3. Physical Properties of the Substances

3. Physical Properties of the Substances

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