Carboxylic acid ketones/aldehydes

Studies on reaction mechanisms and by-product analysis have indicated that short-chain carboxylic acids, ketones, aldehydes, and alcohols are the major oxidation intermediates under near-critical conditions, but at supercritical conditions, with T above 650 °C, no intermediate compounds have been found [7]. 

Ozonolysis is a convenient and highly effective method of oxidatively cleaving a double bond to give an array of compounds including carboxylic acids, ketones, aldehydes, and alcohols. The final... 

This latter thought has an important consequence if compounds with C=0 double bonds are sorted in decreasing order of resonance stabilization of their C=0 group they are at the same time sorted according to their increasing propensity to enolization. So as the resonance stabilization of the C=0 double bond decreases from 22 kcal/mol to somewhere near zero in the order carboxylic acid amide > carboxylic acid ester/carboxylic acid > ketone > aldehyde > carboxylic acid chloride/-bromide, the enol content increases in this same order (Figure 12.2). These circumstances immediately explain why no enol reactions whatsoever are known of carboxylic acid amides, virtually none of normal carboxylic acid esters/carboxylic acids, but are commonly encountered with ketones, aldehydes and carboxylic acid halides. 

Well known examples are oxidations with Mn04 where the latter is transferred into an apolar organic medium such as benzene, purple benzene , by complexed macrocyclic polyethers or quaternary cations, both in liquid-liquid and solid-liquid phase-transfer systems This procedure eliminates the self-catalyzed decomposition of Mn04 which occurs with evolution of O2. Olefins, alcohols, alkylated arenes, etc. are thus oxidized to carboxylic acids, ketones, aldehydes, or glycols. 

V )nonamide-(c=o)-nexttoH) + -(c=oy- in carboxylic acid, ketone, aldehyde + 22Vod,gr-(c=0) + 47 nitrogen atoms in six-membered aromatic ring... 

Carboxylic acid Ketone Aldehyde Amide 1° amine 2° amine 3° amine Alkyl chloride Alkyl bromide Nitrile... 

Various oxygen nucleophiles such as water, alcohols, carboxylic acids, ketones, aldehydes, carbonates, amides, have been employed in gold catalysis to functionalize alkynes, allenes, or even alkenes [8], Their use allows the easy and generally efficient creation of at least one new C-O bond. A short selection of representative examples is shown in Scheme 16.13 [17]. 

Pyrolysis of biomass is carried out under inert atmosphere and forms, depending on the residence time and temperature, char, oil, and gas. Pyrolysis with long residence time at low temperamre (400°C) produces a black solid (charcoal), while fast pyrolysis at high temperarnre (500°C) favors the formation of a black liquor (bio-oil). The short contact times (<2s at ca. 500" C) thus maximize the liquid yield. Fast pyrolysis is preferred by the chemical industry because of the relative ease of handling liquids. However, bio-oil produced by pyrolysis of bulk biomass contains more than 400 different components like carboxylic acids, ketones, aldehydes, sugars, furans, (substituted) phenols, aromatics, and tar (Table 1). Separation of useful chemicals from this complex pool is very difficult. As an alternative, pyrolysis can also be used as a first step for generating heat or electricity, followed by combusting the pyrolytic products. Excellent papers and reviews that describe fast pyrolysis in more detail are available [27-32]. 

Organoboron compounds are known as useful reagents or reaction intermediates for the preparation of a wide variety of functional compounds such as alcohols, amines, carboxylic acids, ketones, aldehydes, olefins, and halides (1-3). For several decades. Brown and his coworkers have studied this chemistry. 

Esterification of carboxylic acids involves nucleophilic addition to the carbonyl group as a key step In this respect the carbonyl group of a carboxylic acid resembles that of an aldehyde or a ketone Do carboxylic acids resemble aldehydes and ketones m other ways Do they for example form enols and can they be halogenated at their a carbon atom via an enol m the way that aldehydes and ketones can ... 

An excellent review by Roth and Eisner (63) summarized the chemical defense substances found in arthropods up to 1962. These authors listed 31 defense substances of known structure one anhydride, three carboxylic acids, nine aldehydes, one furan, three hydrocarbons, two ketones, one lactone, eight quinones, and three inorganic compounds. Many of these same compounds (unsaturated aldehydes and quinones) have been found in other arthropods since 1962 (38). The compounds are discharged when the animal is disturbed by predators, and there can be no doubt that the action of most of them... 

Pd-catalyzed carbonylation of heteroaryl halides provides a quick entry to heteroaryl carbonyl compounds such as heteroaryl aldehydes, carboxylic acids, ketones, esters, amides, a-keto esters and a-keto amides. In addition, Pd-catalyzed alkoxycarbonylation and aminocarbonylation are compatible with many functional groups, and therefore, are more advantageous than conventional methods for preparing esters and amides [78],... 

