Squalane, oxidation

Squalene is also an intermediate in the synthesis of cholesterol. StmcturaHy, chemically, and biogeneticaHy, many of the triterpenes have much in common with steroids (203). It has been verified experimentally that squalene is the precursor in the biosynthesis of all triterpenes through a series of cyclization and rearrangement reactions (203,204). Squalene is not used much in cosmetics and perfumery formulations because of its light, heat, and oxidative instabiUty however, its hydrogenated derivative, squalane, has a wide use as a fixative, a skin lubricant, and a carrier of Hpid-soluble dmgs. 

The conclusion that chain-breaking inhibition by zinc dialkyl dithiophosphates involves electron transfer was reached independently by Burn (6) following a more detailed qualitative study of the inhibition of the azonitrile-initiated oxidation of squalane and cumene and the noninitiated oxidation of indene by metal dialkyl dithiophosphates and related compounds (I to IV) ... 

Induction Periods. Induction periods for squalane oxidation were measured using an automatic recording oxygen absorption apparatus (23). 

We have carried out a limited study of the effect of metal dialkyl dithiophosphates on a hydroperoxide-autocatalyzed oxidation system. Table III summarizes induction periods for the oxidation of squalane at 140 °C. These results do not unambiguously reflect the peroxide-decomposing property of each dithiophosphate radical capture also occurs. 

Table III. Effect of Metal Dialkyl Dithiophosphates, [ (RO)2PS2]a.M, (at 4 X 10 n gram atoms of Phosphorus per liter) on the Oxidation of Squalane at 140°C.

Figure 10. Induction period for squalane oxidation at 160°C. as a function of ZnP concentration...

We have developed new reaction systems based on colloidal dispersions [23, 24], namely highly concentrated water-in-oil (gel) emulsions, which could overcome most of the disadvantages of the aqueoussolvent mixtures such as inactivation of the aldolase and incomplete aldehyde solubilization in the medium. These emulsions are characterized by volume fractions of dispersed phase higher than 0.73 [25] therefore, the droplets are deformed and/or polydisperse, separated by a thin film of continuous phase. Water-in-oil gel emulsions of water/Ci4E4/oil 90/4/6 wt%, where C14E4 is a technical grade poly(oxyethylene) tetradecyl ether surfactant, with an average of four moles of ethylene oxide per surfactant molecule and oil can be octane, decane, dodecane, tetradecane, hexadecane, or squalane, were typically chosen as reaction media [23, 26]. 

Crude fats and oils consist primarily of glycerides. However, they also contain many other hpids in minor quantitites. Com oil, for example, may contain glycerides plus phosphoUpids, glycolipids, many isomers of sitosterol and stigmasterol (plant steroids), several tocopherols (vitamins E), vitamin A, waxes, unsaturated hydrocarbons such as squalane and dozens of carotenoids and chlorophyll compounds, as well as many products of decomposition, hydrolysis, oxidation, and polymerization of any of the natural constituents. 

A comparison between a HAS and a PAO as stabilizers against the oxidation of PP showed that they behave differently [4]. Based on experiment showing the ability of the HAS and the PAO to reduce the oxidation rate of decalin, squalane and decalin/lauryl aldehyde mixtures, it is shown that the HAS is mainly active in the presence of aldehydes. For unstabilized PP it is shown that aldehydes play an important role in its oxidation [5]. These results are used to propose an oxidation mechanism for PP and a mechanism underlying the action of HAS. 

Oxidation of Decalin, Squalane and a Mixture of Lauryl aldehyde and Decalin [4]... 

The influence of the stabilizers mentioned in Figure 1 was studied by oxidizing three different model compounds decalin (a cyclic hydrocarbon which, like PP, contains secondary and tertiary carbons), squalane (a high molecular weight aliphatic hydrocarbon which also contains secondary and tertiary carbons), a mixture of 10% lauryl aldehyde in decalin, which could serve as a model for partly oxidized PP. All reactions were initiated with 1% of t-bulylhydroperoxide and performed at 120°C (for details see ref. 4). 

