Subject complex, thermal

Electron-rich olefins are nucleophilic and therefore subject to thermal cleavage by various electrophilic transition metal complexes. As the formation of tetraaminoethylenes, i.e., enetetramines, is possible by different methods, various precursors to imidazolidin-2-ylidene complexes are readily available. " Dimerization of nonstable NHCs such as imidazolidin-2-ylidenes is one of the routes used to obtain these electron-rich olefins [Eq. (29)]. The existence of an equilibrium between free NHC monomers and the olefinic dimer was proven only recently for benzimidazolin-2-ylidenes. In addition to the previously mentioned methods it is possible to deprotonate imidazolidinium salts with Grignard reagents in order to prepare tetraaminoethylenes. " The isolation of stable imidazolidin-2-ylidenes was achieved by deprotonation of the imidazolidinium salt with potassium hydride in THF. ... 

The formation of BA is a highly complex thermal process. Varying input materials are subject to high temperature for a short time only, whereby equilibrium conditions may occur only locally in the BA. Chemical and mineralogical analyses of BA coming from 28 MSWI plants in Switzerland with comparable technology show... 

I find it interesting that in the strata studied by Schopf and Long, the sills lay above the coal seams. This means that the temperature gradient owing to the sill was of opposite sign to the geothermal gradient, and therefore in sequences of samples like those in the table on pp. 166-7, it is the coals that were initially of lowest rank that were more intensely subjected to thermal alteration. This situation may account for the observed variations in H/C-O/C relations with depth below the sill (which are complex) however, since the samples were not taken from vertical boreholes, some lateral variations in the strata no doubt also affect the relations. 

Carbohydrates ranging from cellulose to simple sugars are subject to thermal alteration. Factors such as temperature, pH, compound concentration, and other reactants present can alter both the rate and complexity of decomposition reactions. Carbohydrate types are reviewed relative to degradation/carameli-zation pathways and endproducts. Some of the resulting typical food flavors produced are also discussed. 

The spinless variant of the present theory was already discussed in Section V.D and its interrelationship with IET and a number of other theories of exciplexes or stable complexes was disclosed. In the next Section XI.D we also consider not an excited-state but a ground-state particle. It is subjected to thermal dissociation to radicals followed by their geminate and subsequent bimolecular recombination into the fluorescent product. 

Complexes of monoamide derivatives of dtpa with Ln + ions have been studied. Their stability constants are, as expected, less than those of dtpa itself Using [Gd(DTPA)] it has now been shown that these complexes get absorbed by the DNA of the cell they have been used to locate. If the gadolinium is subjected to thermal neutron treatment, short-range high-energy electrons are emitted that can kill the tumour cell whilst nearby healthy tissue is unaffected. ... 

When composite materials are pyrolysed, more than one molecular species is subject to thermal degradation. However, for composite materials each component can be considered as starting the pyrolytic process independently, which reduces somewhat the complexity of the problem. 

The complex subject of thermal radiation transfer has received much study in recent years and is covered in a number of texts. The following introductory treatment discusses the following topics emission of radiation, absorption by opaque solids, radiation between surfaces, radiation to and from semitransparent materials, and combined heat transfer by conduction-convection and radiation. 

E -cyclooctene is subject to thermal racemization. The molecular motion allows the double bond to slip through the ring, giving the enantiomer. The larger and more flexible the ring, the easier the process. The rates of racemization have been measured for E-cyclooctene, Zf-cyclononene, and Zi-cyclodecene. For E-cyclooctene the half-life is Ih at 183.9° C. The activation energy is 35.6 kcal/mol. E-cyclononene, racemizes much more rapidly. The half-life is 4 min at 0° C, with an activation energy of about 20 kcal/mol. F-cyclodecene racemizes immediately on release from the chiral platinum complex used for its preparation. ... 

This simple, effective and time-saving method can be used to analyze any complex piping structure subjected to thermal expansion without any tiresome computations. 

Exposure of the 8-bromo-2,2 -dimethyl-6-nitro-l -phenyl-(2H-[l]benzospiro-pyran-2,2 -indoline) to light causes it to isomerize into the coloured form. In a solvent it rapidly converts to the bleached form and exhibits first-order kinetics.The process is thermally activated and will require volume for the relative rotation of the two parts of the molecule to effect ring closure. However, if the same process is carried out with the dye in a polymer matrix the process now depends on there free volume available for the rotation of the molecule required for ring closure to occur. Studies of the kinetics (Figure 7.15) indicate that simple kinetics is no longer followed and that a more complex analysis is required. Good fits of the data can be obtained if it is assumed that the process is split into two processes. The initial fast decay is essentially the same as that seen in a liquid and indicates that the ring closure process is only subject to thermal control. This implies that these molecules have sufficient free volume available to execute the process. 

During injection molding, very complex thermal and flow conditions prevail in the cavity. The surface layer of the flowing melt is subjected to extensional stresses, and subsurface layers to shear stresses. This results... 

These water-insoluble acid-resistant complex iron cyanides are widely used as pigments and hence their detection, if need be in the presence of other materials, is of technical significance. The rapid test given here is based on the finding that Prussian Blue (I) and TurnbulFs Blue (II) yield dicyanogen when subjected to thermal decomposition. This volatile product responds to the reaction with oxine and alkali cyanide described on page 356. The partial reactions underlying the thermal production of (CN)2 are ... 

The purpose of the analysis is to evaluate the failure probability of a component when it is subject to a severe situation. The failure occurs when the loading L applied to the component exceed the strength S of its composing materials. L and S are estimated by a chain of complex thermal-hydraulics and mechanics calculations. In the deterministic assessment, a margin factor ME), which is equal to the ratio S L, must exceed a safety factor equal io 1.2. The deterministic rule to be complied with is thus ME >1.2. The failure probability is therefore defined as ... 

The asymmetry of approaching equilibrium demonstrates a relaxation process subject to more complex thermal histories. That is, the material is initially equilibrated at temperature To that departs AT from the test temperature Ti, i.e.. To = Ti + AT or To = Ti - AT, in cases of down-jump or up-jump, respectively. Subsequently, the temperature is controlled to jump to Ti, where the volumetric evolution is then measured in the relaxation induced from the temperature jump. Although the magnitude of the temperature jump AT in both cases of the up-jump and down-jump is the same, the volume recovery towards equilibrium is found to be much faster in the down-jump experiment (Ti < To) than in the up-jump experiment (Ti > To). This result indicates the inherent nonlinearity of the structural relaxation process and has been widely used to determine that the aging response depends upon the instantaneous state of the material. 

Guo, Y., Bradshaw, R.D. Long-term creep of polyphenylene sulfide (pps) subjected to complex thermal histories The effects of nonisothermal physical aging. Polymer 50, 4048 (2009)... 

An alternative method of studying the molecular motions of a polymeric chain is to measure the complex permitivity of the sample, mounted as dielectric of a capacitor and subjected to a sinusoidal voltage, which produces polarization of the sample macromolecules. The storage and loss factor of the complex permitivity are related to the dipolar orientations and the corresponding motional processes. The application of the dielectric thermal analysis (DETA) is obviously limited to macromolecules possessing heteroatomic dipoles but, on the other hand, it allows a range of frequency measurement much wider than DMTA and its theoretical foundations are better established. 

---