Fatty Acids, Alcohols, and Esters

The determination of double-bond position in unsaturated fatty acids has traditionally seemed to be an intractable problem for MS alone. Recourse to GC/MS and comparison of the column retention times of unknowns with those of standards has usually solved the problem. However, several techniques have recently managed to overcome the difficulties without using GC. 

The ammonia-CI spectrum exhibits an abundant [M + H] and two prominent fragment ions which correspond to the ions (26,27) retaining the NMe2 group. The double bond position is therefore readily identifiable and if CAD/tandem MS analysis is further used, each component of a fatty acid mixture can be thus identified. The approach was employed to analyze a mixture of monosubstituted fatty acids from Mycobacterium phleL 

It is usually impossible to determine by EIMS the double bond position(s) in unsaturated fatty acids, esters or alcohols merely by comparison of spectra with literature values. However, empirical methods can be employed to achieve this aim under carefully controlled mass spectrometric conditions, particularly where the mass spectrometer is dedicated to a particular compound class or problem. 

This principle has been neatly applied to the spectra of straight chain Cio —Cj8 acetates and alcohols, some of which are sex attractant pheromones in Lepidoptera (95). El mass spectra of these compounds are repeatedly measured under reproducible GC/MS conditions. The ratio of intensities, [mjz 55] [mjz 54] increases linearly as the double bond is located more distally from the acetate or alcohol functional group. As a check, the intensity of mlz 61 is also correlated with the double bond position. The reproducibility of measurements was such that this position was predictable within 1 carbon atom. 

FABMS has been shown to distinguish readily between some simple unsaturated dicarboxylic acids (96). The [M + H] ions from the Z-acids (28) are much less prone to fragment than those from the corresponding E -acids (29). The Z-acids probably form the stable proton-bridged complex (30). In contrast, protonation of the -acids on the carbon-carbon double bond becomes an energetically feasible process relative to carbonyl protonation. The ion formed can readily undergo the observed elimination of H2. 

---

It is well established that the location of a solubilized molecule in a micelle relative to the different structural components of the surfactant molecule will be determined primarily by the chemical structure of the additive (Fig. 16.1). In aqueous solutions, nonpolar additives such as hydrocarbons are intimately associated with the core of the micelle (Fig. 16.1 ), while slightly polar materials, such as fatty acids, alcohols, and esters, will usually be located in what is termed the palisades layer—the transition region between the hydrophobic core and surface head groups (Fig. 16.16). The orientation of such molecules is probably more or less radial with the hydrocarbon tail remaining closely... 

Beeswax is a mixture of organic compounds such as unsaturated and saturated fatty acids, alcohols, and esters, and polybutadiene contains unsaturated alkenes Lifetime calculated for coating prepared by cast solution Lifetime for dip coated Lifetime for spin coated Source Data from Muller et al. (2011)... 

Chem. Descrip. Mixt. of natural long chain fatty acids, alcohols, and esters Uses Emulsifier, oil binder in lubricating greases, polishes, anticorrosion compds. Features Stable high adhesion to various surfs. high soften, pt. low iodine value Properties Brn. tenacious, unctuous mass si. char, odor sol. in min. oils, many org. soivs. such as benzene, toluene, trichloroethylene, min. spirits insol. in water soften, pt. 50-60 C acid no. 120-135 sapon. no. 140-160 hyd. no. 65-90 flash pt. (OC) 455 F 100% NV 2% max. moisture 0.5% ash 14% max. unsapon-Iflable... 

A liquid film on the fiber surface may increase the contact area and promote adhesion. It is well known that an oily film on fibers increases soiling. Kissa [19,23] found that liquids belonging to different classes of chemical compounds (hydrocarbon, fatty acid, alcohol, and ester) increased soiling of a hydrophilic fabric (cotton) and a hydrophobic fabric (polyester) with different types of particulate soil. Attempts to correlate soiling with the refractive index, viscosity, surface tension, dipole moment, and dielectric constant showed that soiling increases with the ratio of the viscosity to the dielectric constant of the liquid. Because hydrocarbons are nonpolar and have a low dielectric constant, a viscous hydrocarbon film is especially prone to capture particulate soil. 

We Umit this section to a discussion of stereochemical studies that sought to demonstrate discriminating enantiomeric interactions in monolayers of simple surfactants having one hydrophobic chain of methylenes and, generally, a single chiral center. Work in this area includes derivatives of long chain fatty acids, alcohols, or esters whose chiral center is included in the methylene chain. 

