Compounds, chemical, formation dissociation

Dissociation of exothermic compounds and formation of endothermic compounds by rise in temperature.—Some purely chemical applications will indicate more clearly the importance of the law stated by Van Hoff. 

To obtain thin films with stable values of refractive index, there must be no variation in the structure or composition of the film. However, variations in structure may happen during crystal growth with increasing film thickness. Unwanted variations in the chemical composition can occur with less stable compounds through decomposition, dissociation, and fractionation during the evaporation process, and through insufficient recombination during the film formation. 

Fluorine chemical shifts are very sensitive to temperature and solvent even in the absence of chemical changes (e.g. electrostatic solute-solvent interactions such as hydrogen bond formation, dissociation and change in the structure of the compounds examined). 

When a compound contains at least one ion that is not soluble (insoluble), the compound does not dissociate and remains in its solid state. When the chemical reaction is written with the phase designation(s) included, this indicates the formation of a precipitate or that the product is a solid it does not signify that it is soluble. 

A partial pressure curve which is concave to the concentration axis, i.e. a positive curve, indicates the dissociation of a polymerised component, whilst a curve which is convex to the same axis, i.e., a negative curve, indicates the formation of a chemical compound of the two components. In the first case the concentration of the constituent passing into the vapour would be increased, in the second case reduced, by the assumed change. As examples, Dolezalek quotes ... 

The decarboxylation reaction usually proceeds from the dissociated form of a carboxyl group. As a result, the primary reaction intermediate is more or less a carbanion-like species. In one case, the carbanion is stabilized by the adjacent carbonyl group to form an enolate intermediate as seen in the case of decarboxylation of malonic acid and tropic acid derivatives. In the other case, the anion is stabilized by the aid of the thiazolium ring of TPP. This is the case of transketolases. The formation of carbanion equivalents is essentially important in the synthetic chemistry no matter what methods one takes, i.e., enzymatic or ordinary chemical. They undergo C—C bond-forming reactions with carbonyl compounds as well as a number of reactions with electrophiles, such as protonation, Michael-type addition, substitution with pyrophosphate and halides and so on. In this context,... 

Ionic dissociation of carbon-carbon a-bonds in hydrocarbons and the formation of authentic hydrocarbon salts, 30, 173 Ionization potentials, 4, 31 Ion-pairing effects in carbanion reactions, 15, 153 Ions, organic, charge density-NMR chemical shift correlations, 11,125 Isomerization, permutational, of pentavalent phosphorus compounds, 9, 25 Isotope effects, hydrogen, in aromatic substitution reactions, 2,163... 

Chemical interferences are more common and more problematic. Principal reactions in the flame are (i) formation of compounds of low volatility (ii) dissociation and (iii) ionization. These are considered in turn ... 

It is well known that oxidation of carbamates leads to the formation of N-acyliminium ions via dissociation of the C-H bond a. to nitrogen. The electrochemical,4 metal-catalyzed,5 and chemical methods6 have been reported in the literature to accomplish this transformation. The transformation serves as a useful tool for organic synthesis, although only compounds of high oxidation potentials such as methanol and cyanide ion can be used as nucleophile. It... 

---