Reductions. Silicon hydrides such as 1, which can achieve intramolecular pentacoordination, show enhanced reducing properties. Thus they can reduce aldehydes or ketones to alcohols,1 and reduce carboxylic acids to aldehydes via thermal decomposition of a silyl carboxylate (equation I).2 Reaction of acid chlo-... 

Tungsten-catalysed oxidation of alcohols by hydrogen peroxide is achieved in high yield in the presence of tetra-n-butylammonium hydrogen sulphate [20-22]. Secondary alcohols are converted into ketones (>90%) [e.g. 21], but primary alcohols generally are oxidized completely to the carboxylic acids [21], Aldehydes are also oxidized to the carboxylic acids [e.g. 21]. In contrast, using procedure 10.7.8.B, which is adaptable to scale up, benzyl alcohols are converted into the aldehydes benzoic acids are only formed with an excess of hydrogen peroxide [22],... 

Scheme 25 Cathodic reduction of activated aliphatic carboxylic acids to aldehydes (R alkyl, yields 70-82%) and ketones (R benzyl, yields 66- 72%).

Alcohols are oxidized to aldehydes by the liver enzyme alcohol dehydrogenase, and aldehydes to carboxylic acids by aldehyde dehydrogenase. In mammals, monooxygenases can be induced by plant secondary metabolites such as a-pinene, caffeine, or isobornyl acetate. Reduction is less common and plays a role with ketones that cannot be further oxidized. Hydrolysis, the degradation of a compound with addition of water, is also less common than oxidation. 

TABLE 30. Comparison of the results of metal-catalyzed alcohol oxidation to ketones, carboxylic acids or aldehydes using H2O2 or TBHP... 

There are many important [5 + 1] two-bond formation heterocyclic syntheses and in certain instances this approach constitutes the method of choice for the preparation of particular classes of heterocycle. Where a carbon atom constitutes the one-atom fragment it is almost invariably present in the form of an electrophilic species such as an aldehyde, carboxylic acid, ketone, ester, acid chloride, urea, etc., and fundamentally condensation consists of reaction of this electrophilic species with a 1,5-dinucleophilic reagent. Where the one-atom fragment is either nitrogen, oxygen or sulfur then the heteroatom may function either as a nucleophile or, in the case of nitrogen and sulfur, also as an electrophile. Almost... 

A series of cyclohept[l,2-A5,4-3 ]bisindole derivatives have been obtained by the reaction of l,2-bis(17/-indol-2-yl)-ethane 208 with carboxylic acids, orthoesters, aldehydes, or ketones under acid conditions (Equation 138 Table 17) <2000T1911>. In the case of the reaction with TEA, the major product is the fully conjugated derivative (Section 10.21.5.1.3). 

Aldehydes and Ketones. Many metabolic routes are possible, including both oxidation and reduction. However, oxidations are more common. Aldehydes are very susceptible to oxidation, which is catalyzed by various enzymes including aldehyde oxidase and aldehyde dehydrogenase this oxidation yields a carboxylic acid. Ketones, on the other hand, tend to be stable to oxidation. Conversely, aldehydes are seldom metabolized by reduction. Ketones, however, frequently undergo reduction to a secondary alcohol this is particularly true for a,P-unsaturated ketones. 

N -(C=O)- in-carboxyiic-acid, ketone, aldehyde is the total number of carbonyl groups in carboxylic acid, ketone, and aldehyde. 

Although the alkyl and acyl products shown in Eqs- 15.140 and 15 141 have been isolated and characterized, they are frequently allowed to simply form as intermediates. which are then treated directly to produce aldehydes, carboxylic acids, ketones, esters, or amides. 

Solid heteropoly compounds are suitable oxidation catalysts for various reactions such as dehydrogenation of O- and N-containing compounds (aldehydes, carboxylic acids, ketones, nitriles, and alcohols) as well as oxidation of aldehydes. Heteropoly catalysts are inferior to Mo-Bi oxide-based catalysts for the allylic oxidation of olefins, but they are much better than these for oxidation of methacrolein (5). Mo-V mixed-oxide catalysts used commercially for the oxidation of acrolein are not good catalysts for methacrolein oxidation. The presence of an a-methyl group in methacrolein makes the oxidation difficult (12). The oxidation of lower paraffins such as propane, butanes, and pentanes has been attempted (324). Typical oxidation reactions are listed in Table XXXI and described in more detail in the following sections. 

Aldehydes are oxidized by these reagent to carboxylic acids. Ketones are not oxidized under these conditions. Secondary alcohols are oxidized to ketones. 

Carboxylic -acids, nitriles, aldehydes, ketones Steam - distillation, solvent extraction, ion exchange chromatography, GC [677]... 

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