Carboxylic acids haloalkane oxidation

Catalysed oxidation of non-activated haloalkanes by hypochlorite provides an attractive low-cost and convenient procedure for their conversion into carbonyl compounds [6] primary haloalkanes produce carboxylic acids and secondary haloalkanes are converted into ketones (Table 10.12). Secondary amines are oxidized to ketones under analogous conditions, whereas primary amines yield nitriles (Table 10.13) [1,2], o-Nitroanilines are oxidized to benzofurazan-1-oxides [15]. 

Regarding ozonation processes, the treatment with ozone leads to halogen-free oxygenated compounds (except when bromide is present), mostly aldehydes, carboxylic acids, ketoacids, ketones, etc. [189]. The evolution of analytical techniques and their combined use have allowed some researchers to identify new ozone by-products. This is the case of the work of Richardson et al. [189,190] who combined mass spectrometry and infrared spectroscopy together with derivatization methods. These authors found numerous aldehydes, ketones, dicarbonyl compounds, carboxylic acids, aldo and keto acids, and nitriles from the ozonation of Mississippi River water with 2.7-3 mg L 1 of TOC and pH about 7.5. They also identified by-products from ozonated-chlorinated (with chlorine and chloramine) water. In these cases, they found haloalkanes, haloalkenes, halo aldehydes, haloketones, haloacids, brominated compounds due to the presence of bromide ion, etc. They observed a lower formation of halocompounds formed after ozone-chlorine or chloramine oxidations than after single chlorination or chlorami-nation, showing the beneficial effect of preozonation. 

In this section, we study the acidity and basicity of alcohols, their dehydration to alkenes, their conversion to haloalkanes, and their oxidation to aldehydes, ketones, or carboxylic acids. 

The oxidation of primary alcohols and aldehydes to carboxylic acids by aqueous Cr(VI) was described in Sections 8-6 and 17-4. This section presents two additional reagents suitable for this purpose. It is also possible to introduce the carboxy function by adding a carbon atom to a haloalkane. This transformation can be achieved in either of two ways the carbonation of organometaUic reagents or the preparation and hydrolysis of nitriles. 

In Summary Several reagents oxidize primary alcohols and aldehydes to carboxylic acids. A haloalkane is transformed into the carboxylic acid containing one additional carbon atom either by conversion into an organometaUic reagent and carbonation or by displacement of halide by cyanide followed by nitrile hydrolysis. 

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