Rate Constant and Mechanism of the Reaction of OH Radicals with Acetic Acid in the Temperature Range of 229−300 K

The thermodynamic stability of 11 complexes of Cu(II) and 26 complexes of Fe(III) is studied, comprising the ligands pyridoxamine (PM), ascorbic acid (ASC), and a model Amadori compound (AMD). In addition, the secondary antioxidant activity of PM is analyzed when chelating both Cu(II) and Fe(III), relative to the rate constant of the first step of the Haber-Weiss cycle, in the presence of the superoxide radical anion (O2•−) or ascorbate (ASC−). Calculations are performed at the M05(SMD)/6-311+G(d,p) level of theory. The aqueous environment is modeled by making use of the SMD solvation method in all calculations. This level of theory accurately reproduces the experimental data available. When put in perspective with the stability of various complexes of aminoguanidine (AG) (which we have previously studied), the following stability trends can be found for the Cu(II) and Fe(III) complexes, respectively: ASC < AG < AMD < PM and AG < ASC < AMD < PM. The most stable complex of Cu(II) with PM (with two bidentate ligands) presents a ΔGf0 value of −35.8 kcal/mol, whereas the Fe(III) complex with the highest stability (with three bidentate ligands) possesses a ΔGf0 of −58.9 kcal/mol. These complexes can significantly reduce the rate constant of the first step of the Haber-Weiss cycle with both O2•− and ASC−. In the case of the copper-containing reaction, the rates are reduced up to 9.70 × 103 and 4.09 × 1013 times, respectively. With iron, the rates become 1.78 × 103 and 4.45 × 1015 times smaller, respectively. Thus, PM presents significant secondary antioxidant activity since it is able to inhibit the production of ·OH radicals. This work concludes a series of studies on secondary antioxidant activity and allows potentially new glycation inhibitors to be investigated and compared relative to both PM and AG.

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Photooxidation of 1,3-butadiene containing systems: Rate constant determination for the reaction of acrolein with?OH radicals

International Journal of Chemical Kinetics ◽

10.1002/kin.550121202 ◽

1980 ◽

Vol 12 (12) ◽

pp. 905-913 ◽

Cited By ~ 27

Author(s):

Andrea Maldotti ◽

Claudio Chiorboli ◽

Carlo A. Bignozzi ◽

Carlo Bartocci ◽

Vittorio Carassiti

Keyword(s):

Rate Constant ◽

Oh Radicals ◽

Constant Determination

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Bacterial Spoilage of Citrus Products at pH Lower than 3.51

Journal of Milk and Food Technology ◽

10.4315/0022-2747-39.12.819 ◽

1976 ◽

Vol 39 (12) ◽

pp. 819-822 ◽

Cited By ~ 15

Author(s):

B. J. JUVEN

Keyword(s):

Acetic Acid ◽

Lactic Acid ◽

Thermal Resistance ◽

Tartaric Acid ◽

Lactobacillus Brevis ◽

Acid Inhibition ◽

Temperature Range ◽

Ph Values ◽

Sugar Syrup ◽

Z Value

A strain of Lactobacillus brevis, L-3, was isolated from a blown can of grapefruit segments in sugar syrup; it caused spoilage of citrus products having pH values lower than 3.5. When inoculated into orange (pH 3.38) and grapefruit (pH 2.99) juices, after 5 h at 30 C L-3 produced 15 and 22 μg diacetyl/ml, respectively, and off-flavor was detectable. L-3 grew in APT broth acidified to pH 3.0 with citric, hydrochloric, phosphoric, or tartaric acid. However, its growth was inhibited at pH 3.6 if the acidulant was lactic acid, while with acetic acid inhibition occurred at a pH between 3.7 and 4.0. The thermal resistance of L-3 in orange serum (pH 3.4) was studied in the temperature range of 52 to 60 C: a z value of 8.3 was obtained. A simple and reliable capillary technique for studying the thermal resistance of gas-producing organisms in liquid foods and media is presented.

