PubMed · 7388672
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H Gutfreund. 1980. Future problems in enzymology.. https://doi.org/10.1139/o80-001
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Properties of mixtures of Portland cements and "waste steel foundry dust (WSFD)" from Czech steel works were examined. It was found that WSFDs are formed by microporous clusters of spherical particles of iron oxides, ranging in size from 10 to 100 nm. The content of ZnO in WSFD affects markedly the hydration of cement + WSFD mixtures both in solidification time and strength development. Properties of WSFD are very similar to those of very fine silicon flue dusts formed during Si and FeSi production. Cement + WSFD mixtures show long term strength stability and low heavy metals leaching even at WSFD content of 70-80wt.% The above results document the perspectives of WSFD solidification, disposal and the use of this waste material as a new additive to building materials.
Energies of two tautomeric forms of 10 tetrazole derivatives substituted at C5 were established by DFT/B3LYP calculations carried out at the 6-311++G level. In each case the calculated energy of the 2H-tautomer was lower than that of the 1H. Furthermore, three geometric aromaticity indices of both forms were calculated, as were the values of nuclear independent nuclear shift and aromatic stabilization energy. The electronic properties were evaluated with the help of the natural bonding orbital theory. Following this a new pi-delocalization parameter, the root-mean square of pi-electron density localized on the atoms of the five-membered tetrazole ring, SDn, was introduced. It was concluded that the electronic delocalization can be described equally well by three different parameters: SDn, the extent of the transfer of electron density from the p(z) orbital of one nitrogen to the rest of the pi electron system, and population of two antibonding pi orbitals. Arguably, the information provided by the electronic parameters is similar to that contained in the geometric (structural) aromaticity indices except for tetrazole substituted by -BH(2).
The transfer of a hydrogen atom-a proton and an electron-is a fundamental process in chemistry and biology. A variety of hydrogen atom transfer reactions, involving iron complexes, phenols, hydroxylamines, tBuOOH, toluene, and related radicals, are shown to follow the Marcus cross relation. Thus, the Marcus theory formalism based on ground-state energetics and self-exchange rates, originally developed for electron transfer processes, is also valuable for hydrogen atom transfer. Compounds that undergo slow proton transfer (C-H bonds) or slow electron transfer (cobalt complexes) also undergo slow hydrogen atom transfer. Limitations of this approach are also discussed.