Phenol-4-phenylenediamine complex

Plasticiser/oil in rubber is usually determined by solvent extraction (ISO 1407) and FTIR identification [57] TGA can usually provide good quantifications of plasticiser contents. Antidegradants in rubber compounds may be determined by HS-GC-MS for volatile species (e.g. BHT, IPPD), but usually solvent extraction is required, followed by GC-MS, HPLC, UV or DP-MS analysis. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out. The determination of antioxidants in rubbers by means of HPLC and TLC has been reviewed [58], The TLC technique for antidegradants in rubbers is described in ASTM D 3156 and ISO 4645.2 (1984). Direct probe EIMS was also used to analyse antioxidants (hindered phenols and aromatic amines) in rubber extracts [59]. ISO 11089 (1997) deals with the determination of /V-phenyl-/9-naphthylamine and poly-2,2,4-trimethyl-1,2-dihydroquinoline (TMDQ) as well as other generic types of antiozonants such as IV-alkyl-AL-phenyl-p-phenylenediamines (e.g. IPPD and 6PPD) and A-aryl-AL-aryl-p-phenylenediamines (e.g. DPPD), by means of HPLC. 

Four main types of antioxidants are commonly used in polypropylene stabilizer systems although many other types of chemical compounds have been suggested. These types include hindered phenolics, thiodi-propionate esters, aryl phosphites, and ultraviolet absorbers such as the hydroxybenzophenones and benzotriazoles. Other chemicals which have been reported include aromatic amines such as p-phenylenediamine, hydrocarbon borates, aminophenols, Zn and other metal dithiocarbamates, thiophosphates, and thiophosphites, mercaptals, chromium salt complexes, tin-sulfur compounds, triazoles, silicone polymers, carbon black, nickel phenolates, thiurams, oxamides, metal stearates, Cu, Zn, Cd, and Pb salts of benzimidazoles, succinic acid anhydride, and others. The polymeric phenolic phosphites described here are another type. 

In 1998, Loehlin and co-workers [44] reported the structures of five new crystals of the super-tetrahedral type formed by complementary amines and alcohols. They described the H-bonding networks of three complexes of the diamine type with monoalcohols 4-phenylenediamine (5)-phenol (16) (ratio 1 2, as in 5 16), 4-phenylenediamine (5)-4-phenylphenol (17) (ratio 1 2, as in 5 17), and 4-phenylenediamine (5)-4-chlorophenol (18) (ratio 1 2, as in 5 18) (Scheme 6). Two complexes of 4-phenylenediamine with diols were also reported 4-phenylenediamine (5)-2,6-dihydroxynaphthalene (19) (ratio 1 1, as in 5 19), and 4-phenylenediamine (5)-l,6-hexanediol (20) (ratio 1 1, as in 5 20). The H-bonded networks were... 

Laccase shares with tyrosinase the ability to oxidize dihydric phenols, like catechol, to the corresponding quinones. Whether the enzyme is active in the oxidation of monohydric phenols like cresol is a matter of controversy since the purity of preparations said to catalyze such oxidations has been questioned 107), Much more important is the ability of laccase to oxidize various aminophenols, like p-phenylenediamine, which is in fact the best substrate for the enzyme (Table III). The enzyme is important commercially because it oxidizes some complex... 

The amino group attached to a phenyl ring activates the o- and p- positions on the benzene ring similarly to the OH group in phenols. For this reason, a condensation reaction of aniline and formaldehyde leads to the formation of polymeric compounds. However, the amino group also can react with formaldehyde, and more complex reactions occur. For example, in the condensation of an aromatic diamine such as m-phenylenediamine with formaldehyde, the reaction can be written as follows ... 

The crystal structures of many o- and p-chlorophenols, but only of a few m-chloro-phenols, are known. Representative examples are l,5-dichloro-2,6-dihydroxynaphthalene (45), a complex between 3,5-dichlorophenol (46) and 2,6-dimethylphenol , and a complex of p-chlorophenol (47) with 1,4-phenylenediamine. The C—OH bond lengths in 45 and 47 are normal (1.364 and 1.361 A, respectively). The same bond in 46 is significantly longer (1.387 A) for unknown reasons. 

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. 

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