Single structure

Empirical molecular formulas and molecular weights usual identify a whole class of compounds (chemical isomers) rather than a single structure. Further-... 

Figure 1.1 shows a typical stress-volume relation for a solid which remains in a single structural phase, along with a depiction of idealized wave profiles for the solid loaded with different peak pressures. The first-order picture is one in which the characteristic response of solids depends qualitatively upon the material properties relative to the level of loading. Inertial properties determine the sample response unlike static high pressure, the experimenter does not have independent control of stresses within the sample. 

Elastomers or rubbers are almost-linear polymers with occasional cross-links in which, at room temperature, the secondary bonds have already melted. The cross-links provide the "memory" of the material so that it returns to its original shape on unloading. The common rubbers are all based on the single structure... 

Figure 5. Single structure type wet-dry cooling tower.

We have seen a variety of manufacturing processes, but certainly not all possible processes. Those processes would likely be used to produce many different parts with different characteristics and purposes. The diversity of parts might well be combined to form a single structural part such as a wirig n Figure 1-19. After each process, every part is nondestructively inspected. 

To deal with circumstances such as the bonding in ozone, the notion of resonance between Lewis structures was developed. According to the resonance concept, when more than one Lewis structure may be written for a molecule, a single structure is insufficient to describe it. Rather, the true structure has an electron distribution that is a hybrid of all the possible Lewis structures that can be written for the molecule. In the case of ozone, two equivalent Lewis structures may be written. We use a double-headed aiTow to represent resonance between these two Lewis structures. 

By reaction of zinc-copper couple with diiodomethane 2 an organozinc species 4 is formed, similar to a Grignard reagent. Its structure cannot be fully described by a single structural formula. The actual structure depends on the reaction conditions—e.g. the solvent used this corresponds to the Schlenk equilibrium as it is observed with the Grignard reaction ... 

Note the difference between tautomers and resonance forms. Tautomers are constitutional isomers—different compounds with different structures—while resonance forms arc different representations of a single structure. Tautomers have their atoms arranged differently, while resonance forms differ only in the position of their electrons. Note also that tautomers are rapidly interconvertible. Thus, keto and enol isomers are tautomers, but aJkene isomers such as 1-butene and 2-butene are not, because they don t interconvert rapidly under normal circumstances. 

Plastics provides a means to producing monocoque constructions such as has been done in different applications that include toys to automotive body, motor truck, railroad car, aircraft fuselage and wings, and houses. Its construction is one in which the outer covering skin carries all or a major part of the stresses. The structure can integrate its body and chassis into a single structure. Unreinforced and RPs are used in these constructions (14, 34). 

Which of these options is the best Lewis structure Actually, no single Lewis structure by itself is an accurate representation of NO3. Any single structure of the anion shows nitrate with one NDO double bond and two N— O single bonds. In Section 9 1, we show that single and double bonds between the same types of atoms have different lengths and different energies. In contrast, experiments show that the three nitrate N—O bonds are identical. To show that the nitrate N—O bonds are all alike, we use a composite of the three equivalent Lewis structures. These are traditionally called resonance structures. Resonance stmctures are connected by double-headed arrows to emphasize that a complete depiction requires all of them. 

Complex ions, also called coordination complexes, have well-defined stoichiometries and structural arrangements. Usually, the formula of a coordination complex is enclosed in brackets to show that the metal and all its ligands form a single structural entity. When an ionic coordination complex is isolated from aqueous solution, the product is composed of the complex ion and enough counter-ions to give a neutral salt. In the chemical formula, the counter-ions are shown outside the brackets. Examples include the sulfate salt of [Ni (NH3)g, ... 

So each bond has a bond order of 1.5, which is consistent with the observed bond length. These two resonance structures are often called Kekule structures because they were first proposed in 1865 by Kekule, who imagined that the molecule converted very rapidly from one form to the other. This, however, is not the case the molecule never has either of the Kekule structures but only a single structure, which is intermediate between these two hypothetical structures and is approximately represented as follows ... 

Mesomeric betaine structure 7, which is a rough simplification of the real situation indescribable by a single structure, represents another degree of saturation. The real structure of mesomeric betaines is a resonance hybrid of several dipolar structures <1977T3203>. Additional unsymmetrical substitution or aza substitution increases the number of possible distinct dipolar structures. 

No single structure can uniquely describe the bonding of mesomeric betaines and their true structure is a resonance hybrid of several dipolar structures. The possible dipolar structures for basic compounds of this class were discussed in CHEC-II(1996) <1996CHEC-II(8)747>. 

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