Interaction of methoxy- and methylenedioxyamphetamines with carbon and polymeric adsorbents in polar liquids

Solid phase extraction (SPE) of methoxy- and methylenedioxyamphetamines from diluted aqueous solutions was investigated on carbon and polymeric adsorbents of different textures and chemical compositions. Those adsorbents were applied cartridges packed with three chemically modified carbons prepared from plum stones (initial A2PS, oxidized A2PS-O, and reduced A2PS-H) and commercially available adsorbents (polymeric LiChrolut EN, graphitized Hypercarb and Carboprep). Several factors influence the recovery rates of amphetamine derivatives such as the polarity of adsorbates (free energy of salvation), the specific surface area and surface composition of adsorbents, and the solvent characteristics. Different combinations of these factors affect the recovery rate (R1) for high- and low-surface area adsorbents. The minimal R1 values are observed for an amphetamine derivative at a maximal solvation effect and for a set of amphetamines adsorbed on graphitized carbons.      

Cadmium ion adsorption on different carbon adsorbents from aqueous solutions. Effect of surface chemistry, pore texture, ionic strength, and dissolved natural organic matter

Adsorption of Cd(II) species at pH = 5 was studied on three carbon adsorbents: granular activated carbon, activated carbon fiber, and activated carbon cloth. As-received and oxidized adsorbents were used. Cd(II) adsorption greatly increased after oxidation due to the introduction of carboxyl groups. The use of a buffer solution to control the pH introduced some changes in the surface chemistry of carbons through the adsorption of one of the compounds used, biphthalate anions. The increase in ionic strength reduced Cd(II) uptake on both as-received and oxidized carbons due to a screening of the electrostatic attractions between the Cd(II) positive species and the negative surface charge, which in the case of as-received carbons derived from the biphthalate anions adsorbed and in the oxidized ones from the carboxyl groups. Tannic acid was used as a model compound for natural organic matter. Its adsorption was greatly reduced after oxidation, and most of the carbon adsorbents preadsorbed with tannic acid showed an increase in Cd(II) uptake. In the case of competitive adsorption between Cd(II) species and tannic acid molecules, there was a decrease in Cd(II) uptake on the as-received carbon whereas the contrary occurred with the oxidized carbons. These results illustrate the great importance of carbon surface chemistry in this competitive adsorption process. Finally, under all experimental conditions used, when the adsorption capacity of carbons was compared under the same conditions it increased in the following order: granular activated carbon < activated carbon fiber < activated carbon cloth.     

Cis-Trans Isomerization and Oxidation of Radical Cations of Stilbene Derivatives

Isomerization from cis stilbene derivatives (c-S (S = RCH=CHC(6)H(5): 1, R = C(6)H(5); 2, R = 4-CH(3)C(6)H(4); 3, R = 4-CH(3)OC(6)H(4) (= An); 4, R = 2,4-(CH(3)O)(2)C(6)H(3); 5, R = 3,4-(CH(3)O)(2)C(6)H(3); 6, R = 3,5-(CH(3)O)(2)C(6)H(3); 7, AnCH=C(CH(3))C(6)H(5); 8, AnCH=CHAn)) to trans isomers (t-S) and oxidation of S with O(2) were studied in gamma-ray radiolyses of c-S in Ar-saturated 1,2-dichloroethane (DCE) and of S in O(2)-saturated DCE, respectively. On the basis of product analyses, it is suggested that a smaller barrier to c-t unimolecular isomerization for c-3(*+)-5(*+) and 8(*+) than for c-1(*+), 2(*+), and 6(*+) due to the single bond character of the central C=C double bond for c-3(*+)-5(*+) and 8(*+) with a p-methoxyl group but not for c-1(*+), 2(*+), and 6(*+) without a p-methoxyl group because of the contribution of a quinoid-type structure induced by charge-spin separation. The isomerization proceeds via chain reaction mechanisms involving c-t unimolecular isomerization and endergonic hole transfer or dimerization and decomposition. The isomerization of c-3(*+) to t-3(*+) is catalyzed by addition of 1,4-dimethoxybenzene but terminated by triethylamine. The regioselective formation of 3d in oxidation of 3(*+) with O(2) is explained by spin localization on the beta-olefinic carbon in 3(*+). The results of product analyses are compared with the rate constants of the unimolecular isomerization and the oxidation for S(*+) measured with pulse radiolyses.     

