scholarly journals Chemical structure and biodegradability of halogenated aromatic compounds. Halogenated muconic acids as intermediates

1980 ◽  
Vol 192 (1) ◽  
pp. 331-337 ◽  
Author(s):  
E Schmidt ◽  
G Remberg ◽  
H J Knackmuss
Keyword(s):  
Chemical Structure ◽  
Acidic Solution ◽  
Pseudomonas Sp ◽  
Trans Form ◽  
Solution Ph ◽  
Muconic Acid ◽  
Acidic Solutions ◽  
Ph Conditions ◽  
Ylacetic Acid ◽  
Halogenated Aromatic Compounds

Substituted muconic acids were prepared from the corresponding catechols by pyrocatechase II from Pseudomonas sp. B13. The stabilities of substituted muconic acids were compared under different pH conditions. 3-Substituted cis, cis-muconic acids cycloisomerized readily in slightly acidic solutions, whereas 2-chloro- and 2-fluoro-cis, cis-muconic acids were stable under these conditions and could be isolated as crystalline compounds. They were isomerized to the cis, trans-form in highly acidic solution (pH 1), particularly when heated to 80 degrees C. Cycloisomerization of 2-chloro-cis, cis-muconic acid in 75% (v/v) H2SO4 yields 4-carboxymethyl-2-chloro-but-2-en-4-olide (4-chloro-2,5-dihydro-5-oxo-3H-furan-2-ylacetic acid). THe cis, cis-configuration of 2-chloromuconic acid was certified by 1H n.m.r. spectroscopy and by enzymic cycloisomerization. Although the cis, cis-configuration of 2-fluoromuconic acid was confirmed by corresponding spectroscopic data, it was not cycloisomerized by crude extracts or cycloisomerase II preparations from Pseudomonas sp. B13.

scholarly journals Chemical structure and biodegradability of halogenated aromatic compounds. Conversion of chlorinated muconic acids into maleoylacetic acid

1980 ◽  
Vol 192 (1) ◽  
pp. 339-347 ◽  
Author(s):  
E Schmidt ◽  
H J Knackmuss
Keyword(s):  
Aromatic Compounds ◽  
Chemical Structure ◽  
Pseudomonas Sp ◽  
Muconic Acid ◽  
Low Activity ◽  
Muconate Cycloisomerase ◽  
Halogenated Aromatic Compounds

1. An enzyme for the cycloisomerization of 2- and 3-chloro-cis, cis-muconic acid was isolated from 3-chlorobenzoate-grown cells of Pseudomonas sp. B13. It was named muconate cycloisomerase II, because it could it clearly be differentiated by its Km and Vmax. values from an ordinary muconate cycloisomerase, which functioned in benzoate catabolism and exhibited low activity with the chlorinated substrates. 2-Chloro-cis, cis-muconic acid was converted into trans- and 3-chloro-cis, cis–muconic acid into cis-4-carboxymethylenebut-2-en-4-olide together with dehalogenation. 2. An enzyme was isolated from chlorobenzoate-grown cells, which converted the 4-carboxymethylenebut-2-en-4-olides into maleoylacetic acid.

scholarly journals Chemical structure and biodegradability of halogenated aromatic compounds. Substituent effects on 1,2-dioxygenation of catechol

1978 ◽  
Vol 174 (1) ◽  
pp. 85-94 ◽  
Author(s):  
E Dorn ◽  
H J Knackmuss
Keyword(s):  
Chemical Structure ◽  
Substituent Effects ◽  
Alcaligenes Eutrophus ◽  
Reaction Rates ◽  
Pseudomonas Sp ◽  
Substituent Constant ◽  
Binding Studies ◽  
Km Value ◽  
Michaelis Constants ◽  
Halogenated Aromatic Compounds

