Sodium bisulphite reagent

This sodium bisulphite reagent Is prepared by treating a saturated aqueous solution of sodium bisulphite with 70 per cent, of its volume (if rectified (or methylated) spirit, and then adding just sufiScient water to produce a clear solution. 

Sodium bisulphite reagent, 332 Sodium borohydride, reductions with, 881-882... 

The most satisfactory reagent is a saturated solution of sodium bisulphite containing some alcohol it must be prepared aa required since it oxidises and decomposes on keeping. Frequently, a saturated aqueous solution is used without the addition of alcohol. 

Aromatic aldehydes react with the dimedone reagent (Section 111,70,2). All aromatic aldehydes (i) reduce ammoniacal silver nitrate solution and (ii) restore the colour of SchifiF s reagent many react with sodium bisulphite solution. They do not, in general, reduce Fehling s solution or Benedict s solution. Unlike aliphatic aldehydes, they usually undergo the Cannizzaro reaction (see Section IV,123) under the influence of sodium hydroxide solution. For full experimental details of the above tests, see under Ali-phalic Aldehydes, Section 111,70. They are easily oxidised by dilute alkaline permanganate solution at the ordinary temperature after removal of the manganese dioxide by sulphur dioxide or by sodium bisulphite, the acid can be obtained by acidification of the solution. 

Free cydohexene from peroxides by treating it with a saturated solution of sodium bisulphite, separate, dry and distil collect the fraction, b.p. 81-83°. Mix 8 -2 g. of cycZohexene with 55 ml. of the reagent, add a solution of 15 mg. of osmium tetroxide in anhydrous butyl alcohol and cool the mixture to 0°. Allow to stand overnight, by which time the initial orange colouration will have disappeared. Remove the solvent and unused cydohexene by distillation at atmospheric pressure and fractionate the residue under reduced pressure. Collect the fraction of b.p. 120-140°/15 mm. this solidifies almost immediately. Recrystallise from ethyl acetate The yield of pure cis-l 2 cydohexanediol, m.p. 96°, is 5 0 g. 

Separations based upon differences in the chemical properties of the components. Thus a mixture of toluene and anihne may be separated by extraction with dilute hydrochloric acid the aniline passes into the aqueous layer in the form of the salt, anihne hydrochloride, and may be recovered by neutralisation. Similarly, a mixture of phenol and toluene may be separated by treatment with dilute sodium hydroxide. The above examples are, of comse, simple apphcations of the fact that the various components fah into different solubihty groups (compare Section XI,5). Another example is the separation of a mixture of di-n-butyl ether and chlorobenzene concentrated sulphuric acid dissolves only the w-butyl other and it may be recovered from solution by dilution with water. With some classes of compounds, e.g., unsaturated compounds, concentrated sulphuric acid leads to polymerisation, sulphona-tion, etc., so that the original component cannot be recovered unchanged this solvent, therefore, possesses hmited apphcation. Phenols may be separated from acids (for example, o-cresol from benzoic acid) by a dilute solution of sodium bicarbonate the weakly acidic phenols (and also enols) are not converted into salts by this reagent and may be removed by ether extraction or by other means the acids pass into solution as the sodium salts and may be recovered after acidification. Aldehydes, e.g., benzaldehyde, may be separated from liquid hydrocarbons and other neutral, water-insoluble hquid compounds by shaking with a solution of sodium bisulphite the aldehyde forms a sohd bisulphite compound, which may be filtered off and decomposed with dilute acid or with sodium bicarbonate solution in order to recover the aldehyde. 

TSie processes depending on the use of sodium bisulphite or sulphite, and in which the aldehyde or ketone compounds dissolve in the solution of the reagent, are known as absorption processes, and are those most commonly employed for oils containing a high proportion of aldehydes and ketones, the use of sodium bisulphite being probably still the method most usually adopted for aldehydes, though the use of neutral sodium sulphite is the official process in the British Pharmacopoeia of 1914, and is also that most suitable for the estimation of ketones. 

Aldehydes and Ketones. The best derivative from which an aldehyde can be recovered readily is its bisulphite addition compound, the main disadvantage being the lack of a sharp melting point. The aldehyde (sometimes in ethanol) is shaken with a cold saturated solution of sodium bisulphite until no more solid adduct separates. The adduct is filtered off, washed with a little water, then alcohol. A better reagent is freshly prepared saturated aqueous sodium bisulphite solution to which 75% ethanol is added to near-saturation. (Water may have to be added dropwise to render this solution clear.) With this reagent the aldehyde need not be dissolved separately in alcohol and the adduct is finally washed with alcohol. The aldehyde is recovered by dissolving the adduct in the least volume of water and adding an equivalent quantity of sodium carbonate (not sodium hydroxide) or concentrated hydrochloric acid to react with the bisulphite, followed by steam distillation or solvent extraction. 

Reagents 1. Schiff s reagent. To a litre of distilled water are added 150 c.c. of fresh 01% aqueous fuchsine (not sulphonate) solution and then 100 c.c. of sodium bisulphite solution of sp. gr. 1-36 and, after mixing, 15 c.c. of pure concentrated sulphuric add. After some hours the mixture should be clear and colourless it should be kept in the dark in well-stoppered bottles and should not be used until some days old. 

The reaction of alkenes with osmium tetroxide (0s04) is an example of an oxidation reaction (Following fig.). In this case the alkene is not split, but, a 1,2-diol is obtained which is also called a glycol. The reaction involves the formation of a cyclic intermediate where the osmium reagent is attached to one face of the alkene. On treatment with sodium bisulphite, the intermediate is cleaved such that the two oxygen atoms linking the osmium remain... 

Uranium Sulphite.—The existence of normal uranous sulphite has not been established. The addition of a saturated solution of an alkali sulphite to uranous chloride solution precipitates a greyish-green basic sulphite of composition UO.SO3.2H2O. When solutions of uranyl salts are treated with sodium bisulphite, a reddish-browm precipitate is produced which dissolves in excess of the reagent by boiling such solutions the above basic sulphite is again precipitated. It is insoluble in water, but dissolves in a solution of sulphurous acid. 

The adrenochrome-sodium bisulphite addition product [28, 29] has been isolated in the solid state as a pale yellow crystalline solid [194, 195]. This substance reacts with substituted hydrazine-type ketone reagents (such as semicarbazide) to give mono-condensation products, which can be easily converted to the corresponding adrenochrome monohydrazone derivative by the action of either heat or alkali [194]. This, together with other evidence [28, 29], suggested that the bisulphite residue was not attached to the C-5-carbonyl group directly [194]. 

Iron Reagents, (a) Ferrous sulphate solution is prepared by dissolving 1 5 g of ferrous sulphate in 200 ml of water containing 0 3 ml of dilute hydrochloric acid and 10 g of sodium bisulphite. (6) To 10 ml of this solution add 0 5 g of sodium citrate and 0 5 g of sodium bisulphite. 

---