Self-assembly of diorganotin(IV) moieties and 2-pyrazinecarboxylic acid: syntheses, characterizations and crystal structures of monomeric, polymeric or trinuclear macrocyclic compounds

A series of diorganotin(IV) compounds of the type [R(2)Sn(pca)Cl](3)(R = CH(3); (n)Bu; C(6)H(5); C(6)H(5)CH(2); Hpca = 2-pyrazinecarboxylic acid), R(2)Sn(pca)(2)(mH(2)O)xnH(2)O (m= 1: R = CH(3), n= 2, R =(n)Bu, n= 0; m= 0, n= 0: R =(n)Bu, C(6)H(5), C(6)H(5)CH(2)) and (Et(3)NH)(+)[R(2)Sn(pca)(2)Cl](-)xmH(2)O (m= 0: R = CH(3), (n)Bu, C(6)H(5)CH(2); m= 1: R = C(6)H(5)) have been obtained by reactions of 2-pyrazinecarboxylic acid with diorganotin(iv) dichloride in the presence of sodium ethoxide or triethylamine. All compounds were characterized by elemental, IR and NMR spectra analyses. Except for compounds, and, the others were also characterized by X-ray crystallography diffraction analyses, which revealed that compounds and were trinuclear macrocyclic structures with six-coordinate tin(IV) atoms, compounds and were monomeric structures with seven-coordinate tin(IV) atoms, compounds and were polymeric chain structures with seven-coordinate tin(IV) atoms and compounds and were stannate with seven-coordinate tin(IV) atoms.     

The synthesis, structure and ethene polymerisation catalysis of mono(salicylaldiminato) titanium and zirconium complexes

The silyl ethers 3-But-2-(OSiMe3)C6H3CH=NR (2a-e) have been prepared by deprotonation of the known iminophenols (1a-e) and treatment with SiClMe3 (a, R = C6H5; b, R = 2,6-Pri2C6H3; c, R = 2,4,6-Me3C6H2; d, R = 2-C6H5C6H4; e, R = C6F5). 2a-c react with TiCl4 in hydrocarbon solvents to give the binuclear complexes [Ti{3-But-2-(O)C6H3CH=N(R)}Cl(mu-Cl3)TiCl3] (3a-c). The pentafluorophenyl species 2e reacts with TiCl4 to give the known complex Ti{3-But-2-(O)C6H3CH=N(R)}2Cl2. The mononuclear five-coordinate complex, Ti{3-But-2-(O)C6H3CH=N(2,4,6-Me3C6H2)}Cl3 (4c), was isolated after repeated recrystallisation of 3c. Performing the dehalosilylation reaction in the presence of tetrahydrofuran yields the octahedral, mononuclear complexes Ti{3-But-2-(O)C6H3CH=N(R)}Cl3(THF) (5a-e). The reaction with ZrCl4(THF)2 proceeds similarly to give complexes Zr{3-But-2-(O)C6H3CH=N(R)}Cl3(THF) (6b-e). The crystal structures of 3b, 4c, 5a, 5c, 5e, 6b, 6d, 6e and the salicylaldehyde titanium complex Ti{3-But-2-(O)C6H3CH=O}Cl3(THF) (7) have been determined. Activation of complexes 5a-e and 6b-e with MAO in an ethene saturated toluene solution gives polyethylene with at best high activity depending on the imine substituent.     

Syntheses and reactions of hexavalent organotellurium compounds bearing five or six tellurium-carbon bonds

