Question

help of your TA. Questions to be discussed in the discussion section (please see your rubrics next page) 1. Explain why we did not synthesize the target molecule p-bromoaniline by direct bromination of aniline. (1 pt) 2. Explain why we did not synthesize acetanilide by refluxing a mixture of aniline and acetic anhydride. (1pt) 3. In the synthesis of acetanilide, aniline is regenerated from its salt using sodium acetate rather than sodium hydroxide. Explain using an equation what complication might arise if sodium hydroxide is used. (1 pt) The 'HNMR spectrum of acetanilide, one of the intermediates in the above multistep synthesis is shown below. Interpret the spectrum. Also predict the 'H NMR spectra for p-bromoacetanilide and p-bromoaniline. (1pt) 111

The experiment was a multi-step synthesis of p-bromoaniline . Aniline was protected with acetic anhydride . Please help answer the 4 questions posted in
the first picture .

Answer 1

1) Aniline contains amino group attached to the aromatic ring and hence it activates the benzene ring via +R resonance effect. This makes -NH2 ortho para directing group. Hence, if we do the direct bromination of aniline it may result in to multiple bromination of aromatic ring. Thus to avoide this unwanted reaction we do not use direct bromination. NH2 NH2 Br. Br o Br 2(1) aniline Br 2,4,6-tribromoaniline 2) Aniline is reactive compound as the -NH2 group activates the aromatic ring. Hence if we reflux the aniline with anhydride it may lead to acylation of aromatic ring instead of -NH2.

HN 4) a: 2.0ppm: 3H, S: CH3-C=O b: 7.2ppm: 2H, dd: ortho protons c: 7.4ppm: 1H, dd: para proton d: 7.6ppm: 2H, dd: meta protons e: 7.18ppm: 1H broad s: NH proton N-phenylacetamide HN CH a: 2.0ppm: 3H, S: CH3-C=O b: 7.4ppm: 2H, dd: ortho protons to bromine c: 7.8 ppm: 2H, dd: meta to bromine d: 6ppm: 1H, bs: -NH proton having variable shift. N-(4-bromophenyl)acetamide b NH2a by a: 5.Oppm: 2H, bs: -NH2 variable postion b: 6.8ppm: 2H, dd: ortho protons to NH2 c: 7.2 ppm: 2H, dd: ortho to bromine Br 4-bromoaniline