Perchlorates reduction

Cao, J., Elliott, D. and Zhang, W. (2005) Perchlorate reduction by nanoscale iron particles. Journal of Nanoparticle Research, 7, 499-506. 

Ader M, Chaudhuri S, Coates JD, Coleman M (2008) Microbial perchlorate reduction a precise laboratory determination of the chlorine isotope fractionation and its possible biochemical basis. Earth Planet Sci Lett 269 604-612... 

The electron-impact mass spectra of bromides, iodides, and fluorobo-rates of the 2,4,6-triphenyl-substituted cations 8 and 9 have the base peak at the mass number of the cation (74OMS80). No molecular ion peak of an adduct between the cation and the anion has been found the fluoroborates show also weak peaks with the elemental composition of an adduct between the cation and F". On the contrary, the spectra of perchlorates do not show the peaks at the mass number of the cation but peaks indicating the addition of an oxygen atom and the removal of a hydrogen atom. From ionization potential measurements it has been shown that the bromides, iodides, and fluoroborates of 8 and 9 are thermally reduced in the mass spectrometer to volatile free radicals 50 and 51 prior to evaporation, presumably with concomitant oxidation of the anion. In the presence of a nonoxidizable anion, e.g., perchlorate, reduction of the cations to free radicals does not take place. Interestingly, the order of ionization potentials of the radicals, 50 < 51, indicates that the LUMO energy level of pyrylium is higher than that of thiopyrylium, consistent with electrochemical studies (Section II,D). 

In DMF containing lithium perchlorate, reduction of o -bromopropiophenone at mercury gives l,4-diphenyl-2,3-dimethylbutan-l,4-dione in 65% yield [236]. However, electrolysis of a-bromopropiophenone in the presence of benzoyl chloride affords only l,3-diphenyl-2-methylpropan-l,3-dione. Other studies involving reduction of phenacyl bromides include the electrosynthesis of 4-aryl-2-methylfurans [237] and the regioselective synthesis of enol carbonates [238] semicarbazones of phenacyl bromide can be converted into 3,7-diaryl-2/7-imidazo[2,l-Z>][l,3,4]oxadiazines [239]. Reduction of 1,2-dibenzoyl-chloroethane at mercury in DMF containing lithium perchlorate affords mixtures of phenyl tribenzoyl cyclopentanols and diphenyl dibenzoyl butanediones [240]. 

An important detail consists in suppression of perchlorate reduction by sulfate and chloride in mixed solutions. For sulfate-containing systems, it is also important to remember that when chloride appears it suppresses sulfate adsorption and induces smoothing of ascending branch of adsorption vs. potential curves. In any case a search for other reference with weakly adsorbing anions is reasonable. 

Nerenberg, R., Rittmann, B. E. and Najm, I. 2002. Perchlorate reduction in a hydrogen-based membrane-biofilm reactor. AWWA Journal, 94,103-114. 

Green, S.J., Verstraete, W., and Nerenberg, R. (2010) Bioelectrochemi-cal perchlorate reduction in a microbial fuel cell. Environ. Sci. Technol, 44 (12), 4685-4691. 

Recent tests have also shown that perchlorate can be electrochemically stimulated, but it is not clear whether perchlorate reduction was accomplished through electron transfer into the bacteria or by bacteria growing on hydrogen evolved as a result of water electrolysis Thrash et al. 2007). Initially, perchlorate reduction required the addition of a mediator (AQDS) but later it was found that an isolate could achieve perchlorate reduction in the absence of the mediator. However, there were low coneentrations of hydrogen at the cathode surface. Recent studies have found that zero valent iron can stimulate perchlorate reduction by hydrogen oxidizing bacteria, and autotrophic bacteria... 

Yu, X., Amrhein, C., Deshusses, M.A. and Matsumoto, M.R. (2006) Perchlorate reduction by autotrophic bacteria in the presence of zero-valent iron. Environ. Sci. Technol. 40(4), 1328-1334. 

Zhang, H., Bruns, M.A. and Logan, B.E. (2002) Perchlorate reduction by a novel chemolithoautotrophic hydrogen-oxidizing bacterium. Environ. Microbiol. 4(10), 570-576. 

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