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

Preparation of mixed polysulphanes

Polysulphanes are interesting compounds. At room temperature they exist as toxic yellow liquids. The three stable polysulphanes are disulphane, trisulphane and pentasulphane. They are all very sensitive to alkalies so the glassware used to make these compounds must be washed with acid to remove trace amounts of alkali. They have few applications and uses.

I decided to try making disulphane. The reaction produces all three polysulphanes. In a future post I will perform a distillation to isolate disulphane.

The first step is to prepare a solution of sodium polysulphides.

To a 500ml beaker, I poured a solution containing 17g of sodium hydroxide and 150ml of water. I added in 20g of sulphur and began boiling the mixture. The sulphur gradually dissolved and the mixture turned a beautiful dark red colour. After all the sulphur had dissolved, 120ml of dark red liquid were left. This is the polysulphide solution.

Next the sodium polysulphides must be acidified to yield the polysulphanes. All equipment used in this procedure was washed with 5% acetic acid to prevent decomposition of the polysulphanes.

In a 500ml beaker, I chilled down 20ml of the solution prepared in step one to 0 C. The reaction is best performed at -15 C but 0 C was as cold as I could get. After this temperature had been reached, I added the solution to 60ml of 33% hydrochloric acid (also chilled to 0 C). If the starting solution and the acid aren't chilled, only hydrogen sulphide and sulphur will be formed. Anyway, after the addition, a bit of hydrogen sulphide was produced along with some solid sulphur. I stirred the mixture then let it settle. After this, the polysulphanes could be seen as a vivid yellow liquid at the bottom of the container separate from the surrounding liquid. 

The product was collected with a syringe and placed in an acid-washed vial. I got 0.7ml of mixed polysulphanes.

S8 + 12 NaOH = 4 Na2S + 2 Na2S2O3 + 6 H2O  /  S8 + 4 Na2S = 4 Na2S3

S8 + 8 Na2S = 8 Na2S2  /  S8 + 2 Na2S = 2 Na2S5  /  Na2Sx + 2 HCl = H2Sx + 2 NaCl

Nitrocellulose

Cellulose hexanitrate, commonly called nitrocellulose, is a very interesting explosive. When ignited unconfined, it bursts into a large ball of flame. This happens so fast that it's actually safe to ignite it on your hand. When the nitrocellulose is tightly confined it detonates, resulting in a violent explosion. Nitrocellulose was first prepared by Henri Braconnot in 1832. The synthesis of nitrocellulose is a chemistry classic.

Nitrocellulose is usually prepared from sulphuric and nitric acids, however I substituted the nitric acid with potassium nitrate.

To a beaker in an ice bath, I added 50ml of 98% sulphuric acid. I let the acid cool for 5 minutes, then over the course of 30 minutes added 25g of potassium nitrate in portions. This forms the required nitric acid in situ. After the nitrate addition, using a glass stir rod, I pushed pieces of cotton wool in until no more could be covered by the mixture. I left this overnight. The cellulose in the cotton reacts with the acids to form nitrocellulose. Anyway the next morning, I removed the nitrocellulose and added it to a bucket of water. I left it in the bucket for about 15 minutes to soak, then swirled it around in the water until it uncaked and started looking like cotton wool again.

I washed the nitrocellulose with 500ml of saturated sodium bicarbonate solution to remove traces of sulphuric/nitric acid. Then I washed it with water again to remove the sodium salts from the product.
I then dried it. I couldn't weigh the nitrocellulose as the pieces were too big to fit on my scales.

Left = dry nitrocellulose  /  Right = nitrocellulose deflagration unconfined
H2SO4 + KNO3 ==> HNO3 + KHSO4  /  HNO3 + 2 H2SO4 ==> 2 HSO4 (-) + NO2 (+) + H3O (+)

Synthesis of boron

Boron is an interesting element used in high strength fibers. It burns with a nice green flame. I plan to use it to make boron tribromide. I tried making some boron from boric acid.

The first step is to convert the boric acid to boron trioxide.

To a metal can, I added 15g of boric acid. Then I heated the can on a medium heat. After 5 minutes the boric acid had began to melt and decompose. Ten minutes after this, the mixture had turned to a bubbling sticky mess. I kept the heat on for another 10 minutes. After this, a sticky glassy mass remained in the can. Upon cooling, it solidified into rock-hard crystals of boron trioxide. The boron trioxide was scraped off the can and collected.

The final step is to reduce the boron trioxide to elemental boron.

I ground up the boron trioxide crystals from step one into a fine powder. This was very difficult and took several hours. Then I added a roughly equal amount of magnesium powder and cuttings to the boron trioxide. I blasted the mix with a butane torch until all the mixture had turned black. I was expecting the mixture to act like a thermite and not need to be torched. I think the reason this didn't happen was because half my magnesium was not powdered. Anyway, after this I added the black residue to a beaker and added about 50ml of water. I then slowly added 12M hydrochloric acid until the acid stopped affecting the mixture. The mixture fizzed and lots of gas was produced during the addition.

I noticed a disgusting smell. This is most likely borane gas. Once the mixture had stopped bubbling, I added 400ml of water to dissolve any residual boron trioxide. Then I filtered the mixture to collect the boron product. I got 0.06g of boron as a black powder, which is a miserable 1.2% yield.

I blame the extremely low yield on the thermite not working. The butane torch probably didn't do a very good job.

2 B(OH)3 ==> B2O3 + 3 H2O  /  B2O3 + 3 Mg ==> 3 MgO + 2 B

Acetone semicarbazone

Acetone semicarbazone is an organic compound derived from semicarbazide. It's got quite an interesting structure. I plan to use acetone semicarbazone to make semicarbazide.

I made acetone semicarbazide using a synthesis from www.prepchem.com which I modified slightly.

To a 250ml conical flask, I added 2.29g of hydrazine sulphate, 2g of sodium carbonate and 2ml of water.

After stirring, I poured in a solution of 1.14g of sodium cyanate in 25ml water along with 2ml of acetone. I stirred the mixture well for 10 minutes then left it to stand for 24 hours. After this, I filtered the mixture, collecting the filtrate. I evaporated the filtrate down to dryness, then to it I added 50ml of ethanol. The original procedure called to use a soxhelt extractor but I don't have this. Anyway I stirred the mixture so the ethanol could dissolve as much product as possible. Then I filtered the mixture again collecting the ethanolic filtrate.

I dried the filtrate in a crystallizing dish and was left with a pathetic amount of acetone semicarbazone. The amount was so small that I didn't bother weighing it. So I'm not sure what the yield was.

I think a larger quantity could have been obtained if I had used a soxhelt extractor or a least used hot ethanol. Warming the mixture before the cyanate addition would probably have helped as well.

see here for how this reaction works