Reference no: EM132366867
AIM
To prepare N-(4-bromophenylacetamide) using electrophilic aromatic substitution and confirm its identity.
INTRODUCTION
Electrophilic aromatic substitution is a key reaction for preparing new molecules. Bromination is a very useful example of one of these reactions. Traditionally, a solution of acetic acid and molecular bromine (Br2) has been used to brominate aromatic systems. Bromine is a hazardous and difficult reagent to handle. This synthesis takes advantage of a "greener" method using metal halide in the presence of an oxidising agent in acidic conditions to generate molecular bromine. This is somewhat safer as the bromine generated is quickly consumed. Further reading: McMurry (8th ed.), Chapter 16
Scheme 1: Reaction scheme for this experiment. Conditions: (a) (CH3CO)2O; (b) NaOCl, NaBr.
In the first step, you will prepare N-phenylacetamide by acetylation of aniline using acetic anhydride (step a in Scheme 1). Electrophilic aromatic substitution of N-phenylacetamide using sodium bromide in the presence of sodium hypochlorite as an oxidising agent (step b). Proton NMR spectra allows the location of bromination to be determined..
EXPERIMENTAL INSTRUCTIONS
Day 1: Acetylation of aniline
– Wear protective gloves when handling aniline, acetic anhydride and acetic acid; only work in the fumehood as these chemicals can be harmful when inhaled.
Day 2: Bromination of N-phenylacetamide
– Wear protective gloves whenhandling sodium hypochlorite; only work in the fumehood as these chemicals can be harmful when inhaled.
REPORT
A Lab report is required to be written for this experiment and must contain the below sections.
• Aim
• Introduction
• Method
• Results
• Discussion
• Conclusion
NOTE:
o All spectra (IR/NMR/UV-Vis/AAS...etc) must be attached in reports
o all graphs must be drawn in excel and pasted in the reports
ADDITIONAL QUESTIONS
1. Use the proton NMR spectrum of N-(4-bromophenylacetamide) to justify where the electrophilic aromatic substitution has taken place.
2. If bromine were used in excess, dibromoacetamide could be produced as a byproduct. What would be the structure of the major dibrominated byproduct? Would the second bromination occur faster than the first, or slower? Explain why.
3. What are the advantages of green chemistry?
Quality of writing and presentation:
• clarity, structure (following academic conventions), grammar, spelling, expression, formatting of references, presentation, etc.
Quality of the practical work:
• quality and consistency of the data
• appearance, melting point, spectra and yield of the product (for synthetic experiments)
Attachment:- Green Bromination of Aromatic Ring.rar