Epichlorhydrin in der Wachssynthese

Epichlorohydrine in the Synthesis of Waxes Waxes that are soluble in usual wax solvents are of interest in special fields of application. It is not possible to prepare clear solutions of appreciable concentration using natural waxes, such as carnauba wax or derivatives of montana wax. Although these waxes are well soluble when hot, however, on cooling they separate out as crystalline or pasty masses. For preparing easily soluble waxes a new path of synthesis was found. Thus, waxes having ether or ester groups which were also easily soluble in the cold were prepared by reacting epichlorohydrine with such compounds, which, apart from having a long hydrocarbon chain also possessed a functional group with one active hydrogen atom.     

Kälteadaptation der Wachssynthese in der Harder'schen Drüse der Ratte

Adaptation to Coldness in the Synthesis of Wax Esters in the Harderian Gland of the Rat The Harderian gland of the rat has been shown to contain characteristic wax esters of [n-7] unsaturated alcohols and fatty acids. The change of the temperature in the surroundings from 25 to 4° C for six weeks does not change the pattern of exclusively [n-7] monoenoic fatty acids. The adaptation of this exocrine eye gland results in an increased synthesis of [n-5] monounsaturated alcohols and shortening of the chain length. Different pathways of unsaturation and/or chain modification and the regulation of lipid synthesis in this gland are discussed, as well as the biological role of these waxes.     

Die gemischte Guerbet-Reaktion zwischen cyclischen und acyclischen Alkoholen

Mixed Guerbet Reaction between Cyclic and Acyclic Alcohols In a mixed Guerbet reaction secondary cyclic alcohols were alkylated by primary alcohols in view of a mechanistic relationship to alcohol condensation. In addition to the main expected reaction, following was observed: The cyclic alcohol undergoes self condensation. This reaction occurs preferentially as compared to self condensation of the primary acyclic alcohol. When the cyclic alcohol possesses two unsubstituted methylene groups adjacent to the hydroxymethyl group, preferential alkylation of both positions occur. The final product is a mixture of alcohols and ketones.     

Bestimmung der Verzweigungen in Polyvinylchlorid mittels kernmagnetischer Resonanz

Various samples of polyethylene and polyvinylchloride (PVC) were investigated by NMR-spectroscopy for determination of the degree of branching. The PVC-samples were reduced with LiAIH₄ to polyethylenes. The NMR-method was calibrated with a vinyl chloride/2.4-dichloropentene-1-copolymer with a known number of branches. The results were compared with IR-spectroscopic values.     

Vereinfachte Auslegung der simulierten Gegenstromchromatographie mittels des Hodographenraums

A simplified and explicit shortcut method for the design of simulated moving bed processes is derived on the basis of equilibrium theory. The applicability of this approach is discussed using the hodograph plane for competitive adsorption equilibria with nonconstant selectivity, namely modified Langmuir‐, Bi‐Langmuir, and Jovanovic isotherms. The approach shows excellent accuracy when validated against literature data. Furthermore, it is demonstrated that systems described by modified or Bi‐Langmuir isotherms may comprise complex nonlinear phenomena.     

Quantifizierung der Trenneffizienz einer strukturierten Packung mittels numerischer Simulation

The numerical simulation of the distillation and absorption/desorption process is made possible by coupling a transient two‐phase simulation in a structured packing with a model for the simulation of the species transfer. The two‐phase flow is modeled by the volume of fluid (VoF) method. The simulation of the locally resolved species transfer is conducted using the generalised continuous species transfer (GCST) model. The simulation data are evaluated for the separation efficiency of the tested packing by calculating the HETP value.     

Spin-Trapping von Radikalen bei der Zersetzung aromatischer Diazoniumsalze mittels Ultraschall

Spin Trapping of Radicals Formed during the Decomposition of Aromatic Diazonium Salts by Ultrasound The decomposition of aromatic diazonium compounds ArN₂^⊕X^⊖ (Ar = phenyl, 2,5-diethoxy-4-(N-morpholino)phenyl; X = BF₄, PF₆, B(C₆H₅)₄, SCN, OCN,N₃; 1a , 1c–f , 2b–f ) by ultrasonic waves has been studied by e.s.r. The spin trapping technique has been shown to be a suitable method for the detection of free radical intermediates.     

Reaktionen in vernetzten Polymeren, 5. Zur Messung der Vernetzung mittels der Gleichgewichtsquellung

A method for the kinetical investigation of crosslinking reactions is described. A physical property E of the polymer is measured which depends on the crosslinking degree. At first a “calibration curve” with E as a function of the crosslinking substance V reacted completely under the given conditions is determined. With the calibration curve in kinetical measurements V effective in crosslinking is obtained for different reaction times. In the experimental example the equilibrium swelling of the polymer in benzene at 25°C is measured. Natural rubber (cis-1,4-polyisoprene) is cross-linked with dicumylperoxide in the absence of additives and in the presence of n-hexadecanthiol.     

Beschleunigung der gelenkten Umesterung mittels periodischer,variabler Temperaturführung

Acceleration of the Directed Interesterification of Oils by Periodic Variation of the Reaction Temperature By means of directed interesterification the solid phase content in an oil can be increased without affecting the physiologically important linoleic acid. However, the directed interesterification of highly unsaturated oils proceeds very slowly. Calculations with a mathematical model demonstrate that the directed interesterification can be accelerated considerably, by periodically decreasing the reaction temperature for a short period. This procedure applied on laboratory scale to the directed interesterification of e. g. sunflowerseed oil and lard accelerated the reaction by approximately a factor of 3. Further it appeared to be possible to prepare a margarine of which the fat phase had been composed entirely of directed inter-esterified sunflowerseed oil.     

Absicherung von Zulaufreaktoren durch Überwachung der Reaktantenakkumulation mittels On-line-Energiebilanzierung

Safe Operation of Semi-Batch Reactors by Supervising the Accumulation of Reactants Through Online Energy Balance . An essential part of the strategy for ensuring safe operating conditions for semi-batch reactors is the permanent guarantee of an admissible accumulation of reactants. Thus, even in case of a failure or a breakdown of the cooling system or the agitator, the maximum possible pressure and temperature in the reactor still remain within their permissible limits. The energy balance method makes it possible to monitor online the reactant concentration and to limit the accumulation by switching off the feed of reactant in time. Practical experience with a production plant is presented in which, over a period of 2 years, numerous process cycles were calculated and subjected to comparative analysis. The results show that the reproducibility as well as the accuracy of calculation are high and that the energy balance method can be regarded as reliable. In addition, recommendations for the implementation of this safety strategy as a reliable tool in plants are obtained. On this basis, the energy balance method provides additional information about the process and, thus, can provide an increase of plant safety and product quality by maintaining process availability.