Nitro group drawing

Table 3.56). An explanation was put forward by postulated formation of Ji-complex of cuprous chelate which coordinates to aryl halide could be affected by nitro group drawing electron density from the benzene moiety.

The systematic name of TNT, a well-known explosive, is 2,4,6-trinitrotoluene (as seen in SkillBuilder 18.1). There are only five constitutional isomers of TNT that contain an aromatic ring, a methyl group, and three nitro groups. Draw all five of these compounds, and provide a systematic name for each. 

When the following compound is treated with a mixture of nitric and sulfuric acid at 50°C, nitration occurs to afford a compound with two nitro groups. Draw the structure of this product ... 

Picric acid is a military explosive formed via the nitration of phenol under conditions that install three nitro groups. Draw the structure and provide an lUPAC name for picric acid. 

In nitrobenzene the nitro group has a large electron affinity, and accordingly draws electrons away from the ring. The resonance effect works in the same direction, and, as a result, all positions have a deficiency of electrons. The meta positions are least affected, and the substitution takes place there with difficulty. In aniline, the inductive effect and the resonance effect oppose each other, but the latter wins out, and very easy o-p substitution takes place. 

The anion of 4-nitrophenol is stabilized by resonance directly into the nitro group. The anion of 3-nitrophenol can t do this. Draw resonance structures to convince yourself of this. 

Note that m-nitrophenol has pATa 8.4, and is a lot less acidic than o-nitrophenol or p-nitrophenol. We can draw no additional resonance structures here, and the nitro group cannot participate in further electron delocalization. The increased acidity compared with phenol can be ascribed to stabilization of resonance structures with the charge on a ring carbon through the nitro group s inductive effect. 

Exercise 22-24 Draw the structures of the intermediate cations for nitration of nitrobenzene in the 2, 3, and 4 positions. Use the structures to explain why the nitro group is meta-orienting with deactivation. Use the same kind of arguments to explain the orientation observed with —CF3, —CHO, —CH2Ci, and —NH2 groups in electrophilic aromatic substitution (Table 22-6),... 

The nitro group (NO2) is often incorrectly drawn with five bonds to nitrogen which you will see in Chapter 4, is impossible. Make sure you draw it correctly when you need to draw it out in detail. If you write just NO2 you are all right ... 

In drawing the mechanism it is best to draw the intermediate and to emphasize that the positive charge must not be delocalized to the carbon atom bearing the nitro group. 

Thyroxine has two aromatic rings, and you should be prepared to draw upon what you learned about aromatic chemistry in Chapters 22 and 23. It is also an amino acid and, in order to make the synthesis as cheap as possible, the chemists at Glaxo who developed the method used the amino acid tyrosine as a starting material. Nitration of tyrosine puts two nitro groups ortho to the OH group in an electrophilic aromatic substitution (make sure that you understand why ). 

Always draw out the nitro group In full when using It In mechanisms. 

At the same time, rotation about the formally single bond between N-l and C-2 in these compounds is more restricted than the drawing of a single bond implies, just as it was with amides. The two A-methyl groups in both enamines 2.63 and 2.82 have different chemical shifts and coalescence measurements show that the free energy of activation for rotation is 56 kJ mol 1 (13 kcal mol-1) for the former and 69 kJ mol-1 (16.5 kcal mol-1) for the latter. Decreasing the stabilisation of the anionic centre in the transition structure with a less powerful acceptor than a nitro group, as in the ester 2.83 reduces the barrier to rotation about the N—C bond to 58 kJ mol-1 (14 kcal mol-1). 

Once again, start by drawing the structure of the conjugated parent compound and then add an electron to form the radical anion. Only a few of the possible resonance forms are drawn. Nonetheless, it can be seen that the anion and radical can be delocalized onto both nitro groups simultaneously for the -dinitrobenzene, and this leads to more possible resonance forms. Because there is more delocalization in the intermediate from the para compound, it should be easier to transfer an electron to /7-dinitrobenzene, and hence, it should be a better radical trap. 

The nitro group is conjugated with the Jt system of the benzene ring and is strongly electron-wit/f-drawing—and it withdraws electrons specifically from the ortho and para positions. We can use curly... 

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