Trimethyl benzene

 

Trimethyl benzene
aka Mesitylene

Chemical formula	C9H12
OTP appearance	clear colorless liquid
Index of refraction	1.49541
Molar Mass(g/mol)	120.19
Density(g/cc)	0.8637
Melting Point(°C)	-44.8
Boiling Point(°C)	164.7
Solubility in water(g/L)	non
NFPA 704	2 2 0

Uses

Justification Questioned

Other

• Preferred extractant for ABE Fermentation
• An aromatic compound that can be created from non-aromatic compounds
• Precursor to key industrial chemical benzene, 1,3-dimethylbenzene and other aromatics

Natural occurrence

• Trimethyl benzene does not occur naturally.

Production

Synthesis

from propanone

Trimethyl benzene is produced in a very slow (2 days per campaign) and inefficient (15% yield) process from propanone.

Dehydrate propanone using sulfuric acid

1. Slowly (over hours) add sulfuric acid to chilled propanone, never allowing the temperature to exceed 10°C.

   3 C₃H₆O

   {H₂SO₄

   →

   0-10°C 5-10h}

   C₉H₁₂ + 3 H₂O

2. Continue to mix for 3-4 hrs
3. Allow temp to rise to room temperature and stand for 18-24 hours

   Steam distill

4. Heat until sulfur dioxide begins to form, continue until it stops
5. Steam distil for three minutes, collecting a rich water/trimethyl benzene phase
6. Retain distillate as "distillate 1"
7. Continue to distil for 17 minutes, collecting dilute trimethyl benzene
8. Retain distillate as "distillate 2"

   Separate/Wash both distillates in the same way

9. Allow the distillates to stand until they separate into two layers (top: trimethyl benzene, bottom: water)
10. Discard bottom layer
11. Combine the distillate with sodium hydroxide
12. Agitate until no scent of sulfur dioxide is noted
13. Wash twice with water
14. Distill, retaining everything up to 210°C

    Sodium purification, removing aldehyde and ketone side-products

15. Combine all distillates
16. Add sodium metal
17. Heat (reflux) at just below bp for 3h
18. Distill until volume is 1/3 original
19. Discard distillate
20. Filter
21. Discard residue
22. Fractionally distill residue
23. Retain fraction at 163-167°C

Accounts

400 g of clean dry sand are placed in a 2000 ml retort connected with a condenser. 250 g of acetone are added, and then a cooled mixture of 560 g of concentrated sulfuric acid and 150 g of water is run in, in a slow continuous stream, the retort being meantime cooled in cold water. After 24 hours standing, the mixture is slowly distilled, directly or in steam. When oily drops appear in the neck of the retort, the receiver is changed, and the distillate collected until only very small quantities of the oil appear. The color of the liquid (if directly distilled) changes to deep brown, and finally to black, sulfur dioxide is evolved, and the mass froths up considerably. The upper yellowish layer of the distillate is separated from the lower aqueous layer, washed with sodium hydroxide and water, and dehydrated over calcium chloride. It is then fractionated, the fraction 100-200° C being redistilled four times over thin slices of metallic sodium, when about two-thirds of it is obtained as pure mesitylene coming over at 161-166° C. Yield variable, about 25% theoretical (40 g). Colorless, strongly refracting liquid; b.p. 163° C; d= 0.8694 at 10° C.

See Also

• Benzene
• Wheeler, Henry L.; Hoffman, Charles (1910) "ALKYLATION OF AROMATIC AMINO ACIDS AMINOMETHYLBENZOIC ACIDS"
  American Chemical Journal 44 Eschenbach printinc company
  link courtesy Google Books.