Electronic Interactions of Cyclopropyl Groups: Synthesis and Photoelectron Spectra of Model Compounds Derived from Triasterane,Nortricyclane and Norbornane

The syntheses of the new hydrocarbons trimethylenetriasterane 12 , trispirocyclopropanetriasterane 3 , trispirocyclopropanenortricyclane 4 , and of the trispirocyclopropanenorbornanes 5, 6 , and 7 are reported. 12 contains six vinylcyclopropane units rigidly held in an antiperiplanar (ap) conformation in a D_3h symmetric framework. 3 and 4 are the first model compounds with bicyclopropyl units rigidly fixed in an s-trans (ap) conformation (Θ = 180°). Their PE spectra reveal that the interaction parameter β_ww = −1.73 eV for this arrangement is the same as that for Θ = 0°.     

Synthesis of Aminopyridazines from Aminocyclopropenylium Salts and Diazomethyl Compounds [1]

Amino-substituted cyclopropenylium salts ( 11a,b ) react with diazomethyl compounds ( 12a-i ) in dichloromethane or acetonitrile in the presence of a base (ethyldiisopropylamine, 1,5-diazabicyclo[4.3.0] non-5-ene) to form 4-aminopyridazines ( 13a-i ) specifically. The reaction is interpreted in terms of an initial electrophilic diazoalkane substitution to give diazomethylcyclopropenes ( 11 + 12 → 14 ) which undergo a [1.5]-cyclisation to form the betaines 16 which, in turn, isomerise with opening of the bridging bond to give the aminopyridazines 13 . In a similar manner, the tris[amino] cyclopropenylium salts 8a,b and 10a-c are converted to the 3,4,5-tris[amino]-pyridazines ( 21a-k ) by treatment with diazomethyl compounds ( 12a, c-f ).     

Determination of carbon black fillers in vulcanizates of natural rubber by metathesis degradation

A method for the determination of carbon black fillers in peroxide vulcanizates or sulfur vulcanizates of natural rubber (NR, cis-1,4-polyisoprene) by metathesis degradation with 1-octene was developed using the catalyst WCl₆? (C₂H₅)₃Al₂Cl₃. The carbon black was separated from the reaction mixture by centrifuging and determined by weighing. In this connection, investigations were also performed with the catalyst WCl₆? C₂H₅Al₂Cl₃ which was less suitable for filler determination. The rate of degradation of crosslinked NR with (E)-4-octene was measured. Metathesis reactions of 2-methyl-2-pentene (low-molecular-weight model compound of NR) with 7-tetradecene showed the importance of double bond shift for the degradation of NR.     

Spatial distributions of O2, CO2 and SO2 in a pilot-scale fluidized bed combustor operated with different coals

Axial concentration profiles of O₂, CO₂ and SO₂ have been measured at different radial positions in a coal-fired fluidized bed combustor. The profiles show some spatial inhomogeneity in the bed, the degree of which depends on fluidizing velocity and amount of excess air. Comparison of SO₂- with CO₂-concentration profiles reveals that SO₂ is formed in proportion to CO₂ only with anthracite as fuel. With bituminous coals, SO₂ is preferentially formed near the coal feed point. These results are discussed with regard to characteristic times of mixing and chemical reaction in fluidized beds, and SO₂-formation characteristics of the employed coals obtained in a thermobalance.     

Quantification of Yttria in Stabilized Zirconia by Raman Spectroscopy

The relationship between Y₂O₃ content in tetragonal and cubic ZrO₂ phases and the shift of the Raman band at ～645/cm was investigated. With increasing Y₂O₃ content, the 645/cm Raman band position decreases to lower Raman shift values. A fit of x = Y₂O₃ content in wt% and y = Raman band position in per cm, was found to be valid for low Y₂O₃‐stabilized t‐ZrO₂, t′′‐ZrO₂ transition, and fully stabilized c‐ZrO₂. Modeling the change in lattice parameters due to the incorporation of Y₂O₃ in ZrO₂ as obtained from Rietveld‐refined XRD data confirms that the peculiar sigmoidal form of the band shift with Y₂O₃ content is mainly due to a variation of the amount of oxygen vacancies. The resultant method is highly attractive in fields of Y₂O₃ determination in ZrO₂ materials where a fast, spatially resolved, and nondestructive analysis is required.     

Struktur und Aufbau moderner Analyse-Meßeinrichtungen

Structure and modular nature of modern analytical measuring equipment . Modern analytical instrumentation exhibits excellent adaptability to a wide range of demands arising from the process concerned and the site of application. Optimization of the specific plant structure according to criteria such as performance data, reliability, and economic factors demands a versatile modular system of components for matching the sensors to the process, the process control system, the discharge locations, and the environment. In addition, functions such as handling, control, and monitoring are steadily increasing in importance.     

Antimony removal from dilute solutions using a restrained bed electrochemical reactor

The electrochemical removal of Antimony from 1m sulphuric acid in a restrained bed reactor was studied in terms of current, flow velocity, bed depth, bead size and pressure drop. Current efficiencies are quoted as a function of current density and information is given so that they may be calculated in terms of the above variables. Experimentally-obtained limiting current densities are compared with calculated values, using empirical formulae from the literature.     

Zur reaktionsbeschleunigung bei der substanzpolymerisation von acrylnitril

Conversion/time-plots for the bulk polymerization of acrylonitrile measured dilatometrically at 50°C and 60°C have been analysed in a new way. It could be shown, that the polymerization can be described very accurately by a simple two-parametric equation of the type (U: conversion, t: time, A: constant) which has been derived from a Taylor-series for the time dependance of the monomer-concentration. In this equation n is an order of reaction that is constant at a given temperature and consists of high negative values. These values are ?70,8±0,8 at 50°C and ?218±7 at 60°C.