Synergism in the solvent extraction of samarium by thenoyltrifluoroacetone and triphenyl or trioctyl phosphine oxide mixture

Synergistic extraction of samarium with TTA(HA) and TPPO or TOPO (B) mixtures were investigated. The extracted complex was proved to have the general formula SmA₃ · 2B. A graphical determination for the formation constants of these complexes gave the values 3.9 × 10¹³ and 8.2 × 10¹⁰ for SmA₃ · 2TOPO and SmA₃ · 2TPPO in benzene, respectively.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS–XV. ANTHRALIN and ITS OXIDATION PRODUCT 1,8-DIHYDROXYANTHRAQUINONE

The photochemistry (Type I and II) of anthralin and its photo-oxidation product 1,8-dihydroxyanthraquinone (1,8-DHAQ) has been studied in ethanol, acetonitrile and dimethylsulfoxide using spin-trapping and direct detection of singlet oxygen (1O2) luminescence techniques. In ethanol, where it exists in its neutral form (AN), anthralin does not undergo either Type I or II reactions upon UV-irradiation. In contrast, irradiation of anthralin in acetonitrile, a solvent in which anthralin is partially converted to its corresponding mono-anion (AN-), generates both superoxide and singlet oxygen. Irradiation of anthralin in dimethylsulfoxide, where the AN- form is present in substantial quantity, generates superoxide and solvent derived radicals but no detectable singlet oxygen. UV-irradiation of 1,8-DHAQ in ethanol and acetonitrile produces both superoxide and singlet oxygen in significant yields. In dimethylsulfoxide, on the other hand, only superoxide and solvent derived radicals are observed. The 1O2 quantum yield for AN- and 1,8-DHAQ in acetonitrile were determined to be 0.14 and 0.88 relative to rose bengal in the same solvent. These findings suggest that the AN photosensitization occurs via Type I and II pathways, is solvent dependent and involves AN- as well as its oxidation product 1,8-DHAQ, which is a more potent generator of both singlet oxygen and superoxide.     

A study of peroxyoxalate-chemiluminescence of acriflavine

The chemiluminescence arising from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of acriflavine has been studied. The relationship between the chemiluminescence intensity and concentrations of TCPO, H2O2, acriflavine and the base sodium salicylate are reported. The kinetic parameters for the peroxyoxalate-chemiluminescence (PO-CL) of acriflavine were evaluated from the computer fitting of the corresponding chemiluminescence intensity-time plots.     

Evaluating the residence time for cesium removal from simulated Hanford tank wastes using SuperLig® 644 resin

Batch contact and column experiments were performed to evaluate the effect of residence time on cesium removal from two simulated Hanford tank wastes using SuperLig^® 644 resin. The two waste simulants mimic the compositions of tanks 241-AZ-102 and 241-AN-107 at the U.S. Department of Energy (DOE) Hanford site. A single column made of glass tube (2.7-cm i.d.), which contained ~100 ml of H-form SuperLig^® 644 resin was used in the column experiments. The experiments each consisted of loading, elution, and regeneration steps were performed at flow rates ranging from 0.64 to 8.2 BV/h for AZ-102 and from 1.5 to 18 BV/h for AN-107 simulant. The lowest flow rates of 0.64 and 1.5 BV/h were selected to evaluate less than optimal flow conditions in the plant. The range of the flow rates is consistent with the River Protection Project design for the waste treatment plant (WTP) columns, which will operate at a flow rate between 1.5 to 3 BV/h. Batch contact experiments were also performed for two batches of SuperLig^® 644 to determine the equilibrium distribution coefficients (K _d) as a function of Cs concentration. The column experiments revealed that adequate column loading for Cs on SuperLig^® 644 (50% breakthrough at 100 bed volumes) can be achieved for the two simulated Hanford tank wastes at the nominal plant flow rates of 1.5 and 3 BV/h (residence times 40 and 20 minutes). The column performance was marginally improved at flow rates below the nominal rates. At flow rates higher than the nominal, the Cs loading deteriorated significantly. The SuperLig^® 644 was eluted effectively with 0.5M nitric acid. The elution required approximately 15 BVs to reduce Cs concentration to below 1% of initial Cs concentration in the feeds.     

Alkenyl selenols and selenocyanates: synthesis, spectroscopic characterization by photoelectron spectroscopy, and quantum chemical study

Vinyl, allyl, and homoallyl selenols were easily prepared by a chemoselective reduction of the corresponding selenocyanates with aluminum hydrides. Two stable vinyl and five stable allyl conformers of both series were predicted on the potential-energy surface. The interaction of SeH or SeCN groups with the vinyl group has been investigated with UV photoelectron spectroscopy and quantum chemical calculations, using the MP2/cc-pVTZ and B3LYP/cc-pVTZ levels. In the vinyl derivatives, a surprisingly strong direct conjugation of the selenium lone electron pair and the C=C double bond was observed. On the other hand, in allyl position the selenium lone pair is independent on the C=C double bond, and the hyperconjugation between the Se-C bond and the double bond is the ruling effect. Thus is clarified the type and extent of the interaction between the SeH or SeCN group and the unsaturated moiety.     

O-silylated enolate phenylthialkylation: A synthesis of α,β-unsaturated 5- and 6-membered lactones.

ZnBr₂-catalysed phenylthioalkylation of ketene bis(trimethylsilyl)acetals, obtained from carboxylic acids, with appropriate α-chlorosulphides can be used to prepare γ- and δ- lactones.     

