Unsaturated fatty alcohols

Fatty alcohols are obtained by direct hydrogenation of fatty acids or by hydrogenation of fatty acid esters. Typically, this is performed over copper catalysts at elevated temperature (170°C-270°C) and pressure (40-300 bar hydrogen) [26], By this route, completely saturated fatty alcohols are produced. In the past, unsaturated fatty alcohols were produced via hydrolysis of whale oil (a natural wax occurring in whale blubber) or by reduction of waxes with sodium (Bouveault-Blanc reduction). Today, they can be obtained by selective hydrogenation at even higher temperatures (250°C-280°C), but lower pressure up to 25 bar over metal oxides (zinc oxide, chromium oxide, iron oxide, or cadmium oxide) or partially deactivated copper chromite catalysts [26],... 

Rokanol K3 and K7 are nonionic surfactants (oxyethylenated unsaturated fatty alcohols, of the general formula R0(CH2CH20)wH, R = Cu-22r where = 3 or = 7, respectively). U-15 is silane pro-adhesive compotmd (N-2-aininoethyl-3-aininopropyltrimethoxysilane). 

Jojoba (jojoba oil). A perennial, dioecious plant (Sim-mondsia chinensis, Buxaceae) indigenous to California and Mexico. Oil content of seeds 45-50%, protein up to 30%. J. oil mp. 6.8-7°C, bp. 389°C. J. oil is an exception among the plant oils since it does not contain triglycerides but ra er a liquid wax ester. The main components of J. oil are docosenyl eicosenoate (37 %), eicosenyl eicosenoate (24%), and eicoseny 1 do-cosenoate (11%), thus mainly wax esters with 40 and 42 C atoms. The wax esters of J. oils are very stable to oxidation (see linoleic acid) since they consist to > 95% of mono-unsaturated fatty alcohols and acids of the ffl9-series. 

Unsaturated fatty alcohols can also be epoxidized by lipase-catalyzed perhydrol-ysis (16). Interestingly, the outcome of the reaction depends on the ester applied for peroxy acid generation (Fig. 5). Fatty acid esters such as butyric acid ethylester react to epoxyalkanolacylates in a three-step one-pot reaction. Carbonic acid esters such as diethyl carbonate also form peroxy acids (percarbonic acid derivatives) and epox-idize the unsaturated alcohol however, in a water-containing environment, they are obviously not stable enough to esterify the hydroxyl group. Thus, the end product is the epoxy alcohol. 

Fig. 5. Chemoenzymatic epoxidation of unsaturated fatty alcohols with ethylbutyrate vs. diethylcarbonate as the peroxy acid source.

Sperm oil occurs in the blubber and in the head cavities of the sperm whale (this cavity helps the whale keep part of his head above water to breathe). The oil contains a solid fraction (spermaceti, cetin, cetylpalmitate) which can be cristallised.The liquid fraction mainly contains oleyloleate and higher mono-unsaturated fatty acid monesters of unsaturated fatty alcohol. 

Fatty acid esters of mono- and polyfunctional alcohols are the workhorses of oleochemistry. In many fields of application fatty acid methyl esters replace fatty adds because they are less corrosive. Chemical reactions can often be carried out under milder conditions. They have lower boiling points and require less energy to distil and to fractionate than the corresponding fatty acids. The elimination of methanol from the reaction products can be more easily achieved than that of water. Therefore fatty acid methyl esters are primarily used for the production of saturated and unsaturated fatty alcohols. Methyl esters are manufactured by acid catalyzed esterification of fatty acids in counter-current reaction columns or by alkaline transesterification starting directly from the triglyceride oils in a batch, semi-batch or continuous process (Figure 9.1.37> ° ° ... 

Using special catalysts (cadmium modified catalysts for example), trickle-bed reactors have also been used to obtain unsaturated fatty alcohols. The New Japan Chemical Company (38) operates a plant of 6000 t/a capacity to produce octadecenol by hydrogenation. This could decrease the consumption of sperm whale oil from which the product has been formerly obtained. 

The commercial exploitation of sperm oil has led to the depletion of whale populations and is banned in some countries. Attention has, therefore, turned to the jojoba plant whose oil also consists of wax esters. Most fatty chemicals obtained from natural sources have chain lengths of Cig-Cig. The limited availability of compounds with 12-14 carbon atoms, which are important in surfactants, was one of the driving forces behind the development of petrochemical processes for the production of fatty alcohols. Higher alcohols, such as C20-C22 alcohols, can be produced from rapeseed oils rich in erucic acid and fish oils. Unsaturated fatty alcohols may be manufactured in the presence of selective catalysts. 