1. The influence of halogen substituents on the 1,2-dioxygenation of catechols was investigated. The results obtained with the two isoenzymes pyrocatechase I and pyrocatechase II from the haloarene-utilizing Pseudomonas sp. B 13 and the pyrocatechase from benzoate-induced cells of Alcaligenes eutrophus B.9 were compared. 2. Substituents on catechol were found to interfere with O2 binding by the two isoenzymes from Pseudomonas sp. B 13, whereas the Km value for catechol kept constant at different O2 concentrations. 3. Electron-attracting substituents decreased the Km values for catechols. 4. Results from binding studies with substituted catechols demonstrated narrow stereospecificities of pyrocatechase I from pseudomonas sp. B 13 and the pyrocatechase from alcaligenes eutrophus B.9. In contrast, a low steric hindrance by substituents in the binding of catechols with pyrocatechase II was observed. 5. Low pK′1 values of substituted catechols resulted in low Michaelis constants. 6. Electron-attracting substituents such as halogen decreased the reaction rates of catechol 1,2-dioxygenation. The correlation of the Vmax. values observed with pyrocatechase II from Pseudomonas sp. B 13 with the substituent constant sigma+ (Okamoto–Brown equation) was distinctly greater than with Hammett's sigma values. The corresponding logVmax. against sigma+ correlation for pyrocatechase I was considerably disturbed by steric influences of the substituents.

scholarly journals Chemical structure and biodegradability of halogenated aromatic compounds. Two catechol 1,2-dioxygenases from a 3-chlorobenzoate-grown pseudomonad

1978 ◽  
Vol 174 (1) ◽  
pp. 73-84 ◽  
Author(s):  
E Dorn ◽  
H J Knackmuss
Keyword(s):  
Heavy Metals ◽  
Aromatic Compounds ◽  
Chemical Structure ◽  
Specific Activity ◽  
Pseudomonas Sp ◽  
Ph Optimum ◽  
Molecular Weights ◽  
Halogenated Aromatic Compounds

1. Two catechol 1,2-dioxygenases, pyrocatechase I and pyrocatechase II, were found in 3-chlorobenzoate-grown cells of Pseudomonas sp. B 13. The latter enzyme showed high relative activities with 3- and 4-chlorocatechol compared with catechol. 2. In benzoate-grown cells, only pyrocatechase I was induced. It was purified 29-fold with a final specific activity of 20 mumol of catechol oxygenated/min per mg of protein and an overall yield of 22%. Because of the instability of pyrocatechase II on chromatography and dialysis, no increase of specific activity was obtained during the purification experiments. 3. Molecular weights of pyrocatechase I and pyrocatechase II were 82000 and 67000 respectively. 4. For both pyrocatechases the pH optimum was found to be at 8.0.5. Inhibitions of the two pyrocatechases by Cu2+ and Hg2+ ions and p-chloromercuribenzoate were different. The effect on pyrocatechase I after incubation for 20 h with the heavy metals was decreased by addition of 1 mM-2-mercaptoethanol to the reaction mixture. The inhibition of pyrocatechase II was even enhanced under these conditions. 6. Extradiol cleavage of 3-methylcatechol in addition to intradiol fission at a ratio of 1:14 was observed only with pyrocatechase I.

Aged Co-Mo alloy thin film catalyst for hydrogen evolution reaction in acidic solution

2021 ◽  
pp. 2151018
Author(s):  
Cihan Kuru
Keyword(s):  
Thin Film ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Current Density ◽  
Acidic Solution ◽  
Alloy Film ◽  
Surface Oxide Layer ◽  
Alloy Thin Film ◽  
Acidic Solutions ◽  
Thin Film Catalyst

In this study, aged Co–Mo (3:10) alloy film has been demonstrated as an efficient and durable catalyst for hydrogen evolution reaction (HER) in acidic solution. The Co–Mo alloy films with varying Co/Mo atomic ratios have been deposited by magnetron sputtering. The catalytic activity of Mo film is outperformed by the Co–Mo alloys, among which the Co–Mo (3:10) alloy exhibits the highest HER activity with an overpotential of 310 mV at 10 mA cm[Formula: see text] current density, exchange current density of 1.74 × 10[Formula: see text] A cm[Formula: see text] and a Tafel slope of 61 mV dec[Formula: see text]. Combined with the good stability provided by the surface oxide layer, the aged Co–Mo (3:10) alloy is a promising catalyst for HER in acidic solutions.

