Bisulphite compound

Bisulphite addition compound. The formation of the bisulphite compound is delayed and appears only after 2-3 minutes shaking. 

Alkali bisulphite compound of (a) aldehyde, (b) ketone Sulphonic acids. 

About 0-1 per cent, of hydroquinone should be added as a stabiliser since n-hexaldehyde exhibits a great tendency to polymerise. To obtain perfectly pure n-/iexaldehyde, treat the 21 g. of the product with a solution of 42 g. of sodium bisulphite in 125 ml. of water and shake much bisulphite derivative will separate. Steam distil the suspension of the bisulphite compound until about 50 ml. of distillate have been collected this will remove any non-aldehydic impurities together with a little aldehyde. Cool the residual aldehyde bisulphite solution to 40-50 , and add slowly a solution of 32 g. of sodium bicarbonate in 80 ml. of water, and remove the free aldehyde by steam distillation. Separate the upper layer of n-hexaldehyde, wash it with a little water, dry with anhydrous magnesium sulphate and distil the pure aldehyde passes over at 128-128-5°. 

A condition of equilibrium is reached (70-90 per cent, of bisulphite compound with equivalent quantities of the reagents in 1 hour), but by using a large excess of bisulphite almost complete conversion into the... 

The carbonyl compound may be mixed with an aqueous solution of sodium or potassium cyanide and mineral acid is added, or the bisulphite compound may be treated with an equivalent quantity of sodium cyanide, for example ... 

A. Purification of commercial o cfohexanone through the bisulphite compound... 

Prepare a saturated solution of sodium bisulphite at the laboratory temperature from 40 g. of finely powdered sodium bisulphite about 70 ml. of water are required. Measure the volume of the resulting solution and treat it with 70 per cent, of its volume of rectified spirit (or methylated spirit) add sufficient water (about 45 ml.) to just dissolve the precipitate which separates. Introduce 20 g. of commercial cycZohexanone into the aqueous-alcoholic bisulphite solution with stirring and allow the mixture to stand for 30 minutes stir or shake occasionally. FUter off the crystalline bisulphite compound at the pump, and wash it with a little methylated spirit. 

Transfer the bisulphite compound to a separatory funnel and decompose it with 80 ml. of 10 per cent, sodium hydroxide solution. Remove the liberated cycZohexanone, saturate the aqueous layer with salt and extract... 

Place 45 g. (43 ml.) of benzal chloride (Section IV,22), 250 ml. of water and 75 g. of precipitated calcium carbonate (1) in a 500 ml. round-bottomed flask fltted with a reflux condenser, and heat the mixture for 4 hours in an oil bath maintained at 130°. It is advantageous to pass a current of carbon dioxide through the apparatus. Filter off the calcium salts, and distil the filtrate in steam (Fig. II, 40, 1) until no more oil passes over (2). Separate the benzaldehyde from the steam distillate by two extractions with small volumes of ether, distil off most of the ether on a water bath, and transfer the residual benzaldehyde to a wide-mouthed bottle or flask. Add excess of a concentrated solution of sodium bisulphite in portions with stirring or shaking stopper the vessel and shake vigorously until the odour of benzaldehyde can no longer be detected. Filter the paste of the benzaldehyde bisulphite compound at the pump... 

The cj/cioheptan9ne is readily separated by taking advantage of the experimental fact that it alone forms a soUd bisulphite compound. Diazomethane is conveniently generated in situ from p-tolyl.sulphonylmethylnltrosamlde (Section VII,20). 

Introduce a solution of 100 g. of sodium bisulphite 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 anhydrous magnesium sulphate, remove the ether at atmospheric pressure, and distil the residual oil under reduced pressure from a Qaisen flask with fractionating side arm (Fig. II, 24, 5). Collect the cyclo-heptanone at 64r-65°/12 mm. the yield is 23 g. 

Bisulphite compounds of aldehydes and ketones. These substances are decomposed by dilute acids into the corresponding aldehydes or ketones with the liberation of sulphur dioxide. The aldehyde or ketone may be isolated by steam distillation or by extraction with ether. Owing to the highly reactive character of aldehydes, the bisulphite addition compounds are best decomposed with saturated sodium bicarbonate solution so um carbonate solution is generally employed for the bisulphite compounds of ketones. 

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. 

Sulphate sulphite or sulphide may indicate a sulphate, sulphonate, mercaptan, or bisulphite compound of an aldehyde or ketone. 

Aldehydes are usually most easily separated from the essential oils in which they occur, by means of acid sodium sulphite. The oil—or the suitable fraction thereof— is well shaken for a time varying according to the nature of the aldehyde, with an equal volume of a saturated solution of sodium bisulphite, with a little ether added, in order to hinder the non-aldehydic portion of the oil from becoming occluded in the crystals of the bisulphite compound of the aldehyde. These crystals are separated and washed well with ether They are then decomposed by warming with a solution of sodium carbonate, and the regenerated aldehyde is extracted by means of ether. 

Citral forms condensation compounds with sulphites and lacid sulphites which are exceedingly useful in the estimation of the alde-hy. Tiemann has isolated three separate hydrosulphonic acid compounds. The normal bisulphite compound is best prepared by shaking citral with a hot solution of sodium bisulphite containing free sulphurous acid. 

When the normal sodium bisulphite compound is dissolved in water and submitted to steam distillation, half of the citral passes over, the remainder being converted into the sodium salt of the so-called stable citraldihydrodisulfonic acid —... 

Citronellal which was originally termed citronellone, is one of the characteristic constituents of citronella oil, in which it occurs to a considerable extent. It can be prepared by shaking the essential oil with a hot solution of sodium bisulphite, and decomposing the resulting bisulphite compound by means of sodium carbonate and distilling the citronellal in a current of steam. Citronellal is optically active, and it is probable that the specimens isolated from natural sources are mixtures of the two optically active isomers, so that the actual theoretical rotation is not known with certainty. 

When the reaction is complete the oil is distilled, or more nsually decanted off, and the benzaldehyde thoroughly agitated with fifteen times its weight of bisulphite of soda. This results in the formation of the solid sodium bisulphite compound. This is washed with alcohol and then decomposed by a solution of sodium carbonate, and finally the benzaldehyde is distilled in a current of steam. 

Cinnamic aldehyde, C HgO, is the principal odorous constituent of dnnamon and cassia oils, and is manufactured to a considerable extent, artificially. It can be extracted from the oils in which it occurs by means of sodium bisulphite, the sodium bisulphite compound being decomposed with dilute sulphuric acid, and distilled in a current of steam. The preparation of artificial cinnamic aldehyde, which is used in perfumery as a substitute for the natural oils, is usually carried out. by a condensation of benzaldehyde and acetaldehyde, according to the following reaction —... 

There is a solid aubepine met with in commerce, which appears usually to be the sodium bisulphite compound of anisic aldehyde. 

According to Read and Smith i piperitone is, under natural conditions, optically inactive. By fractional distillation under reduced pressure, it is prepared, by means of its sodium bisulphite compound, in a laavo-rotatory form. The slight laevo-rotation is probably due to the presence of traces of cryptal. By fractional distillation alone, it is usually obtained in a laevo-rotatory form whether this is due to decomposition products or not is unknown. Piperitone has a considerable prospective economic value, as it forms thymol by treatment with formic chloride, inactive menthone by reduction when a nickel catalyst is employed, and inactive menthol by further reduction. Its char-Mters are as follows —... 

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