Hydrocarbons acids, decarboxylation

FIGURE 3 Cn hydrocarbons from dodeca-3,6,9-trienoic acid. Loss of C(l) and a single hydrogen from C(5) yield the acyclic hydrocarbon finavarrene. Decarboxylation and loss of a single hydrogen from C(8) results in (6S)-ectocarpene. No other hydrogen atoms are lost during the biosynthetic sequence. 

R-COOH > R-H R-COOH R-H H- shorter-chain acids and hydrocarbons C Decarboxylation Cooper-Bray (6) degradation Irreversible... 

Kolbe electrolytic synthesis. Formation of hydrocarbons by the electrolysis of alkali salts of carboxylic acids (decarboxylative dimerization). 

Substituted phenanthrenecarboxylic acids can be obtained in this way and yield the phenanthrene hydrocarbons on decarboxylation. Weisbach and his co-workers803 applied this reaction to synthesis of aporphine. 

The physical properties of cyanoacetic acid [372-09-8] and two of its ester derivatives are Hsted ia Table 11 (82). The parent acid is a strong organic acid with a dissociation constant at 25°C of 3.36 x 10. It is prepared by the reaction of chloroacetic acid with sodium cyanide. It is hygroscopic and highly soluble ia alcohols and diethyl ether but iasoluble ia both aromatic and aUphatic hydrocarbons. It undergoes typical nitrile and acid reactions but the presence of the nitrile and the carboxyUc acid on the same carbon cause the hydrogens on C-2 to be readily replaced. The resulting malonic acid derivative decarboxylates to a substituted acrylonitrile ... 

The methyl and ethyl esters of cyanoacetic acid are slightly soluble ia water but are completely miscible ia most common organic solvents including aromatic hydrocarbons. The esters, like the parent acid, are highly reactive, particularly ia reactions involving the central carbon atom however, the esters tend not to decarboxylate. They are prepared by esterification of cyanoacetic acid and are used principally as chemical iatermediates. 

The principal steps in the mechanism of polyisoprene formation in plants are known and should help to improve the natural production of hydrocarbons. Mevalonic acid, a key intermediate derived from plant carbohydrate via acetylcoen2yme A, is transformed into isopentenyl pyrophosphate (IPP) via phosphorylation, dehydration, and decarboxylation (see Alkaloids). IPP then rearranges to dimethylaHyl pyrophosphate (DMAPP). DMAPP and... 

Composition. Rosin is primarily a complex mixture of monocarboxyUc acids of alkylated hydrophenanthrene nuclei. These constituents, known as resin acids, represent about 90% of rosin. The resin acids are subdivided into two types, based on their skeletal stmcture. The abietic-type acids contain an isopropyl group pendent from the carbon numbered 13. The pimaric-type acids have a methyl and vinyl group pendent from the same carbon atom. Figure 1 shows the stmcture of typical resin acids abietic acid, C2QH2QO2 (1) is predominant. The remaining 10% of commercial rosin consists of neutral materials that are either hydrocarbons or saponifiable esters. These materials are derived from resin acids by decarboxylation or esterification. 

In 1869 Berthelot- reported the production of styrene by dehydrogenation of ethylbenzene. This method is the basis of present day commercial methods. Over the year many other methods were developed, such as the decarboxylation of acids, dehydration of alcohols, pyrolysis of acetylene, pyrolysis of hydrocarbons and the chlorination and dehydrogenation of ethylbenzene." ... 

The photo-Kolbe reaction is the decarboxylation of carboxylic acids at tow voltage under irradiation at semiconductor anodes (TiO ), that are partially doped with metals, e.g. platinum [343, 344]. On semiconductor powders the dominant product is a hydrocarbon by substitution of the carboxylate group for hydrogen (Eq. 41), whereas on an n-TiOj single crystal in the oxidation of acetic acid the formation of ethane besides methane could be observed [345, 346]. Dependent on the kind of semiconductor, the adsorbed metal, and the pH of the solution the extent of alkyl coupling versus reduction to the hydrocarbon can be controlled to some extent [346]. The intermediacy of alkyl radicals has been demonstrated by ESR-spectroscopy [347], that of the alkyl anion by deuterium incorporation [344]. With vicinal diacids the mono- or bisdecarboxylation can be controlled by the light flux [348]. Adipic acid yielded butane [349] with levulinic acid the products of decarboxylation, methyl ethyl-... 

