Thiodipropionate

1 Fieser, Experiments in Organic Chemistry, 2nd ed., p. 311, D. C. Heath and Company, Boston, 1941. 

METHYL p-THIODIPROPIONATE (Propionic acid, p,p -thiodi-, dimethyl ester) 

Cautionl This preparation should be conducted in a hood to 

A good grade of commercial methyl acrylate containing hy-droquinone is entirely satisfactory. Material of doubtful quality may be redistilled (into a receiver containing hydroquinone), b.p. 78-81°. 

Either methanol or 95% ethanol may be used as the solvent. No ester interchange was observed to occur under the conditions employed. 

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Peroxide-decomposing antioxidants destroy hydroperoxides, the sources of free radicals in polymers. Phosphites and thioesters such as tris(nonylphenyl) phosphite, distearyl pentaerythritol diphosphite, and dialkyl thiodipropionates are examples of peroxide-decomposing antioxidants. 

PEROXIDESAND PEROXIDECOMPOUNDS - ORGANIC PEROXIDES] (Vol 18) Didodecyl 3,3y-thiodipropionate [123-28-4]... 

Additions of mercaptans with alkaline catalysts give 3-alk5ithiopropionates (29). In the case of hydrogen sulfide, the initially formed 3-mercaptopropionate reacts with a second molecule of acrylate to give a 3,3 -thiodipropionate (30,31). 

A.ntioxidants. PhenoHc antioxidants, added at about 0.1—0.5 phr, are usually chosen from among butylated hydroxytoluene [128-37-0] (BHT), and Nnonylphenol [104-40-5] for Hquid stabilizer formulations and bisphenol A [80-05-7] (2,2-bis-(/)-hydroxyphenyl)propane) for the soHd systems. Low melting thioesters, dilauryl thiodipropionate [123-28-4] (DLTDP) or distearyl thiodipropionate [693-36-7] (DSTDP) are commonly added along with the phenoHcs to enhance their antioxidant performance. Usually a 3 1 ratio of thiodipropionate to phenoHc antioxidant provides the desired protection. Most mixed metal stabilizer products contain the antioxidant iagredient. 

Divalent Sulfur Derivatives. A diaLkyl ester of thiodipropionic acid (16) is capable of decomposing at least 20 moles of hydroperoxide (17). Some of the reactions contributing to the antioxidant activity of these compounds are shown in Figure 3. 

When used alone at low temperatures, diaLkyl thiodipropionates are rather weak antioxidants. However, synergistic mixtures with hindered phenols are highly effective at elevated temperatures and are used extensively to stabilize polyolefins, ABS, impact polystyrene (IPS), and other plastics. 

The synergistic effect of a hydroperoxide decomposer, eg, dilauryl thiodipropionate [123-28-4] (34), and a radical scavenger, eg, tetrakis[methylene(3,5-di-/ f2 butyl-4-hydroxyhydrocinnamate)]methane (9), ia protecting polypropylene duting an oxygen-uptake test at 140°C is shown ia Table 3. 

Tetiakis[methylene(3,5-di-/( /f-butyl-4-hydioxyhydio-ciiinamate)]methane. Dilauryl thiodipropionate. 

Dialkyl esters of 3,3 -thiodipropionic acid (53), cycHc phosphonites such as neopentylphenyl phosphite, derivatives of phosphaphenathrene-lO-oxide (54), secondary aromatic amines, eg, diphenylamine (55), and epoxidi2ed soybean oils (56) are effective stabili2ers for preventing discoloration of cellulose esters during thermal processing. 

Materials that promote the decomposition of organic hydroperoxide to form stable products rather than chain-initiating free radicals are known as peroxide decomposers. Amongst the materials that function in this way may be included a number of mercaptans, sulphonic acids, zinc dialkylthiophosphate and zinc dimethyldithiocarbamate. There is also evidence that some of the phenol and aryl amine chain-breaking antioxidants may function in addition by this mechanism. In saturated hydrocarbon polymers diauryl thiodipropionate has achieved a preeminent position as a peroxide decomposer. 

The peroxide decomposer will drastically reduce the number of radicals, which can then be more effectively mopped up by the chain-breaking materials. A widely used combination is 4-methyl-2,6,di-t-butylphenol and dilauryl thiodipropionate. It is possible to envisage most powerful combinations where a chain-breaking antioxidant, a regenerating agent, a peroxide decomposer, a metal deactivator and an ultraviolet absorber are all employed together. 

Figure II. 8. Synergistic effect of two antioxidants in polypropylene (DLTP=dilauryl thiodipropionate. MCPC-2,2 -methylenebis[6-(l-melhylcyclohexyl-p-cresol)]. (After Leyland and Watls )...

Chromatographic methods were developed for the systematic determination of five classes of additives in PE for food packaging [170]. In Soxhlet extractions phenolic AOs and acid amides were determined by HPLC and CGC, respectively. Thiodipropionic acid esters were determined by HRGC as higher alcohols obtained after saponification of the extracts with KOH. Glycerol fatty acid esters and stearates were determined... 

NMR spectroscopy is most effective in qualitative analysis when the samples examinated are substantially pure compounds and has been used to confirm the theoretically predicted low-energy conformations of the Af-acylated hindered amine light stabiliser Tinuvin 440 [210]. Trace amounts of PDMS (quantification limit 0.1 ppm) in plastic additives, dyes and pigments were determined by 111 NMR after Soxhlet extraction [211]. ll NMR was also used for the detection of octadecanol, an impurity in Irganox PS 802 (3,3 -dioctadecyl thiodipropionate). NMR has identified the nature of a supposedly UV stabiliser of empirical formula C17H18N3CIO [44] (Scheme 5.2). 

Act to decompose hydroperoxides into stable molecules such as alcohols and ethers, before they can react with light to form free radicals. Main chemical classes are trivalent phosphorous compounds and thio-synergists (esters of thiodipropionic acid). Sulfur-based organic antioxidants decompose hydroperoxides by non-radical reactions. Typical peroxide decomposers are Irgafos 168, Ultranox 626, Irganox PS 800 and others. 

Dilauryl thiodipropionate Didodecyl 3,3 -thiodipropionate Thiobis(dodecyl propionate) Thiodipropionic acid dilauryl ester Bis(dodecyloxycarbonylethyl) sulfide... 

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