The earlier compiled self-consistent spectrophotometric basicity scale in acetonitrile (AN) was expanded to range from 3.8 to 32.0 pKa units, that is 28 orders of magnitude. Altogether 54 new relative basicity measurements (ΔpKa measurements) were carried out and 37 new compounds were introduced to the scale (it now includes altogether 89 bases). The relative basicity of any two bases in the scale can be obtained by combining at least two independent sets of measurements. Multiple overlapping measurements make the results more reliable. The overall consistency (as defined earlier) of the measurements is s = 0.03 pKa units. Thorough analysis of all of our experimental data (ΔpKa values of this and earlier works) and experimental pKa data in AN available in the literature (works from the groups of Coetzee and Padmanabhan, Kolthoff and Chantooni, Jr., the Schwesinger group, Bren' et al. and some others, altogether 19 papers) was carried out. On the basis of this analysis the anchor point of the scalepyridine...

Extension of the self-consistent spectrophotometric basicity scale in acetonitrile to a full span of 28 pKa units: unification of different basicity scales.

The coordination chemistry of pyrazole-derived ligands

Hydrogen bonds are a key feature of chemical structure and reactivity. Recently there has been much interest in a special class of hydrogen bonds called "strong" or "low-barrier" and characterized by great strength, short distances, a low or vanishing barrier to hydrogen transfer, and distinctive features in the NMR spectrum. Although the energy of an ordinary hydrogen bond is ca 5 kcal mol-1, the strength of these hydrogen bonds may be > or = 10 kcal mol-1. The properties of these hydrogen bonds have been investigated by many experimental techniques, as well as by calculation and by correlations among those properties. Although it has been proposed that strong, short, low-barrier hydrogen bonds are important in enzymatic reactions, it is concluded that the evidence for them in small molecules and in biomolecules is inconclusive.

Strong hydrogen bonds in chemistry and biology

Current research on room-temperature ionic liquids as lubricants is described. Ionic liquids possess excellent properties such as non-volatility, non-flammability, and thermo-oxidative stability. The potential use of ionic liquids as lubricants was first proposed in 2001 and approximately 70 articles pertaining to fundamental research on ionic liquids have been published through May 2009. A large majority of the cations examined in this area are derived from 1,3-dialkylimidazolium, with a higher alkyl group on the imidazolium cation being beneficial for good lubrication, while it reduces the thermo-oxidative stability. Hydrophobic anions provide both good lubricity and significant thermo-oxidative stability. The anions decompose through a tribochemical reaction to generate metal fluoride on the rubbed surface. Additive technology to improve lubricity is also explained. An introduction to tribology as an interdisciplinary field of lubrication is also provided.

Ionic liquids in tribology.

CuO, ZrO2 and ZnO nanoparticles as antiwear additive in oil lubricants

Infrared spectra, in the diffuse reflectance mode, are presented for three common softwoods (Western redcedar, southern pine, and Douglas fir) that have been subjected to a variety of artificial weathering conditions. The surface spectra of the three unweathered woods have distinctly different characteristic features, but after 2400 hours of full artificial weathering the surface features are virtually identical and correspond closely with those of the cellulosic polymer components. Weathering with light alone has a less pronounced effect on the wood surfaces, whereas weathering with water alone has virtually no effect in comparison to the result of both light and water used in conjunction. A photochemically induced reaction pathway for the weathering process, consistent with the experimental findings, is discussed.

https://www.fpl.fs.fed.us/documnts/pdf1991/ander91b.pdf

Infrared Studies of Wood Weathering. Part II: Hardwoods

Abstract The present paper is based on experimental studies of self-lubricated porous sliding bearings with hexagonal boron nitride (h-BN) as an additive. The friction coefficients of powder matrix lubricated by (h-BN + oil) were measured at varying loads of 1.05–2.0 MPa and sliding speeds of 1.35 and 2.5 m/s. The results are discussed in the form of performance characteristics such as the coefficient of friction, bearing temperature, and load-carrying capacity. The micro-particles of the h-BN additive were between 1 and 2 μm in diameter. The effect of the PV (pressure–velocity) parameter on the transition time to seizure for porous bush composites impregnated by the lubricant has been studied. It was found that the addition of the micro-particles to the oil decreased the friction coefficient about twice as compared to self-lubricated bearings lubricated only by oil. The main effect of (h-BN micro-particles + oil) in comparison to Mobil DTE-BB lubricant appears to be that the impregnation of h-BN micro-particles persists for a long period of time and the micro-particles are gradually released, being supplied to the contact surfaces. For a manufacturing application, the porous bearings were assembled in a car clutch.

A comparative study on the tribological behaviour of hexagonal boron nitride (h-BN) as lubricating micro-particles - An additive in porous sliding bearings for a car clutch

A comparative study on the tribological behaviour of hexagonal boron nitride (h-BN) as lubricating micro―particles―An additive in porous sliding bearings for a car clutch

Part 1 Lubrication chemistry: the role of lubricants in engines lubricant additives tribochemical interactions of additives synthetic engine oils lubricant requirements and specifications problems. Part 2 Micellar structure of lubricating formulations: reverse micelles in tribochemical processes micellar solubilization in lubrication tribochemistry of hard-core reverse micelles tribochemical interactions of acid-base chemistries problems. Part 3 Tribochemical nature of antiwear films: tribochemical characterization of antiwear films the chemistry of tribofilm formation techniques for evaluation of metal surfaces problems. Part 4 Surface tribochemistry of activated processes: chemical nature of metal surfaces catalytic activity of rubbing surfaces tribochemical reactions on surfaces organomolybdenum compounds in surface engines protection problems. Part 5 Analytical techniques in lubricating practices: evaluation of the degradation of lubricants engine oil condition monitoring oil acidity and basicity engine oil evaluation tests problems. Part 6 Environmental issues: recyclability, biodegradability and toxicity clean air and energy efficient cars problems.

Zenon Pawlak

Papers

Infrared Studies of Wood Weathering. Part II: Hardwoods

A comparative study on the tribological behaviour of hexagonal boron nitride (h-BN) as lubricating micro-particles - An additive in porous sliding bearings for a car clutch

A comparative study on the tribological behaviour of hexagonal boron nitride (h-BN) as lubricating micro―particles―An additive in porous sliding bearings for a car clutch

Tribochemistry of Lubricating Oils

Modification of iodometric determination of total and reactive sulfide in environmental samples.