The oxidation of squalane is slower than the oxidation of the mixture of decalin and lauiyl aldehyde (compare Figures 7 and 8). Although squalane is a hydrocarbon similar to decalin, in squalane HAS are capable of reducing the oxidation rate effectively, while they were not effective against the oxidation of decalin. In squalane HAS-1 even outperformed PAO-1 (Figure 8). 

Figure 8. Influence of 0.1 wt % stabilizer on the oxidation rate of squalane at 120°C. Control (+), HAS-1 ( l) and PAO-1 (o). Bars show the standard...

It is clear that the efficiency of the different stabilizers highly depends on the model system. PAOs are effective in all systems, but HAS are not effective in decalin. The oxidation of decalin mainly takes place at the tertiary carbon, leading to cyclodecanone and cyclodecanol [8]. This oxidation does not lead to the formation of aldehydes and acids. When aldehydes are added to decalin HAS becomes effective, so HAS is effective against the oxidation of aldehydes. HAS is also effective against the oxidation of squalane, which, like decalin, is a hydrocarbon containing secondary and tertiary carbons. However, because of its... 

The sunblocking 4% cream contains 40 mg hydroquinone USP in a tinted sunblocking-cream base of purified water USP, stearic acid NF, talc USP, polyoxyl 40 stearate NF, polyoxyethylene (25) propylene glycol stearate, propylene glycol USP, glycerol monostearate, iron oxides, light mineral oil NF, squalane NF, edetate disodium USP, sodium metabisulfite NF, and potassium sorbate NF. 

Sulfur. To assess whether sulfur can be used as a partial oxidant for propane, exploratory experiments have been made at Worcester Polytechnic Institute in which propane and propane-helium mixtures were saturated partially with sulfur at atmospheric pressure and then passed over commercially available chromia-alumina catalysts. No methyl-acetylene was detected by thermal conductivity gas chromatography using a 20-foot squalane column, but significant amounts of methyl and ethyl mercaptans were found. Figure 7 illustrates the nature of the gaseous products obtained. Continued experimentation will establish the system more concretely. No coking data or results from sustained operation are available as yet. The results shown in Figure 7, while preliminary, show that the reaction... 

The similarity between the spreading behavior of impure squalane on clean stainless steel and on steel coated with a monolayer of barium dinonylnaphthalene sulfonate provides further support for the explanation of spreading offered here. The surface energy of the monolayer-coated steel is only a fraction of that for the clean oxide-coated surface, but the monolayer s critical surface tension for spreading, 29 dynes per cm., is above the surface tension of the squalane. Consequently... 

Perhydrogeraniol. See 3,7-Dimethyl-1 -octanol Perhydrol-urea. See Urea peroxide Perhydronaphthalene. See Decahydronaphthalene cis-Perhydronaphthalene. See cis-Decalin Perhydrosqualene. See Squalane 97% HLS Periclase] 98% 1LS Periclase] 98% 3LS Periclase] Periclase 96/H-D/8-1] Periclase 97% HLS] Periclase 98/1-1] Periclase 98% 3LS] Periclase 98% ILS] Periclase. See Magnesium oxide... 

Myristyl myristate Oleamide DEA PEG-10 castor oil PEG-8 dilaurate PEG-2 lactamide PEG-50 shea butter Polyglyceryl-10 hexaoleate Potassium castor oil sulfate PPG-10 cetyl ether PPG-20 cetyl ether PPG-9 diethylmonium chloride PPG-40 diethylmonium chloride PPG-11 stearyl ether Silicone Squalane Steareth-80 Stearyl phosphate Tallowamidopropylamine oxide lubricant, pesticides Lauroyl sarcosine Oleth-5 lubricant, PET fibers resin-bonded filters, food-contact... 

Fig. 2 Predicted Kovats retention indices for various analytes in gas-liquid chromatography with squalane and polyethylene oxide stationary phases. See text for description of the analyte molecules...

A derivative of squalene called squalane, where all the double bonds are saturated by hydrogenation, has better scope of appHcations than the squalene due to its improved oxidative stability. 

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