Acyclic versus cyclic π-electron delocalization. How is the substituent effect related to π-electron delocalization?

2009 ◽  
Vol 74 (1) ◽  
pp. 115-129 ◽  
Author(s):  
Michał A. Dobrowolski ◽  
Jędrzej Kaniewski ◽  
Tadeusz M. Krygowski ◽  
Michał K. Cyrański
Keyword(s):  
Electron Donor ◽  
Electron Acceptor ◽  
Substituent Effect ◽  
Electron Donors ◽  
Electron Delocalization ◽  
Benzene Derivatives ◽  
Phenol Derivatives ◽  
Stabilization Energies ◽  
Derivatives Of ◽  
Substituted 1

Substituent effect stabilization energies were estimated for sets of 27 para-substituted phenol derivatives, meta- and para-homodisubstituted benzene derivatives, trans-substituted ethenes, 4-substituted 1-hydroxy-1,3-cyclohexadienes and 1,4-homodisubstituted 1,3-cyclohexadienes based on the optimizations at the B3LYP/6-311+G** DFT level of theory. The following substituents were taken into account: C≡CH, C(CN)3, CF3, CH2NH2, CH3, CH=CH2, CHO, Cl, CN, COCH3, COCl, CONH2, COOCH3, COOH, F, NH2, NHCH3, N(CH3)2, NHOH, NO, NO2, OCH3, OH, Ph, H, SH, SO2CN. For hydroxyethenes and phenol derivatives the electron-acceptor substituents stabilize the systems, whereas the electron-donors lead to their destabilization. Both electron-acceptor and electron-donor substituents destabilize homodisubstituted ethene and meta- and para-homodisubstituted benzene species. The strongest destabilization is observed for derivatives of ethene, a weaker one for derivatives of cyclohexadiene and the weakest for benzene derivatives.

Microbial Perchlorate Reduction in Groundwater with Different Electron Donors

2013 ◽  
Vol 295-298 ◽  
pp. 1402-1407
Author(s):  
Rui Wang ◽  
Ming Chen ◽  
Jia Wen Zhang ◽  
Fei Liu ◽  
Hong Han Chen
Keyword(s):  
Removal Efficiency ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Reduction Rate ◽  
Electron Donors ◽  
Monod Equation ◽  
Hydrogen Addition ◽  
Perchlorate Reduction ◽  
Perchlorate Removal

Effects of different electron donors (acetate and hydrogen), acetate and perchlorate concentrations on microbial perchlorate reduction in groundwater were studied. The results showed that acetate and hydrogen addition as an electron donor can significantly improve perchlorate removal efficiency while a longer period was observed for hydrogen (15 d) than for acetate (8 d). The optical ratio of electron donor (acetate)-to-electron acceptor (perchlorate) was approximately 1.65 mg COD mg perchlorate-1. The highest specific reduction rate of perchlorate was achieved at the acetate-to-perchlorate ratio of 3.80 mg COD mg perchlorate-1. The perchlorate reduction rates corresponded well to the theoretical values calculated by the Monod equation and the parameters of Ks and Vm were determined to be 15.6 mg L-1 and 0.26 d-1, respectively.

scholarly journals Diversity and Ubiquity of Bacteria Capable of Utilizing Humic Substances as Electron Donors for Anaerobic Respiration

2002 ◽  
Vol 68 (5) ◽  
pp. 2445-2452 ◽  
Author(s):  
John D. Coates ◽  
Kimberly A. Cole ◽  
Romy Chakraborty ◽  
Susan M. O'Connor ◽  
Laurie A. Achenbach
Keyword(s):  
Energy Source ◽  
Carbon Source ◽  
Humic Substances ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Electron Donors ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
Couple Growth ◽  
Probable Number

