Macro-language planning for multilingual education : focus on programmes and provision

This overview identifies some common features of macro-level language planning and briefly summarises the changing approaches to the analysis of macro-planning in the field. It previews six cases of language-in-education planning in response to linguistic diversity presented by the contributors to this issue. The cases show how macro-planning can either fail to recognise diverse ethnolinguistic identities or work to acknowledge them. Three common themes in language planning for multilingual education can be identified from the contributions: (i) top-down definitions of what counts as mother tongue can have both intended and unintended outcomes; (ii) language-as-problem responses to linguistic diversity can work to reinforce social exclusion; and (iii) the acknowledgement of diversity and minority language rights needs to flow through from statements of intent to on-the-ground implementation if they are to become a reality

Sulfur-Directed Olefin Oxidations: Observation of Divergent Reaction Mechanisms in the Palladium-Mediated Acetoxylation of Unsaturated Thioacetals

The Pd-mediated oxidation of unsaturated thioacetals gives either allyl or vinyl esters, depending on the substrate structure. We report the characterization of a range of sulfur-stabilized palladium intermediates via a combined computational and experimental NMR approach, demonstrating that the oxidation proceeds via two divergent reaction mechanisms. We were also able to synthesize an unusual sigma-bound Pd complex, via acetoxypalladation of an unsaturated dithiane, which was characterized by X-ray crystallography

Alkylation of (π-Allyl)palladium systems. Mechanism and regiocontrol

Palladium-catalyzed alkylation of 3-methyl-2-butenyl acetate with anions of dialkyl malonates gives the same product pattern as the stoichiometric alkylations of (η3-3-methylbutenyl)palladium chloride and the corresponding cationic complex. Consequently a (π-allyl)palladium intermediate is probable in the catalytic reaction. According to NMR evidence the reactive intermediate is a η3-allyl complex rather than a η1-allyl complex. Acceptor ligands, even weak ones such as phosphines, have a strong electronic influence on the reaction and direct the attack toward the more substituted position. The formal charge of the complexes is important to the reactivity, but when phosphines are present as acceptor ligands, the formation of cationic intermediates may not be necessary. © 1984 American Chemical Society

Removal of per- And polyfluoroalkyl substances (PFAS) from water by ceric(iv) ammonium nitrate

Ceric(iv) ammonium nitrate (CAN) in aqueous medium acts as an excellent precipitating agent for perfluorooctanesulfonic acid (PFOS). The Ce(iv) center plays a crucial role. Interestingly, Ce(iii) chloride showed much less effectiveness under similar conditions. The efficacy of CAN was reduced upon changing the substrate to perfluorooctanoic acid (PFOA)

Fast reductive defluorination of branched perfluorooctane sulfonic acids by cobalt phthalocyanine: electrochemical studies and mechanistic insights

Branched perfluorooctane sulfonic acid (PFOS) is recognized as a threatening environmental pollutant due to its high persistence and bioaccumulation in various environmental matrices as well as for its toxic effects on humans and wildlife even at very low concentrations. This study reports the first investigation of branched PFOS defluorination catalyzed by metal phthalocyanines. The reaction conditions were optimized using different reductants and temperatures. CobaltII phthalocyanine, when combined with TiIII citrate as a reducing agent, was able to defluorinate 10.9% of technical PFOS within 8 hours. In contrast, vitamin B12 only showed 2.4% defluorination during the same time period, under similar conditions. The defluorination mediated by the cobaltII phthalocyanine and TiIII citrate system corresponds to 54.5% of all branched PFOS isomers (br-PFOS isomers). Isomer-specific degradation was also investigated via high-resolution LC-orbitrap followed by their relative rates. The difference in catalytic efficacy of various phthalocyanine complexes is rationalized by their structures and electrochemical response. Lastly, a new defluorination mechanism is proposed based on the newly detected degradation products after the phthalocyanine treatment and previous studies

Efficient Reductive Defluorination of Branched PFOS by Metal-Porphyrin Complexes

Vitamin B12(VB12) has been reported to degrade PFOS in the presence of TiIIIcitrate at 70 °C. Porphyrin-based catalysts have emerged as VB12analogues and have been successfully used in various fields of research due to their interesting structural and electronic properties. However, there is inadequate information on the use of these porphyrin-based metal complexes in the defluorination of PFOS. We have therefore explored a series of porphyrin-based metal complexes for the degradation of PFOS. CoII-5,10,15,20-tetraphenyl-21H,23H-porphyrin (CoII-TPP), CoII-5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphyrin (CoII-M-TPP), and CoIII-M-TPP exhibited efficient reductive defluorination of the branched PFOS. Within 5-8 h, these compounds achieved the same level of PFOS defluorination as VB12achieved in 7-10 days. For branched isomers, the specific removal rate of the CoII-TPP-TiIIIcitrate system is 64-105 times higher than that for VB12-TiIIIcitrate. Moreover, the CoII-TPP-TiIIIcitrate system displayed efficient (51%) defluorination for the branched PFOS (br-PFOS) in 1 day even at room temperature (25 °C). The effects of the iron and cobalt metal centers, reaction pH, and several reductants (NaBH4, nanosized zerovalent zinc (nZn0), and TiIIIcitrate) were systematically investigated. Based on the analysis of the products and previously published reports, a new possible defluorination pathway of branched PFOS is also proposed