Barrier to internal rotation in 2,3- and 3,3-difluoropropenal and their methyl derivatives

The conformational stability and structure of 2,3-dimethylpropenal, 2,3-difluoropropenal and their 3,3-dimethyl and 3,3-difluoro derivatives were investigated utilizing ab initio calculations with 3-21G and 6-31G basis sets. For 2,3-dimethylpropenal and 3,3-difluoropropenal the s-trans was predicted to be the low-energy form. In the case of 3,3-dimethylpropenal and 2,3-difluoropropenal the s-cis was predicted by both levels of calculation to be the more stable conformer. Full optimization was performed at the transition states and the barriers to internal rotation were calculated. Methyl and fluorine substitution were found to significantly increase the barrier to interconversion in propenal. The relative change in the barrier depends on the position and the type of the substituent. The trans to cis barrier in 2,3-dimethylpropenal was calculated to be about 3 kcal mol⁻¹ greater than that in 3,3-dimethylpropenal, while the cis to trans barrier in 2,3-difluoropropenal was predicted to be about 7 kcal mol⁻¹ higher than the corresponding one in 3-3-difluoropropenal.     

A heterocyclic peptide nanotube

An open-ended hollow tubular structure is designed based on hydrogen-bond-directed self-assembly of a chimeric cyclic peptide subunit comprised of alternating alpha- and epsilon-amino acids. The design features a novel 1,4-disubstituted-1,2,3-triazole epsilon-amino acid and its utility as a peptide backbone substitute. The N-Fmoc-protected epsilon-amino acid was synthesized in high yield and optical purity in three steps from readily available starting materials and was employed in solid-phase peptide synthesis to afford the desired cyclic peptide structure. The cyclic peptide self-assembly has been studied in solution by (1)H NMR and mass spectrometry and the resulting tubular ensemble characterized in the solid state by X-ray crystallography.     

Determination of trace elements in Egyptian molasses by instrumental neutron activation analysis

Multielement neutron activation analysis has been applied to the determination of macro, micro and trace amounts of Al, Br, Ca, Cl, Co, Cr, Cs, Fe, K, La, Mg, Mn, Na, Rb, Sc and V in molasses of Kom Ombo, Edfu, Armant, Naga Hammady and Abu Korkass cane sugar factories. The threshold element concentrations are acceptable and below the safety. Differences in element concentrations may be related to different botanic textures and structures, different compositions of sugar cane plants, corrosion of containers or changes in soil as a result of geochemical differentiation. The method is sensitive down to 0.038 ppm of V. The relative errors due to counting statistics are in the range of 0.2–11%.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS. XVIII. INDOMETHACIN

Abstract— The photochemistry, photophysics, and photosensitization (Type I and II) of indomethacin (IN) (N-[p-chlorobenzoyl]-5-methoxy-2-methylindole-3-acetic acid) has been studied in a variety of solvents using NMR, high performance liquid chromatography-mass spectroscopy, transient spectroscopy, electron paramagnetic resonance in conjunction with the spin trapping technique, and the direct detection of singlet molecular oxygen (^l O₂) luminescence. Photodecomposition of IN (λ_ex > 330 nm) in degassed or air-saturated benzene proceeds rapidly to yield a major (2; N-[p-chlorobenzoyl]-5-methoxy-2-methyl-3-methylene-indoline) and a minor (3; N-[p-chlorobenzoyl]-5-methoxy-2, 3-dimethyl-indole) decarboxylated product and a minor indoline (5; 1-en-5-methoxy-2-methyl-3-methylene-in-doline), which is formed by loss of the p-chlorobenzoyl moiety. In air-saturated solvents two minor oxidized products 4 (N-[p-chlorobenzoyl]-5-methoxy-2-methylindol-3-aldehyde) and 6 (5-methoxy-2-methyl-indole-3-aldehyde) are also formed. When photolysis was carried out in ¹⁸O₂-saturated benzene, the oxidized products 4 and 6 contained ¹⁸O, indicating that oxidation was mediated by dissolved oxygen in the solvent. In more polar solvents such as acetonitrile or ethanol, photodecomposition is extremely slow and inefficient. Phosphorescence of IN at 77 K shows strong solvent dependence and its emission is greatly reduced as polarity of solvent is increased. Flash excitation of IN in degassed ethanol or acetonitrile produces no transients. A weak transient is observed at 375 nm in degassed benzene, which is not quenched by oxygen. Irradiation of IN (λ_ex > 325 nm) in N₂-gassed C₆H₆ in the presence of 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO) results in the trapping of two carbon-centered radicals by DMPO. One adduct was identified as DMPO/^.COC₆H₄-p-CI, while the other was probably derived from a radical formed during IN decarboxylation. In air-saturated benzene, (hydro) peroxyl and alkoxyl radical adducts of DMPO are observed. A very weak luminescence signal from ¹O₂ at 1268 nm is observed initially upon irradiation (λ_ex= 325 nm) of IN in air-saturated benzene or chloroform. The intensity of this ¹O₂ signal increases as irradiation is continued suggesting that the enhancement in ¹O₂ yield is due to photoproduct(s). Accordingly, when 2 and 3 were tested directly, 2 was found to be a much better sensitizer of ¹O₂ than IN. In air-saturated ethanol or acetonitrile no IN ¹O₂ luminescence is detected even on continuous irradiation. The inability of IN to cause phototoxicity may be related to its photo stability in polar solvents, coupled with the low yield of active oxygen species (¹O₂, O₂^?_-) upon UV irradiation.