ABSTRACT Previous studies have demonstrated that reduced humic substances (HS) can be reoxidized by anaerobic bacteria such as Geobacter, Geothrix, and Wolinella species with a suitable electron acceptor; however, little is known of the importance of this metabolism in the environment. Recently we investigated this metabolism in a diversity of environments including marine and aquatic sediments, forest soils, and drainage ditch soils. Most-probable-number enumeration studies were performed using 2,6-anthrahydroquinone disulfonate (AHDS), an analog for reduced HS, as the electron donor with nitrate as the electron acceptor. Anaerobic organisms capable of utilizing reduced HS as an electron donor were found in all environments tested and ranged from a low of 2.31 × 101 in aquifer sediments to a high of 9.33 × 106 in lake sediments. As part of this study we isolated six novel organisms capable of anaerobic AHDS oxidation. All of the isolates coupled the oxidation of AHDS to the reduction of nitrate with acetate (0.1 mM) as the carbon source. In the absence of cells, no AHDS oxidation was apparent, and in the absence of AHDS, no cell density increase was observed. Generally, nitrate was reduced to N2. Analysis of the AHDS and its oxidized form, 2,6-anthraquinone disulfonate (AQDS), in the medium during growth revealed that the anthraquinone was not being biodegraded as a carbon source and was simply being oxidized as an energy source. Determination of the AHDS oxidized and nitrate reduced accounted for 109% of the theoretical electron transfer. In addition to AHDS, all of these isolates could also couple the oxidation of reduced humic substances to the reduction of nitrate. No HS oxidation occurred in the absence of cells and in the absence of a suitable electron acceptor, demonstrating that these organisms were capable of utilizing natural HS as an energy source and that AHDS serves as a suitable analog for studying this metabolism. Alternative electron donors included simple volatile fatty acids such as propionate, butyrate, and valerate as well as simple organic acids such as lactate and pyruvate. Analysis of the complete sequences of the 16S rRNA genes revealed that the isolates were not closely related to each other and were phylogenetically diverse, with members in the alpha, beta, gamma, and delta subdivisions of the Proteobacteria. Most of the isolates were closely related to known genera not previously recognized for their ability to couple growth to HS oxidation, while one of the isolates represented a new genus in the delta subclass of the Proteobacteria. The results presented here demonstrate that microbial oxidation of HS is a ubiquitous metabolism in the environment. This study represents the first description of HS-oxidizing isolates and demonstrates that microorganisms capable of HS oxidation are phylogenetically diverse.

Electrical properties of crystal compounds of graphite - III. The role of electron donors

1960 ◽  
Vol 258 (1294) ◽  
pp. 339-349 ◽  
Keyword(s):  
Alkali Metal ◽  
Thermoelectric Power ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Electrical Resistance ◽  
Pyrolytic Graphite ◽  
Electron Donors ◽  
Aluminium Chloride ◽  
Metal Atoms ◽  
Donor And Acceptor

Crystal compounds between potassium and well-oriented pyrolytic graphite have been prepared with a range of compositions up to saturation. Measurements have been made of changes of electrical resistance and of thermoelectric power as a function of composition in both a - and c -axis directions. Anisotropy of electrical resistance becomes smaller, and of thermoelectric power sinks to practically zero, on compound formation. Compounds between graphite and rubidium or caesium have been studied more briefly under conditions approximating to saturation. In the direction of the a -axis, the large decreases of electrical resistance observed can be interpreted on the basis that the alkali metal atoms inject electrons into the upper π -band of graphite. This is confirmed by the observed changes of thermoelectric power. Changes resemble but do not completely mirror those observed with electron acceptor compounds; the fractional transfer of electrons appears to be less complete with the electron donors. In the direction of the c -axis, intercalation of the electron donor alkali metal atoms leads to a much more striking decrease of electrical resistance than is observed with various electron acceptor groups. To supplement results previously published, brief studies are reported on crystal compounds between graphite and aluminium chloride, and graphite and iodine monochloride. Possible band models for graphite compounds with both electron donor and acceptor atoms are discussed in the light of the experimental findings.

ChemInform Abstract: N-METHACRYLOYLOXYETHYL DERIVATIVES OF INDOLINE SPIROPYRANS CONTAINING ELECTRON-ACCEPTOR AND ELECTRON-DONOR SUBSTITUENTS

1978 ◽  
Vol 9 (31) ◽  
Author(s):  
S. I. BESHENKO ◽  
N. A. ZAICHENKO ◽  
V. V. BUZAEV ◽  
V. D. ERMAKOVA ◽  
M. I. CHERKASHIN
Keyword(s):  
Electron Donor ◽  
Electron Acceptor ◽  
Derivatives Of

scholarly journals Bis(vinylenedithio)tetrathiafulvalene analogues of BEDT-TTF

2015 ◽  
Vol 11 ◽  
pp. 403-415 ◽  
Author(s):  
Erdal Ertas ◽  
İlknur Demirtas ◽  
Turan Ozturk
Keyword(s):  
Electron Donor ◽  
Electron Donors ◽  
Electron Delocalization ◽  
Current Status ◽  
Phenyl Rings

