Laboratory Report13.11.2007

Organic chemistry practical course (OCP1)

HS 07/08

Lorenz Schwarzer

D-Biol

Assistant: Zhu Liang

Synthesis of4-tert-butyl-o-xylene

(4-tert-butyl-1,2-dimethylbenzene)

Method

Friedel-Crafts-Alkylation:

Synthesis of 4-tert-butyl-o-xylene by alkylation of ortho-xylene with tert-butylchloride as reactant and iron(III)chloride as catalyst.

Reaction equation

o-Xylene t-Butylchloride 4-tert-butyl-o-xylene

Mechanism

Physical properties of the substances

tert-butylchloride
/ Molar weight / 92.57 / g/mol
Density / 0.84 / g/ml
Melting point / -28 / °C
Boiling point / 51 / °C
R-Phrases / R11highly flammable
S-Phrases / S9keep container in a well-ventilated place
S16keep away from sources of ignition – no smoking
S29must not get to the canalization
ortho-xylene
/ Molar weight / 106.17 / g/mol
Density / 0.88 / g/ml
Melting point / -25 / °C
Boiling point / 144.4 / °C
R-Phrases / R10flammable
R20/21 harmful by inhalation and contact with skin
R38 irritates skin
S-Phrases / S25 avoid contact with eyes
Iron(III)chloride (FeCl3)
FeCl3 / Molar weight / 162.21 / g/mol
Density / 2.9 / g/ml
Melting point / - / °C
Boiling point / - / °C
R-Phrases / R22harmful if swallowed
R38irritating to skin
R41risk of serious eye damage
S-Phrases / S26in case of contact with eyes rinse with a lot of water and seek medical help
S39use safety goggles
Hydrochloric acid (HCl)
H-Cl / Molar weight / 36.46 / g/mol
Density / 1.19 / g/ml
Melting point / -40 / °C
Boiling point / 84 / °C
R-Phrases / R 34Causes burns
R 36 Irritating to eyes
R 37Irritating to respiratory system
R 38Irritating to skin
S-Phrases / S 26In case of contact with eyes, rinse immediately with plenty of water and seek medical advice.
Sodium hydrogen carbonate (NaHCO3)
/ Molar weight / 84.01 / g/mol
Density / 2.22 / g/ml
Melting point / 270 / °C
Boiling point / - / °C
R-Phrases / -
S-Phrases / -
Calcium chloride (CaCl2)
CaCl2 / Molar weight / 110.99 / g/mol
Density / 1.06 / g/ml
Melting point / 772 / °C
Boiling point / > 1600 / °C
R-Phrases / R36Irritating to eyes
S-Phrases / S22 Do not breathe dust.
S23 Do not breathe vapour.
S24 Avoid contact with skin.
4-tert-butyl-o-xylene
/ Molar weight / 162.27 / g/mol
Density / 0.868 / g/ml
Melting point / - / °C
Boiling point / 200-209 / °C
R-Phrases / R36-38 Irritating to eyes and skin and respiratory system
S-Phrases / S23 do not inhale gas/fumes/vapour/spray
S24/25avoid contact with skin and eyes

Educts

Substance / Amount / Molar amount / Volume
g / mol / ml
tert-butylchloride / 3.02 / 0.0326 / 3.60
ortho-xylene / 3.85 / 0.0363 / 4.38
FeCl3 (6H2O) / 0.168 / 0.00104 / -

Experimental accomplishment

  1. tert-butylchloride is mixed with o-xylene in a round bottom flask. The flask is equipped with a reflux condenser. Keeping the fume hood window as low as possible, the FeCl3 (6H2O) is then added to the mixture and, while stirring, HCl is produced. To help solve the FeCl3, the mixture was heated up a bit. When, additional 0.5g of tert-butylchloride was added.
  2. The mixture was then stirred for 1h at room temperature and for 20 min at reflux and cooled down to room temperature.
  3. The solid is filtered and the resulting solution washed with saturated solutions of NaHCO3 and NaClin the separation funnel.
  4. The resulting organic phase is finally dried over CaCl2 and distilled.
    The distillation was very difficult. The boiling point of o-xylene is very high (144.4°C), so it was necessary to distil with vacuum. But the vacuum wavered very strongly and it had to be regulated by hand. Therefore it took a lot of time and only the solvent was evaporated. The product wasn’t distilled.
    The solvent boiled at about 130°C oil bath temperature and 68 mbar. The vapour temperature was between 45°C and 60°C.
  5. The infrared spectrum and the refractive index were measured.

Experimental setup

Heating apparatus Filtration apparatus

Separation funnel Distillation Apparatus

Results

Refractive index:Taken: 1.499

4-tBu-oXylene (lit.):1.499-1.5

o-Xylene (lit.):1.505

IR-Spectrum-bands [cm-1]2961.84C-H stretch (alkanes)

2865.44C-H stretch (alkanes)

1617.07C6 - ring (aromatics)

1507.18C6 - ring (aromatics)

With the aid of the interpretation of the IR-spectrum, the product can be identified as an aromatic C6-ring with certain alkane-substituents.

But it’s not possible to distinguish between o-xylene and 4-tert-butyl-o-xylene, because the only difference is a tert-butyl-substituent and there is no specific wave number for this group. The IR-spectra of o-xylene and 4-tert-butyl-o-xylene are also very similar.

The refractive index is a better property to distinguish the two molecules. The taken value and also the literature value of 4-tert-butyl-o-xylene is a bit lower then the refractive index of o-xylene. So the product can probably be identified as 4-tert-butyl-o-xylene.

IR-Spectrum of the Product
Reference IR-spectrum 4-tert-butyl-o-xylene

Literature

  • Script Organic chemistry II, Prof. Dr. Hans-Jürg Borschberg, ETH Zürich
  • Table of Characteristic IR Absorptions

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