2-Naphthol [135-19-3-A] C10H8O
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For the following alkali fusion, it is best to use a 1 mm thick copper crucible approximately 9 cm high, 8 cm in diameter at the top, and 5 cm in diameter at the bottom, held by an iron ring and containing a reasonably thick thermometer (up to 360 °C), which is protected against the molten alkali in an approximately 18 cm long and 10 mm wide copper sleeve with some oil bath liquid (for heat transfer). To pour out the melt, a copper sheet about 25 x 35 cm with edges 1 cm high to form a tray is needed. During the experiment, which must be carried out under the fume hood, protective glasses and gloves must be worn. Place 210 g (5.25 mol) of sodium hydroxide in the copper crucible, add 20 ml of water, and heat while stirring. Once the temperature reaches 280 °C, add 70 g (0.30 mol) of finely powdered sodium 2-naphthalenesulfonate fairly quickly while stirring, maintaining the temperature between 260 and 280 °C. Then increase the flame slightly, causing the melt to become slimy with steam development and swelling, until finally the actual reaction occurs at 310 °C. Maintain the temperature at 310-320 °C for about 5 minutes until the melt becomes thin and the reaction is complete. Immediately pour the melt (with a strong crucible tong) onto the copper sheet in a thin layer, cool, and crush it. Dissolve the crushed melt in 1 l of water. Precipitate the naphthol with 500 ml of concentrated hydrochloric acid and extract once with 200 ml and twice with 100 ml of ether. Dry the combined ether extracts over sodium sulfate, distill off the ether, and purify the residue by vacuum distillation in a 100-ml Claisen flask or Kugelrohr. After a small fore-run, 25 g (58%) of 2-naphthol distills over at 153 °C and 12 Torr, which is melted out of the Claisen flask or Kugelrohr and pulverized in a mortar. The melting point of the almost colorless preparation is 119-121 °C. Recrystallization from benzene yields colorless flakes with a melting point of 121-122 °C.
Source: Gattermann, Ludwig - The Practice of the Organic Chemist, 43rd Edition, Walter de Gruyter, Berlin / New York 1982
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Last updated: 24/10/2005
Other name: β-Naphthol