Lewis structure state

Molecular models such as the one shown often do not explicitly show double and triple bonds Write a Lewis structure for this hydrocarbon showing the location of any multiple bonds Specify the hybndization state of each carbon (You can view this model in more detail on Learn mg By Modeling)... 

It is not possible to draw unambiguous Lewis structures for excited states of the sort that are so useful in depicting ground-state chemistry. Instead, it is common to asterisk the normal carbonyl structure and provide information about the nature and multiplicity of the excited state ... 

Although Lewis structures of this type are not entirely adequate descriptions of the structure of the excited states, they do correspond to the MO picture by indicating distortion of chaige and the presence of polar or radical-like centers. The excited states are much more reactive than the corresponding ground-state molecules. In addition to the increased energy content, this high reactivity is associated with the presence of half-filled orbitals. The two SOMO orbitals in the excited states have enhanced radical, cationic, or anionic character. 

Does your transition state drawing look more like a sing Lewis structure or a resonance hybrid If the latter, whi resonance contributors must you combine to generate a of the features of this hybrid ... 

Examine spin densities for the two transition states. Draw a Lewis structure (or sequence of Lewis structures) for each which properly conveys the location(s) of the unpaired electron. 

Examine the sequence of structures corresponding to Ziegler-Natta polymerization of ethene, or more specifically, one addition step starting from a zirconocene-ethene complex where R=CH3. Plot energy (vertical axis) vs. frame number (horizontal axis). Sketch Lewis structures for the initial complex, the final adduct and the transition state. Indicate weak or partial bonding by using dotted lines. 

Use geometries, electrostatic potential maps and spin densities to help you draw Lewis structures for butanal radical cation, the transition state and product. Where is the positive charge and the unpaired electron in each Is the positive charge (the unpaired electron) more or less delocalized in the transition state than in the reactant In the product ... 

Finally, examine the geometry of the lower-energy transition state. Measure all CC bond lengths. Draw a Lewis structure representing partial bonds in terms of... 

Compare the geometry of maleic anhydride+propene, the ene transition state, to those of the reactants (maleic anhydride and propene). Is bond making and breaking occurring at once In particular, is the migrating hydrogen partially bonded to two carbons (rather than being fully bonded to one carbon ) Draw a Lewis structure to represent the transition state. Use dashed lines (.. and to represent partial bonds. 

Mechanistically the 1,3-dipolar cycloaddition reaction very likely is a concerted one-step process via a cyclic transition state. The transition state is less symmetric and more polar as for a Diels-Alder reaction however the symmetry of the frontier orbitals is similar. In order to describe the bonding of the 1,3-dipolar compound, e.g. diazomethane 4, several Lewis structures can be drawn that are resonance structures ... 

Figure 7.5 (page 177) shows the geometries predicted by the VSEPR model for molecules of the types AX2 to AX. The geometries for two and three electron pairs are those associated with species in which the central atom has less than an octet of electrons. Molecules of this type include BeF2 (in the gas state) and BF3, which have the Lewis structures shown below ... 

Seif-Tfst 2.4B Write the Lewis structure for the compound HBr and state how many lone pairs each atom in the compound possesses. 

Write the Lewis structure and state the number of lone pairs on xenon, the central atom of each of the following compounds (a) XeOF2 (b) XeF4 (c) XeOF4. 

Write three Lewis structures that follow the octet rule (including the most important structure) for the isocyanate ion, CNO. State which of the three Lewis structures is the most important and explain why it is probably the most important. 

In the solid state, sulfur is sometimes found in rings of six atoms, (a) Draw a valid Lewis structure for Sb. (b) Is resonance possible in S6 If so, draw one of the resonance structures. 

For each of the following species, write the Lewis structure, predict the shape and hybridization about each central atom, give the bond angles, and state whether it is polar or nonpolar (a) SnCl3 (b) TeO, (c) NO (d) IC1,. 

Due to its strong hydrogen bonds, in the vapor state hydrogen fluoride is found as short chains and rings. Draw the Lewis structure of an (HF)3 chain and indicate the approximate bond angles. 

Not only molecules with LLPCN > 4, but all molecules of the elements in period 3 and beyond in their higher valence states, including most of their numerous oxides, oxoacids, and related molecules such as SO3 and (H0)2S04 should be regarded as hypervalent if AO bonds are described as double bonds (1). However, Lewis did not regard these molecules as exceptions to the octet rule because he wrote the Lewis structures of these molecules with single bonds and the appropriate formal charges (2). 

The H-bonded H HOH product species was previously depicted in Fig. 5.16, while the structure and leading n— a interaction for the corresponding H2 OH-reactant species are shown in Fig. 5.33. Figure 5.34 similarly depicts the structure of the transition-state species and principal n—a interaction for the reactant-like Lewis structure that better describes the resonance hybrid (see below). 

In general, first bond the multicovalent atoms to each other and then, to achieve their normal covalences, bond them to the univalent atoms (H, Cl, Br, I, and F). If the number of univalent atoms is insufficient for this purpose, use multiple bonds or form rings. In their bonded state, the second-period elements (C, N, O, and F) should have eight (an octet) electrons but not more. Furthermore, the number of electrons shown in the Lewis structure should equal the sum of all the valence electrons of the individual atoms in the molecule. Each bond represents a shared pair of electrons. 

A comparison of the calculated and observed bond lengths shows that neither structure is correct. Nevertheless, these contributing (resonance) structures tell us that the actual resonance hybrid has some double-bond character between N and O, and some triple-bond character between N and N. This state of affairs is described by the non-Lewis structure... 

Since both MO and VB approaches have been shown to be equivalent (Shaik, 1981), in principle either may be used. However, the VB approach is simpler to use, more chemical in its application and well-suited to questions of transition state structure and charge distribution, intermediate formation, and mechanistic variations within a reaction family. Of particular importance is the fact that the qualitative VB procedure is far more general than the qualitative MO procedure, since it is based on simple Lewis structures. A qualitative MO treatment of elimination reactions, for example, (see Section 3, p. 161) would be too unwieldy and impractical to apply while, in contrast, a VB approach is entirely straightforward in its application. 

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