A variety of hexaorganotellurium compounds, Ar(6-n)(CH3)nTe [Ar=4-CF3C6H4, n=0 (1a), n=1 (3a), n=2 (trans-4a and cis-4a), n=3 (mer-5a), n=4 (trans-6a); Ph, n=0 (1b), n=1 (3b), n=2 (trans-4b); 4-CH3C6H4, n=0 (1c), n=1 (3c), n=2 (trans-4c), n=4 (trans-6c); 4-BrC6H4, n=0 (1d)] and Ar5(R)Te [Ar=4-CF3C6H4, R=4-CH3OC6H4 (8); Ar=4-CF3C6H4, R=vinyl (9), Ar=Ph, R=vinyl (10), Ar=4-CF3C6H4, R=PhSCH2 (11), Ar=Ph, R=PhSCH2 (12), Ar=4-CF3C6H4, R=nBu (13)] and pentaorganotellurium halides, Ar5TeX [Ar=4-CF3C6H4, X=Cl (2a-Cl), X=Br (2a-Br); Ar=Ph, X=Cl (2b-Cl), X=Br (2b-Br); Ar=4-CH3C6H4, X=Cl (2c-Cl), X=Br (2c-Br); Ar=4-BrC6H4, X=Br (2d-Br)] and (4-CF3C6H4)4(CH3)TeX [X=Cl (trans-7a-Cl) and X=Br (trans-7a-Br)] were synthesized by the following methods: 1) one-pot synthesis of 1 a, 2) the reaction of SO2Cl2 or Br2 with Ar5Te(-)Li+ generated from TeCl4 or TeBr4 with five equivalents of ArLi, 3) reductive cleavage of Ar(6-m)(CH3)(m)Te (m=0 or 2) with KC8 followed by treatment with CH3I, 4) valence expansion reaction from low-valent tellurium compounds by treatment with KC8 followed by reaction with CH3I, 5) nucleophilic substitution of Ar(6-y-z)(CH3)zTeX(y-z) (X=Cl, Br, OTf; z=0, 1; y=1, 2) with organolithium reagents. The scope and limitations and some details for each method are discussed and electrophilic halogenation of the hexaorganotellurium compounds is also described.     

Synthesis and Characterization of a New Alkenyldecaborane and Alkenyl Monocarbon Carboranes

Decaborane(14) reacts with 1-(CH(3))(3)SiC&tbd1;CC(4)H(9) in the presence of dimethyl sulfide to give the new alkenyldecaborane 5-(S(CH(3))(2))-6-[(CH(3))(3)Si(C(4)H(9))C=CH]B(10)H(11) (I). Crystal data for 5-(S(CH(3))(2))-6-[(CH(3))(3)Si(C(4)H(9))C=CH]B(10)H(11): space group P2(1)/n, monoclinic, a = 9.471(1) ?, b = 13.947(3) ?, c = 17.678(3) ?, beta = 100.32(1) degrees. A total of 3366 unique reflections were collected over the range 2.0 degrees /= 3sigma(F(o)(2)) and were used in the final refinement. R(F)() = 0.083; R(w)(F)() = 0.094. The single-crystal X-ray structure of 5-(S(CH(3))(2))-6-[((CH(3))(3)Si)(2)C=CH]B(10)H(11) (A) is also reported. Crystal data for 5-(S(CH(3))(2))-6-[((CH(3))(3)Si)(2)C=CH]B(10)H(11): space group, P2(1)2(1)2(1), orthorhombic, a = 9.059 (3) ?, b = 12.193(4) ?, c = 21.431(3) ?. A total of 4836 unique reflections were collected over the range 6 degrees /= 3sigma(F(o)(2)) and were used in the final refinement. R(F)() = 0.052; R(w)(F)() = 0.059. The reactions of 5-(S(CH(3))(2))6-[(CH(3))(3)Si(C(4)H(9))C=CH]B(10)H(11) and 5-(S(CH(3))(2))6-[((CH(3))(3)Si)(2)C=CH]B(10)H(11) with a variety of alkyl isocyanides were investigated. All of the alkenyl monocarbon carboranes reported are the result of incorporation of the carbon atom from the isocyanide into the alkenyldecaborane framework and reduction of N&tbd1;C bond to a N-C single bond. The characterization of these compounds is based on (1)H and (11)B NMR data, IR spectroscopy, and mass spectrometry.     

Correlated C-C and C-O bond conformations in saccharide hydroxymethyl groups: parametrization and application of redundant 1H-1H, 13C-1H, and 13C-13C NMR J-couplings

