High levels of strain

Hydrogenation was carried out in acetic acid solution. Ahyd// of the first double bond to form bicyclo[2.2.2]octa-2,5-diene was -37.6 kcal mol 1 as determined by difference (see Turner, R. B. Meador, W. R. Winkler, R. E. J. Amer. Chem. Soc.. 1957, 79,4116-4121) reflecting a high level of strain in the reactant molecule and little or no delocalization stabilization in the diene. 

Wiliams and Ford developed plain strain compression test which was initially applied to metals [Williams and Ford, 1964]. It was based on the fact that strain is easier to measure in compression test. The same test method may be used for polymer blends to obtain total deformation curves up to high levels of strain that may be encountered in engineering applications. Williams had further explained the application of this technique to polymers [Williams, 1964]. 

As mentioned in Chapter 2, these molecules all suffer a high level of strain in the rings. Medium sized rings experience steric strain and the introduction of trans double bonds increases this significantly. This stored energy has dramatic effects on the chemistry of the caryophyllenes and humulenes as we shall see. 

Fig. 1.19 Fault-tolerance of CNT electrodes. DEAs with CNT electrodes are able to withstand puncture and maintain a high level of strain due to self-clearing of CNT around punctiure. From left to right-, prestrained VHB acrylic actuator with CNT electrodes actuated actuated with a cactus pin through the active area...

There are two types of IMDA reactions Type-I and Type-II. Type-I reactions are those in which the diene is attached to the dienophile by a tether from its terminus while in Type-II reactions, the tether is attached to an internal diene position (Figure 4.18). In general, both Type-1 and Type-11 IMDA reactions only occur if the tether contains three or more atoms. This is due to the high level of strain involved in the transition states of reactions of precursors with one or two atoms in the connecting chains. 

The short-term stress/strain data of different grades of PP (and for other plastics) is of limited use and should only be used for pre-selection of material. In reality, plastic components are seldom designed and subjected to such high levels of strain as applied in short-term tensile tests. In addition, most of the cases of product failure are brittle in nature. Consequently, the long-term creep and fatigue properties of PP, discussed in Sections 4.3.3 to 4.3.5, are more important for structural applications. 

A four-carbon tether (49a) yields only the trans-isomer. This is likely due to a high level of strain in the polycyclic product 50a. The crystal structure of a dihydro derivative of 50a found the tether-derived cyclohexane to be in a boat conformation, a substantial contribution to the strain of this adduct. An analog carrying an additional methyl group at a carbon involved in bond formation, 49b, does not undergo cycloaddition. ... 

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