This review aims to give an overview of the current status of our research on the synthesis of π-electron donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF, ET) analogues prepared from 1,8-diketones via a ring forming reaction. The new synthesized π-electron donors have vinyl moieties producing extended π-electron delocalization over the substituent phenyl rings at the peripheries.

scholarly journals Anaerobic Oxidation of Arsenite in Mono Lake Water and by a Facultative, Arsenite-Oxidizing Chemoautotroph, Strain MLHE-1

2002 ◽  
Vol 68 (10) ◽  
pp. 4795-4802 ◽  
Author(s):  
Ronald S. Oremland ◽  
Shelley E. Hoeft ◽  
Joanne M. Santini ◽  
Nasreen Bano ◽  
Ryan A. Hollibaugh ◽  
...  
Keyword(s):  
Electron Donor ◽  
Electron Acceptor ◽  
Chemical Oxidation ◽  
Electron Donors ◽  
Mono Lake ◽  
Mineral Salts ◽  
Gene Encoding ◽  
16S Ribosomal Dna ◽  
Aerobic And Anaerobic ◽  
Ribosomal Dna Sequence

ABSTRACT Arsenite [As(III)]-enriched anoxic bottom water from Mono Lake, California, produced arsenate [As(V)] during incubation with either nitrate or nitrite. No such oxidation occurred in killed controls or in live samples incubated without added nitrate or nitrite. A small amount of biological As(III) oxidation was observed in samples amended with Fe(III) chelated with nitrolotriacetic acid, although some chemical oxidation was also evident in killed controls. A pure culture, strain MLHE-1, that was capable of growth with As(III) as its electron donor and nitrate as its electron acceptor was isolated in a defined mineral salts medium. Cells were also able to grow in nitrate-mineral salts medium by using H2 or sulfide as their electron donor in lieu of As(III). Arsenite-grown cells demonstrated dark 14CO2 fixation, and PCR was used to indicate the presence of a gene encoding ribulose-1,5-biphosphate carboxylase/oxygenase. Strain MLHE-1 is a facultative chemoautotroph, able to grow with these inorganic electron donors and nitrate as its electron acceptor, but heterotrophic growth on acetate was also observed under both aerobic and anaerobic (nitrate) conditions. Phylogenetic analysis of its 16S ribosomal DNA sequence placed strain MLHE-1 within the haloalkaliphilic Ectothiorhodospira of the γ-Proteobacteria. Arsenite oxidation has never been reported for any members of this subgroup of the Proteobacteria.

One-electron bonds as intermolecular bonds for molecular complexes involving Mulliken n-electron donors and as-electron acceptors

1975 ◽  
Vol 28 (4) ◽  
pp. 881 ◽  
Author(s):  
RD Harcourt
Keyword(s):  
Hydrogen Bonding ◽  
Charge Transfer ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Molecular Complexes ◽  
Electron Acceptors ◽  
Electron Donors ◽  
Water Dimer ◽  
Intermolecular Bond

For 1 : 1 molecular complexes involving an n-type electron donor and an aσ-type electron acceptor, it is proved that the simplest Mulliken description, ΨN ≈ Ψ(D,A)+λΨ(D+-A-), is equivalent to using a one-electron bond as the intermolecular bond between the donor (D) and the acceptor (A). The theory is illustrated with reference to the Hassel compound Me3N...I2, and the charge-transfer aspects of hydrogen bonding for the water dimer.

Synthesis, characterization and biological activities of 1,3,4-oxadiazole derivatives of nalidixic acid and their copper complexes

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Nalidixic Acid ◽  
Copper Complexes ◽  
Biological Activities ◽  
Bidentate Coordination ◽  
Antibacterial And Antifungal Activities ◽  
Elemental Analyses ◽  
Oxadiazole Derivatives ◽  
Antibacterial And Antifungal ◽  
Derivatives Of ◽  
Substituted 1

A series of novel 1, 3, 4-oxadiazole analogues was synthesized from cyclization of hydrazones of substituted 1-ethyl-1,4-dihydro-7-methyl-4-oxo-1,8-naphthyridine-3-carbohydrazides were prepared from nalidixic acid. The structures of synthesized oxadiazole derivatives and their copper complexes were elucidated on the basis of FTIR, elemental analyses, 1H-NMR and atomic absorption spectral analysis. It was observed from spectral data that metal ligand ratio was 1:1 in all copper complexes and they were bidentate, coordination was found to be done through oxygen of 4-oxo group and nitrogen of oxadiazole ring. The synthesized compounds were further evaluated with biological activities and compared with parent hydrazones. Copper complexes possess antibacterial and antifungal activities better than the oxadiazoles while they have better antioxidant activity then copper complexes. Parent hydrazones were better in all biological activities than synthesized oxadiazoles.

