Chlorobenzene, resonance structures

The darkest regions in the slices indicate the greatest electron density. The meta form of nitrated chlorobenzene and the para form of nitrated nitrobenzene retain the resonance structure to a much greater degree throughout the extent of the electron density. In contrast, the density in the less-favored conformations becomes more localized on the substituent as one moves outward from the plane of the carbon atoms. 

Problem 16.8 Write resonance structures for chlorobenzene to show the electron-donating resonance effect of the chloro group. 

The energy balance of photodissociation the importance of stabilization of the free radicals. When chlorobenzene or chloro-Np loses the halogen atom, a phenyl or a naphthyl radical is formed with the odd electron localized in an sp2 orbital which is orthogonal to the aromatic zr orbitals such a radical is not stabilized through resonance, unlike the benzyl- or the methyl-Np radicals for which several resonance structures can be drawn (Figure 4.32). 

Exercise 14-11 a. Write resonance structures analogous to structures 5a through 5d to show the activating effect of—CsN and —S02R groups in nucleophilic substitution of the corresponding 4-substituted chlorobenzenes. 

The difference between the chemical behaviour of the substitution products of benzene and the corresponding aliphatic derivatives are well known and are reflected in the values of their dipole momcnxs [Table XCVI), In chlorobenzene, in addition to the bond resonance structures, I and //, there are three additional structures ///, IV and V contributing to the molecular resonance and the dipole moment is lowered in comparison with the alkyl halides. 

Resonance structures for the Whe-land intermediates resuiting from ortho, meta, and para attack of an electrophile on chlorobenzene. 

The contribution from the last form, however, will be small. A similar series of structures occurs in chlorobenzene although in this case additional structures are possible in view of the resonance of the benzene ring. 

However, we see that this is not the case. Chlorobenzene and bromobenzene have dipole moments of only 1.7 d, and vinyl chloride and vinyl bromide have dipole moments of only 1.4 d. This is consistent with the resonance picture of these molecules. In the structures that contain doubly-bonded halogen (III, IV,... 

In 1993, it was found that alkyl azides react with C o in a 1,3-dipolar cycloaddition manner [35]. The course of the reaction is closely analogous to the 1,3-di-polar addition of alkyl diazo compounds. Preliminary results on the reaction of Cso with organic azides were complicated. Treatment of Qo with SEM azide in refluxing chlorobenzene afforded two major products 3 and 4 (Fig. 2). While isN-i C spin-spin coupling experiments supported the structure for 4, the NMR spectrum of 3 contained a resonance at 160 ppm coupled to which was... 

---