Sodium—continued metabisulphite

Fit a 1-litre three-necked flask with two double surface condensers and a sealed stirrer unit. Place 25 g (29 ml, 0.25 mol) of mesityl oxide (Expt 5.213), 50 ml of dioxane and a cold (10 °C) solution of sodium hypochlorite in 750 ml of water (1) in the flask, and stir the mixture. Heat is evolved in the reaction and after about 5 minutes chloroform commences to reflux. As soon as the reaction becomes very vigorous, stop the stirrer and cool the flask with water so that the chloroform refluxes gently after 20-30 minutes, when the reaction has subsided, resume the stirring and continue it until the temperature of the mixture has fallen to that of the laboratory (2-3 hours). Decompose the slight excess of hypochlorite by the addition of sodium metabisulphite (about 1 g), i.e. until a test-portion no longer liberates iodine from potassium iodide solution. 

Oxidation of toluene-o-sulphonamide to saccharin. In a 600-ml beaker, mounted on an electric hot plate and provided with a mechanical stirrer, place 12 g (0.07 mol) of toluene-o-sulphonamide, 200 ml of water and 3g of pure sodium hydroxide. Stir the mixture and warm to 34-40 °C until nearly all has passed into solution (about 30 minutes). Introduce 19g (0.32 mol) of finely powdered potassium permanganate in small portions at intervals of 10-15 minutes into the well-stirred liquid. At first the permanganate is rapidly reduced, but towards the end of the reaction complete reduction of the permanganate is not attained. The addition occupies 4 hours. Continue the stirring for a further 2-3 hours, and then allow the mixture to stand overnight. Filter off the precipitated manganese dioxide at the pump and decolourise the filtrate by the addition of a little sodium metabisulphite solution. Exactly neutralise the solution with dilute hydrochloric acid (use methyl orange or methyl red as external indicator). Filter off any o-sulphonamidobenzoic acid (and/or toluene-o-sulphonamide) which separates at this point. Treat the filtrate with concentrated hydrochloric acid until the precipitation of the saccharin is complete. Cool, filter at the pump and wash with a little cold water. Recrystallise from hot water. The yield of pure saccharin, m.p. 228 °C, is 7.5 g (58%). 

Introduce a solution of 100 g of sodium metabisulphite in 200 ml of water and continue the stirring, preferably for 10 hours with exclusion of air. A thick precipitate separates after a few minutes. Collect the bisulphite compound by suction filtration, wash it with ether until colourless and then decompose it in a flask with a lukewarm solution of 125 g of sodium carbonate in 150 ml of water. Separate the ketone layer, extract the aqueous layer with four 30 ml portions of ether, dry the combined organic layers over magnesium sulphate, remove the ether at atmospheric pressure and distil the residual oil under reduced pressure through a short fractionating side-arm. Collect the cycloheptanone at 64-65 °C/12mmHg the yield is 17 g (31%). 

Transfer 100 ml of the sample to a continuous extraction apparatus containing a suitable volume of a mixture of 3 volumes of chloroform and 1 volume of wobutyl alcohol. Make the aqueous layer distinctly alkaline with strong ammonia solution, add a little sodium metabisulphite to the aqueous layer and to the flask of the apparatus, which should also contain about 50 ml of the chloroform/f obutyl alcohol mixture, and reflux for two hours or until the morphine is completely extracted. Cool the solution, filter into a separator through a cotton-wool plug and wash... 

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