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Preparation of 2-naphthol

First 2-naphthalene sulfonate

The open 250 ml round bottom flask mix together 150 g (1.17 mol) of finely minced naphthalene and 180 g (98 ml) conc. sulfuric acid and heated in an oil bath at a temperature of 170-180 ° C. Then the mixture is cooled and poured into a beaker with 300 ml of cold water. Unreacted naphthalene filter off. A solution of 2-naphthalenesulfonic acid Heat the beaker to boiling, and adding an aqueous suspension of calcium hydroxide, prepared from 210 g (3.7 mol) of calcium oxide. While still hot reaction mixture was filtered and the precipitate on the filter with boiling water. This filter thicken to crystallize. On cooling overnight, crystallized calcium salt. After filtering off the crystals dissolve in hot water and add sodium carbonate solution until alkaline. After cooling, the precipitated calcium carbonate filter out a solution to thicken the interference crystallization. Within a few hours, excluding about 140 g (66%) naftalensulfonanu solution.

2-naphthol - preparation, the reaction

Second 2-naphthol

In nickel or cast-iron pot (ceramics I tried, but it is possible that aggressive alkaline environment will survive - he wants to try) on volume of about 500 ml melted by heating using direct flame 240 g KOH (alternatively 171 g NaOH) and 10 ml of water. When the melt temperature reaches 250 ° C, interrupt heating and stirring rapidly add 100 g of finely minced 2-Naftalensulfonanu solution (0.43 mol). In 5-10 minutes raise the temperature to 300 ° C (note mixture foams), will soon be released once colored layer 2-Naftolátu pasty layer of potassium hydroxide. The temperature of the mixture will increase further in the course of 5-10 minutes at 310 ° C, then heating is interrupted and the adhesive material of the walls of the crucible pressed down into the melt. Let cool melt into a pasty consistency and transfer to a 2 l beaker half filled with ice. The rest of jar with plenty of water and pour the pastovitému share in the beaker. From this solution naftolátu vysrážíme 2-naphthol by adding the necessary amount of conc. hydrochloric acid until it starts to release carbon dioxide.
Heat the suspension clot (clot packs and better filters). Precipitate after cooling in an ice bath, filtered and transferred into a beaker of water, where it dissolve by adding the required amount of 5% NaOH. To prevent oxidation of 2-naftolátu add 2 g of sodium dithionite solution and filtered from any impurities. The filtered solution vysrážíme 2-naphthol with acetic acid and briefly cook, so we get better filterable precipitate. The suspension is cooled in an ice bath and filtered and dry air between the filter papers.
This gives about 50 g of 2-naphthol (80%)

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