P-Cresols, 2,6-di-r-butyl

Iodovanillin, 164 4-Iodoveratrole, 495,1018-1019 lodoxybenzene, 488-489, 511,1085 2-Iodo-1,4-xylene, 496 Ion-exchange resins, 332, 473, 511-519 lonol, see 2,6-Di-r-butyl-p-cresol /3-Ionone, 573 2 Ionylidene-ethanol, 637... 

Fuchigami and coworkers have formed emlates with electrogenerated bases (equations 10 and 11). - The basic anions of 2,6-di-r-butyl-p-cresol and a-pyrrolidone were obtained by cathodic reduction. Countercations with a weak affinity for the fluorine atom e.g. quaternary ammonium, phosphonium or tertiary sulfonium cations) had to be used in the example shown in equation (11) in order to impede defluorination. 

Prior to the discussion of the spectroscopic characteristics of tetrahydrofuran (THF), it should be noted that THF and many other ether compounds are chemically unstable. Over time, THF breaks down to form peroxides. Peroxides are chemically reactive and unstable. In order to help control peroxide levels in a solvent such as THF, manufacturers typically add a chemical scavenger, called a preservative or stabilizer such as 2,6-di-r-butyl-4-mefhylphenol (2,6-di-r-butyl-p-cresol, BHT). This type of THF is referred to as preserved or nonspectral grade THF. BHT has large molar absorptivity values in the UV below 280nm with the peak maximum at about 270 nm. As a consequence, preserved THF is rarely used in conjunction with UV detectors (see Fig. 1.4). 

THF is available unstabilized, or stabilized with 25 ppm (typical for GC use) to 250 ppm (typical for HPLC use) butylated hydroxytoluene (BHT 2,6-di-r-butyl-p-cresol), which is added to scavenge the peroxide breakdown products of THF. Ethyl ether can be purchased unstabilized or stabilized with ethanol ( 2-3%), BHT (1-10 ppm), or a blend of ethanol, water, and BHT (1.5-3.5%, 0.2-0.5%, and 5-10 ppm, respectively). Isopropyl ether is available unstabilized or stabilized widi 0.01% hydroquinone or 5-100 ppm BHT. Dioxane is available unpreserved or with 25-1500 ppm BHT as preservative. From the above, it is important that the correct solvent be chosen for use, since most are available unstabilized or stabilized and with a range of stabilizers and stabilizer concentrations. 

Richardson [334] also examined the decomposition of tert-hntyl hydroperoxide in the presence of copper(II) 2-ethylhexanoate in chlorobenzene at 50 C. The product composition was approximately 87% cr/-butyl alcohol, 11% di-r-butyl-peroxide, 1-2% acetone and a large amount of oxygen. Reaction is 0.55 order in copper salt and less than first order dependence on hydroperoxide was observed. Trapping experiments with 2,6-di-r-butyl-p-cresol indicate a radical mechanism. The kinetic data indicate a mechanism involving a hydroperoxide complex, [Cu(II)2(ROOH)2], and NMR spectral evidence was obtained for axial hydroperoxide ligands [334]. 

BHA, 2,6-di-r-butyl-p-cresol Silica gel Chloroform 20% Molybdophosphoric acid + ammonia vapour [15]... 

Gyclohexene-l,3,3-d3, HBr in dry acetic acid, and 2,6-di-ferf-butyl-p-cresol to inhibit free-radical addition sealed in an ampoule and kept a few hrs. at 15° in a thermostat trans-addition product. Y 75-95% purity 91%. — This transaddition offsets the many examples of cts-addition to olefins and emphasizes that the stereochemistry of electrophilic additions is a sensitive function of olefin structure. R. G. Fahey and R. A. Smith, Am. Soc. 86, 5035 (1964). 

Straightforward UV spectroscopy is liable to be in error because of interference by other highly absorbing impurities that may be present in the sample [59-62], Interference by such impurities in direct UV spectroscopy has been overcome or minimised by selective solvent extraction or by chromatography [60], However, within prescribed limits UV spectroscopy is of use and, as an example, procedures are described next for the determination of lonol (2,6-di- e -butyl-p-cresol) and of Santonox R (4,4"-thio-bis-6-terUbutyl-m-cresol) in polyolefins [63-66],... 

The oxidation is followed by reaction of the ferrous iron produced, with 2, 2 -dipyridyl to form a coloured complex, the intensity of which is proportional to the concentration of antioxidant present. The procedure has been applied to various phenolic and amine type antioxidants, namely, Succanox 18, BHT, lonol (2,6-di-tert-butyl-p-cresol), and Nonox Cl (N-N-di- 3-napthyl-p-phenylenediamine). A typical application of the procedure is given next, namely to the determination of down to 0.01% of Santonox R in PE. As the Metcalfe and Tomlinson [5] procedure determines Santonox R only in its reduced form, it does not include any Santonox R which may be present in the oxidised form in the original polymer, for example produced by atmospheric oxidation of the additive during polymer processing at elevated temperatures. Total reduced plus oxidised Santonox R can be determined by UV spectroscopic procedures. 

Campbell and Wise [2] applied column chromatography to the determination of known phenolic antioxidants in polyethylene (PE). This method is applicable to the analysis of mixtures of Santowhite powder (4, 4"-butylidene-bis-(6- er -butyl-w-cresol) with BHT (2,6-di-ter -butyl-p-cresol) and mixtures of Santonox R (4, 4 -thio-bis-(6-fert-butyl-m-... 

Spell and Eddy [3] described infrared (IR) spectroscopic procedures for the determination of up to 500 ppm of various additives in polyethylene (PE) pellets following solvent extraction of the additives at room temperature. They showed lonol (2,6-di-ter -butyl-p-cresol) and Santonox R (4,4 -thio-bis(6-ter -butyl- /-cresol)) are extracted quantitatively from PE pellets by carbon disulfide in 2-3 hours and by isooctane in 50-75 hours. The carbon disulfide extract is suitable for scanning in the IR region between 7.8 and 9.3 (xm, while the isooctane extract is suitable for scanning in the UV region between 250 and 350 nm. 

Cyclohexene in acetic acid added at 25° to a soln. of thiocyanogen chloride, prepared from Pb-thiocyanate and chlorine in acetic acid with subsequent addition of 2,6-di-fer -butyl-p-cresol as radical inhibitor rran -l-chloro-2-thio-cyanatocyclohexane. Y 77%. F. e. s. R. G. Guy and I. Pearson, Soc. Perkin I 1973, 281. 

Phenolic antioxidants including dicresylol propane and Santonox R ((4-4, -thio-bis-(3-napthyl-6-tert butyl phenol Phenolic antioxidants including Succonox 18, butylated hydroxy toluene, lonol, (2,6-di-tert butyl-p-cresol). Nonox Cl (N-N di-beta napthyl-p-phenylenediamine, Santonox R (4,4 thio-bis-3 methyl-6-tert-butylphenol) Phenolic antioxidants including Agerite Alba ((hydroquinone monobenzyl ether), Agerite Spar (styrenated phenol),... 

Spell and Eddy [58] have described IR spectroscopic procedures for the determination of up to 500 ppm of various additives in PE pellets following solvent extraction of additives at room temperature. They showed that lonol (2,6-di- -butyl-p-cresol) and Santonox R... 

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