Dimerization of oleic acid

A similar reaction occurs with fatty acids (such as stearic acid) or methyl stearate, which undergo isomerization, cracking, dimerization, and oligomerization reactions. This has been used to convert solid stearic acid into the more valuable liquid isostearic acid [102] (Scheme 5.1-70). The isomerization and dimerization of oleic acid and methyl oleate have also been found to occur in chloroaluminate(III) ionic liquids [103]. 

Polyanhydrides were synthesized from dimer and trimer of unsaturated fatty acids. The dimers of oleic acid and erucic acid, prepared by radical coupling via... 

The degradation rates for a number of polyanhydrides are available in the literature [1, 82,83], However, recently, a new class of polyanhydrides poly(FAD-SA) have been synthesized from non-linear hydrophobic dimer of oleic acid or erucic acid and relatively hydrophilic sebacic acid. This copolymer can be prepared in various ratios of the monomers to achieve the desired degree of hydrophobicity increasing the percentage of FAD, a more hydrophobic copolymer, is obtained. Another advantage of this copolymer is its ability to be formulated as films, microspheres, and beads [84],... 

Dimerization of unsaturated fatty acids, to. so-called dimer acids, is widely practised in industry, where acid-treated clays are invariably used as a catalyst. In the case of oleic acid the major products are dimers, trimers, and isosteric acid. Koster et al. (1998) have investigated the relative importance of the various acid sites as well as structural and textural parameters of montmorrilonite. The interlamellar space dominates the oleic acid dimerization and the active site is the tetrahedrol substitution site. 

Xu et al. (2001) synthesized the copolymers of a dimer fatty acid (dimer of oleic and linoleic acids) and sebacic acid (P(DA-SA)) by melt polycondensation of acetylated prepolymers. Degradation and drug release kinetics showed that increasing dimer acid content decreased the release rate (Xu et al., 2001). 

Fats and oils (triglycerides) from plants and animals are renewable sources of chemicals, but the amounts of the chemicals made from them are small compared with those made from petroleum and natural gas. This may change if biodiesel fuel (e.g., ethyl oleate) made by the alcoholysis of oils becomes common. Such esters may be useful as environmentally friendly solvents.50 Unsaturated oils, such as linseed oil, are the basis of oil-based paints, which cure by cross-linking through oxidation by air. Soaps are the potassium or sodium salts of the long-chain fatty acids obtained by the hydrolysis of the triglycerides. The dibasic dimer fatty acids obtained by the dimerization of oleic and linoleic acids (both Cig acids) are made into oligomeric fatty amides which are used to cure epoxy resins. The un-... 

Thus, the dimerisation of unsaturated fatty acids takes place at higher temperatures in the presence of catalysts (for example acidic clays, montmorillonite type). One molecule of oleic acid (having one double bond) reacts with one mol of linoleic acid (having two double bonds) and this forms a dimeric acid with a cycloaliphatic structure. 

Definition Mixture of mono and diesters of oleic acid and a dimer of glycerin Properties HLB 3.5 nonionic Uses Emulsifier in cosmetics, foods, and pharmaceuticals Reguiatory FDA 21CFR 172.854 Manuf./Distrib. A E Connock http //www. connock. co. uk Trade Name Synonyms Hostacerin DGO [Clariant/Functional Chems.]... 

Figure 3.21 Formation of dimers from free radicals of oleic acid.

Thermal decomposition of capsaicin yields capsaicin dimer ( )-JV-vanillyl-di(8-methylnon-6-en)imide (10-35), various amides, acids, hydrocarbons and phenols. The main product is E)-S-methylnon-6-enamide, nonanamide, pentanamide and other amides, ( )-8-methylnon-6-enoic acid, nonanoic acid, ( )-hept -2-ene, vanillin and other substituted phenols (2-methoxy-4-methylphenol and 2-methoxyphenol), which are produced by decomposition of vanillin. Roasting of peppers in oil may produce fatty acid amides. For example, reaction with oleic acid yields (Z)-N-vanillyloctadec-9-enamide reaction of oleic acid with ammonia, originating from capsaicin, gives rise to (Z)-octadec-9-enamide (oleamide). 

The dimer acids [61788-89-4] 9- and 10-carboxystearic acids, and C-21 dicarboxylic acids are products resulting from three different reactions of C-18 unsaturated fatty acids. These reactions are, respectively, self-condensation, reaction with carbon monoxide followed by oxidation of the resulting 9- or 10-formylstearic acid (or, alternatively, by hydrocarboxylation of the unsaturated fatty acid), and Diels-Alder reaction with acryUc acid. The starting materials for these reactions have been almost exclusively tall oil fatty acids or, to a lesser degree, oleic acid, although other unsaturated fatty acid feedstocks can be used (see Carboxylic acids. Fatty acids from tall oil Tall oil). 

Most of the products Hsted in Tables 1—3 are based on manufacture from tall oil fatty acids. Dimer acids based on other feedstocks (eg, oleic acid) may have different properties. A European manufacturer recently announced availabiUty of a 44-carbon dimer acid, presumably made from an emcic acid feedstock (7). 

Structure and Mechanism of Formation. Thermal dimerization of unsaturated fatty acids has been explaiaed both by a Diels-Alder mechanism and by a free-radical route involving hydrogen transfer. The Diels-Alder reaction appears to apply to starting materials high ia linoleic acid content satisfactorily, but oleic acid oligomerization seems better rationalized by a free-radical reaction (8—10). 

