This study investigated the reaction kinetics on the oxidative transformation of lead( ii ) minerals by free chlorine (HOCl) and free bromine (HOBr) in drinking water distribution systems. According to chemical equilibrium predictions, lead( ii ) carbonate minerals, cerussite PbCO 3(s) and hydrocerussite Pb 3 (CO 3 ) 2 (OH) 2(s) , and lead( ii ) phosphate mineral, chloropyromorphite Pb 5 (PO 4 ) 3 Cl (s) are formed in drinking water distribution systems in the absence and presence of phosphate, respectively. X-ray absorption near edge spectroscopy (XANES) data showed that at pH 7 and a 10 mM alkalinity, the majority of cerussite and hydrocerussite was oxidized to lead( iv ) mineral PbO 2(s) within 120 minutes of reaction with chlorine (3 : 1 Cl 2 : Pb( ii ) molar ratio). In contrast, very little oxidation of chloropyromorphite occurred. Under similar conditions, oxidation of lead( ii ) carbonate and phosphate minerals by HOBr exhibited a reaction kinetics that was orders of magnitude faster than by HOCl. Their end oxidation products were identified as mainly plattnerite β-PbO 2(s) and trace amounts of scrutinyite α-PbO 2(s) based on X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopic analysis. A kinetic model wasmore »
Palladium( ii )-assisted activation of thioglycosides
Described herein is the first example of glycosidation of thioglycosides in the presence of palladium( ii ) bromide. While the activation with PdBr 2 alone was proven feasible, higher yields and cleaner reactions were achieved when these glycosylations were performed in the presence of propargyl bromide as an additive. Preliminary mechanistic studies suggest that propargyl bromide assists the reaction by creating an ionizing complex, which accelerates the leaving group departure. A variety of thioglycoside donors in reactions with different glycosyl acceptors were investigated to determine the initial scope of this new reaction. Selective and chemoselective activation of thioglycosides over other leaving groups has also been explored.
- Award ID(s):
- 1800350
- Publication Date:
- NSF-PAR ID:
- 10276724
- Journal Name:
- Organic & Biomolecular Chemistry
- Volume:
- 19
- Issue:
- 9
- Page Range or eLocation-ID:
- 2044 to 2054
- ISSN:
- 1477-0520
- Sponsoring Org:
- National Science Foundation
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- https://doi.org/10.1039/D1OB00004G
