Notes

Dehydration caused about 50% of the reaction centers to become photochemically inactive
For the component that remained active, the photochemical quantum efficiency was about 0 at room temperature, rising to 0 or more as the temperature was brought below 250 K. The yield of 900 nm fluorescence was approximately the same in air-dried films as in aqueous suspensions; dehydration of a film raised the fluorescence yield about 3-fold. The yield of this fluorescence in a dehydrated film was independent of temperature (+/- 10%) between 300 and 70 K. The back reaction after illumination, return of electrons from reduced ubiquinone to oxidized bacteriochlorophyll, has kinetics in which a most rapid first-order component is mixed with slower components. The fastest component, identified with the return of electrons from 'primary' ubiquinone to oxidized bacteriochlorophyll, was predominant in the materials tested here. Its half time in an aqueous suspension of reaction centers fell from 86 ms at 300 K to 33 MS AT 200 K and declined more gradually to 15 ms at 50 K.

An air-dried film showed similar behavior. The dramatic change of half-time between 300 and 200 K can be ascribed to one or more phase transitions involving water; in a dehydrated film the half-time of the fastest decay component was about 22 +/- 5 ms, independent of the temperature between 300 and 70 K. Organic Synthesis of 6-butyl-n-hydroxynaphthimide trifluoromethanesulfonic acid of an air-dried film were restored fully, after dehydration, by exposure to either H2O or 2H2O vapor. There was no significant difference, in these measurements, between H2O-restored Aromaticity in Fully π-Conjugated Multicyclic Macrocycles.The research on aromaticity has mainly focused on monocyclic [n]annulene-like systems or polycyclic aromatic hydrocarbons. For fully π-conjugated multicyclic macrocycles (MMCs), the electronic coupling between the individual constitutional macrocycles would lead to unique electronic structures and aromaticity. The studies on MMCs, however, are quite limited, presumably due to the great challenges to design and synthesize a fully π-conjugated MMC molecule.

Herein, we report the facile synthesis of two MMCs (2TMC and 3TMC) in which two and three thiophene-based macrocycles are fused together by employing both intramolecular and intermolecular Yamamoto coupling reactions of a properly a model compound. The geometry, aromaticity, and electronic properties of these macrocycles at different oxidation states were investigated by X-ray crystallographic analysis, NMR, and theoretical calculations, which disclosed how the constitutional macrocycles interplay with each other and lead to unique aromatic/antiaromatic character. This study provides new insights into the Biotransformation and biodegradation of N-substituted aromatics in methanogenic N-Substituted aromatic compounds are environmental contaminants associated with the production and use of dyes, explosives, pesticides and pharmaceuticals. In this article, we examine the potential of anaerobic granular sludge from anaerobic treatment systems towards the detoxification, transformation, and mineralization of nitroaromatic and azo compounds. Nitroaromatics and azo dyes with strong electron withdrawing are highly inhibitory to acetoclastic methanogenic bacteria. However, nitro and azo substituted aromatics are readily reductively detoxified in methanogenic consortia to their respective aromatic amines, which are several orders of magnitude less toxic. This reductive detoxification has allowed the successful operation of anaerobic reactors for the treatment of highly toxic aromatic compounds.

In the course of the experiments it was discovered that some aromatic amines were mineralized. These results indicate that some N-substituted aromatic compounds can be completely mineralized and serve as a carbon and energy source for anaerobic bacteria.Anaerobic formation and degradation of toxic aromatic compounds in agricultural Relatively high concentrations of phenol, p-cresol, phenylacetic acid and other aromatic compounds were found in agricultural and communal sewage deposits. These toxic aromatic compounds are products of the bacterial degradation of aromatic amino acids under anaerobic conditions. In laboratory experiments at 26 degrees C and under N2-atmosphere, the same aromatics were formed from the amino acid tyrosine and from gelatine in assays inoculated with sewage sludge. After exhaustion of tyrosine and gelatine, respectively, concentrations of the accumulated phenol and other aromatics remained stable for months, i.e.

, phenol, p-cresol, phenylacetic acid etc. are dead-end products of the bacterial metabolism under these conditions. After addition of sodium nitrate the aromatic compounds are metabolically decomposed by denitrification within weeks.Reversal of reaction type selectivity by Lewis acid coordination: the ortho photocycloaddition of 1- and 2-naphthaldehyde.The value of a specific substrate class for synthetic applications is greatly enhanced if different types of reactions can be performed selectively upon a judicious choice of reaction conditions. In the present study it was shown that the typical photochemical behaviour of naphthaldehydes is completely altered in the presence of Lewis acids.
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