scholarly journals Influence of solution pH on degradation of atrazine during UV and UV/H2O2 oxidation: kinetics, mechanism, and degradation pathways

RSC Advances ◽  
2019 ◽  
Vol 9 (61) ◽  
pp. 35847-35861 ◽  
Author(s):  
Yucan Liu ◽  
Kai Zhu ◽  
Miaomiao Su ◽  
Huayu Zhu ◽  
Jianbo Lu ◽  
...  
Keyword(s):  
Uv Irradiation ◽  
Oxidation Kinetics ◽  
Irradiation Time ◽  
Degradation Mechanism ◽  
Degradation Pathways ◽  
Solution Ph ◽  
H2o2 Oxidation ◽  
Ph Conditions

The kinetics, degradation mechanism and degradation pathways of atrazine (ATZ) during sole-UV and UV/H2O2 processes under various pH conditions were investigated; the effects of UV irradiation time and H2O2 dose were also evaluated.

Porous cobalt–nitrogen-doped hollow graphene spheres as a superior electrocatalyst for enhanced oxygen reduction in both alkaline and acidic solutions

2015 ◽  
Vol 3 (32) ◽  
pp. 16419-16423 ◽  
Author(s):  
Qiangmin Yu ◽  
Jiaoxing Xu ◽  
Chunying Wan ◽  
Chuxin Wu ◽  
Lunhui Guan
Keyword(s):  
Oxygen Reduction ◽  
Alkaline Solution ◽  
Acidic Solution ◽  
Acidic Solutions ◽  
Nitrogen Doped ◽  
Electrocatalytic Performance

Porous cobalt–nitrogen-doped hollow graphene spheres exhibit an excellent electrocatalytic performance, not only in alkaline solution, but also in acidic solution.

Investigation of Luminescent Poly(propylene imine) Dendrimer

2008 ◽  
Vol 8 (9) ◽  
pp. 4329-4334 ◽  
Author(s):  
Kana Tamano ◽  
Toyoko Imae
Keyword(s):  
Emission Band ◽  
Nmr Spectra ◽  
Chemical Structure ◽  
Acidic Solution ◽  
Structure Change ◽  
H Nmr ◽  
Long Time ◽  
Poly Propylene ◽  
Nmr Signals ◽  
Comparable Intensity

Luminescence phenomenon from NH2-terminated third generation poly(propylene imine) dendrimers in water was investigated. Two excitation bands (340 and 370 nm) and corresponding emission bands (∼400 and ∼450 nm, respectively) were detected. Emission bands were intensified with time, heating and air-bubbling and converged at certain intensities, where the ∼400 nm band was red-shifted. The initially weak emission band at ∼450 nm in an alkaline solution was intensified up to the comparable intensity to the strongest emission band at ∼400 nm in an acidic solution, after long time. While 1H NMR spectra depended on pH owing to the protonation of amine, those were slightly affected by the time, heating and air-bubbling. However, no new 1H NMR signals appeared even after long time, indicating no finding of chemical structure change of dendrimer. This suggests that the luminescent property should result from any interaction of amine with oxygen but not the chemical reaction.

scholarly journals Polyethyleneimine impregnated alginate capsule as a high capacity sorbent for the recovery of monovalent and trivalent gold

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yub Raj Dangi ◽  
John Kwame Bediako ◽  
Xiaoyu Lin ◽  
Jong-Won Choi ◽  
Che-Ryong Lim ◽  
...  
Keyword(s):  
Adsorption Mechanism ◽  
Acidic Solution ◽  
High Capacity ◽  
Uptake Capacity ◽  
Acidic Solutions ◽  
Prepared Material ◽  
New Type ◽  
Amine Groups ◽  
Ph Range ◽  
First Time