Methyl alpha- and beta-pyranosides of d-glucose and d-galactose 1-4 were prepared containing single sites of (13)C-enrichment at C4, C5, and C6 (12 compounds), and (1)H and (13)C[(1)H] NMR spectra were obtained to determine a complete set of J-couplings ((1)J, (2)J, and (3)J) involving the labeled carbon and nearby protons and carbons within the exocyclic hydroxymethyl group (CH(2)OH) of each compound. In parallel theoretical studies, the dependencies of (1)J, (2)J, and (3)J involving (1)H and (13)C on the C5-C6 (omega) and C6-O6 (theta;) torsion angles in aldohexopyranoside model compounds were computed using density functional theory (DFT) and a special basis set designed to reliably recover the Fermi contact contribution to the coupling. Complete hypersurfaces for (1)J(C5,C6), (2)J(C5,H6)(R), (2)J(C5,H6)(S), (2)J(C6,H5), (2)J(C4,C6), (3)J(C4,H6)(R), (3)J(C4,H6)(S), and (3)J(C6,H4), as well as (2)J(H6)(R)(,H6)(S), (3)J(H5,H6)(R), and (3)J(H5,H6)(S), were obtained and used to parametrize new equations correlating these couplings to omega and/or theta;. DFT-computed couplings were also tested for accuracy by measuring J-couplings in (13)C-labeled 4,6-O-ethylidene derivatives of d-glucose and d-galactose in which values of omega and theta; were constrained. Using a new computer program, Chymesa, designed to utilize multiple J-couplings sensitive to exocyclic CH(2)OH conformation, the ensemble of experimental couplings observed in 1-4 were analyzed to yield preferred rotamer populations about omega and theta;. Importantly, due to the sensitivity of some couplings, most notably (2)J(H6)(R)(,H6)(S), (2)J(C5,H6)(R), and (2)J(C5,H6)(S), to both omega and theta;, unique information on correlated conformation about both torsion angles was obtained. The latter treatment represents a means of evaluating correlated conformation in 1,6-linked oligosaccharides, since psi and theta; are redundant in these linkages. In the latter regard, multiple, redundant scalar couplings originating from both sides of the glycosidic linkage can be used collectively to evaluate conformational correlations between psi/theta; and C5-C6 bond rotamers.     

Kinetics and mechanism of a catalytic chloride ion effect on the dissociation of model siderophore hydroxamate-iron(III) complexes

Proton-driven ligand dissociation kinetics in the presence of chloride, bromide, and nitrate ions have been investigated for model siderophore complexes of Fe(III) with the mono- and dihydroxamic acid ligands R(1)C(=O)N(OH)R(2) (R(1) = CH(3), R(2) = H; R(1) = CH(3), R(2) = CH(3); R(1) = C(6)H(5), R(2) = H; R(1) = C(6)H(5), R(2) = C(6)H(5)) and CH(3)N(OH)C(=O)[CH(2)](n)C(=O)N(OH)CH(3) (H(2)L(n); n = 2, 4, 6). Significant rate acceleration in the presence of chloride ion is observed for ligand dissociation from the bis(hydroxamate)- and mono(hydroxamate)-bound complexes. Rate acceleration was also observed in the presence of bromide and nitrate ions but to a lesser extent. A mechanism for chloride ion catalysis of ligand dissociation is proposed which involves chloride ion dependent parallel paths with transient Cl(-) coordination to Fe(III). The labilizing effect of Cl(-) results in an increase in microscopic rate constants on the order of 10(2)-10(3). Second-order rate constants for the proton driven dissociation of dinuclear Fe(III) complexes formed with H(2)L(n)() were found to vary with Fe-Fe distance. An analysis of these data permits us to propose a reactive intermediate of the structure (H(2)O)(4)Fe(L(n)())Fe(HL(n))(Cl)(OH(2))(2+) for the chloride ion dependent ligand dissociation path. Environmental and biological implications of chloride ion enhancement of Fe(III)-ligand dissociation reactions are presented.     

五羰基锰烷基化合物的合成及光化学反应研究

用五羰基锰钾盐和相应的卤代物在乙醚中的金属化反应合成了五羰基锰烷基合物 (CO)5MnR（R = CH3,p-CH2C6H4CH3, p-CH2C6H4OCH3 ）,产率达到72-93％,将这些化合物与1-2当量(CH3)2(C6H5)SiH和(CH3)(C6H5)2SiH的C6D6溶液在5℃光解,分别得到五羰基锰硅烷基化合物(CO)5MnSi(C6H5)(CH3)2和(CO)5MnSi(C6H5)2(CH3)（产率达到70-88％）。在光化学反应中,还观察到相应甲烷,对二甲苯,和对甲基苯甲醚的定量生成,以及少量的Mn2(CO)10（<2％-4％）,(CO)4MnH(SiR3)2（<9%）副产物。     

On the adsorption/oxidation of hydrogen sulfide on activated carbons at ambient temperatures

