Oxidation to acids

Oxidation to acids. Varm together in a small conical flask on a water-bath for lo minutes a mixture of 0 5 ml. of benzaldehyde or salicylaldehyde, 15 ml. of saturated KMn04 solution, and 0-5 g. of NajCOj. Then acidify with cone. HCl, and add 25% sodium sulphite solution until the precipitated manganese dioxide has redissolved. On cooling, benzoic or salicylic acid crystallises out. 

C) Acids. Employ oxidation to acids (see 6 above) only if C4H5CHO or a substituted derivative is suspected. Aliphatic aci may be too soluble for ready isolation. 

Propylene oxide and carboxyUc acids ia equimolar ratios produce monoesters of propylene glycol. Higher ratios of oxide to acid produce polypropylene glycol monoesters. In the presence of basic catalysts these monoesters can undergo transesterification reactions that yield a product mixture of propylene glycols, monoesters, and diesters (57,60). 

The reaction mechanism in the irradiated flue gas is probably quite complex, but basically the EB excites the gas molecules and promotes reactions that convert the oxides to acids. These then react with ammonia or calcium compounds to give solid products that are removed by the filter. The initiation reaction is believed to be brought about by radical formation, such as OH,... 

Biosynthesis is performed in one step by the enzyme L-histidine decarboxylase (HDC, E.C. 4.1.1.22). Histamine metabolism occurs mainly by two pathways. Oxidation is carried out by diamine oxidase (DAO, E.C. 1.4.3.6), leading to imidazole acetic acid (IAA), whereas methyla-tion is effected by histamine N-methyltransferase (HMT, E.C. 2.1.1.8), producing fe/e-methylhistamine (t-MH). IAA can exist as a riboside or ribotide conjugate. t-MH is further metabolized by monoamine oxidase (MAO)-B, producing fe/e-methylimidazole acetic acid (t-MIAA). Note that histamine is a substrate for DAO but not for MAO. Aldehyde intermediates, formed by the oxidation of both histamine and t-MH, are thought to be quickly oxidized to acids under normal circumstances. In the vertebrate CNS, histamine is almost exclusively methylated... 

Primary alcohols are readily oxidized to acids by Ni(III) hydroxide as the electron carrier. An example is the electrooxidation of isoamyl alcohol (92) in H2O-NaOH/Ni(OH)3-(Pt) to give isovaleric acid (93) in a good yield (Scheme 34) [127]. 

Ozonides and alkoxyhydroperoxides from 1-octene and ethyl 10-undecenoate were isolated by column chromatography and oxidized to acids, RCOOH, using (a) 02 at 95°C.,... 

Oxidation to acids 59 nevertheless, sometimes the oxidation of primary alcohols can be stopped at the aldehyde stage60,61 Oxidation to lactones19,62 Oxidation to sulfoxides52 or sulfones53... 

Sometimes, over-oxidation of benzylic alcohol to benzoic acid is observed with IBX.88a This over-oxidation does not happen in all benzylic alcohols and can be avoided by running the oxidation under anhydrous conditions. In fact, IBX is quite resistant to produce over-oxidation to acids even in the presence of a great excess of water. The water-soluble IBX analogue 46 is able to transform a number of benzylic alcohols into the corresponding benzaldehydes with no over-oxidation to acid, using water as solvent.92 When the oxidation of alcohol to acid is purposefully looked after, it can be performed with IBX in DMSO with the addition of certain nucleophilic catalysts, such as 2-hydroxypyridine (HYP) or TV-hydro-xysuccinimide (NHS).110... 

As mentioned above, almost 60% of unreacted starting material could be recovered after a reaction period of 25 hours. The characteristic break in the pH curve was observed after a reaction period of about 9 hours. This means that at this early stage part (less than 40%) of the starting material has been oxidized to acidic compounds like carboxylic acids and... 

Alkenes are oxidized to acids by heating them with solutions of potassium permanganate (KMn04) or potassium dichromate (K2Cr207). 

The ozonolysis of alkenes produces aldehydes that can easily be further oxidized to acids. 

Analysis of the total acid titration data indicates that 33-39 mmoles of acid and peracid have been formed from aldehyde oxidation. Furthermore, 34-36 mmoles of aldehyde should have been formed in the first stage and oxidized in the second stage. If aldehyde had been oxidized solely to peracid, the active oxygen determination should have showed 34-36 mmoles of peracid instead of at the most 13 mmoles (meq./2). Enough acid but not enough peracid has been formed. This means that there are at least two paths by which aldehyde can be oxidized to acid, one of which involves peracid formation. 

Because aldehydes are easily oxidized to acids, one might wonder whether acids are easily reduced back to aldehydes. Aldehydes tend to be more reactive than acids, however, and reducing agents that are strong enough to reduce acids also reduce aldehydes even faster. 

Primary alcohols and aldehydes are commonly oxidized to acids by chromic acid (H2Cr04, formed from Na2Cr207 and H2SO4). Sodium hypochlorite (bleach, NaOCl) is a chromium-free alternative to chromic acid (Sections 11-2B and 18-19). 

Aqueous methods like the Jones oxidation are no good for this, since the aldehyde that forms is further oxidized to acid via its hydrate. The oxidizing agent treats the hydrate as an alcohol, and oxidizes it to the acid. 

Since aldehydes are readily oxidized in air to the corresponding acids, the extracts of the dispensers were also analyzed for acid (GC using a 10% AT-1000 column at 250°C). No acla was detected in dispensers aged as long as 8 weeks based on known quantities of acid, less than 5%, if any, of the aldehyde originally present in the dispenser had oxidized to acid. Thus, the combination of polymer laminate... 

The first preparation of 1,3,4-thiadiazole aldehydes was described by Ohta and Isowa, who used the Krohnke reaction on 2,5-dimethyl- and 2-methyl-5-phenyl-l,3,4-thiadiazole. They described 2,4-dinitrophenylhydrazones and thiosemicarbazones, oxidation to acid, and acyloin condensation. Bacchetti has shown that 2-phenyl-... 

Acid bromides. Aldehydes can be oxidized to acid bromides by NBS under irradiation. For example, the reaction with benzaldehyde results in benzoyl bromide (48% yield). In general, the acid bromide is converted into an ester or an amide in situ. ... 

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