Nitrobenzene 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 16.7 Write resonance structures for nitrobenzene to show the electron-withdrawing reso-] nance effect of the nitro group. 

Problem 16.14 Draw resonance structures for the intermediates from reaction of an electrophile at the ortho, meta, and para positions of nitrobenzene. Which intermediates are most stable ... 

Ionic or dipolar valence-bond resonance structures of nitrobenzene (53a,b) and aniline (54a,b) illustrate the difference of 7r-electron density in the ring of these two compounds85. 

Use Spartan View to obtain the dipole moments of aniline, nitrobenzene, and 4-nitro-aniline. Is the dipole moment of 4-nitroani ine the sum of the dipole moments of aniline and nitrobenzene Compare electrostatic potential maps and geometries for all three structures, and draw resonance structures for 4-nitroaniline that account for your observations. 

Predict the order of relative stability of the three benzylic cations derived from chloromethylbenzene (benzyl chloride), l-(chloromethyl)-4-methoxybenzene (4-methoxybenzyl chloride), and l-(chloromethyl)-4-nitrobenzene (4-nitrobenzyl chloride). Rationalize your answer with the help of resonance structures. 

Add curved arrows to nitrobenzene at the top of the page showing how you would change it into one of the second-order resonance structures. Then use curved arrows to generate each of the subsequent second-order resonance structures. 

FIGURE 12.35 Resonance structures of the possible intermediates for the electrophilic substitution of nitrobenzene. 

Two classes of material will be described here - the metal dithiolenes and rare earth metallocenes. In the metal dithiolenes a strong, low energy pi-pi transistion occurs in the near IR (9.10). This can be tuned from about 700 nm to 1400 nm by altering the metal ion, substituents or charge state of the dithiolene. The dithiolenes are particularly attractive because of their optical stability which has been exploited in their use as laser Q-switch materials. In the rare earth complexes the near IR band is provided by/-/transistions of the rare earth ion rather than the cyclopentadienyl ring structure various nonlinear optical phenomena have been observed in glasses incorporating similar ions. Previous studies have shown that dicyclopentadienyl complexes such as ferrocene have off-resonant nonlinearities similar to nitrobenzene or carbon disulphide (11-13)... 

The 2,i-orientation of an azine-nitrogen and a leaving group is characterized by activation which is exceptionally poor compared to other resonance activations. The poor activation, which is often grossly underrated, is still substantial relative to the substituted naphthalene 10 -10 -fold increase in the rates of alkoxylation and of alkylamination. The properties of 2,3,-orientation come into play in ail 3-substituted naphthalenes or azanaphthalenes which bear an azine-nitrogen or activating substituent in the 2-position (Section IV, A, 2). This orientation is subject to such a decrease in activation due to the relatively poor stabilization of charge in the ortho,ortho-quinoid structure (352) that 3-substituted isoquinolines and 2-nitro-naphthalenes are less reactive than 2-substitnted pyridines and nitrobenzenes (Section IV, A, 2). Insertion of a 3-aza moiety into a... 

In tlie aliphatic nitro derivatives, Raman frequencies characteristic for the nitro group occur at 1,383 cm and 1,555 cm These values are between those observed in compounds containing a single N—O bond (approximately 1,000 cm ) and those containing a double N=0 bond (approximately 1,640 cm ). In nitrobenzene these characteristic frequencies are lower, being 1,345 cm i and 1,523 cm respectively, which is most probably due to molecular resonance with the benzene ring and the contribution of the structure ... 

The less than unity tt electron populations in the same positions of nitrobenzene require resonance involving structures that deviate from the octet rule ... 

---