Boston University Chemistry Worksheet

CHEMISTRY 437MeO
A.
C₂H100₂
(150.2)
MeO.
O
CH₂
C₂H₂BrO₂
(229.1)
PROCEDURE
Reaction of Methyl (4-Bromomethyl)benzoate with Phenol
+
O
Br
N-Br
O
C₂H₂BNO₂
(178.0)
hexane
toluene
dichloromethane
+
CHARACTERIZATION
CHEMISTRY 437
-OH
Preparation of Methyl (4-BromomethyDhenzoate
ISOLATION AND PURIFICATION
C₁4H1004
(242.2)
K₂CO3
C₂H₂O
(94.1)
(MW’s are given in parentheses)
K₂CO3
(138.2)
CHCl3, A
acetone, A
MeO
WARNING: Benzoyl peroxide is a powerful oxidizing agent and is an explosion hazard. Please read about
handling peroxides in HM&P.
To a 25-ml, round-bottomed flask equipped with a reflux condenser and a magnetic stir bar is added 3.33
mmol of methyl 4-methylbenzoate followed by 6.7 mL of chloroform. To this solution is added 3.50 mmol
of recrystallized N-bromosuccinimide and 0.07 mmol of fresh benzoyl peroxide. The reaction solution is
heated to reflux in a sand bath for 1.5 h with stirring (Note 1). Before proceeding to workup, the progress
of the reaction is checked by TLC to assure the consumption of starting material (Note 2).
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The reaction solution is allowed to cool to room temperature and is filtered through a plug of silica gel (20
mm x 5 cm) in a fritted glass funnel (medium) and the plug is rinsed with three 25-mL portions of
chloroform. The filtrate is concentrated by rotary evaporation to furnish a white solid. The yield (g) and
melting point of the crude product are determined.
For recrystallization the following solvents are tested (Note 3):
bp 69 °C
bp 111 °C
bp 40 °C
C₂H₂BrO₂
(229.1)
The mp and IR (neat), and ¹H NMR (CDC) spectra of the purified product are recorded.
Br
The yield (g) and mp of the purified compound are determined. The IR (neat) and NMR spectra of the pure
compound are recorded.
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B.Reaction of Methyl (4-Bromomethylbenzoate with Phenol
PROCEDURE
To a 25-mL, round-bottomed flask equipped with a reflux condenser and a magnetic stir bar is added 0.92
mmol of phenol, 0.96 mmol of potassium carbonate, and 1.5 mL of acetone. The solution is heated to reflux
(Note 4). After 30 min of stirring at reflux, a solution of 0.873 mmol of 4-(bromomethyl)benzoate in 1.0
mL of acetone is added dropwise through the condenser while still heating. This solution is heated at reflux
for 1.5 h with stirring and then the solution is allowed to cool to room temperature.
ISOLATION AND PURIFICATION
The reaction mixture is quenched with 5.0 mL of sat. aq. ammonium chloride solution and the resulting
mixture is transferred to a 60-mL, separatory funnel containing 20 mL of EtOAc and 15 mL of water. The
layers are separated and the aqueous phase is extracted twice with 10-mL portions of EtOAc. The combined
organic extracts are washed with 20 mL of water, 20 mL of brine, and are dried over magnesium sulfate.
The dried extracts are filtered through a glass filter frit and the filtrate is concentrated by rotary evaporation
to furnish a white solid (may remain as an oil, in which case recrystallization is not performed). The yield
(g) and melting point of the crude product are determined.
For recrystallization the following solvents are tested (Note 3):
hexane
toluene
bp 69 °C
dichloromethane
bp 111 °C.
bp 40 °C
The yield (g) and mp of the purified compound are determined. The IR (neat) and ‘H-NMR spectra of the
pure compound are recorded.
CHARACTERIZATION
IR (neat) and ¹H-NMR (CDCI) spectra of the purified product are recorded
CONCEIVABLE PRODUCTS
17 18
15
0.
14
NOTES
6 12
4
Br
17
16
18
15 14
20
23
21
127
18
17
14
16
15
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12
3
4 15
OH
16
1. After a short time, the color changes to red-orange.
2. The reaction mixture becomes colorless when complete. Work out a TLC analysis system
(hexane/EtOAc) with a little of the starting material while the reaction is running.
CHEMISTRY 437
3. The recrystallizations must be done fairly concentrated to obtain high yields of the products.
18
17
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