Replacement of aldehyde groups

Diuranium pentoxide-alumina Replacement of aldehyde groups by hydrogen via carboxylic acids... 

X0 compounds HCifO aldehydes (s. a. De-carbonylation of aldehydes, Replacement of aldehyde groups)... 

Replacement of phenyl groups with AT-methyl imidazole moieties in the catalyst Cl structure led to catalyst C4 (Figure 8.2). ° This catalyst worked efficiently in aqueous media. Catalyst C4 catalysed Michael additions of aldehydes to nitroalkenes in a mixture of brine and NaHCOs. 

Replacement of methoxy groups by chlorine in Vilsmeier aldehyde synthesis... 

Section 17 1 The substitutive lUPAC names of aldehydes and ketones are developed by identifying the longest continuous chain that contains the carbonyl group and replacing the final e of the corresponding alkane by al for aldehydes and one for ketones The chain is numbered m the direction that gives the lowest locant to the carbon of the carbonyl group... 

Other than nucleophilic addition to the carbonyl group the most important reac tions of aldehydes and ketones involve replacing an a hydrogen A particularly well stud led example is halogenation of aldehydes and ketones... 

The limitations of this reagent are several. It caimot be used to replace a single unactivated halogen atom with the exception of the chloromethyl ether (eq. 5) to form difluoromethyl fluoromethyl ether [461 -63-2]. It also caimot be used to replace a halogen attached to a carbon—carbon double bond. Fluorination of functional group compounds, eg, esters, sulfides, ketones, acids, and aldehydes, produces decomposition products caused by scission of the carbon chains. 

Oxidation. Oxidation of hydroxybenzaldehydes can result in the formation of a variety of compounds, depending on the reagents and conditions used. Replacement of the aldehyde function by a hydroxyl group results when 2- or 4-hydroxybenzaldehydes are treated with hydrogen peroxide in acidic (42) or basic (43) media pyrocatechol or hydroquinone are obtained, respectively. 

Replacement of hydrogen with halogen can be carried out in the alpha position of fluorinated ethers, amines, aldehydes, or nitriles In 2,2,3,4,4,4 hexafluoro-bulyl methyl ether, chlorination occurs predominantly at the methyl, however, bromination occurs mostly at the internal position of the fluorobutyl group 133] (equation 20)... 

---