AbstractFor the first time, a polyethyleneimine-impregnated alginate capsule (PEIIAC) with a high adsorption capacity is developed for the recovery of monovalent and trivalent gold from an acidic solution. The strategy results in a new type of adsorbent, polyethyleneimine impregnated alginate capsule (PEIIAC) with a core–shell structure having a large number of amine groups as cationic binding site, facilitating maximum uptake of anionic auric chloride. The maximum uptake of PEIIAC was 3078 and 929 mg/g for Au (III) and Au (I), respectively, are recordable compared to other reported adsorbents to date. The as-prepared material was executed to check the sorption efficacy for Au (III) and Au (I) in the pH range of 1–12. With an increment in pH, the uptake capacity for Au (III) increased, while the uptake capacity for Au (I) decreased. The FTIR, XRD, and XPS studies revealed that the gold adsorption mechanism includes ionic interactions and reduction, wherein the amine, hydroxyl, and carboxyl groups are involved. The capsule showed a higher adsorption efficiency than other reported sorbents, making the material applicable in acidic solutions for the recovery of Au (I) and Au (III).

Study of the Iron Behavior in Acid Rain Water Solution by Application of Two Green Corrosion Inhibitors

2021 ◽  
Vol 6 (1) ◽  
pp. 19
Author(s):  
Meryem Zouarhi ◽  
Said Abbout ◽  
Hind Hammouch ◽  
Mohamed Chellouli ◽  
Hamid Erramli ◽  
...  
Keyword(s):  
Corrosion Inhibitors ◽  
Inhibition Efficiency ◽  
Acidic Solution ◽  
Water Solution ◽  
Solution Ph ◽  
Environment Friendly ◽  
Ohmic Drop ◽  
Acidic Rain ◽  
Corrosion Of Iron ◽  
Green Corrosion Inhibitors

The corrosion of iron in an acidic medium similar to acid rainwater (pH = 3.6) at various rotation speeds was investigated. The investigation included the inhibiting effect of two new green formulations containing oils extracted from the seeds of Jatropha curcas (labeled JAC) and Aleurite moluccana (labeled ALM). The inhibition efficiency was evaluated using electrochemical measurements, after performing an automatic ohmic drop compensation (ZIR). The results obtained show that an increase in the rotation speed leads an increase in the current density (from 75.57 µA/cm2 at 0 rpm to 99.09 µA/cm2 at 1500 rpm). This increase can be explained by the increase in the amount of dissolved oxygen at the electrode surface in the acidic rain solution (pH = 3.6). Also, the two environment-friendly corrosion inhibitors both act as mixed type inhibitors that protect iron against corrosion in the acidic solution. The inhibition efficiency increases with an increase in the inhibitor concentration to attain a maximum of 97% and 96% at 250 ppm of the ALM and the JAC, respectively.

Structure of early actinides(V) in acidic solutions

2009 ◽  
Vol 97 (7) ◽  
Author(s):  
M. V. Di Giandomenico ◽  
C. Le Naour ◽  
E. Simoni ◽  
D. Guillaumont ◽  
Philippe Moisy ◽  
...  
Keyword(s):  
Quantum Chemical Calculations ◽  
Hydrofluoric Acid ◽  
Quantum Chemical ◽  
Acidic Medium ◽  
Acidic Solution ◽  
Structural Information ◽  
Theoretical Calculations ◽  
Acidic Solutions ◽  
The Media ◽  
Actinide Series

AbstractProtactinium occupies a key position in the actinide series between thorium and uranium. In aqueous acidic solution, it is stable at oxidation state (V), occurring either as an oxocation or as a naked ion, depending on the media. Very few structural information on the hydration sphere of Pa(V) in acidic medium is available, in particular in hydrofluoric acid. Combined EXAFS and theoretical calculations have been used in this work to characterize the protactinium coordination sphere at various HF concentrations. The correlation of the XAFS data with quantum chemical calculations provides complementary structural and electronic models from

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