Stability energetics

The stabilization energetics associated with both types of molecules have been probed by looking at factors, including temperature, that disrupt their three-dimensional structures, but do not break the bonds that keep their primary structure intact. It is believed that much information about the nature of the forces that hold the molecule in its three-dimensional structure can be gained by understanding under what conditions these forces can be overcome. 

Certainly detailed theoretical treatments of the stabilities, energetics, and electronic states of the doubly-charged negative ions, both monatomic and polyatomic, are now warranted. It was noted eariier that the EHT calculations employed here are only a zerot/i order approximation the results obtained, however, now justify an effort to employ more sophisticated approaches. The MINDO and LCAO-MO-SCF calculations mentioned above are a distinct improvement over the EHT calculations. Other calculational techniques should be brought to bear on an improved understanding of doubly-charged negative ions. 

These molecules are stabilized (energetically favored) by intramolecular hydrogen bonds shown as dashed lines. Simple ketones such as acetone cannot form such intramolecular hydrogen bonds as they have only a single carbonyl group, and for this reason simple ketones do not form hydrates. 

Reactions in solution are very important in chemistry the solvent plays a crucial role in these processes. For example, trapping reactive species in a solvent cage (see the centre part of Figure 1.7 for a schematic of the principle), on the time-scale for reaction, can enhance bond formation. The solvent may also act as a chaperone , stabilizing energetic species. Studies in solvent environments have only become possible recently, once again aided by the advent of ultrafast lasers, which allowed the investigation of the solvation dynamics in real time. 

For chemical reactions in solution, the solvent plays an important role in the elementary processes of bond making and breaking. For example, it may enhance bond formation by trapping reactive species in a solvent cage on the time-scale of the reaction it also may act as a chaperone that stabilizes energetic species. One of the most studied reactions in the condensed phase is that of dissociation of neutral iodine molecules most recently, it has been studied using ultrafast lasers to investigate its femtosecond dynamics. 

The energetics and kinetics of film formation appear to be especially important when two or more solutes are present, since now the matter of monolayer penetration or complex formation enters the picture (see Section IV-7). Schul-man and co-workers [77, 78], in particular, noted that especially stable emulsions result when the adsorbed film of surfactant material forms strong penetration complexes with a species present in the oil phase. The stabilizing effect of such mixed films may lie in their slow desorption or elevated viscosity. The dynamic effects of surfactant transport have been investigated by Shah and coworkers [22] who show the correlation between micellar lifetime and droplet size. More stable micelles are unable to rapidly transport surfactant from the bulk to the surface, and hence they support emulsions containing larger droplets. 

Reference to Figure 3.4 shows that the reduction is not feasible at 800 K. but is feasible at 1300 K. However, we must remember that energetic feasibility does not necessarily mean a reaction will go kinetic stability must also be considered. Several metals are indeed extracted by reduction with carbon, but in some cases the reduction is brought about by carbon monoxide formed when air, or air-oxygen mixtures, are blown into the furnace. Carbon monoxide is the most effective reducing agent below about 980 K, and carbon is most effective above this temperature. 

Here too there is an overall loss of resonance stabilization, but it is monomer stabilization which is lost, and this is energetically less costly than reaction (7.H). 

This reaction suffers none of the reduction in resonance stabilization that is present in reactions (7.H) and (7.1). It is energetically more favored than both of these, but not as much as the reaction in which. ... 

The fluid plasticizer (solvent) consists of an energetic compound, eg, nitroglycerin, an inert carrier, and a stabilizer. The system is evacuated to remove volatiles, moisture, and air, and the plasticizer is then pressurized and passed slowly upward through the powder bed while the powder is held stationary by a pressure plate on the powder column. Casting solvent may also be added from the top of the mold. 

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