CH 2290 Electrophilic Aromatic Substitution – Nitration of Methyl Benzoate
(adapted from Organic Chemistry: A Short Course, H. Hart, L. E. Craine, D. J. Hart, and T.K.
Vinod 13th ed. Houghton-Mifflin, Boston, 2012.)
Materials
From the Chemicals Hood:
Concentrated sulfuric acid
Methyl benzoate
50/50 sulfuric acid/ nitric acid solution
Methanol
Saturated sodium bicarbonate aqueous solution
From the Stockroom (Blue Bin):
1” stirbar
Stirbar retriever
Procedure
Into a clean, dry 125-mL Erlenmeyer flask, add 7 mL concentrated sulfuric acid. Place the flask
in an ice-water bath on top of the stirplate and stir the contents with a magnetic stirbar. Add 4
mL methyl benzoate dropwise. In a separate, 50-mL Erlenmeyer flask obtain 6 mL of a premixed 50/50 sulfuric acid/ nitric acid solution, and cool this solution to ice-cold in the ice-water
bath. Keeping the methyl benzoate-sulfuric acid solution in the ice-water bath, slowly add the
50/50 sulfuric acid/ nitric acid solution drop by drop with a disposable pipet over a period of
about 5 minutes, stirring constantly. After the addition is complete, remove the ice bath and
allow the reaction to stir at room temperature for 10 minutes.
Fill a 25-mL graduated cylinder up to the 10 mL mark with crushed ice and then fill the
remainder of the graduated cylinder with water. Pour this ice-water into a 150-mL beaker.
Transfer the magnetic stirbar to the beaker containing the ice-water and begin stirring quickly
(~500 rpm). Slowly drizzle the reaction mixture into the ice-water. After the ice melts, collect
the solid product by vacuum filtration and rinse several times with small portions of cold water
to remove all the acid. Rinse the product twice with 5-mL portions of ice-cold methanol.
Transfer the solid into a 50-mL Erlenmeyer flask and recrystallize from 5 mL methanol. Heat
(with a wooden stick) on the steam bath until all the product dissolves. Allow the flask to slowly
cool to room temperature, then chill in an ice-water bath to allow complete crystallization.
Collect the crystals by vacuum filtration and allow to dry until the next lab period.
Weigh the product and determine the percent yield for the reaction. Analyze the product via
NMR and FTIR spectroscopy and melting point analysis to identify which isomer of methyl
nitrobenzoate was formed.
Isomer
Melting Point
Methyl o-nitrobenzoate
-13 °C
Methyl m-nitrobenzoate
78 – 80 °C
Methyl p-nitrobenzoate
94 – 96 °C
Waste Disposal
Place the aqueous filtrate from the first filtration in the ACIDIC organic waste container. Place
the methanol mother liquor from the recrystallization in the FLAMMABLE organic waste
container.
Safety
Concentrated sulfuric acid is corrosive and may cause severe burns to the skin. The mixture of
sulfuric acid/ nitric acid is a powerful nitrating agent and may cause discoloration of the skin.
Remove contaminated gloves immediately. Neutralize any acid spills with sodium bicarbonate
solution.
Notes
Methyl benzoate density = 1.08 g/mL
Concentrated sulfuric acid ~ 18 moles/L
Concentrated nitric acid ~ 17 moles/L