The decarboxylation of carboxylic acid in the presence of a nucleophile is a classical reaction known as the Hunsdiecker reaction. Such reactions can be carried out sometimes in aqueous conditions. Man-ganese(II) acetate catalyzed the reaction of a, 3-unsaturated aromatic carboxylic acids with NBS (1 and 2 equiv) in MeCN/water to afford haloalkenes and a-(dibromomethyl)benzenemethanols, respectively (Eq. 9.15).32 Decarboxylation of free carboxylic acids catalyzed by Pd/C under hydrothermal water (250° C/4 MPa) gave the corresponding hydrocarbons (Eq. 9.16).33 Under the hydrothermal conditions of deuterium oxide, decarbonylative deuteration was observed to give fully deuterated hydrocarbons from carboxylic acids or aldehydes. 

Biosynthesis of triene pheromone components with a triene double bond system that is n-3 (3,6,9-) are probably produced from linolenic acid [49]. Moths in the families Geometridae, Arctiidae, and Noctuidae apparently utilize linoleic and linolenic acid as precursors for their pheromones that must be obtained in the diet,since moths can not synthesize these fatty acids [50]. Most of the Type II pheromones are produced by chain elongation and decarboxylation to form hydrocarbons [51]. Oxygen is added to one of the double bonds in the polyunsaturated hydrocarbon to produce an epoxide [49]. 

As pointed out previously, controlled degradation reactions are very difficult with aliphatic or alicyclic hydrocarbons, and most of the relabeling work has been concentrated on aromatic reaction products. Procedures have been extensively described by Pines and co-workers (e.g., 97, 96, also 87, 89-98, 95, 98). For the present purpose, it suffices to note that the 14C contents of the methyl side-chains and the rings in aromatic reaction products are readily estimated by oxidation of the methyl to carboxyl, followed by decarboxylation, while ethyl side-chains may be oxidatively degraded one carbon atom at a time. Radiochemical assays may be made on CO2 either directly in a gas counter, or after conversion to barium carbonate, while other solid degradation intermediates (e.g., benzoic acid or the phthalic acids) may be either assayed directly as solids or burned to CO2. Liquids are best assayed after burning to CO2. 

Prior to 1985, decarboxylation of metal (hydrocarbon) arenedicarboxy-lates was restricted to mercury and to acids with two adjacent carboxylate groups. 

Ruthenium(in) catalyses the oxidative decarboxylation of n-butyric acid and isobutyric acid by ceric sulfate in aqueous acid. A mechanism for the Ru(III)-catalysed oxidation of o-hydroxybenzoic acid by an acidic solution of bromamine-B (PhS02-NNaBr, BAB) has been proposed based on a kinetic smdy. An ionic mechanism is suggested for the ruthenium(III) analogue of the Udenfriend-type system Ru(III)-EDTA-ascorbate-02, for the selective oxygen-atom transfer to saturated and unsaturated hydrocarbons. The kinetics of the oxidation of p-XC6H4CHPhOH(X =... 

The plausible deoxygenation routes for production of diesel like hydrocarbons from fatty acids and their derivates are decarboxylation, decarbonylation, hydrogenation and decarbonylation/hydrogenation. The main focus in this study is put on liquid phase decarboxylation and decarbonylation reactions, as depicted in Figure 1. Decarboxylation is carried out via direct removal of the carboxyl group yielding carbon dioxide and a linear paraffinic hydrocarbon, while the decarbonylation reaction yields carbon monoxide, water and a linear olefinic hydrocarbon. 

Decarboxylation.1 Esters of carboxylic acids are converted to the corresponding nor-hydrocarbons by reaction with n-Bu3SnH in the presence of AIBN as radical initiator. The reaction involves fragmentation to RC02 followed by loss of COz to give R-, which is reduced to RH. Yields arc in the range 60 90%. 

In the synthesis of fatty acids the acetyl irnits are condensed and then are reduced to form straight hydrocarbon chains. In the oxo-acid chain elongation mechanism, the acetyl unit is introduced but is later decarboxylated. Tlius, the chain is increased in length by one carbon atom at a time. These two mechanisms account for a great deal of the biosynthesis by chain extension. However, there are other variations. For example, glycine (a carboxylated methylamine), under the influence of pyridoxal phosphate and with accompanying decarboxylation, condenses with succinyl-CoA (Eq. 14-32) to extend the carbon chain and at the same time to introduce an amino group. Likewise, serine (a carboxylated ethanolamine) condenses with... 

Another type of elimination reaction favoured under plasma conditions is the decarboxylation. Carbocyclic acids easily lose carbon dioxide to form the parent hydrocarbons. In acid anhydrides decarboxylation is followed by a decar-bonylation. Cyclic or bicyclic anhydrides fragment forming unsaturated compounds, a reaction which has been studied with phthalie anhydride 24>. This anhydride decomposes to dehydrobenzene which, in the absence of other compounds, dimerizes, trimerizes or polymerizes. Orientation experiments indicated similar results for aliphatic acid anhydrides. 

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