substrat‐Radikalen und in Gegenwart von Sauerstoff zu den entsprechenden Substratperoxyl‐Radikalen reagieren. Auch kann man die experimentellen Bedingungen so wählen, daß ausschließlich HO 2·/O 2·⊖‐Radikale gebildet werden, die dann mit Substraten zur Reaktion gebracht werden können. Dies erlaubt somit auch einen Zugang zu diesen in biologischen Systemen so wichtigen Intermediaten. Durch eine detaillierte Produktanalyse und kinetische Untersuchungen mit Pulsradiolyse wurde die Chemie einer Reihe von Peroxyl‐Radikalen aufgeklärt, so daß jetzt ausreichend Material vorliegt, um die Vielfalt der mit strahlenchemischen Methoden untersuchten Peroxyl‐Radikalreaktionen zusammenfassend darstellen zu können. Nach einer etwas generelleren Übersicht über die physikalischen Eigenschaften der Peroxyl‐Radikale und ihre unimolekularen und bimolekularen Reaktionen wird auf ausgewählte Vertreter verschiedener Verbindungsklassen eingegangen. Wegen der großen biologischen Bedeutung der radikalinduzierten DNA‐Schädigung wird auch dieses Gebiet kurz gestreift.

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Determination of the Rate Constants of the Reactions CO₂+ OH^– → HCO₃— and Barbituric Acid → Barbiturate Anion +H⁺ Using the Pulse Radiolysis Technique

Cited by 16 publications

References 6 publications

A Kinetic Study of the Hydrolysis of Phosgene in Aqueous Solution by Pulse Radiolysis

A Kinetic Study of the Hydrolysis of Phosgene in Aqueous Solution by Pulse Radiolysis

Photodecarboxylation of Ketoprofen in Aqueous Solution. A Time-resolved Laser-induced Optoacoustic Study¶

Aufklärung von Peroxyl‐Radikalreaktionen in wäßriger Lösung mit strahlenchemischen Techniken

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