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Die Reaktionen chlorierter Äthylene mit hydratisierten Elektronen und OH-Radikalen in wäßriger Lösung / The Reaction of Chlorinated Ethylenes with Hydrated Electrons and OH-Radicals in Aqueous Solution

Zeitschrift für Naturforschung B ◽

10.1515/znb-1971-1107 ◽

1971 ◽

Vol 26 (11) ◽

pp. 1108-1116 ◽

Cited By ~ 31

Author(s):

R. Köster ◽

K.-D. Asmus

Keyword(s):

Rate Constant ◽

Oh Radicals ◽

Capture Process ◽

Chlorinated Ethylenes ◽

Diffusion Controlled ◽

Hydrated Electrons ◽

Cl Atoms ◽

Type Radical ◽

Cl Atom ◽

Steric Hinderance

The reactions of chlorinated ethylenes with hydrated electrons and OH radicals have been investigated by using the method of pulse radiolysis. In addition γ-ray experiments were carried out. The reduction of the solutes occurs via a dissoziation electron capture process. The rate constant for the reaction of eaq⊖ with the more chlorinated compounds is essentially diffusion controlled (k= (1 - 2×1010 l-mole-1 sec-1). Vinylchloride and 1,2-trans-dichloroethylene react more slowly. This can be related to the higher stability of the C-Cl bond in these compounds.Hydroxyl radicals add to the C=C double bond of the chlorinated ethylenes. The rate constant for the reaction with vinylchloride was determined to 7.1 × 109 1 · mole-1 sec-1, and decreases with increasing degree of chlorination of the ethylenes. This effect is explained by the decreasing electron density on the C-atoms and steric hinderance. The hydroxyl radical always adds to the C-atom carrying the smallest number of Cl-atoms. In its reaction with 1,2-dichloro-, trichloro- and tetrachloroethylene a radical is produced with an OH group and a Cl-atom on the same C-atom. It eliminates HCl to form a C=O bond with k>7 × 105 sec-1. The type radical produced in this reaction has an optical absorption in the near UV (ε265 nm = (1-3)×103 1 · mole-1 cm-1).The OH radical addition products of vinylchloride and 1,1-dichloroethylene do not eliminate HCl and have no absorption in the visible and near UV.

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Theoretical and Experimental Study of the Product Branching in the Reaction of Acetic Acid with OH Radicals

The Journal of Physical Chemistry A ◽

10.1021/jp044679v ◽

2005 ◽

Vol 109 (10) ◽

pp. 2401-2409 ◽

Cited By ~ 31

Author(s):

F. De Smedt ◽

X. V. Bui ◽

T. L. Nguyen ◽

J. Peeters ◽

L. Vereecken

Keyword(s):

Experimental Study ◽

Acetic Acid ◽

Oh Radicals ◽

Product Branching

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Heterogeneous loss of OH on NaCl and NH<sub>4</sub>NO<sub>3</sub> at tropospheric temperatures

Annales Geophysicae ◽

10.1007/s00585-996-0659-5 ◽

1996 ◽

Vol 14 (6) ◽

pp. 659-664 ◽

Cited By ~ 1

Author(s):

A. V. Ivanov ◽

Y. M. Gershenzon ◽

F. Gratpanche ◽

P. Devolder ◽

J.-P. Sawerysyn

Keyword(s):

Temperature Dependence ◽

Detection Method ◽

Tropospheric Chemistry ◽

Minor Role ◽

Oh Radicals ◽

Flow Tube ◽

Temperature Range ◽

Uptake Coefficients

Abstract. The uptake coefficients (Γ) for OH radicals on some dry salts of tropospheric interest (NaCl and NH4NO3) have been investigated as a function of temperature using the flow tube technique combined with an EPR spectrometer as a detection method. The temperature dependence of Γ-values measured over the temperature range 245–340 K can be expressed in Arrhenius form: ΓOHNaCl=(1.2±0.7)×10–5exp[(1750±200)/T] and ΓOHNH4NO3=(1.4±0.5)×10–4exp[(1000±100)/T]. These Arrhenius expressions lead to very similar Γ-values (~4×10–3) for both salts studied at 300 K. It is shown that the heterogeneous OH sinks on solids aerosol play a very minor role in tropospheric chemistry in comparison with the homogeneous sinks.

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