Edwin H. Abbott

ENVIRONMENTAL APPLICATION OF MINERAL SULFIDES FOR REMOVAL OF GAS-PHASE HG(0) AND AQUEOUS HG2+

Synthesized and commercially available metal sulfides were evaluated for their ability to adsorb elemental and ionic mercury. The coinage group metal sulfides adsorb elemental Hg(0) vapor stoichiometrically. The mechanism of Hg(0) uptake by the copper and gold sulfides is a redox process resulting in the formation of HgS. The mechanism in the case of Ag2S involves redox but there is no HgS formation. The relative rates of Hg(0) adsorption increases in the order CuS > Ag2S > Au2S > Au2S3 corresponding to the metal ion reduction potentials. The relative rate of Hg(0) adsorption for commercial grade CuS is increased by an activation process which involves making a slurry of the metal sulfide in concentrated oxalic acid followed by drying and then exposure to Hg(0). Relative rates of Hg(0) adsorption were also increased by decreasing the particle size of the metal sulfides. Particle sizes were decreased by synthesis of the metal sulfide in the presence of the particle-size mediating agent CTAB. The metal sulfides remove ionic mercury from acidic solutions by precipitation with the dissolved sulfide forming HgS. In acidic solution there was no evidence of physical or chemical adsorption between Hg(0) and the metal sulfide. The quantity of ionic Hg2+ removal from aqueous solutions is correlated with the solubility of the metal sulfide. Cu2S was the most soluble metal sulfide tested and thus removed the most ionic mercury from solution by precipitating HgS.

Spectral properties and desmotropy of the Schiff base of diethylaminomalonate and pyridoxal hydrochloride

Abstract Evidence is presented indicating that in aqueous solution, the product formed between diethyl aminomalonate and pyridoxal (vitamin B 6 )is the Schiff base, and not the 1,4-dihydropyridine tautomer which exists in the solid state. The structure of the Schiff base is established unequivocally by its 1 H and 13 C NMR spectra. Reflectance spectroscopy shows that the solid dihydropyridine tautomer absorbs at 560 nm.

Thermodynamics of the formation of cisbis(dialkylsulfide)-dimethylplatinum(II) complexes from bis(μdialkylsulfide)bisdimethylplatinum(II) and free dialkylsulfide

Abstract Dialkylsulfides react with bis- μ -dialkylsulfidebisdimethylplatinum(II) to form monomeric cis -bis(dialkylsulfide)dimethylplatinum(II). The thermodynamic parameters of these reactions are reported for methyl, ethyl and propyl sulfides. Reactions are spontaneous for the formation of the monomeric compound. Equilibrium constants at 303 K are 2600±300 M −1 (R = Me), 50 ± 10 M −1 (R = Et), and, 130 ± 10 M −1 (R = Pr). Enthalpies are negative for each reaction, indicating that the bridging three center sulfur-platinum bonds of the dimeric compounds are weaker than the two center bonds in the respective monomers. The dimeric compounds owe their existence to the unfavorable entropy of the addition of two moles of dialkylsulfide when the dimers break into two monomeric compounds. For R = Me, Δ H ⊖ is −60 ± 10 kJ mol −1 and Δ S ⊖ is − 120 ± 30 J mol − K −1 for the reaction. Likewise, for R = Et Δ H ⊖ is −40 ± 10 kJ mol −1 and Δ S ⊖ is −90 ± 30 J mol −1 K −1 , and, for R = Pr, Δ H ⊖ is −40 ± 10 kJ mol −1 and Δ S ⊖ is −100 ± 40 J mol −1 K −1 .

A platinum-195 nuclear magnetic resonance investigation of some dihydroxo bridged binuclear platinum(II) sulfoxide complexes

Abstract Seven binuclear complexes form when di-μ-hydroxo-bis(tetramethylene sulfoxide)platinum(II) reacts with di-μ-hydroxo-bis(diethylsulfoxide)platinum (II). The seven complexes are readily observed by 195 Pt NMR and their structures are assigned. Chemical shifts and coupling constants are reported. Also observed for these dihydroxo bridged species is a significant (45 ppm) shift of the 195 Pt resonance as a function of pH suggesting a pH-dependent equilibrium which appears fast on the NMR timescale.

Vitamin B-6 Model Reactions (V): Synthesis, Conformation and Differential Reactivity of the A-(S,S) and A-(S,S) Diastereoisomers of Bis(Pyridoxylidene-L-Valinato)Cobalt(III) Complexes

Abstract The A(S,S) and A(S,S) diastereoisomers of the bis(pyridoxylidene-L-valinato)cobalt(III) complex have been synthesized and separated from one another. Nuclear magnetic resonance investigations show that the Schiff base chelate ring conformations are different for the two isomers. These measurements also determine the absolute configuration. The rate of carbon-hydrogen bond breaking has been studied by monitoring the intial rate of loss of the amino acid α-proton resonance for each complex. In acidic solution, the A isomer reacts about five times more rapidly than the A isomer. Four-bond proton-proton spin coupling constants show that the most rapidly reacting complex is the one where the bond to be broken is most nearly dihedrally perpendicular to the plane of the aromatic ring. However, conductivity studies show substantial differences in solvation which could also explain differences in reactivity.