Activated carbons of various origins (bituminous coal, wood, coconut shells, and peat) were studied as adsorbents of hydrogen sulfide. Before the experiments the surface of the adsorbents was characterized by using the sorption of nitrogen, Boehm and potentiometric titrations, thermal analysis, and FTIR. The adsorbents were chosen to differ in their surface areas, pore volumes, and surface acidities. To broaden the spectrum of surface acidity, carbons were oxidized by using nitric acid and ammonium persulfate. After hydrogen sulfide adsorption the species present on the surface were analyzed using thermal analysis, ion chromatography, and elemental analysis. The H(2)S breakthrough capacity tests showed that the performances of different carbons differ significantly. For a good performance of carbons as hydrogen sulfide adsorbents a proper combination of surface chemistry of carbon and porosity is needed. It was demonstrated that a more acidic environment promotes the formation of sulfur oxides and sulfuric acid despite yielding small H(2)S removal capacities. On the other hand, a basic environment favors the formation of elemental sulfur (sulfur radicals) and yields high capacities. The presence of a sufficient amount of water preadsorbed on the carbon surface to facilitate dissociation also plays an important role in the process of H(2)S adsorption/oxidation. The results showed that there is a critical value in carbon surface acidity, which when exceeded results in a negligible hydrogen sulfide breakthrough capacity. This is consistent with the mechanism of H(2)S adsorption on unmodified carbons, where the rate-limiting step is the reaction of adsorbed hydrogen sulfide ion with dissociatively adsorbed oxygen. When the acidity is expressed as pH, its value should be higher than 5 to ensure the effective removal of hydrogen sulfide from the gas phase. Study of carbon regeneration using water washing and heat treatment showed that the adsorbents can be regenerated to about 40% of their initial capacity.     

Synthesis, characterization and ethylene reactivity of 2-diphenylphosphanylbenzamido nickel complexes

Addition of primary amines to N-[2-(diphenylphosphanyl)benzoyloxy]succinimide affords 2-diphenylphosphanylbenzamides, Ph2PC6H4C(O)NHR (R = C(CH3)3, 3; R = H, 4; R = CH2CH2CH3, 5; R = CH(CH3)2, 6). Addition of NiCl(eta3-CH2C6H5)(PMe3) to the deprotonated potassium salts of the amides and subsequent treatment of two equivalents of B(C6F5)3 to the resulting products furnishes eta3-benzyl zwitterionic nickel(II) complexes, [Ph2PC6H4C(O)NR-kappa2N,P]Ni(eta3-CH2C6H5) (R = C6H5, 9; R = C(CH3)3, 10; R = H, 11; R = CH2CH2CH3, 12; R = CH(CH3)2, 13). Solid structures of 9, 11, 13 and the intermediate eta1-benzyl nickel(II) complexes, [Ph2PC6H4C(O)NR-kappa2N,P]Ni(eta1-CH2C6H5)(PMe3) (R = C6H5, 7; R = C(CH3)3, 8) were determined by X-ray crystallography. When ethylene is added to the eta3-benzyl zwitterionic nickel(II) complexes, butene is obtained by the complexes 9-12 but complex 13 provides very high molecular-weight branched polyethylene (Mw, approximately 1300000) with excellent activity (up to 5200 kg mol-1 h-1 at 100 psi gauge).     

Ortho-hydroxyphenylhydrazo-β-diketones: tautomery, coordination ability, and catalytic activity of their copper(II) complexes toward oxidation of cyclohexane and benzylic alcohols

