The Replacement of Phosphates in Detergents—Possibilities and Limits

Elimination of phosphates from detergents alone, is insufficient to solve the eutrophication problem. Nevertheless, the endeavors of the detergent industry are aimed at finding phosphate subsitutes. Novel approaches for at least a partial replacement of detergent phosphates have been found by using water-soluble organic complexing agents as well as heterogeneous organic or inorganic ion exchangers. So far, a large-scale replacement is not possible. It is not justifiable until all technical requirements are met with and safety with regard to man, animals, plants and drinking water has been established.     

MECHANISMS OF RADIOPROTECTION—A REVIEW

Abstract— Theories of radiation protection can be considered at both the molecular and biochemical-physiological levels. Four molecular level protection hypotheses, radical scavenging, hydrogen transfer reactions, the mixed disulfide hypothesis and the endogenous nonprotein sulhydryl hypothesis, probably describe different aspects of the actual protection mechanism, although each has inconsistencies. At the biochemical-physiological level, hypothermia induction, hypoxia induction and biochemical shock may be involved in protection of the organism against radiation induced damage and death. It is most likely that no single mechanism can account for the protection offered by a radioprotective drug. Certain compounds may operate primarily by means of physiological effects resulting in hypoxia or hypothermia in critical tissues. Others may operate primarily by influencing the intrinsic radiosensitivity of target molecules by causing localized radical scavenging or by donating a hydrogen atom. Metabolic effects such as biochemical shock, release of endogenous nonprotein sulfhydryls, induction of structural changes in target molecules or delay in DNA synthesis and cell division are also possible mechanisms for radioprotection.     

Erinnerungen an Karl Prachar

Ohne Zusammenfassung     

Electrochemical synthesis of conducting polymers from oligomers containing thiophene and furan rings

Oligomers containing 2,5-thienylene and 2,5-furanylene units were synthesized by NiCl₂ (dppp) (dppp = Ph₂PCH₂CH₂CH₂PPh₂) coupling of Grignard compounds with the appropriate bromothiophene or bromofuran; UV and electrochemical data are given and discussed in terms of number and kind of heterolene units in the oligomeric species.     

Computer simulation of nickel in blood-plasma following the in vitro investigations of complex formation chemistry with polyamine(amide) ligands

In- and out-of-cell potentiometric techniques have been used to determine the formation constants for nickel(II) with 3,3,9,9-tetramethyl-4,8-diazaundecane-2,10-dione dioxime (L(1)), N,N[prime or minute]-bis(2-hydroxyiminopropionyl)propane-1,3-diamine (L(2)) and 1,15-bis(N,N-dimethyl)-5,11-dioxo-8-(N-benzyl)-1,4,8,12,15-pentaazapentadecane (L(3)) at 25 degrees C and an ionic strength of 0.15 mol dm(-3). Nickel(II) forms stable complexes with L(1) and L(2) where square-planar [NiLH(-1)] and [NiLH(-2)] species predominate under alkaline conditions. The square-planar coordination of nickel by L(1) has been confirmed by a single-crystal X-ray structure, UV/Vis spectrometry and molecular mechanics calculations of the [NiL(1)H(-1)] complex. The introduction of a third amine group into L(3) dramatically decreases the ligand's ability to complex Ni(II). This results from a change in structure of the complex which decreases the ability of the metal ion to promote the dissociation of the amide protons. Using a model of blood plasma, the high binding ability of L(1) towards Ni(II) is calculated to decrease the mobilisation of Cu(II) in plasma by approximately 65%. [CuL(1)H(-1)] is currently under investigation as an anti-inflammatory agent.     

Perturbations by phenyl on the 1,5-hydrogen shift in 1,3(Z)-pentadiene. Another chameleonic transition region?

The acyclic 1,5-dienyl hydrogen shift is accelerated by radical-stabilizing phenyl substituents without regard to the type of position occupied in the 1,3(Z)-pentadiene system. 1-Phenyl-5-p-tolyl-1,3(Z)-pentadiene has a corrected energy of activation 5.8 kcal mol(-)(1) lower than that of the parent, while the 2- and 3-phenyl analogues, examined in cyclic systems specifically designed to obviate the otherwise general need for a thermochemical correction to the immediately precursory s-cis conformation, reveal stabilizing effects of 3.6 and 3.4 kcal mol(-)(1), respectively. These relatively small effects are consistent with a chameleonic conceptual scheme for the transition region.     

Exploring phase-transfer catalysis with molecular dynamics and 3D/4D quantitative structure-selectivity relationships

Quantitative Structure-Selectivity Relationships (QSSR) are developed for a library of 40 phase-transfer asymmetric catalysts, based around quaternary ammonium salts, using Comparative Molecular Field Analysis (CoMFA) and closely related variants. Due to the flexibility of these catalysts, we use molecular dynamics (MD) with an implicit Generalized Born solvent model to explore their conformational space. Comparison with crystal data indicates that relevant conformations are obtained and that, furthermore, the correct biphenyl twist conformation is predicted, as illustrated by the superiority of the resulting model (leave-one-out q(2) = 0.78) compared to a random choice of low-energy conformations for each catalyst (average q(2) = 0.22). We extend this model by incorporating the MD trajectory directly into a 4D QSSR and by Boltzmann-weighting the contribution of selected minimized conformations, which we refer to as '3.5D' QSSR. The latter method improves on the predictive ability of the 3D QSSR (leave-one-out q(2) = 0.83), as confirmed by repeated training/test splits.     

Chemistry of trifluoromethyl compounds : I. NMR evidence for bis(trifluoromethyl)zinc and methyl(trifluoromethyl)zinc

Bis(trifluoromethyl)zinc and methyl(trifluoromethyl)zinc have been identified by ¹⁹F and ^1H NMR methods. The compounds were formed in the following reactions: (1) dimethylzinc and bis(trifluoromethyl)mercury and (2) dimethylzinc and bis(trifluoromethyl)cadmium.