1,3,5-Trimethylbenzene

1,3,5-Trimethylbenzene commonly called mesitylene, is an aromatic hydrocarbon occasionally used as a ligand or solvent. Its also used as an additive to plane fuel and as a precursor to 2,4,6-trimethylaniline. Upon mild oxidation with Manganese dioxide, mesitylene forms 3,5-Dimethylbenzaldehyde, I may have a post on this in the future. Mesitylene can be made by the dehydration of acetone with sulphuric acid. I tried this method out.

To a 1000ml round-bottom flask in an ice bath I added 127ml of acetone. Once the acetone had cooled to 5 C, I (over the course of 5 hours) began adding 90ml of 98% sulphuric acid in small portions. I made sure the temperature never rouse above 22 C during the additions. Towards the end of this, the mixture started becoming red in colour. I left the mixture to stand for 24 hours then set up for simple distillation. as the distillation progressed a green liquid started coming over. Soon after this, huge amounts of sulphur dioxide started being generated. The distillation setup must be equipped with a gas outlet to dispose of the toxic sulphur dioxide. Anyway, after a few minutes, a yellow oil began to come over. it formed a layer on top of the previous distillate. I presumed this was the crude mesitylene.

I stopped the distillation when the foam in the distilling flask reached the bottom of the still-head.
Using a syringe I collected the top mesitylene layer in the receiving flask. I washed the mesitylene with 20ml of dilute sodium hydroxide solution, then dried it over anhydrous calcium chloride.
I then distilled the crude product collecting the fraction boiling at 100-200 C. As I was collecting the mesitylene distillate I accidentally spilled some. Due to this I only got 3ml of mesitylene product and my yield was 2.1%. The procedure I followed claimed a 25% yield.

3 (CH3)2CO  ==H2SO4==>  C6H3(CH3)3 + 3 H2O