Hydrocarbons from carboxylate salts

In poly-basic adds, all the carboxyl groups can be replaced by hydrogen. In this way an add may be transformed into the hydrocarbon from which it was derived. In the above case, the potassium salt may be used instead of the calcium salt. 

A selection of important anionic surfactants is displayed in table C2.3.1. Carboxylic acid salts or tire soaps are tire best known anionic surfactants. These materials were originally derived from animal fats by saponification. The ionized carboxyl group provides tire anionic charge. Examples witlr hydrocarbon chains of fewer tlran ten carbon atoms are too soluble and tliose witlr chains longer tlran 20 carbon atoms are too insoluble to be useful in aqueous applications. They may be prepared witlr cations otlrer tlran sodium. 

An additional useful test for aromatic carboxylic acids is to distil the acid or its sodium salt with soda-lime. Heat 0.5 g of the add or its sodium salt with 0.5 g of soda-lime in an ignition tube to make certain that there is no danger of explosion. Then grind together 0.5 g of the acid with 3 g of soda-lime, place the mixture in a Pyrex test tube and cover it with an equal bulk of soda-lime. Fit a wide delivery tube dipping into an empty test tube. Clamp the tube near the mouth. Heat the soda-lime first and then the mixture gradually to a dull-red heat. Examine the product this may consist of aromatic hydrocarbons or derivatives, e.g. phenol from salicylic acid, anisole from anisic acid, toluene from toluic acid, etc. 

A number of experimental techniques by measurements of physical properties (interfacial tension, surface tension, osmotic pressure, conductivity, density change) applicable in aqueous systems suffer frequently from insufficient sensitivity at low CMC values in hydrocarbon solvents. Some surfactants in hydrocarbon solvents do not give an identifiable CMC the conventional properties of the hydrocarbon solvent solutions of surfactant compounds can be interpreted as a continuous aggregation from which the apparent aggregation number can be calculated. Other, quite successful, techniques (light scattering, solubilization, fluorescence indicator) were applied to a number of CMCs, e.g., alkylammonium salts, carboxylates, sulfonates and sodium bis(2-ethylhexyl)succinate (AOT) in hydrocarbon solvents, see Table 3.1 (Eicke, 1980 Kertes, 1977 Kertes and Gutman, 1976 Luisi and Straub, 1984 Preston, 1948). 

Like carboxylates acetylacetonates are bidentate ligands for the Nd center. In the mid 1970s Monakov et al. started investigations on the use of Nd acetylacetonates for the polymerization of dienes [323,324]. Nd-acetylacetonate and Nd-benzoylacetonate were again mentioned in 1980 by Shen et al. [92], During the time of Nd-BR commercialization the influence of acetylace-tone on Nd-based catalyst systems was intensely studied by JSR. The increase of the solubility of Nd-salts in hydrocarbon solvents by acetylacetone was claimed in 1983 [325,326]. From this time onwards JSR filed numerous patents in which acetylacetone containing Nd catalyst systems were described [327-343]. 

Aromatic acids are reduced by metal-ammonia solutions very much more readily than simple hydrocarbons and ethers. In contrast to the normal requirements for the latter derivatives, it is often possible to achieve reduction with close to stoichiometric quantities of metal. The addition of aromatic carboxylic acids to liquid ammonia (or vice versa) results in the immediate precipitation of the ammonium salt. As the metal is added, however, the precipitate usually dissolves as reduction proceeds, especially if lithium is used. If reduction is carried out in carefully dried, redistilled ammonia, as little as 2.2 mol of lithium are consumed in some cAses, thereby demonstrating that the substrate is reduced much more readily than the ammonium ions, which instead react with the intermediates from reduction of the substrate. However, protonation by NH4 is not essential since reduction proceeds equally well on preformed metal car-boxylates (although low solubility is then often a problem). The addition of an alcohol is not necessary, but it may serve as a useful buffer and can often improve solubility. The presence of alcohol can nevertheless be deleterious, since it facilitates isomerization of the initially formed 1,4-dihydro isomer to the 3,4-isomer and in this way affords the possibility of further reduction. ... 

This synthesis of 1,2,3,4-tetraphenylnaphthalene (7) demonstrates the transient existence of benzyne (5), a hydrocarbon that has not been isolated as such. The precursor, diphenyliodonium-2-carboxylate (4), is heated in an inert solvent to a temperature at which it decomposes to benzyne, iodobenzene, and carbon dioxide in the presence of tetraphenylcyclo-pentadienone (6) as trapping agent. The preparation of the precursor (4) illustrates oxidation of a derivative of iodobenzene to an iodonium salt (2) and the Friedel-Crafts-like reaction of the substance with benzene to form the diphenyliodonium salt (3). Neutralization with ammoniuim hydroxide then liberates the precursor, inner salt (4), which, when obtained by crystallization from water, is the monohydrate. 

Electrolytic decarboxylative coupling of sodium salts of carboxylic acids takes place during their electrolysis. Carbon dioxide is eliminated, and the free radicals thus generated couple to form hydrocarbons or their derivatives. The reaction is referred to as the Kolbe electrosynthesis and is exemplified by the synthesis of 1,8-difluorooctane from 5-fluorovaleric acid (equation 469) [574]. Yields of homologous halogenated acids range from 31% to 82% [574]. 

In this reaction one carbon atom is oxidized from the carboxyl stage to carbon dioxide. It is to be noted, therefore, that the carboxyl group cannot be directly reduced to the hydrocarbon without the loss of one carbon atom. The method is not practical. It is a traditional experiment, as it illustrates the difficulty in reducing the carboxyl group. The elimination of the carboxyl group is also effected by electrolysis of concentrated solutions of the alkali salts. The products in the case of sodium acetate are ethane and carbon dioxide ... 

A new decarboxylative route to free radicals, which has proved particularly successful in preparative work, embodies the thermal (or photochemical) decomposition reaction of 1-hy-droxypyridine-2(l/f)-thione esters 23 with tributyltin hydride, /er/-butanethiol, or a similar hydrogen donor.These esters can be easily prepared from acyl halides and the sodium salt of l-hydroxypyridine-2(l//)-thione, or from the carboxylic acid, dicyclohexylcarbodiimide and l-hydroxypyridine-2(l/f)-thione. The intermediate radicals were readily reduced to the corresponding hydrocarbons 24 in efficient chain reactions with organotin hydrides or thiols as reaction partners, and the proportion of rearranged to unrearranged products could be controlled by the choice of hydrogen donor, its concentration and the temperature. This system was sufficiently quantitative and well behaved for use in kinetic studies, and the rate constants of the (S-scission reactions of the listed cyclopropylmethyl species were determined. 

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