The surface tensions of liquid mixtures and solutions of non-electrolytes show a different relation to composition as compared with electrolyte solutions. Duclaux and Traube found that alcohols, fatty acids, aldehydes, and esters decrease the surface tension of water according to their observations the surface tension of a solution containing x per cent by volume of such a substance is given by ... 

The interpretation of mass spectra of common wax components are described elsewhere (Hamilton, 1995b Evershed, 1992b Christie, 1994). The mass spectra of fatty acids, alcohols, wax esters and other lipids can be found in an open access website (The AOCS Lipid Library, 2011). Briefly, the identification is performed on the basis of the characteristic fragment and molecular ions. For example, the mass spectra of saturated fatty add methyl... 

The wax associated with suberin has also been examined, but only recently. Hydrocarbons, wax esters, very-long-chain fatty acids, alcohols and terpenes have all been found. These are all typical... 

Styrene-DVB 275 Separation of fatty acids, alcohols, glycols, esters, ketones, aldehydes, and ethers and hydrocarbons. 

Sodium Dispersions. Sodium is easily dispersed in inert hydrocarbons (qv), eg, white oil or kerosene, by agitation, or using a homogenizing device. Addition of oleic acid and other long-chain fatty acids, higher alcohols and esters, and some finely divided soHds, eg, carbon or bentonite, accelerate dispersion and produce finer (1—20 -lm) particles. Above 98°C the sodium is present as Hquid spheres. On cooling to lower temperatures, soHd spheres of sodium remain dispersed in the hydrocarbon and present an extended surface for reaction. Dispersions may contain as much as 50 wt % sodium. Sodium in this form is easily handled and reacts rapidly. For some purposes the presence of the inert hydrocarbon is a disadvantage. 

Ether carboxylates are used not only in powdered detergents but in liquid laundry detergents for their hard water stability, lime soap dispersibility, and electrolyte stability they improve the suspension stability and rheology of the electrolyte builder [130,131]. Formulations based particularly on lauryl ether carboxylate + 4.5 EO combined with fatty acid salt and other anionic surfactants are described [132], sometimes in combination with quaternary compounds as softeners [133,163]. Ether carboxylates show improved cleaning properties as suds-controlling agents in formulations with ethoxylated alkylphenol or fatty alcohol, alkyl phosphate esters or alkoxylate phosphate esters, and water-soluble builders [134]. 

For long-chain alcohol esters it is interesting to see that the interfacial tension between a 0.01 wt % aqueous solution and octane or xylene has a minimum for ester sulfonates with a total 22 carbon atoms in the fatty acid chain and the ester chain [60]. The balance in length between the two chains has only a poor effect. Thus, a-sulfonated fatty acid esters with a total number of 22-26 carbon atoms in the molecule have excellent interfacial activities. To attain the same magnitude in the interfacial tension between linear alkylbenzenesulfonate (LAS) solution and octane, the required concentration of LAS is 0.1 wt %. This is 10 times the concentration needed for a-sulfonated fatty acid esters [60]. 

The triacylglycerols (Figure 14—6) are esters of the tri-hydric alcohol glycerol and fatty acids. Mono- and di-acylglycerols wherein one or two fatty acids are esteri-fied with glycerol are also found in the tissues. These are of particular significance in the synthesis and hydrolysis of triacylglycerols. 

The formation of an ester from an alcohol and an acid is an equilibrium reaction. The reverse reaction can be promoted by removing the acid from the reaction mixture, for example by treating it with NaOH. Animal fats are converted to soaps (fatty acid salts) and glycerine (a trialcohol) in this manner. 

The repertoire of chemicals that can be used for communication is limited by the biosynthetic ability of the insect. Compared to other insect orders, pheromone biosynthesis in Hymenoptera has received little study [191]. However, the biosynthetic origins of chemically diverse hymenopteran semiochemicals likely include aromatic, fatty acid, and terpenoid pathways as well as simple modifications of host-derived precursors. Notable recent studies include the biosynthesis of the fatty acid components (2 )-9-oxodec-2-enoic acid 52 and (2 )-9-hydroxydec-2-enoic acid of the honeybee queen mandibular pheromone from octadecanoic acid [192,193], and the aliphatic alcohol and ester... 

Coenzyme A is used as the alcohol part of thioesters, which are more reactive than oxygen esters (see Section 7.9.3) and are thus exploited in biochemistry in a wide range of reactions, e.g. fatty acid biosynthesis and metabolism (see Section 15.5). 

Fats and oils are esters of the trihydric alcohol glycerol with long-chain fatty acids. The descriptor fat or oil is applied according to whether the material is a solid or liquid at room temperature it has no chemical meaning. All three fatty acids in the ester may be the same, or they may be different. Common saturated fatty acids... 

---