Relative Reactivity of Anilines
Abstract: Various Anilines were tested with Br2/HBr solution, the products were crystallized and melting points attained to verify relative reactivity. My assignment, 2,4-Dibromoanisol, was prepared in a yield of 52% with a melting point of 55-58 C . Reaction:
Procedure: Anisole (0.35mL, 0.0378mol) was obtained and placed in a pre-weighed 25 mL round bottom flask, along with 2.5 mL of glacial acetic acid and a magnetic stir bar. Then the reaction apparatus was assembled, the dry tube was charged with conc. sodium bi sulfate, the 25 mL round bottom was attached to the apparatus, and 5 mL of Br2/HBr mixture was obtained and placed in the round bottom. The reaction took place for 20 minutes. An orange liquid was obtained and placed in a 125 mL Erlenmeyer flask along with 25 mL of water and 2.5 mL of conc. Sodium bisulfate soln. The solution was then placed in an ice bath to precipitate and then the solid product was filter in a Buchner funnel. These crystals were then re-dissolved minimum amount of hot solvent (heptane) and recrystallized. Once a dry product was obtained, a melting point was established (2,4-Dibromoanisol mp 55-58 C) and percent yield was established (52%). Results: Through a melting point reading, it was determined that the product obtained was 2,4-Dibromoanisol mp 55-58 C. The products obtained by my partners, were determined to be: (p-bromoacetanilide mp 160-165 C) and (2,4,6 tribromoaniline, mp of 108-110 C) respectively. Discussion and Conclusions: Interpreting these results have concluded that relative reactivity of these three anilines in order of most reactive to least reactive go; Aniline > Anisole > Acetanilide. Aniline, has an NH2 , the most active substituent , and adds to any ortho/para position available on the ring. This data is confirmed with the product obtained, (2,4,6 tribromoaniline, mp of 108-110 C). As for anisole, it has a strongly activating group...
References: Pavia, Donald L; Lampman, Gary M; Kriz, George S; Engel, Randall G, "Introduction to Organic Laboratory Techniques, 2nd edition", Thompson Learning Inc. ©2005.
Carey, Francis A., "Organic Chemistry, fifth edition", McGraw Hill ©2003.
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