Solubility of aldehydes and ketones

Write the lUPAC and common names for aldehydes and ketones draw the condensed stmctural formulas. Describe the solubility of aldehydes and ketones in water. 

The imides, primaiy and secondary nitro compounds, oximes and sulphon amides of Solubility Group III are weakly acidic nitrogen compounds they cannot be titrated satisfactorily with a standard alkaU nor do they exhibit the reactions characteristic of phenols. The neutral nitrogen compounds of Solubility Group VII include tertiary nitro compounds amides (simple and substituted) derivatives of aldehydes and ketones (hydrazones, semlcarb-azones, ete.) nitriles nitroso, azo, hydrazo and other Intermediate reduction products of aromatic nitro compounds. All the above nitrogen compounds, and also the sulphonamides of Solubility Group VII, respond, with few exceptions, to the same classification reactions (reduction and hydrolysis) and hence will be considered together. 

Physical constants such as melting point boiling point and solubility in water are collected for a variety of aldehydes and ketones in Appendix 1... 

The carbonyl oxygen of aldehydes and ketones can form hydrogen bonds with the pro tons of OH groups This makes them more soluble m water than alkenes but less solu ble than alcohols... 

The reaction has been extended to include carbanions generated from phosphonates. This is often referred to as the Horner-Wittig or Homer-Emmons reaction. The Horner-Emmons reaction has a number of advantages over the conventional Wittig reaction. It occurs with a wider variety of aldehydes and ketones under relatively mild conditions as a result of the higher nucleophilicity of the phosphonate carbanions. The separation of the olefinic product is easier due to the aqueous solubility of the phosphate by-product, and the phosphonates are readily available from the Arbusov reaction. Furthermore, although the reaction itself is not stereospecific, the majority favor the formation of the trans olefin and many produce the trans isomer as the sole product. 

Addition of sodium dithionite to formaldehyde yields the sodium salt of hydroxymethanesulfinic acid [79-25-4] H0CH2S02Na, which retains the useful reducing character of the sodium dithionite although somewhat attenuated in reactivity. The most important organic chemistry of sodium dithionite involves its use in reducing dyes, eg, anthraquinone vat dyes, sulfur dyes, and indigo, to their soluble leuco forms (see Dyes, anthraquinone). Dithionite can reduce various chromophores that are not reduced by sulfite. Dithionite can be used for the reduction of aldehydes and ketones to alcohols (348). Quantitative studies have been made of the reduction potential of dithionite as a function of pH and the concentration of other salts (349,350). 

Styrene is a colourless mobile liquid with a pleasant smell when pure but with a disagreeable odour due to traces of aldehydes and ketones if allowed to oxidise by exposure to air. It is a solvent for polystyrene and many synthetic rubbers, including SBR, but has only a very limited mutual solubility in water. Table 16.1 shows some of the principal properties of pure styrene. 

Lithium aluminum hydride, LiAIH4/ is another reducing agent often used for reduction of aldehydes and ketones. A grayish powder that is soluble in ether and tetrabydrofuran, LiAlH4 is much more reactive than NaBH4 but also more dangerous. It reacts violently with water and decomposes explosively when heated above 120 °C. 

Besides direct reduction, a one-pot reductive amination of aldehydes and ketones with a-picoline-borane in methanol, in water, and in neat conditions gives the corresponding amine products (Scheme 8.2).40 The synthesis of primary amines can be performed via the reductive amination of the corresponding carbonyl compounds with aqueous ammonia with soluble Rh-catalyst (Eq. 8.17).41 Up to an 86% yield and a 97% selectivity for benzylamines were obtained for the reaction of various benzaldehydes. The use of a bimetallic catalyst based on Rh/Ir is preferable for aliphatic aldehydes. 

While ether is the common solvent for LiAlH4, in which it is soluble, hydroxylic solvents like water, methanol and ethanol are preferred for NaBH4, It is more soluble in methanol than in ethanol, but since it reacts with the former at an appreciable rate than the latter, hence ethanol is the preferred solvent. Isopropanol, in which NaBH4 is stable, is used for kinetic studies of the reduction of aldehydes and ketones. 

A detailed stu of over 45 catalysts, primarily from Group VIII metal salts and complexes, showed palladium(II) compounds to be the most effective in the dehydrogenation of a variety of aldehydes and ketones. Soluble palladium(II) salts and complexes such as dichloro(tTiphenylphosphine)palladium(II) and palladium(II) acetylacetonate have been shown to be optimal, with the salts of rhodium, osmium, iridium and platinum having reduced efficacy. Since the d ydrogenation reaction is accompanied by reduction of the palladium(II) catalyst to palladium(0), oxygen and a cooxidant are required to effect reoxidadon. Copper(II) salts are favored cooxidants, but quinones, and especially p-benzoquinone, are also effective (Scheme 24). - ... 

In contrast to the Collins i oxide (2) is vny soluble in i in the minimum amount of solvmt Gomally, 2.5 equiv. of complex, generated in situ, gives good yields of aldehydes and ketones. In addition, iqion wotk-up most of die chn um salts may te xedpitated by dilution widi diethyl etho. ... 

Diverse soluble enzymes, called aldo-keto reductases. cany out bioreduction of aldehydes and ketones. They are found in the liver and other tissues (e.g.. kidney). As a general class, these soluble en7.ynie.s have similar physi-ochemical properties and broad substrate specificities and require NADW as a cofactor. Oxidoreductase enzymes that catty out both oxidation and reduction reactions also can reduce aldehydes and ketones. " For example. Ihe important liver alcohol dehydrogenase is an NAD -dependent oxido-icductase that oxidizes ethanol and other aliphatic alcohols to aldehydes and ketones. In the presence of NADH or... 

The water-soluble iridium(III) complex, [IrCp (H20)3]2+ (Cp = p5-C5Me5) was found a suitable catalyst precursor for reduction of aldehydes and ketones by hydrogen transfer from aqueous formate [254], Under the conditions of Scheme 3.34 turnover frequencies in the range of 0.3-4.3 h-1 were determined. Of the several water-soluble substrates the cyclic cyclopropanecarboxaldehyde reacted faster than the straight-chain butyraldehyde, and aldehydes were in general more reactive than the only simple ketone studied (2-butanone). While glyoxylic acid was reduced fast, pyruvic acid did not react at all. 

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