Toxicity of Para-Chloro Substituted Benzene Derivatives in the Microtox™ Test

1985 ◽  
Vol 20 (2) ◽  
pp. 36-43 ◽  
Author(s):  
Klaus L.E. Kaiser ◽  
Juan M. Ribo ◽  
Brian M. Zaruk
Keyword(s):  
General Formula ◽  
Functional Group ◽  
Structural Parameters ◽  
Systematic Investigation ◽  
Photobacterium Phosphoreum ◽  
Benzene Derivatives ◽  
Quantitative Structure ◽  
Chlorinated Benzenes ◽  
Chloro Derivatives ◽  
Derivatives Of

Abstract This paper gives the results of part of a systematic investigation into contaminant toxicity to Photobacterium phosphoreum in the Microtox™ test. Reported are the toxicity values for 39 para-chloro substituted benzene derivatives of the general formula l-Cl-C6h4-4-X=CH2CH(NH2)COOH, F, SO2NH2, OCH2COOH, CH2COOH, CONHNH2, NHCOCH3, CONH2, CH=CHCOOH, SeOOH, CH2NH2, CH2CH2NH2, NO2, H, CF3, CHO, CH2OH, OH, CH3, CCl3, COCH3, COOH, NH2, SO2C6H5, Cl, CH2COCH3, COCl, CN, OCH3, NCO, NHCH3, I, COC6H5, CH2Cl, SH, CH2SH, NCS, CH2CN and SO2C6H4Cl. Except for the last compound, whose solubility is below the required concentration, the toxicities increase in the presented order with a total range of more than three orders of magnitude. The data are discussed in terms of quantitative structure-toxicity correlations with compound-specific structural parameters. In combination with a previously developed submodel on chlorinated benzenes, phenols, nitrobenzenes and anilines, the observed relationships allow the prediction of the toxicity of some 780 possible chloro derivatives of the general formula C6H5-nClnX, where n=<5 and X is a functional group as listed above.

scholarly journals A Microcosm Treatability Study for Evaluating Wood Mulch-Based Amendments as Electron Donors for Trichloroethene (TCE) Reductive Dechlorination

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1949
Author(s):  
Edoardo Masut ◽  
Alessandro Battaglia ◽  
Luca Ferioli ◽  
Anna Legnani ◽  
Carolina Cruz Viggi ◽  
...  
Keyword(s):  
Electron Donor ◽  
Environmental Sustainability ◽  
Reductive Dechlorination ◽  
Environmental Remediation ◽  
Low Cost ◽  
Chlorinated Solvents ◽  
Electron Donors ◽  
Chlorinated Ethenes ◽  
Dehalococcoides Mccartyi ◽  
Wood Mulch

In this study, wood mulch-based amendments were tested in a bench-scale microcosm experiment in order to assess the treatability of saturated soils and groundwater from an industrial site contaminated by chlorinated ethenes. Wood mulch was tested alone as the only electron donor in order to assess its potential for stimulating the biological reductive dechlorination. It was also tested in combination with millimetric iron filings in order to assess the ability of the additive to accelerate/improve the bioremediation process. The efficacy of the selected amendments was compared with that of unamended control microcosms. The results demonstrated that wood mulch is an effective natural and low-cost electron donor to stimulate the complete reductive dechlorination of chlorinated solvents to ethene. Being a side-product of the wood industry, mulch can be used in environmental remediation, an approach which perfectly fits the principles of circular economy and addresses the compelling needs of a sustainable and low environmental impact remediation. The efficacy of mulch was further improved by the co-presence of iron filings, which accelerated the conversion of vinyl chloride into the ethene by increasing the H2 availability rather than by catalyzing the direct abiotic dechlorination of contaminants. Chemical analyses were corroborated by biomolecular assays, which confirmed the stimulatory effect of the selected amendments on the abundance of Dehalococcoides mccartyi and related reductive dehalogenase genes. Overall, this paper further highlights the application potential and environmental sustainability of wood mulch-based amendments as low-cost electron donors for the biological treatment of chlorinated ethenes.

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