1. Organic Synthesis O OCH3 O C OH C H NO2
starting with the aromatic ester methyl benzoate
and finishing with the nitro aromatic acid 3-nitro benzoic acid:
ester O C
OCH3
acid O C OH
NO2 H
nitro
in three separate stages

2. Stage 1 O C OCH3 O C OCH3 NO2 + HNO3 + H2O
Nitration of the aromatic ring
to form methyl 3-nitrobenzoate O C
OCH3 O C
OCH3
NO2
+ HNO3
+ H2O
Cool with concentrated H2SO4

3. Identification of methyl 3-nitrobenzoate
OCH3
NO2
White crystalline solid at room temperature
Melting point 77.5 oC
Impurities reduce melting point and discolour the solid
Compare with 3-nitrobenzoic acid

4. mass spectrum of methyl 3-nitrobenzoate
OCH3
NO2 +
m/z relative intensity
Mass of molecular ion:181
C6H4(NO2)CO+
C6H4(NO2)COOCH3+
C6H4+
C6H4CO+
Compare with 3-nitrobenzoic acid

5. Infra red spectrum of methyl 3-nitrobenzoate
Compare with 3-nitrobenzoic acid
The “finger print” region
< 1500 cm-1
C=O
1750 cm-1
unique pattern
for each molecule

6. nmr spectrum of methyl 3-nitrobenzoate
nuclear magnetic resonance A B C D E
1H NMR MHz
C8H7NO4
0.038 g in 0.5 ml CDCl3
Assign. Shift(ppm) A B C D E
Compare with 3-nitrobenzoic acid

7. Stage 2 O OCH3 O C C + OH - + CH3OH NO2 NO2
Hydrolysis of the ester group
to form the 3-nitrobenzoate ion O C
OCH3
NO2 O C
NO2
+ OH -
+ CH3OH
Reflux with concentrated NaOH
alkaline hydrolysis

8. Stage 3 O C NO2 O C OH NO2 + H+ Displacement of weak acid
to form 3-nitrobenzoic acid O C
NO2 O C OH
NO2
+ H+
Warm with HCl
acid displacement

9. Identification of 3-nitrobenzoic acidOH
NO2
White crystalline solid at room temperature
Melting point oC
Impurities reduce melting point and discolour the solid
Compare with methyl 3-nitrobenzoate

10. mass spectrum of 3-nitrobenzoic acidOH
NO2 +
m/z relative intensity
Mass of molecular ion:167.0
C6H4(NO2)CO2H+
C6H4(NO2)+
Compare with methyl 3-nitrobenzoate

11. Infra red spectrum of 3-nitrobenzoic acid
Compare with methyl 3-nitrobenzoate
The “finger print” region
< 1500 cm-1
C=O
1700 cm-1
acid O-H
2600 cm-1
unique pattern
for each molecule

12. nmr spectrum of 3-nitrobenzoic acid
1H NMR MHz
C7H4NO4
0.025 g in 0.5 ml CDCl3
Assign. Shift(ppm) A B C D E
Compare with methyl 3-nitrobenzoate

13. References
Steve Lewis for the Royal Society of Chemistry
Source of the spectral information