Preparation reaction with sodium sulphite

Sulphonyl halides, other than fluorides, have also been produced by halide exchange. Thus, sulphonyl chlorides may be made from the fluoride by refluxing with aluminium trichloride622,623. Sulphonyl bromides may be prepared from the sulphonyl chloride by reaction with sodium sulphite and base, followed by bromine (equation 158)624... 

The carbanions take up 02 and these take up protons to give hydroperoxides in good yields. But because they are explosive in nature, they are not usually isolated and on reduction with sodium sulphite on trialkyl phosphite give alcohols. Alcohols can also be prepared via hydroperoxy molybdenum complexes and alkyl boranes. These reactions are summarized as follows ... 

Perhaps the most widely utilized su henyl derivatives are the S-sulphonates [160] which can be prepared by oxidative sulphitolysis of a disulphide bond with sodium sulphite and sodium tetrathionate at pH 7-9 [161], by the oxidation of disulphides or thiols with sulphite ion and copper(ll) [160], by the use of small amounts of cysteine together with oxygen and sulphite [162], or by the reaction of halides with sodium... 

C HgNjOjS. Colourless needles, with iH20. Prepared by reducing diazotized sulphanilic acid with an excess of sodium sulphite. It is a typical hydrazine in its reactions with ketones, and with acetoacetic ester. The latter reaction gives rise to the tartrazine dyestuffs, and is much used commercially. 

Phenylhydrazine may be prepared by reducing phenyldiazonium chloride solution with excess of warm sodium sulphite solution, followed by acidification with hydrochloric acid, when the hydrochloride crystallises out on cooling. Treatment of the latter with excess of sodium hydroxide solution liberates the free base. The reaction is believed to proceed through the following stages —... 

H. Landolt s reaction can be demonstrated in the following manner Dissolve 1 8 grm. of iodic acid in a litre of water also prepare a litre of an aq. soln. of 0 9 grm. of sodium sulphite, Na2ROa.7HaO lOper cent, sulphuric acid, and 9 5 grms. of starch made into a paste with hot water. Add 100 c.c. of each soln. to separate beakers and mix the two. Note the time when the soln. are mixed. Count the seconds which pass before the starch blue appears. Dil. each soln. to 0 8, 0 6, 0 4, 0 2th of its former concentration, and repeat the experiments with the dil. soln. Plot the results as has been done in Fig. 12. If the concentration and temp, be constant, the same results can always be reproduced. 

Preparation. Put 3.5 g of sodium sulphite and 50 ml of water into a small conical flask. Weigh 2.5 g of flowers of sulphur and, after wetting the sulphur with ethanol (why ), transfer it into the flask with the sodium sulphite solution. Heat the mixture up to boiling. The end of the process is featured by a neutral reaction of the solution with litmus. Filter the hot solution and evaporate it on a water bath up to the beginning of crystallization. Filter off the crystals that precipitated after cooling in a Buchner funnel. Write... 

Notes. (1) The reduction may also be effected with an alkaline solution of sodium sulphite prepared from 8.4 g of sodium metabisulphite and 7.0 g of sodium hydroxide pellets in 90 ml of water. The reaction is probably ... 

The test is usually carried out by adding the reagent to the solution acidified with dilute hydrochloric acid carbonates, sulphites, and phosphates are not precipitated under these conditions. Concentrated hydrochloric acid or concentrated nitric acid should not be used, as a precipitate of barium chloride or of barium nitrate may form these dissolve, however, upon dilution with water. The barium sulphate precipitate may be filtered from the hot solution and fused on charcoal with sodium carbonate, when sodium sulphide will be formed. The latter may be extracted with water, and the extract filtered into a freshly prepared solution of sodium nitroprusside, when a transient, purple colouration is obtained (see under Sulphides, Section IV.6, reaction 5). An alternative method is to add a few drops of very dilute hydrochloric acid to the fused mass, and to cover the latter with lead acetate paper a black stain of lead sulphide is produced on the paper. The so-called Hepar reaction, which is less sensitive than the above two tests, consists of placing the fusion product on a silver coin and moistening with a little water a brownish-black stain of silver sulphide results. 

A convenient method for preparing sodium thiosulphate in the laboratory consists in dividing a hot saturated solution of sodium carbonate into two equal portions, passing sulphur dioxide through one until absorption ceases, and then adding the other half. The solution of sodium sulphite thus produced is boiled with sulphur until no more dissolves, filtered, and allowed to crystallize. The reactions involved correspond with the equations... 

Spring Reaction It is used for the preparation of sodium thiosulphate. It consists in treating a mixture of sodium sulphide and sodium sulphite with calculated quantity of iodine. 

Reduction by zinc dust yields an oil iodine in chloroform has no action, but chlorine in the same solvent gives selenium tetrachloride and chloroacetylacetone, and bromine yields lachrymatory products and a colourless crystalline substance of melting-point 180° C. Aqueous hydrogen sulphide causes slow decomposition, with liberation of sulphur and selenium. Potassium metabisulphite and sodium hydrogen sulphite transform selenium acetylacetone quantitatively into alkali selenodithionates, a reaction which affords the best known means of preparing these salts. 

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