Byproducts, ketones

Melamine (2,4,6-triamino-l,3,5-triazine) is used with formaldehyde to produce resins for use in counter tops, dishes, and such. A third route reacts carbon dioxide with orthoesters or ketals using an iodide catalyst.35 The byproduct ketone can be reconverted to the ketal (2.11) and used in the next run, so that there is no waste. The selectivity was 86% at 94% conversion using a cesium iodide catalyst. 

The carbonylation of aryl iodides in the presence of alkyl iodides and Zn Cu couple affords aryl alkyl ketones via the formation of alkylzinc species from alkyl iodides followed by transmetallation and reductive elimination[380]. The Pd-catalyzed carbonylation of the diaryliodonium salts 516 under mild conditions in the presence of Zn affords ketones 517 via phenylzinc. The a-diketone 518 is formed as a byproduct[381],... 

The Pd enolates also undergo intramolecular Michael addition when an enone of suitable size is present in the allyl d-keto ester 744[465]. The main product is the saturated ketone 745, hut the unsaturated ketone 746 and ally-lated product 747 are also obtained as byproducts. The Pd-catalyzed Michael... 

The chemistry of fenchyl alcohol, Cj HjgO, must be regarded as in a somewhat unsettled state, as questions of isomerism arise which are as yet unsolved. It was ori nally prepared by Wallach by reducing the ketone fenchone, a natural constituent of several essential oils, by means of sodium. Later he obtained it in fairly large quantities as a byproduct in the preparation of fenchone-carboxylic acid, by passing a current of C(X through an ethereal solution of fenchone in the presence of sodium. Fenchyl alcohol has, so far, been found in one essential oil only, namely, that of the root wood of Pinus palustris. 

The decomposition of the peroxyketals (53) follows a stepwise, rather than a concerted mechanism. Initial homolysis of one of the 0-0 bonds gives an aikoxy radical and an a-peroxyalkoxy radical (Scheme 3.36).306"08"210 This latter species decomposes by P-scission with loss of either a peroxy radical to form a ketone as byproduct or an alkyl radical to form a peroxyester intermediate. The peroxyester formed may also decompose to radicals under the reaction conditions. Thus, four radicals may be derived from the one initiator molecule. 

Visible light systems comprising a photoreducible dye molecule e.g. 87)293 or an a-diketone e.g. 85)2% and an amine have also been described. The mechanism of radical production is probably similar to that described for the ketone amine systems described above (i.e. electron transfer from the amine to the photoexcited dye molecule and subsequent proton transfer). Ideally, the dye molecule is reduced to a colorless byproduct. 

The paraffin wax is oxidized by air in a liquid phase process at 110-130°C. Catalysts for this radical reaction are cobalt or manganese salts [54]. The quality of the obtained mixture of homologous carboxylic acids is impaired by numerous byproducts such as aldehydes, ketones, lactones, esters, dicarboxylic acids, and other compounds. These are formed despite a partial conversion of the paraffin and necessitate an expensive workup of the reaction product [50,55]. 

Reductive alkylation of N-alkylglucamines with a variety of aldehydes or ketones in the presence of Pd/carbon provides the corresponding N,N-dialkylglucamines in high yield. Only minor amounts of aldol byproducts are formed. 

Ethylene Carbonylation. The classical rhodium catalyzed carbonylation of ethylene to propionic acid (Eqn. 1) used ethyl iodide or HI as a co-catalyst (6). In the presence of excess ethylene and CO the process could proceed further to propionic anhydride (Eqn. 2). While additional products, such as ethyl propionate (EtC02Et), diethyl ketone (DEK), and ethanol were possible (See Eqns. 3-5), the only byproduct obtained when using a rhodium-alkyl iodide catalyst was small amounts (ca. 1-1.5%) of ethyl propionate. (See Eqns. 3-5.)... 

This breakdown of fat creates byproducts, chemicals called ketones. Ketones are acidic. Without enough insulin, they begin to build up in the blood. When enough ketones build up, the blood can no longer buffer the acidity. 

Moreover, the Grignard approach has the disadvantage of forming byproducts from the addition of Grignard reagents to the formed ketones. The yields of the benzyl ketones are good and the reaction will tolerate a wide variety of functionality. 

