Synthesis of Indigo
by Markus Arnoldini
Laboratory Report
Synthesis of
Indigo
O
H
N
N
H
O
by Markus Arnoldini
1
Synthesis of Indigo
1.
by Markus Arnoldini
Reaction Equation
O
O
H
N
O
H
NaOH
+
N
H
NO2
O
2.
Mechanism
OH
O
O
O
CH3
NaOH
H
+
NO2
NO2
H 2O
O
O
O
NaOH
+
O
HO
N
H
NO2
O
H
N
N
H
O
2
Synthesis of Indigo
3.
by Markus Arnoldini
Physical properties of the substances
o-Nitrobenzaldehyde [1]
O
H
NO2
molar weight
density
melting point
boiling point
refraction index
WGK
GK (CH)
R-phrases
S-phrases
151.12 g/mol
41 - 43 ºC
156 ºC (20 hPa)
2
3
S 24/25 (avoid contact
with skin and eyes)
molar weight
density
melting point
boiling point
refraction index
WGK
GK (CH)
R-phrases
58.08 g/mol
0.79 g/cm3 (20 ºC)
-95.4 ºC
56.2 ºC (1013 hPa)
1
5
R 11 (Highly flammable)
R 36 (Irritating to eyes)
R 66 (Repeated exposure
may cause skin dryness or
cracking)
R 67 (Vapours may cause
drowsiness and dizziness)
S 9 (Keep container in a
well-ventilated place)
S 16 (Keep away from
sources of ignition - No
smoking)
S 26 (In case of contact
with eyes, rinse
immediately with plenty of
water and seek medical
advice)
Acetone [1]
O
S-phrases
3
Synthesis of Indigo
by Markus Arnoldini
NaOH (Plätzchen) [1]
molar weight
density
melting point
boiling point
refraction index
WGK
GK (CH)
R-phrases
S-phrases
40.00 g/mol
2.13 g/cm3 (20 ºC)
323 ºC
1390 ºC (1013 hPa)
1
R 35 (Causes severe burns)
S 26 (In case of contact
with eyes, rinse
immediately with plenty of
water and seek medical
advice)
S 36/37/39 (Wear suitable
protective clothing, gloves
and eye/face protection)
S 45 (In case of accident or
if you feel unwell, seek
medical advice
immediately. Show the
label where possible)
molar weight
density
46.07 g/mol
0.790 - 0.793 g/cm3
(20 ºC)
-114.5 ºC
78.3 ºC
1
R 11 (Highly flammable)
S 7 (Keep container tightly
closed)
S 16 (Keep away from
sources of ignition - No
smoking)
NaOH
Ethanol [1]
HO
melting point
boiling point
refraction index
WGK
GK (CH)
R-phrases
S-phrases
4
Synthesis of Indigo
by Markus Arnoldini
Indigo [2]
NH
O
HN
4.
molar weight
density
melting point
boiling point
refraction index
WGK
GK (CH)
R-phrases
O
S-phrases
262,26 g/mol
390 - 392 °C (Sublimiert)
R 36/37/38 (Irritating to
eyes, respiratory system
and skin)
S 26 (In case of contact
with eyes, rinse
immediately with plenty of
water and seek medical
advice)
S 36 (Wear suitable
protective clothing)
Experimental accomplishment
0.2 g (0.00132 mol) of o-Nitrobenzaldehyde were put in a 50 ml beaker and first 4 ml
of Acetone and then 2 ml of water were added. While stirring, 1 ml of 1M NaOH
solution was added drop by drop and a blue precipitate crushed out of the solution.
The solid was filtered and washed with water and ethanol with vacuum over filter
paper (without a filtration funnel, to prevent the funnel mess-up). An amount of 0.076
g (0.00029 mol) of Indigo was received.
For the calculation of the yield the molar amount of received product was
divided by half the molar amount of o-Nitrobenzaldehyde used (for one molecule of
Indigo is formed by two molecules of o-Nitrobenzaldehyde) , and then multiplied by
100. This calculation yields a percentage of 43.94 %:
0.00029mol
 100%  43.94%
0.00066mol
5.
Analytical results
Melting point:
391 – 393 °C
5
Synthesis of Indigo
by Markus Arnoldini
6.
Sources
[1]
[2]
[3]
http://ch.chemdat.info/mda/ch/de/
http://de.wikipedia.org/wiki/Indigo
meanings of R-phrases:
http://www.chemie.fu-berlin.de/chemistry/safety/r-saetze_en.html
meanings of S-phrases:
http://www.chemie.fu-berlin.de/chemistry/safety/s-saetze_en.html
[4]
6