Benzene and Activating Group

Topics: Benzene, Electrophilic aromatic substitution, Aromaticity Pages: 3 (852 words) Published: May 17, 2013
Brian HoEAS Lab Report Section: 40788
Chem 51LC/ Tuesdays 1-5pm TA: Sam Mann
Purpose: The goal of this experiment was to explore the degree of activation of the activating groups in aniline, acetamide, phenol, and anisole. A bromination reaction was done with one of the four aromatic compounds and the product was analyzed using melting point calculations. Theory: In general, electrophilic aromatic substitution occurred when the alkene in the benzene ring acted as a nucleophile and attacked the electrophile, which was the Br2 group. In the mechanism, the alkene in the benzene ring attacks the Br2 group leaving a carbocation intermediate and a bromine anion. The Br2 was in an HBr solution, which used as a catalyst similar to FeBr3. The bromine anion then deprotonated a beta hydrogen, forming HBr and a benzene ring with the activating substituent and bromine. This reaction could be repeated up to two more times based on the strength of the orthro/para directing group. As a result, there were many possible different products when the aromatic compounds underwent bromination. For aniline, the prediction was that the product would be 2,4,6-tribromoaniline because anime was a very strong activating group that reacted strongly with halogenations reactions in general. For phenol, the hydroxy group was also a ring activating and electron donating group. A disubstituted bromine product was predicted because the hydroxy group was not as powerful as the amide. Anisole also had an activating group in a methoxy group and the prediction was from the anisole bromination reaction would be a disubstituted product. Lastly, for acetamide, the amide group was considered to be not a strong activating group compared to the anime, hydroxy, and methoxy groups because of the fact that the electrons were not localized in the amide due to resonance. As a result, this reduced the activation of the benzene ring and the predicted product was...
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