The clay-cataly2ed iatermolecular condensation of oleic and/or linoleic acid mixtures on a commercial scale produces approximately a 60 40 mixture of dimer acids and higher polycarboxyUc acids) and monomer acids (C g isomerized fatty acids). The polycarboxyUc acid and monomer fractions are usually separated by wiped-film evaporation. The monomer fraction, after hydrogenation, can be fed to a solvent separative process that produces commercial isostearic acid, a complex mixture of saturated fatty acids that is Hquid at 10°C. Dimer acids can be further separated, also by wiped-film evaporation, iato distilled dimer acids and trimer acids. A review of dimerization gives a comprehensive discussion of the subject (10). 

Other alkenoic acids that have been dimerized with retention of configuration at the double bond are oleic acid (23 % dimer yield), elaidic acid (44%) [143], and erucic acid (40%) [144]. 

Cowan Teeter (1944) reported a new class of resinous substances based on the zinc salts of dimerized unsaturated fatty acids such as linoleic and oleic acid. The latter is referred to as dimer acid. Later, Pellico (1974) described a dental composition based on the reaction between zinc oxide and either dimer or trimer acid. In an attempt to formulate calcium hydroxide cements which would be hydrolytically stable, Wilson et al. (1981) examined cement formation between calciimi hydroxide and dimer acid. They found it necessary to incorporate an accelerator, alimiiniiun acetate hydrate, Al2(OH)2(CHgCOO)4.3H2O, into the cement powder. 

Fatty acids have also been converted to difunctional monomers for polyanhydride synthesis by dimerizing the unsaturated erucic or oleic acid to form branched monomers. These monomers are collectively referred to as fatty acid dimers and the polymers are referred to as poly(fatty acid dimer) (PFAD). PFAD (erucic acid dimer) was synthesized by Domb and Maniar (1993) via melt polycondensation and was a liquid at room temperature. Desiring to increase the hydrophobicity of aliphatic polyanhydrides such as PSA without adding aromaticity to the monomers (and thereby increasing the melting point), Teomim and Domb (1999) and Krasko et al. (2002) have synthesized fatty acid terminated PSA. Octanoic, lauric, myristic, stearic, ricinoleic, oleic, linoleic, and lithocholic acid acetate anhydrides were added to the melt polycondensation reactions to obtain the desired terminations. As desired, a dramatic reduction in the erosion rate was obtained (Krasko et al., 2002 Teomim and Domb, 1999). 

Polyanhydrides prepared from fatty acids are good candidates for the delivery of hydrophilic drugs due to the desired hydrophobicity of the natural fatty acids in the main chain of the polyanhydrides 11). These polyanhydrides have two series of acid monomers one has longer carbon chain, such as dimer erucic or oleic acid another has shorter carbon chain, such as sebacic acid (2). Fatty acids can be incorporated into the polymer chain by one of two ways by... 

In the selection of an appropriate corrosion inhibitor, an important consideration is the problem of adverse competition with other additives designed to adsorb on the liquid-metal interface. Extreme pressure and/or antiwear agents compete for the same sites as the corrosion inhibitor. Eatty amines are good corrosion inhibitors in this type of environment. However, their adverse effect on the performance of ZDDP additives often prohibits their use. Half esters or amides of dodecylsuccinic acid, phosphate esters or thiophosphates are frequently employed. A combination of inhibitors is sometimes used, for example, fatty carboxylic acids or the dimer/trimer analogues of the unsaturated acids, e.g. oleic, used in conjunction with an amine such as an ethanolamine or alkyl amine, or amide such as alkyl imidazoline and sarcosines, Eig. 6.7. Shorter chain carboxylic acid and amines are used as volatile corrosion inhibitors. 

The synthesis of dimeric fatty acids is based on the reaction between a fatty acid with one double bond (oleic acid) and a fatty acid with two double bonds (linoleic acid) or three double bonds (linolenic acid), at higher temperatures in the presence of solid acidic catalysts (for example montmorillonite acidic treated clays). Dimerised fatty acids (C36) and trimerised fatty acids (C54) are formed. The dimer acid is separated from the trimeric acid by high vacuum distillation. By using fatty dimeric acids and dimeric alcohols in the synthesis of polyesters and of polyester polyurethanes, products are obtained with an exceptional resistance to hydrolysis, noncrystalline polymers with a very flexible structure and an excellent resistance to heat and oxygen (Chapter 12.5). Utilisation of hydrophobic dicarboxylic acids, such as sebacic acid and azelaic acid in polyesterification reactions leads to hydrolysis resistant polyurethanes. 

Weakly acidic fatty acids such as oleic acid undergo dissociation to form ions (R ) at high pH values and neutral molecules (RH) at low pH values. In the intermediate pH region, the ions and neutral molecules can associate to form iono-molecular complexes (Kulkarni and Somasundaran, 1980). As the collector concentration is increased, miceUization or precipitation of the collector will occur. In addition, collector species can undergo associative interactions to form other aggregates such as dimers (R ) (Somasundaran and Anantha-padmanabhan, 1979b). Since the surface activities of these species will vary from those of each other, flotation of minerals with these collectors can also be expected to be dependent upon pH and such solution conditions. 

Correlation of oleate adsorption and flotation maximum at about pH 7.5 for a variety of minerals and high abstraction (adsorption + surface precipitation) below this pH with the species distribution diagram (Fig. 4.9) suggests that the role of acid-soap dimer and precipitated oleic acid can be significant in controlling the adsorption and resultant flotation behavior. 

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