Question

I included the lab itself too, since question 3 and 4 can't be answered without the lab

1. Compare the reactivity of PhNH3? and PhNH2 under bromination conditions. Classify each as an activating or deactivating group and explain your reasoning. Hint: draw out the complete structure of each showing all lone pairs.
2. Show all aniline resonance structures involving donation of the –NH2 lone pair into the aromatic ring. Using these resonance structures, explain why –NH2 is an ortho, para directing group.
3. The mechanism for the ortho substitution of aniline is shown in figure 10. Using acetanilide, which is an activating group like aniline, show the mechanism for para addition. Include all resonance structures. Explain why para addition, like ortho addition, is favored when an activating group is on the ring.
4. Based on the discussion of reactivity in the introduction, what do you hypothesize will be the major product of the competitive nitration reaction?

Activating Group Resonance donation into the ring Deactivating Group - Resonance withdrawal out of the ring Figure 6. Resonance Effect of Activating and Deactivating Groups It is also important to note that when an electrophilic aromatic substitution reaction is performed on a mono-substituted benzene ring containing an activating group, the new electrophile will add to the ortho and the para positions of the ring (figure 7a). In the case of most deactivating groups on the ring, the electrophile will add to the meta position (figure 7b). The origin of this selectivity will be discussed in the next section AG DG DG AG Activating Group DG = Deactivating Group Electrophilic Aromatic Substitution with an Activating Group on the Ring Electrophilic Aromatic Substitution with a Deactivating Group on the Ring Figure 7. Directing Group Effects in Electrophilic Aromatic Substitution Aromatic rings containing very strongly activating groups such as -OH (phenol) and -NHz (aniline) can actually be halogenated in the absence of a Lewis acid catalyst. In fact, these strongly activated aromatic rings are so highly activated that it is difficult to stop at mono- halogenation. When three equivalents of bromine are used, the compound is tri-halogenated at both ortho positions and the para position as shown in figure 8. In the first part of the laboratory experiment, you will perform a bromination of phenol to produce tribromophenol NH OH NH2 Br 3 Br2 3 Br2 aniline Br phenol Br Figure 8. Halogenation of a Strongly Activated Aromatic Ring In the second part of the laboratory experiment you will perform an electrophilic nitration on two substituted benzene derivatives. Like bromination, the first step of nitration involves generation of the active electrophile, which is a nitronium ion (NO2P). The aromatic compound then reacts with this electrophile. You will investigate the relative reactivities of methyl benzoate and