Metals in surface water of Ukraine: the migration forms,features of distribution between the abiotic components of aquatic ecosystems,and potential bioavailability

We have generalized the results of long-term studies of coexisting forms of a series of metals (Al, Fe, Mn, Zn, Cu, Cr, Pb, Mo, Cd, and V) in surface water bodies of Ukraine, differing in the hydrological regime and the water chemical composition (rivers, reservoirs, lakes, and ponds). The studied metals content has ranged widely, the concentrations of aluminum, iron, and manganese being typically the highest, and the concentration of molybdenum, vanadium, and cadmium being typically the lowest. The ratio between the suspended and the dissolved forms of the metals has been established. Iron and aluminum migrate mostly as part of the suspended matter, whereas the other metals mainly migrate in the dissolved state. The dissolved manganese form predominates in the water bodies under anaerobic conditions. Copper and molybdenum are present almost always in the dissolved state, regardless of the water body type. The data on the relative content of the labile metal fraction (potentially toxic to aquatic organisms) are reported. The relatively low content of this fraction has been found to be majorly owing to the metal ions complexing with natural organic ligands. The humic compounds, the most widespread group of natural organic compounds, play the primary role in the complexation. Even metals with variable oxidation state (Cr, Mo, and V) are found mainly in the form of anionic complexes with the humic substances. Carbohydrates are also involved in the metals binding in the highly bioproductive water bodies, thus increasing the mass fraction of the neutral complexes during the summer and autumn periods. The molecular weight distribution of anionic metal complexes has been discussed; the substantial part of the metals constitutes the compounds with the molecular weight of below 5.0 kDa.     

Lead,cadmium, and arsenic in commercial algae of the Sea of Japan

The concentrations of toxic elements (arsenic, cadmium, lead) in commercial algae Saccharina japonica and Ahnfeltia tobuchiensis from different habitats of the Sea of Japan have been determined. Bioaccumulation of heavy metals has been analyzed with respect to the habitat and growth conditions. The lead content of Sascharina japonica from all habitats and arsenic content of the same alga species from the Ol’ga Bay, Kievka Bay, and Tatar Strait have been found to exceed maximum permissible levels. Increased lead concentrations have been detected in Ahnfeltia tobuchiensis. Samples of Ahnfeltia tobuchiensis collected from the bottom layer contain more toxic elements than those from the upper layer.     

Reaction of 1-germatranol hydrate with carboxylic acids

Reaction of 1-germatranol hydrate with carboxylic acids RCOOH (R = ClCH₂, PhCH=CH, Ph, 2-FC₆H₄, 3-BrC₆H₄, 3-HOC₆H₄, 3-EtOC₆H₄) in protic (CH₃OH, iso-C₅H₁₁OH) and aprotic polar solvent (CH₃CN) is studied. 1-Acyloxygermatranes RC(O)OGe(OCH{in2}CH{in2}){in3}N are formed in yields from 11 to ~100 % depending on the nature of the acid, solvent, duration of the process and the method of its completion. The reaction is the most effective in acetonitrile. Its topochemical completion (heating of the reaction residue in a vacuum) increases the yield of 1-acyloxygermatranes.     

Calculation of possible stabilization of glycosyl carbocations in furanosides by different theoretical methods

The paper deals with the comparison of different theoretical methods for the calculation of stabilization energies of glycosyl cations from fucofuranoside glycosyl donors containing different protecting groups at atom O(3). The experimental and calculated data on stereoselectivity of glycosylation were compared. The formation of the stabilized glycosyl cations is considered as one of the possible steps of glycosylation reaction, which exerts influence on the stereoselectivity of the process and makes it possible to obtain difficultly accessible 1,2-cis-glycosides. Semi-empirical and ab initio methods without allowance for the electron correlation underestimate the stabilization energy values. The allowance for the electron correlation in the MP2 approximation, as well as the calculations by density functional theory, allowed us to obtain the data corresponding to the experimentally observed stereoselectivity.     

Quantum chemical studies of azoles 4. A novel elimination–addition mechanism of tetrazole and 1,2,4-triazole electrophilic substitution

Thermodynamic parameters of the addition–elimination and elimination–addition electrophilic substitution reactions of 1H-tetrazole and 1,2,4-1H-triazole obtained from DFT B3LYP/ 6-31G(d,p) quantum chemical calculations with proton as model electrophile are compared. According to calculations, the elimination–addition reactions can proceed without preliminary formation of N-protonated azolium salts.     

Chalcogenation of 1,4-dichlorobut-2-yne with organic dichalcogenides in the system hydrazine hydrate–KOH

A reaction of organic dichalcogenides R₂Y₂ (R = Ph, Bn, Pr; Y = S, Se) with 1,4-dichlorobut-2-yne in the system hydrazine hydrate–KOH leads to four principal products: 1,4-bis(organylchalcogenyl)but-2-ynes, 1-organylchalcogenylbut-1-en-3-ynes, 4-organylchalcogenylbut-1-en-3-ynes, and 3(5)-methylpyrazole. The selectivity of the formation of individual products is determined by the ratio of the substrates used and the reaction temperature. A plausible mechanism of chalcogenation considered in the work agrees with the effect of the nature of chalcogene atoms and organic substituents R on stability of intermediates and products. The stabilization of carbanions by α chalcogene-containing groups corresponds to the following order: PhS > PhSe > BnS > BnSe > PrS.     

Interaction of amorphous and crystalline nickel nanoparticles with hydrogen

Nickel nanoparticles were deposited on the surface of highly oriented pyrolytical graphite by laser electrodispersion and precipitation from a solution of reverse micelles. The particles were studied using scanning tunneling microscopy and spectroscopy as well as Auger spectroscopy. The elemental composition of the nanoparticles and specific features of the electronic structure of their surface were determined. Adsorption of molecular hydrogen was also studied.     

Controlled Light‐Mediated Preparation of Gold Nanoparticles by a Norrish Type I Reaction of Photoactive Polymers

Gold nanoparticles (AuNPs) are subjects of broad interest in scientific community due to their promising physicochemical properties. Herein we report the facile and controlled light‐mediated preparation of gold nanoparticles through a Norrish type I reaction of photoactive polymers. These carefully designed polymers act as reagents for the photochemical reduction of gold ions, as well as stabilizers for the in situ generated AuNPs. Manipulating the length and composition of the photoactive polymers allows for control of AuNP size. Nanoparticle diameter can be controlled from 1.5 nm to 9.6 nm.