Aldehyde sodium acid sulphite

Addition Products.—An important property of aldehydes is that they readily take up certain compounds and form addition products. When acetaldehyde reacts with ammonia, sodium acid sulphite or hydrogen cyanide definite crystalline compounds are obtained. The probable reaction is that the double union between carbon and oxygen is broken the oxygen being converted into hydroxyl, while the remainder of the added compound satisfies the other valence as follows ... 

Thus the unsaturated character of the hydrocarbon chain and the presence of the aldehyde group are both proven. As an aldehyde, it also forms addition products with ammonia, hydrogen cyanide and sodium acid sulphite. 

The acid sulphites possess the property of forming crystalline additive compounds with aldehydes and ketones. Sodium hydrogen sulphite is therefore largely used for the purification of compounds of these classes the sulphite adds on at the carbonyl group, >C O, forming the group-OH... 

The oil was shaken, first with dilute sodium carbonate, next with sodium hydrogen sulphite solution, then with dilute sodium hydroxide, and finally with 50 per cent, resorcinol solution to absorb cineol. From the results of this treatment and the subsequent examination of the various products, the composition of the oil was found to be approximately as follows Cineol, 69 per cent., characterised by the crystalline additive product with iodol aldehydes and ketones, 27 5 per cent., consisting mainly of citral, which was characterised by means of the semi-carbazone and the j3-naphtbacinchoninic acid phenols, 1 5 per cent. acids, 1 per cent. A small quantity of crystalline acid, melting-point, 46 to 48 was isolated, but not in sufficient quantity for identification. The residue, amounting to about 1 per cent., seemed, from its odour, to consist chiefly of terpenes. 

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. 

Reduction of the carboxylic acid group passes through the intermediate aldehyde. For a number of examples in the heterocyclic series, the aldehyde becomes a major product because it is trapped as the hydrated vfc.-diol form. Examples include imidazole-2-caiboxylic acid [139], thiazole-2-carboxylic acid [140] and pyridine-4-carboxylic acid [141] reduced in dilute aqueous acid solution. Reduction of imidazole-4-carboxylic acid proceeds to the primary alcohol stage, the aldehyde intermediate is not isolated. Addition of boric acid and sodium sulphite to the electrolyte may allow the aldehyde intermediate to be trapped as a non-reducible complex, Salicylaldehyde had been obtained on a pilot plant scale in this way by... 

Benzaldehyde shows most of the reactions which are characteristic of aliphatic aldehydes. It reduces an ammonaical solution of silver nitrate, forms addition-products with acid sodium sulphite and with hydrocyanic acid, is converted by nascent hydrogen into an alcohol, and yields an oxime and a phenylhydrazone. 

Five C.C. of the oil are placed in the Hirschsohn flask, about 20 c.c. of a saturated solution of neutral sodium sulphite added, together with a few drops of rosolic acid solution as indicator, and the flask placed in a boiling water-bath and continually agitated. The contents of the flask soon become red owing to the liberation of free alkali by the combination of the aldehyde with part of the sodium sulphite, and this coloration is just discharged by the addition of sufficient... 

Place 5 ml of oil in a Hirschsohn flask and add about 50 ml of 20 per cent sodium sulphite solution and a few drops of phenolphthalein solution. Heat the flask on a water-bath with continuous shaking, keeping the reaction mixture neutral by the continuous addition of 10 per cent acetic acid solution from a burette, until no further alkali is liberated. The process usually occupies from one-half to one hour. Drive the uncombined oil into the neck of the flask by the addition of more sulphite solution and measure the volume of non-aldehydic residue after some hours. 

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