Oxidation of toluene to benzoic acid

Benzoic acid is an aromatic carboxylic acid used as an organic building block. It occurs naturally in a wide range of plants, and is used as a food preservative. It's also an ingredient in many cosmetics. I plan to use benzoic acid to synthesize Benzamide and eventually aniline.

Benzoic acid can be made very easily from toluene. I did a test run to see if I could get this to work.

To a 250ml beaker I added 15g of potassium permanganate and 157ml of water. With a bit of stirring, most of the potassium permanganate dissolved giving a dark purple solution. I then added this solution (and the small amount of undissolved potassium permanganate) to a 500ml round-bottom flask. Next I added 35ml of technical grade toluene and attached a liebig condenser to the flask. I then strongly refluxed the mixture for 2.8 hours. The mixture gradually darkened as the potassium permanganate was converted to brown manganese dioxide. After 2.8 hours of reflux, I allowed the mixture to cool to room temperature. The purple colour of permanganate had completely gone, indicating all potassium permanganate had been consumed. I filtered the mixture to remove the manganese dioxide by-product. Manganese dioxide is a useful chemical to have, so I kept mine rather then discarding it.

 Anyway, I transferred the clear filtrate to a 250ml beaker, a small layer of excess toluene floated on top of the surrounding liquid. I removed the toluene with a syringe and saved it for future runs. After this, I was left with about 125ml of liquid in the beaker. This is a solution of potassium benzoate in water. I slowly added 33% hydrochloric acid to the solution and fluffy white crystals of benzoic acid precipitated. I kept adding hydrochloric acid until no more precipitate formed.

I then filtered off the benzoic acid and dried it. I got 2.45g of benzoic acid as fine fluffy white crystals.

The reason for the small amount of product obtained was my scales which were broken and gave a false reading.
Due to this I actually used a lot less than 15g of permanganate. I have no idea how much permanaganate I used so I can't calculate the real yield.

2 KMnO4 + C6H5CH3 ==> KC6H5COO + 2 MnO2 + KOH + H2O

KC6H5COO + HCl ==> C6H5COOH + KCl