Dispersion copolymerization of acrylamide with acrylic acid in an aqueous solution of ammonium sulfate: Synthesis and characterization

Dispersion copolymerization of acrylamide with acrylic acid in an aqueous solution of ammonium sulfate using poly(2-acrylamido-2-methylpropanesulfonic acid sodium) as the stabilizer and ammonium persulfate (APS) as the initiator was investigated. The influence of initiator concentration, stabilizer concentration, ammonium sulfate concentration, chain-transfer agent concentration, and polymerization temperature on the copolymerization was discussed. The results showed that varying the ammonium sulfate concentration could affect the particle size and the intrinsic viscosity of the copolymer significantly. With increasing the stabilizer concentration, the particle size of the copolymer decreased first, and then increased, meanwhile the intrinsic viscosity of the copolymer decreased. The increase of initiator concentration, chain-transfer agent concentration, and polymerization temperature resulted in the increase in the particle size. Polydisperse spherical particles were formed in the system, and the kinetics for the dispersion copolymerization were discussed.

Synthesis and crystal structure of bis(tetrahydrofurfurylindenyl) lanthanide chlorides

Lanthanocene chlorides (C4H7OCH2C9H6)(2)LnCl[Ln=Y(1); Ln=Gd(2)] were synthesized by the reaction of tetrahydrofurfurylindenyl lithium(in situ) with corresponding anhydrous lanthanide chorides in THF. The crystal structures of these two complexes were determined by X-ray diffraction and they were unsolvated monomeric complexes. They were stable in the air for several hours. Complexes 1 and 2 belong to the same crystal system (orthorhombic) and space group(P2(1)2(1)2(1)). The unit cell dimensions of complex 1 were a=1.042 52(9) nm, b=1.47455(12) nm, c=1.497 99(13) nm, Z=4, D-c=1.508 g/cm(3); The unit cell dimensions of complex 2 were a=1.037 01(10) nm, b=1.472 33(12) nm, c=1.513 54(14) nm, Z=4, D-c=1.699 g/cm(3). They have the same structure and different space configurations. The central metal atom is coordinated by two indenyl, two oxygen of the tetrahydrofurfuryl and one chlorine atom to form a distorted trigonal bipyramid.

Ammonium 4-nitrophenylarsonate

In the crystal structure of the title compound, (NH4)[AsO2 (OH)(C6H4NO2)], the 4-nitrophenylarsonate anions and ammonium cations are linked through hydrogen bonds to form infinite chains along the b axis. The hydroxyl O atom of the 4-nitrophenylarsonate anion acts as both an acceptor and a donor of hydrogen bonds. All atoms are located in general positions.

Syntheses and crystal structures of bis(tetrahydrofurfurylindenyl) lanthanocene chlorides (C4H7OCH2C9H6)(2)LnCl (Ln = Nd, Sm, Dy, Ho, Er, Yb)

Reaction of anhydrous lanthanide trichlorides with tetrahydrofurfuryl indenyl lithium in THF afforded bis(tetrahydrofurfurylindenyl) lanthanocene chlorides complexes (C4H7OCH2C9H6)(2) LnCl, Ln = Nd (1), Sm (2), Dy (3), Ho (4), Er (5), Yb (6). The X-ray crystallographic structures of all the six complexes were determined and these indicate that they are unsolvated nine-coordinate monomeric complexes with a trans arrangement of both the sidearm and indenyl rings in the solid state. They belong to the same crystal system (orthorhombic) and space group (P2(1)2(1)2(1)) with the same structure. Especially, they are more stable to air and moisture than the corresponding unsubstituted indenyl lanthanide complexes.

Synthesis, characterisation and catalytic activity of propionamide complexes of rare earth chlorides

Propionamide complexes of rare earth chlorides were synthesized, Formula of the complexes is LnCl(3). 3BA. The ligand is shown to behave as a normal amide donor With the oxygen of the carbonyl group coordinated to the metal ions. Binary system composed Elf propionamide and aluminum alkyl shows higher activity and stereospecificity for butadiene polymerization. The cis-1,4 content of polybutadiene is more than 98%.

INHIBITION OF CORROSION BY HEXADECYL TRIMETHYL AMMONIUM BROMIDE LANGMUIR-BLODGETT MONOLAYERS ON CARBON-STEEL

Langmuir-Blodgett (LB) monolayers of hexadecyl trimethyl ammonium bromide (HTAB) were deposited onto a carbon steel surface to investigate the inhibition of corrosion by measurement of the polarization resistance and cyclic voltammetry. The corrosion proc

DIELS-ALDER REACTIONS CATALYZED BY LANTHANIDE CHLORIDES

Lanthanide chlorides have been found to catalyze the Diels-Alder synthesis of 2-butoxy-3, 4-dihydro-2H-pyran and several norbornene derivatives under mild conditions. In particular, the heavier lanthanide chlorides are very active catalysts for some (4 + 2) cycloaddition reactions. The catalyst activities and selectivities generally increase with increasing atomic number of the rare earth elements.

DIELS-ALDER REACTION CATALYZED BY RARE-EARTH CHLORIDES

Rare earth chlorides were used to catalyze the synthesis of 2-butoxy-3, 4-dihydro-2H-pyran using equimolar acrolein and vinyl butyl either. The cycloadduct is unstable which undergoes catalytic ring opening oligomerization. The way to stabilize the cyclo adduct has been studied, thus high yields of 90-95% were obtained.

Nitrogen isotope fractionation during nitrate, ammonium and urea uptake by marine diatoms and coccolithophores under various conditions of N availability

Stable isotopes of N provide a new approach to the study of algal production in the ocean, yet knowledge of the isotope fractionation (epsilon) in various oceanic regimes is lacking. Here we report large and rapid changes in isotope composition (delta(15)N) of 2 coastal diatoms and 2 clones (open and coastal) of a coccolithophore grown in the simultaneous presence of nitrate, ammonium and urea under varying conditions of N availability (i.e. N-sufficiency and N-starvation followed by N-resupply) and hence different physiological states, During N-sufficiency, the delta(15)N of particulate organic N (PON) was well reproduced, using a model derived from Rayleigh distillation theory, with constant epsilon similar to that for growth on each individual N source. However, following N-resupply, the variations in delta(15)N(PON) could be well explained only in the case of the open ocean Emiliania huxleyi, with epsilon similar to N-sufficient conditions. It was concluded that the mechanism of isotope fractionation changed rapidly with N availability for the 3 coastal clones. However, in the case of E. huxleyi isolated from the Subarctic Pacific Ocean, no evidence of a change in mechanism was found, suggesting that perhaps open ocean species can quickly recover from N-depleted conditions.