0 Tetralone, bisulfite addition product

The mixture is extracted with ten 175-ml. portions of benzene or 1 1 benzene-ether mixture (Note 4). The combined extract is washed with 75-ml. portions of water until the washings are neutral to litmus. The organic solvent is removed by distillation on a steam bath. The crude oily residue is converted directly (Note 5) to the /3-tetralone bisulfite addition product. 

C. Regeneration of 0-tetralone. Fifty grams (0.20 mole) of /3-tetralone bisulfite addition product is suspended in 250 ml. of water, and 75 g. (0.6 mole) of sodium carbonate monohydrate is added. At this point the pH of the solution is approximately 10. The mixture is extracted with five 100-ml. portions of ether (Note 8). The combined extract is washed with 100 ml. of 10% hydrochloric acid, then with 100-ml. portions of water until the washings are neutral to litmus, and is dried over anhydrous magnesium sulfate. The ether is removed by distillation, and the residue is distilled from a Claisen flask under reduced pressure, preferably in a nitrogen atmosphere. The pure /3-tetralone is obtained as a colorless distillate b.p. 70-71°/0.25 mm. (92-940/1.8 mm., 114-11674.5 mm.) n 1.5594. The yield is 17-21 g. (40-50% based on /3-naphthyl ethyl ether). 

B. Bisulfite addition product of /3-tetralone. To a solution of 325 g. (3.12 moles) of sodium bisulfite (commercial purified grade) in 565 ml. of water is added 175 ml. of 95% ethanol. The mixture is allowed to stand overnight, and the precipitated sodium bisulfite is removed by filtration. The filtrate is added to the crude /3-tetralone, and the mixture is shaken vigorously. Within a few minutes the addition product separates as a voluminous precipitate. The mixture is kept cold for several hours, shaken periodically, and then filtered with the aid of suction. The precipitate is washed well, first with 125 ml. of 95% ethanol, then four times with 125-ml. portions of ether (Note 6). The colorless addition product is air-dried (Note 5) and is stored in air-tight containers. The yield is 113-131 g. (60-70% based on /3-naphthyl ethyl ether) (Note 7). 

In this step the /3-tetralone is separated from starting material and other neutral substances in the reaction mixture. /3-Tetralone is sensitive to air oxidation therefore it should not be stored in the free state. The bisulfite addition product is stable, and the dry material can be stored indefinitely without deterioration. 

The ether extract and the water layer may be tested for the presence of /3-tetralone or the bisulfite addition product by the tetralone blue test. 

Naphthol 1 is initially protonated at a carbon center of high electron density (C-2 or C-4). The cationic species 3 thus formed is stabilized by resonance it can add a bisulfite anion at C-3. The addition product can tautomerize to give the more stable tetralone sulfonate 4 the tetralone carbonyl group is then attacked by a nucleophilic amine (e.g. ammonia). Subsequent dehydration leads to the cation... 

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