The reduction proceeds selectively without the production of hydrocarbons and isomerization or hydrogenation of double bonds. Extensive safety measures are required due to the large quantity of metallic sodium used. The process was used until the 1950s to produce unsaturated fatty alcohols, especially oleyl alcohol from sperm oil. These alcohols can now be produced by selective catalytic hydrogenation processes using cheap raw materials, and the sodium reduction process is of interest only in special cases. 

Unsaturated fatty alcohols can only be obtained from natural sources petrochemical processes for... 

The first large-scale hydrogenation plant (Henkel) went into operation in the late 1950s. Previously, unsaturated fatty alcohols could be obtained only by hydrolysis of whale oil. The hydrogenation processes Section 26.7.2.1.2.2 are suitable for the large-scale production of unsaturated fatty alcohols. 

Unsaturated fatty alcohols are used in detergents, cosmetic ointments and creams as plasticizers and antifoaming agents, and textile and leather processing. Oleyl alcohol is also used as an additive in petroleum and lubricating oils. 

As fatty alcohols are comparable in structure and molecular weight to fatty acid methyl esters, they are usually subjected to GC on the same stationary phases and under near-identical conditions. It is certainly possible to separate alcohols in the free form by GC, especially on modem WCOT columns of fused silica, but sharper peaks are obtained if less polar derivatives such as the acetates, trifluoroacetates or TMS ethers are prepared. Suitable preparation procedures are described in detail in Chapter 4. Jamieson and Reid [438] studied the relative retention times of many different saturated and unsaturated fatty alcohols in the free form and as the acetates on packed GC columns containing polar polyester phases, and concluded that very similar separation factors applied as with the equivalent fatty acid methyl esters. The order of elution was - methyl ester < alcohol acetate < free alcohol. A TMS ether derivative would be expected to have a lower retention time than an acetate, but the separation factors for double bonds in the alkyl chain in this instance were found to be lower than with the acetates and resolution in general was poorer some changes in retention sequence for specific isomers was noted, depending on the type of derivative [439]. In contrast, the free alcohol eluted before derivatized forms on non-polar phases [944]. It is therefore possible to use equivalent chain-length data for the provisional identification of fatty alcohols in the same way as with methyl ester derivatives of fatty acids (see Chapter 5). 

The wax found in the cranial cavity of the marine mammal the sperm whale Physeter macrocephalus, syn. P. catodon) and two related species (pygmy sperm whale and dwarf sperm whale) from the sperm whale superfamily has industrial importance. The milky-white waxy substance, or spermaceti, is composed mainly of cetyl palmitate (3-42). The proportion of spermaceti with a lower melting point, containing predominantly unsaturated fatty alcohols, is called sperm oh. 

Jojoba Oil Jojoba oil is often referred to a hquid wax. It is not a triglyceride, but contains more than 90% esters of long-chain unsaturated fatty acids with unsaturated fatty alcohols. Jojoba oil is relatively stable to oxidation. It is widely used in cosmetics. There are numerous derivatives of jojoba available such as waxes or butters that are naturally derived. 

The fractionated methyl esters can be converted into fatty alcohols by the high-pressure hydrogenation process in the presence of a catalyst. Usually, copper chromite catalyst is used. Copper chromite catalyst also converts any unsaturated carbon double bonds so that only saturated fatty alcohols are formed. If unsaturated fatty alcohols are desired, a special zinc-bearing catalyst is employed. 

Catalysts used for the hydrogenation step are usually copper chromite formulations, although copper oxide/zinc oxide catalysts have also been used. The process accounts for about half of the copper chromite catalysts used commer-dally. Both acid group and double bonds in the long carbon chain are hydrogenated during the reaction, which produces a saturated alcohol. When an unsaturated fatty alcohol is required, a more selective zinc chromite catalyst may be used. 

Synonyms Oceol Octadecenol 1-Octadecenol Octadec-9-en-1-ol 9-Octadecen-1-oi cis-9-Octadecen-1-ol (Z)-Octadec-9-enol (Z)-9-Octadecen-1-ol Oleol Ole-oyl alcohol Oleyl fatty alcohol Classification Unsaturated fatty alcohol Ionic Nature Nonionic Empirical C-.HjgO Formula CH3(CH2)7CH=CH(CH2)sOH... 

A new reaction scheme circumvents earlier difficulties by starting from unsaturated fatty alcohol ethoxylates, which are terminally blocked (- fatty alcohol ethoxylates) and finally sulfonated at the double bond(- sulfation/sulfonation). 

J. is a waxy, yellowish oil, which is slow to turn rancid and is undamaged by repeated heating to high temperatures. It is one of the few naturally occurring ->wax esters of unsaturated - fatty acids and unsaturated - fatty alcohols, mainly of a chainlength of C20-C22 The oil is obtained from the seeds of the ->jojoba plant. 

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