The addition of halomethyl metal reagents provides another Darzens-like route to aziridines <06JOC9373>. Reaction of ICH2C1 with MeLi generates a chloromethyllithium reagent, which then adds to the inline 74. A subsequent intramolecular /V-alkylation provides the aziridine 75. The isolation of a chloromethyl ketone byproduct demonstrated that the chloromethyllithium reagent is operative as opposed to a carbene. 

Oxidation. DMSO activated by P205 (1 equiv.) and in combination with triethylamine is useful for oxidation of alcohols to ketones and aldehydes, particularly in cases where the Swern reagent results in chlorinated byproducts. Yields are typically 80-85%. 

Keller (1998) describes the semi-continuous reaction process of a vinyl ketone K with lithium acetylide LA to yield lithium ethinolate LE an intermediate in the vitamin production. In an undesired side reaction an oligomer byproduct BP is produced. During the process, reactant K is fed to the semi-batch reactor at a rate to maximize the selectivity for LE. 

A cobalt catalysed carbonylation reaction converts A-substituted 1-aza-1,3-dienes into A-allylacetamides by a reductive acylation process [31]. Acetamides are byproducts of the reaction. In contrast, Schiff bases undergo a double A,C-acetylation under the same conditions producing a-acetamido ketones and A,A-disubstituted acetamides [32],... 

Current interest in synthetic fuels production by Fischer-Tropsch (FT) reactions have created a need for removal of byproduct oxygenates, formed by the FT reaction. The oxygenates consist of primary and internal alcohols, aldehydes, ketones, esters and carboxylic acids. The hydrocarbon products derived from the FT reaction range from methane to high molecular weight paraffin waxes containing more than 50 carbon atoms. 

These ruthenium catalysts catalyze the racemization of secondary alcohol through a dehydrogenation/hydrogenation cycle with or without releasing ketone as a byproduct (Scheme 1.5). Catalysts 6-9 display good activities at room temperature, while others show satisfactory activities at elevated temperatures. Catalyst 1, for example, requires a high temperature (70 °C) for dissociation into two monomeric species (la and lb) acting as racemization catalysts (Scheme 1.6). 

However, the procedure has some drawbacks to overcome. First, it requires an elevated temperature (70 °C) for the activation of the racemization catalyst Such a high temperature is unacceptable for thermally less-stable enzymes. Second, the racemization proceeds through a mechanism including the release of ketone as a byproduct and thus the lowering of yield is inevitable. Third, PCPA used in an... 

We reported the use of an indenyl ruthenium complex 2 as a racemization catalyst which did not produce ketones as the byproducts [17]. The metal catalyst requires a weak base like triethylamine and molecular oxygen to be activated. The DKR with 2 in combination with an immobilized PCL was carried out at a lower temperature (60°C) to afford good yields and high optical purities (Scheme 1.15). It is noteworthy that 2 does not require ketone as hydrogen mediator for racemization. 

Another important reaction in synthetic chemistry leading to C-C bond formation is the Michael addition. The reaction typically involves a conjugate or nucleophilic 1,4-addition of carbanions to a,/l-unsaturated aldehydes, ketones, esters, nitriles, or sulfones 157) (Scheme 21). A base is used to form the carbanion by abstracting a proton from an activated methylene precursor (donor), which attacks the alkene (acceptor). Strong bases are usually used in this reaction, leading to the formation of byproducts arising from side reactions such as condensations, dimerizations, or rearrangements. 

The Friedel-Crafts acylation of aromatic compounds is an important synthesis route to aromatic ketones in the production of fine and specialty chemicals. Industrially this is performed by reaction of an aromatic compound with a carboxylic acid or derivative e.g. acid anhydride in the presence of an acid catalyst. Commonly, either Lewis acids e.g. AICI3, strong mineral acids or solid acids e.g. zeolites, clays are used as catalysts however, in many cases this gives rise to substantial waste and corrosion difficulties. High reaction temperatures are often required which may lead to diminished product yields as a result of byproduct formation. Several studies detail the use of zeolites for this reaction (1). 

Carbonyl oxides are extremely photolabile even under matrix conditions and irradiation with red light (600 nm) rapidly produces dioxrranes (82). The dioxi-ranes are stable under these conditions but at 400-nm irradiation are converted into esters (83) or lactones. Ketones have been observed as byproducts in the carbene-O2 reactions in frozen matrices. Since the reaction of triplet carbene with O2 is very... 

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