TAML/H2O2 oxidative degradation of metaldehyde: Pursuing better water treatment for the most persistent pollutants.

The extremely persistent molluscicide, metaldehyde, widely used on farms and gardens, is often detected in drinking water sources of various countries at concentrations of regulatory concern. Metaldehyde contamination restricts treatment options. Conventional technologies for remediating dilute organics in drinking water, activated carbon and ozone, are insufficiently effective against metaldehyde. Some treatment plants have resorted to effective, but more costly UV/H2O2. Here we have examined if TAML/H2O2 can decompose metaldehyde under laboratory conditions to guide development of a better real world option. TAML/H2O2 slowly degrades metaldehyde to acetaldehyde and acetic acid. Nuclear magnetic resonance spectroscopy ((1)H NMR) was used to monitor the degradation-the technique requires a high metaldehyde concentration (60 ppm). Within the pH range of 6.5-9, the reaction rate is greatest at pH 7. Under optimum conditions, one aliquot of TAML 1a (400 nM) catalyzed 5% degradation over 10 hours with a turnover number of 40. Five sequential TAML aliquots (2 μM overall) effected a 31% removal over 60 hours. TAML/H2O2 degraded metaldehyde steadily over many hours, highlighting an important long-service property. The observation of metaldehyde decomposition under mild conditions provides a further indication that TAML catalysis holds promise for advancing water treatment. These results have turned our attention to more aggressive TAML activators in development, which we expect will advance the observed technical performance

Whole-Genome Transcriptional Analysis of Chemolithoautotrophic Thiosulfate Oxidation by Thiobacillus denitrificans under Aerobic versus Denitrifying Conditions

Thiobacillus denitrificans is one of the few known obligate chemolithoautotrophic bacteria capable of energetically coupling thiosulfate oxidation to denitrification as well as aerobic respiration. As very little is known about the differential expression of genes associated with key chemolithoautotrophic functions (such as sulfur compound oxidation and CO(2) fixation) under aerobic versus denitrifying conditions, we conducted whole-genome, cDNA microarray studies to explore this topic systematically. The microarrays identified 277 genes (approximately 10% of the genome) as differentially expressed using RMA (robust multiarray average) statistical analysis and a twofold cutoff. Genes upregulated (ca. 6- to 150-fold) under aerobic conditions included a cluster of genes associated with iron acquisition (e.g., siderophore-related genes), a cluster of cytochrome cbb(3) oxidase genes, cbbL and cbbS (encoding the large and small subunits of form I ribulose 1,5-bisphosphate carboxylase/oxygenase, or RubisCO), and multiple molecular chaperone genes. Genes upregulated (ca. 4- to 95-fold) under denitrifying conditions included nar, nir, and nor genes (associated, respectively, with nitrate reductase, nitrite reductase, and nitric oxide reductase, which catalyze successive steps of denitrification), cbbM (encoding form II RubisCO), and genes involved with sulfur compound oxidation (including two physically separated but highly similar copies of sulfide:quinone oxidoreductase and of dsrC, associated with dissimilatory sulfite reductase). Among genes associated with denitrification, relative expression levels (i.e., degree of upregulation with nitrate) tended to decrease in the order nar > nir > nor > nos. Reverse transcription-quantitative PCR analysis was used to validate these trends

TAML/H₂O₂ Oxidative Degradation of Metaldehyde: Pursuing Better Water Treatment for the Most Persistent Pollutants

The extremely persistent molluscicide, metaldehyde, widely used on farms and gardens, is often detected in drinking water sources of various countries at concentrations of regulatory concern. Metaldehyde contamination restricts treatment options. Conventional technologies for remediating dilute organics in drinking water, activated carbon, and ozone, are insufficiently effective against metaldehyde. Some treatment plants have resorted to effective, but more costly UV/H₂O₂. Here we have examined if TAML/H₂O₂ can decompose metaldehyde under laboratory conditions to guide development of a better real world option. TAML/H₂O₂ slowly degrades metaldehyde to acetaldehyde and acetic acid. Nuclear magnetic resonance spectroscopy (¹H NMR) was used to monitor the degradationthe technique requires a high metaldehyde concentration (60 ppm). Within the pH range of 6.5–9, the reaction rate is greatest at pH 7. Under optimum conditions, one aliquot of TAML <b>1a</b> (400 nM) catalyzed 5% degradation over 10 h with a turnover number of 40. Five sequential TAML aliquots (2 μM overall) effected a 31% removal over 60 h. TAML/H₂O₂ degraded metaldehyde steadily over many hours, highlighting an important long-service property. The observation of metaldehyde decomposition under mild conditions provides a further indication that TAML catalysis holds promise for advancing water treatment. These results have turned our attention to more aggressive TAML activators in development, which we expect will advance the observed technical performance

Dimerisations of cinnamates using acidic and acidic/oxidative conditions

It is confirmed that the dimerisation of methyl dialkoxycinnamates in acidic conditions yields trisubstituted indanes. When the reactions are carried out for 1.5 h/0°C in acidic conditions in the presence of DDQ then a variety of lignan types result, two of which represent new classes of lignans

Transformations of lignans. Part 4: Oxidative and reductive rearrangements of dibenzocyclooctadiene and spirodienone lignans

DDQ oxidation of a dibenzocyclooctadiene derived from a 2,3-dibenzylbutane-1,2,4-triol di-O-methyl ether gives an oxygen-bridged dibenzocyclooctadienone and an oxygen-bridged spirodienone. The same products may also be obtained directly from the dibenzylbutane derivative by treatment with excess DDQ. Acid treatment of the spirodienone leads to demethylation and rearrangement to an ortho-benzoquinone. Reductive rearrangement of the spirodienone produces an oxygen-bridged dibenzocyclooctadienone. These reactions yield unique cyclohexadienone lignans and illustrate readily achieved increases in complexity starting from a simple dibenzylbutane derivative