EAS//Nitration of bromobenzene Brief summary of procedure. - Mix sulfuric acid +
ID: 1053689 • Letter: E
Question
EAS//Nitration of bromobenzene
Brief summary of procedure.
- Mix sulfuric acid +nitric acid, then cool in water bath. Add stir bar, condenser and reflux for 10 minutes while slowly adding bromobenzene. Don't exceed 55 degrees celcius
- Heat mixture for 15 minutes below 60 degrees celcius. Cooldown, then pour into 40 mL of cold h2o
- vacuum filtration to isolate crude bromonitrobenzene
- recrystallize with 95% ethanol (cool to room temp, then to 0 degrees celcius on ice)
- isolate product by vacuum and wash with ice-cold 95% ethanol.
- concentrate mother liquor under reduced pressure solvent removal.
Suppose your lab mate wants to make 2,4-dinitrobromobenzene from bromobenzene using a variation of the proceduredescribed in the textbook.
a) What changes should your lab mate make to the procedure to maximize their yield of 2,4-dinitrobromobenzene?
Explanation / Answer
Answer:
Nitration as said above is an Electrophilic Aromatic Substitution reaction. The electrophile here is Nitronium ion NO2+.
Bromobenzene to nitrated double will require stoichiometrically double Nitronium ions (NO2+).
On considering yield of nitration of bromobenzene reaction we can conclude much more drastic reaction conditions like high temperature, high 3/4 fold more concentration of an electrophile NO2+ ions will be required.
Hence we need to carry out reaction at some elevated temperature and for some more time and using excees of nitration mixture i.e. HNO3 + H2SO4.
This will ensure fine yield of 2,4-Dinitrobromobenzene from nitration of bromobenzene.
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