New hydrazone o-HO-phenylhydrazo-β-diketones (OHADB), R(1)NHN═CR(2)R(3) [R(1) = HO-2-C(6)H(4), R(2) = R(3) = COMe (H(2)L(1), 1), R(2)R(3) = COCH(2)C(Me)(2)CH(2)CO (H(2)L(2), 2), R(2) = COMe, R(3) = COOEt (H(2)L(4), 4); R(1) = HO-2-O(2)N-4-C(6)H(3), R(2)R(3) = COCH(2)C(Me)(2)CH(2)CO (H(2)L(3), 3), R(2) = COMe, R(3) = COOEt (H(2)L(5), 5), R(2)R(3) = COMe (H(2)L(6), 6A)], and their Cu(II) complexes [Cu(2)(CH(3)OH)(2)(μ-L(1))(2)] 7, [Cu(2)(H(2)O)(2)(μ-L(2))(2)] 8, [Cu(H(2)O)(L(3))] 9, [Cu(2)(μ-L(4))(2)](n) 10, [Cu(H(2)O)(L(5))] 11, [Cu(2)(H(2)O)(2)(μ-L(6))(2)] 12A and [Cu(H(2)O)(2)(L(6))] 12B were synthesized and fully characterized, namely, by X-ray analysis (4, 5, 7-12B). Reaction of 6A, Cu(NO(3))(2) and ethylenediamine (en) leads, via Schiff-base condensation, to [Cu{H(2)NCH(2)CH(2)N═C(Me)C(COMe)═NNC(6)H(3)-2-O-4-NO(2)}] (13), and reactions of 12A and 12B with en give the Schiff-base polymer [Cu{H(2)NCH(2)CH(2)N═C(Me)C(COMe)═NNC(6)H(3)-2-O-4-NO(2)}](n) 14. The dependence of the OHADB tautomeric equilibria on temperature, electronic properties of functional groups, and solvent polarity was studied. The OHADB from unsymmetrical β-diketones exist in solution as a mixture of enol-azo and hydrazo tautomeric forms, while in the solid state all the free and coordinated OHADB crystallize in the hydrazo form. The relative stabilities of various tautomers were studied by density functional theory (DFT). 7-14 show catalytic activities for peroxidative oxidation (in MeCN/H(2)O) of cyclohexane to cyclohexanol and cyclohexanone, for selective aerobic oxidation of benzyl alcohols to benzaldehydes in aq. solution, mediated by TEMPO radical, under mild conditions and for the MW-assisted solvent-free synthesis of ketones from secondary alcohols with tert-butylhydroperoxide as oxidant.     

Discussion of thermodynamic data obtained by adsorption gas chromatography of hydrocarbons on a new graphitized carbon black with a high specific surface area

Summary A new graphitized carbon black (Carbograph 5) with a specific surface area (560 m² g⁻¹) greater than those of commerically available graphitized carbons was studied by gas chromatography to determine the enthalpy, entropy, and free energy of adsorption of a series of alkanes (C₂−C₆). The adsorption properties were also investigated by considering changes in the isosteric heats and entropies of adsorption when a nonpolar stationary phase (squalane) was added to the adsorbent. The data obtained are discussed and compared with literature values for other graphitized carbon blacks.     

Synthesis and characterization of nickel(II) bis(alkylthio)salen complexes

NiX2(2-RSC6H4CH=NCH2CH2N=CHC6H4SR-2) (NiX2L; L = 5) (1a, X = Br, R = C6H13; 1b, X = Cl, R = C12H25) and NiX2(2-C6H13SC6H4CH2NHCH2CH2NHCH2C6H4SC6H13-2) (NiX2L; L = 6) (2a, X = Br; 2b, X = Cl; 2c, X = OClO3) were prepared from ligands 5 and 6, respectively. The 1:2 metal-ligand complex Ni(OClO3)2(2-RSC6H4CH2NHCH2CH2NHCH2C6H4SR-2)2 3, was obtained from an EtOH solution of 2c. The characterization of paramagnetic 1-3 included single-crystal X-ray diffraction studies of 1a and 3. Complex 2c converted into 3 in the presence of excess ligand 6 in CHCl3.     

Simultaneous Removal of Polymers with Different Ionic Character from Their Mixed Solutions Using Herb-Based Biochars and Activated Carbons

Nettle and the sage herbs were used to obtain carbonaceous adsorbents. For the biochar preparation the precursors were dried and subjected to conventional pyrolysis. Activated carbons were obtained during precursor impregnation with phosphoric(V) acid and multistep pyrolysis. The textural parameters and acidic-basic properties of the obtained adsorbents were studied. The activated carbons prepared from the above herbs were characterized by the largely developed specific surface area. The obtained carbonaceous adsorbents were used for polymer removal from aqueous solution. Poly(acrylic acid) (PAA) and polyethylenimine (PEI) were chosen, due to their frequent presence in wastewater resulting from their extensive usage in many industrial fields. The influence of polymers on the electrokinetic properties of activated carbon were considered. PAA adsorption caused a decrease in the zeta potential and the surface charge density, whereas PEI increased these values. The activated carbons and biochars were used as polymer adsorbents from their single and binary solutions. Both polymers showed the greatest adsorption at pH 3. Poly (acrylic acid) had no significant effect on the polyethylenimine adsorbed amount, whereas PEI presence decreased the amount of PAA adsorption. Both polymers could be successfully desorbed from the activated carbons and biochar surfaces. The presented studies are innovatory and greatly required for the development of new environment protection procedures.     

