Synthesis of Indigo by Markus Arnoldini
Laboratory Report
Synthesis of
Indigo
by Markus Arnoldini
1. Reaction Equation
2. Mechanism
3. Physical properties of the substances
o-Nitrobenzaldehyde[1]/ molar weight / 151.12g/mol
density / -
melting point / 41-43ºC
boiling point / 156ºC (20hPa)
refraction index / -
WGK / 2
GK (CH) / 3
R-phrases / -
S-phrases / S 24/25 (avoid contact with skin and eyes)
Acetone[1]
/ molar weight / 58.08g/mol
density / 0.79g/cm3 (20ºC)
melting point / -95.4ºC
boiling point / 56.2ºC (1013hPa)
refraction index / -
WGK / 1
GK (CH) / 5
R-phrases / 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-phrases / 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)
NaOH (Plätzchen) [1]
NaOH / molar weight / 40.00g/mol
density / 2.13g/cm3 (20ºC)
melting point / 323ºC
boiling point / 1390ºC (1013hPa)
refraction index / -
WGK / 1
GK (CH) / -
R-phrases / R 35 (Causes severe burns)
S-phrases / 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)
Ethanol[1]
/ molar weight / 46.07g/mol
density / 0.790-0.793g/cm3 (20ºC)
melting point / -114.5ºC
boiling point / 78.3ºC
refraction index / -
WGK / 1
GK (CH) / -
R-phrases / R 11 (Highly flammable)
S-phrases / S 7 (Keep container tightly closed)
S 16 (Keep away from sources of ignition - No smoking)
Indigo[2]
/ molar weight / 262,26 g/mol
density / -
melting point / 390 - 392 °C (Sublimiert)
boiling point / -
refraction index / -
WGK / -
GK (CH) / -
R-phrases / R 36/37/38 (Irritating to eyes, respiratory system and skin)
S-phrases / S 26 (In case of contact with eyes, rinse immediately with plenty of water and seek medical advice)
S 36 (Wear suitable protective clothing)
4. 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 of43.94 %:
5. Analytical results
Melting point: 391 – 393 °C
6. Sources
[1]
[2]
[3] meanings of R-phrases:
[4] meanings of S-phrases:
1