2-Aminophenol via hydrolysis

2-Aminophenol, or 2-hydroxyaniline, is an organic compound used in photography. It's a valuable reagent used to synthesize many heterocyclic compounds such as benzoxazoles (many of which are important in the pharmaceutical industry). I plan to use 2-aminophenol to synthesize catechol. Although I'm not sure if I'll ever get around to it.

2-Aminophenol is formed via the acid hydrolysis of 2-benzoxazolinone. I tried this out.

To a 500ml round bottom flask, I added 27ml of 33% hydrochloric acid and 70ml of water. I then added 1.8g of 2-benzoxazolinone and set up for reflux. Using a boiling water bath as the heating source, I gently refluxed the mixture for 2 hours. The 2-benzoxazolinone gradually dissolved leaving a clear brown-yellow solution. After the reflux, I allowed the mixture to cool down to room temperature. As the mixture cooled, fluffy white crystals of 2-aminophenol began to precipitate.

Once the mixture had fully cooled, I filtered off the 2-aminophenol product. After drying I was left with 0.62g of slightly brown 2-aminophenol which is a 42.6% yield.

A note on safety: although the deadly gas phosgene is produced in this reaction, it immediately reacts with the water present as soon as it is formed. Due to this, the risk of phosgene poisoning is extremely low.


C6H4(O)NHCO + 2 HCl ==> C6H4(OH)NH2 + COCl2  /  COCl2 + H2O ==> CO2 + 2 HCl

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

Sodium pyroantimonate

Sodium pyroantimonate is an interesting salt used as a glass clarifier. It's also used in monochrome picture tubes and glass fibers. At room temperature, sodium pyroantimonate exists as white crystals.
I chose to make it because the synthesis seemed interesting. I probably won't use the product for anything though.

To a 125ml beaker I added 20ml of 35% (by weight) sodium hydroxide solution. Next I added 4g of crude antimony trisulphide. The antimony trisulphide dissolved giving a brown-yellow solution. Slight heating was needed to get all of it dissolved. Since my antimony trisulphide was impure, some elemental antimony remained. This was filtered off before continuing. The solution was transferred to a 1000ml conical flask and diluted with 130ml of water. I heated the mixture up to 70 C and slowly added 50ml of 6% hydrogen peroxide in portions with stirring while maintaining the temperature at 70-85 C. The colour of the mixture changed to a light yellow and some crystals of sodium pyroantimonate precipitated. I let the mixture cool down to room temperature then filtered off the sodium pyroantimonate.

 I washed the product with 10ml of equivolume water/ethanol mixture and then 10ml of anhydrous ethanol, then dried it. I got 1.5g of dry sodium pyroantimonate.

Sb2S3 + 6 NaOH ==> Na3SbS3 + Na3SbO3 + H2O

3 H2O + Na3SbO3 + H2O2 ==> NaSb(OH)6 + 2 NaOH

 NaOH + H2O2 + Na3SbS3 + 3 H2O ==> NaSb(OH)6 + 3 NaSH