Adsorption and thermal reactions of alkanethiols on pt(111): Dependence on the length of the alkyl chain

The adsorption and thermal decomposition of alkanethiols (R-SH, where R = CH3, C2H5, and C4H9) on Pt(111) were studied with temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) with synchrotron radiation. Dissociation of sulfhydryl hydrogen (RS-H) of alkanethiol results in the formation of alkanethiolate; the extent of dissociation at an adsorption temperature of 110 K depends on the length of the alkyl chain. At small exposure, all chemisorbed CH3SH, C2H5SH, and C4H9SH decompose to desorb hydrogen below 370 K and yield carbon and sulfur on the surface. Desorption of products containing carbon is observed only at large exposure. In thermal decomposition, alkanethiolate is proposed to undergo a stepwise dehydrogenation: R'-CH2S --> R'-CHS --> R'-CS, R' = H, CH3, and C3H7. Further decomposition of the R'-CS intermediate results in desorption of H2 at 400-500 K and leaves carbon and sulfur on the surface. On the basis of TPD and XPS data, we conclude that the density of adsorption of alkanethiol decreases with increasing length of the alkyl chain. C4H9SH is proposed to adsorb mainly with a configuration in which its alkyl group interacts with the surface; this interaction diminishes the density of adsorption of alkanethiols but facilitates dehydrogenation of the alkyl group.     

Characterization of the surface interacting ability of carbon black by means of electron paramagnetic resonance analysis of adsorbed Cu2+, supported by surface analysis and atomic absorption

Electron paramagnetic resonance (EPR) has been used to investigate the adsorption capability and the surface interacting ability towards Cu(II) solutions (CuCl2, Cu(NO3)2, CuSO4 in water or ethanol) of various carbon blacks, both graphitized and ungraphitized, selected on the basis of the surface area, namely, Carbograph1 (area = 100 m2/g), Carbograph4 (area = 210 m2/g), and Carbograph5 (area = 560 m2/g), which were indicated as C1g, C4g, C5g (g = graphitized), and C1ng, C4ng, C5ng (ng = ungraphitized). The EPR analysis was supported by surface analysis, for evaluating the surface area, the pore volume and the porosity, and by atomic absorption to obtain the adsorbed Cu(II) amounts. Graphitization provokes a decrease in surface area, but C1g, at low surface area, showed a unexpected increase of the adsorption ability ascribed to the formation of new surface porosity closed by graphite layers. The carbon samples showed a broad unresolved EPR signal due to mobile unpaired electrons in the carbon matrix. Graphitized samples presented a narrower signal than ungraphitized samples, which increases in width with the increase in surface area (with the exception of C5ng due to the high exposition of the wide surface to oxydizing external agents) and upon prolonged thermal treatment. The signal intensity of the carbon paramagnetic centers decreases upon Cu(II) adsorption. Computer aided analysis of the EPR spectra of the solids after Cu(II) adsorption allowed to extract structural information on the Cu-surface site complexes. The Cu2+ ions coordinated with surface polar sites, mainly oxygenated. Adsorption depends on the different Cu(II) salts, caused by the salt solubility and the interacting ability of the counter-ion. In several cases the solutions concentrated in the carbon porosity leading to precipitation of the salt. Ethanol solutions are more adsorbed at the carbon surface than water solutions; Cu(II) partially retains its solvation shell and partially presents electron transfer to the carbon surface. Adsorption is favored to ungraphitized carbons with respect to the graphitized ones due to both the higher surface area, and the higher hydrophilicity of the surface. In summary, these carbon powders, widely used for chromatographic applications, show an adsorption capability towards Cu(II) solutions higher than expected due to both a definite porosity, and the presence of polar groups which are not eliminated with chemical surface treatments.     

取代环戊二烯的合成和^1HNMR谱

本文研究了苯基锂和对、间、邻甲苯基锂及对、邻甲氧苯基锂与6,6-二烷基富烯环外双键加成反应的立体效应。在室温下于乙醚溶剂中,6,6-二烷基富烯同上述芳基锂反应,形成取代环戊二烯基锂,经水解给出含或不含手性碳的叔烷基环戊二烯。