palico - 20-2-2024 at 08:08
Hello people,
today we conclude the old classic serie, and synthesise 1,2-naphthoquinone.
The reaction is the oxidation of 1-amino-2-naphthol prepared last time with potassium dichromate.
Procedure
A solution of 4.34 g of potassium dichromate in 70 ml of water is cooled to 2 Celsius in fridge. Apart, 7.12 g of 1-amino-2-naphthol is introduced in
a 250 ml round bottomed flask, and place in ice-water bath. To this substrate a solution of 10 ml concentrated sulfuric acid in 40 ml of water,
pre-cooled at 2 Celsius, is carefully added under stirring. A dark olive suspension is obtained.
Once finished, the dichromate solution is added all at once. A dark-brown solid is immediately formed. The beache is rinsed with water and this added
too. The reaction mixture is left under stirrin in ice bath for 1 hour, then is vacuum filtered, washed with water, pump dried, recovered, pressed on
paper, left dry in open air for three days to get 5.80 g ( 82.03% ) of brown solid.
m.p.: 121 - 126 Celsius
Discussion
There is not so much to discuss, apart that the product is sensitive and preferred to store at -18 Celsius. There is another oxidation procedure which
employ iron chloride, but I could not use it. This short old classic serie ends here, today.
References
Org. Syn. vol. 17, pag. 68, 1937.
" Practical Organic Synthesis " - A.I. Vogel, Third Edition 1974
As usual I thank you for attention, and link to my YT video for a more detailed procedure.
palico