Aldehyde-bisulfite addition compounds

An elegant method for the gentle and selective oxidation of aldehydes to carboxylic acids is the oxidation of the aldehyde-bisulfite addition compound by dimethyl sulfoxide. Depending on the workup of the reaction mixture, the acid, its ester, or its amide can be prepared at room temperature (equation 353) [773]. 

Ketones are more stable to oxidation than aldehydes and can be purified from oxidisable impurities by refluxing with potassium permanganate until the colour persists, followed by shaking with sodium carbonate (to remove acidic impurities) and distilling. Traces of water can be removed with type 4A Linde molecular sieves. Ketones which are solids can be purified by crystallisation from alcohol, toluene, or petroleum ether, and are usually sufficiently volatile for sublimation in vacuum. Ketones can be further purified via their bisulfite, semicarbazone or oxime derivatives (vide supra). The bisulfite addition compounds are formed only by aldehydes and methyl ketones but they are readily hydrolysed in dilute acid or alkali. 

Impurities resulting from storage can be removed by passage through chromatographic grade alumina. Furfural can be separated from impurities other than carbonyl compounds by the bisulfite addition compound. The aldehyde is steam volatile. 

The crude aldehyde (prior to distillation) is sufficiently pure for most purposes. Isolation of the aldehyde may also be achieved by means of the bisulfite-addition compound.2... 

The postulated 1-aminoalkylarsonic acids have something in common with 1-hydroxyalkanesulfonic acids, R—CHOH—S03-. These are not usually known as such, but as bisulfite addition compounds of aldehydes. They are not usually isolable, because of the ease of the reaction shown in Fig. 14. In just the same way we might expect R— CH(—NH3+)—As03H to lose arsenite as H2As03" and H+, i.e., H2As03" overall, leaving the imine R—CH=NH2+, which would equilibrate with R—CH=0 and NH4+. So this would explain why 1-amino-alkylarsonic acids may not exist as stable compounds. 

Seventeen grams of acetaldehyde are dissolved in 20ml of water and added dropwise to a suspension of 40g of sodium bisulfite in 30ml of water. The reaction mixture is kept cold in an ice bath to prevent loss of the aldehyde by volatilization much heat Is liberated by the formation of the bisulfite addition compound. The temperature of the solution is adjusted to 50°C and 17ml of 20% aqueous ammonia are added. The latter is prepared from 13ml of the... 

Cyanohydrins can be formed by the acid- or base-catalyzed reaction of hydrogen cyanide with an aldehyde or ketone, the displacement of bisulfite ion by cyanide ion on the bisulfite addition compounds of aldehydes and... 

Aldoses behave like aldehydes, but react much more slowly. The bisulfite addition compound is much more unstable. When, say, acetaldehyde is added to a glucose-bisulfite solution, the bisulfite will be transferred to it. 

Possible toxic reactions of sulfur dioxide are also indicated in Table I. The reaction of bisulfite with aldehydes has a classic position in biochemistry since Neuberg demonstrated in 1918 that the products of fermentation by yeast were altered by the addition of sodium sulfite, which caused the production of equal amounts of the bisulfite addition compound of acetaldehyde and of glycerol. This was concomitant with the blockage of conversion of acetaldehyde to ethanol. Addition compounds can also be formed with quinones and with ,/ -unsaturated compounds. None of these reactions has been adequately assessed as a possible contributor to toxicity. 

The last nucleophile of this chapter, sodium bisulfite, NaHSC, adds to aldehydes and some ketones to give what is usually known as a bisulfite addition compound. The reaction occurs by nucleophilic attack of a lone pair on the carbonyl group, just like the attack of cyanide. This leaves a positively charged sulfur atom but a simple proton transfer leads to the product. 

The products are useful for two reasons. They are usually crystalline and so can be used to purify liquid aldehydes by recrystallization. This is of value only because this reaction, like several you have met in this chapter, is reversible. The bisulfite compounds are made by mixing the aldehyde or ketone with saturated aqueous sodium bisulfite in an ice bath, shaking, and crystallizing. After purification the bisulfite addition compound can be hydrolysed back to the aldehyde in dilute aqueous acid or base. 

The yields of nitro alcohols from simple nitroparaffins and aliphatic aldehydes or benzaldehyde are usually above 60%. The condensations are generally carried out with aqueous ethanolic sodium hydroxide, although weaker bases are sometimes desirable to prevent polymerization of the aldehyde. Sodium bisulfite addition compounds of the aldehydes are sometimes used. Better results are obtained with sodium methoxide than with alkali hydroxides in the condensation of nitroethane with formaldehyde. Sodium alkoxides are also used to effect the condensation of nitroethane with acetone and cyclohexanone. Condensation proceeds to the nitroalkanediol stage in certain cases with both nitromethane and with formaldehyde. ... 

Since these bisulfite addition compounds are ionic water-soluble compounds and can be formed in up to 90% yield, they serve as a useful means of separating aldehydes and methyl ketones from mixtures of organic compounds. At high sodium bisulfite concentrations these adducts crystallize and can be isolated by filtration. The aldehyde or ketone can be regenerated by adding either a strong acid or base ... 

The acetic acid is added to remove traces of amines that come over in the steam distillation. This method of purification must be used because of the high solubility of the bisulfite addition compound of the aldehyde. 

The conversion of formaldehyde to diethylaminoacetonitrile or of benzaldehyde to mandelonitrile is conveniently done by first converting the aldehyde to its bisulfite addition compound. 

The best derivative from which an aldehyde can be recovered readily is its bisulfite 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 bisulfite until no more solid adduct separates. The adduct is filtered off, washed with a little water, followed by alcohol. A better reagent to use is a freshly prepared saturated aqueous sodium bisulfite 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 bisulfite, followed by steam distillation or solvent extraction. 

Aliphatic aldehydes, their trimers, or bisulfite addition compounds, when refluxed in 95% ethanol with hydroxylamine hydrochloride and a few drops of hydrochloric acid for 6 hrs., give the corresponding nitriles in practically quantitative yield.16... 

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