Phenylenediamine derivatives

Table 3. United States Production of Phenylenediamine Derivatives, t...

Stability. In order to have maximum effectiveness over long periods of time, an antioxidant should be stable upon exposure to heat, light, oxygen, water, etc. Many antioxidants, especially in the presence of an impurity when exposed to light and oxygen, are subject to oxidation reactions with the development of colored species. Alkylated diphenyl amines are least susceptible and the -phenylenediamine derivatives the most susceptible to direct oxidation. 

The best oxidation inhibitors are not usually the best antio2onants (qv). A disubstituted i ra-phenylenediamine such as AJ-isopropyl-AT-phenyl- -phenylenediamine is often selected for that purpose. -Phenylenediamine derivatives iaterfere with cure chemistry and scorchiness, and can stain objects ia contact with the vulcani2ate (114). On balance, /V-(1,3-dimethy1buty1)-/V-phenyl- -phenylenediamine and phenyl /to1y1- -pheny1enediamines have the best combination of properties. They are less scorchy and provide excellent o2one and heat resistance. Additional protection is gained ia blends with a small amount of EPDM mbber (126). 

Amongst other materials sometimes used as deactivators are, l,8-bis(salicyli-deneamino)-3,6-dithiaoctane and certain p-phenylenediamine derivatives. It is interesting to note that the last named materials also function as chain-breaking antioxidants and in part as peroxide decomposers. 

Since the mid-1950s several materials have been found effective in combating ozone-initiated degradation, in particular certain p-phenylenediamine derivatives. The actual choice of such antiozonants depends on the type of polymer and on whether or not the polymer is to be subject to dynamic stressing in service. Since antiozonants are not known to have any use in plastics materials, even those which may have certain rubber particles for toughening, they will not be dealt with further here. Anyone interested further should consult references 3-5. 

Rubber is protected against ozone attack by addition of physical and/or chemical antiozonants. Hydrocarbon waxes are the most common type of physical antiozonants, and p-phenylenediamine derivatives are the prevalent chemical antiozonants. Waxes bloom to the rubber surface and form a protective barrier. 

Sassoon and Rabani [79, 83] constructed an intriguing photoinduced ET system in which the back ET was greatly retarded by the electrostatic repulsion between two different polycations. They prepared poly(3,3-ionene) covalently linked with Ru(bpy)f + (26) and with an iY,Af,/V, Ar -tetraalkyl-/>-phenylenediamine derivative (27). The latter is an electron donor quencher toward the photoexcited Ru(II) complex. 

Watanabe T, T Hirayama, S Fukui (1989) Phenazine derivatives as the mutagenic reaction product from o- or m-phenylenediamine derivatives with hydrogen peroxide. Mutation Res 227 135-145. 

LDPE or HDPE extracts has been determined colorimet-rically at 430 nm by oxidation with H202 in the presence of H2S04 [66]. p-Phenylenediamine derivatives such as Flexzone 3C, used as antiozonants in rubber products, have been determined colorimetrically after oxidation to the corresponding Wurster salts [67]. A wide range of amine AOs in polyolefins has been determined by the p-nitroaniline spectrophotometric procedure [68]. Monoethanolamine (MEA) in a slip agent in PE film has been determined as a salicylaldehyde derivative by spectrophotometric quantification at 385 nm [69]. Table 5.6 contains additional examples of the use of 1JV/VIS spectrophotometry for the determination of additives in polymers. 

The typical transformation of all p-phenylenediamine derivatives by oxidising agents in acid solution consists in a change into a salt of the quinonediimine series. The dye just observed, so called Wurster s red , was long regarded as a simple quinonimonium salt ... 

The new p-phenylenediamine derivative so formed is further dehydrogenated to a quinonoid indamine dye ... 

The thermal cyclization of m-phenylenediamine derivatives (799) by heating in diphenyl ether afforded angular l,7-phenanthroline-3,9-dicarboxylate (800), if a substituent was not present at position 2 of the phenyl ring of 799 (R = H), but the linear pyrido[3,2-g]quinolinecarbox-ylate (801, R = Me, R1 = R2 = H) was prepared from the 2-methyl-substituted derivative (799, R = Me, R1 = R2 = H) (72GEP2220294). 

Benzamides constitute a fourth dass of HDAC inhibitors. One example, MS-275, is a phenylenediamine derivative that exhibits robust HDAC inhibition in patients with advanced myeloid leukemia as well as refractory solid tumors or lymphoma in Phase I studies [72]. MS-275 is currently in Phase II trials. In a recent study aimed at optimizing the benzamide scaffold, several bis-(aryl) type analogs were synthesized and evaluated for their activity against a panel of HDACs [85]. Moradei et al. found that a thienyl substitution para to the free amino group in the phenylenediamine core rendered inhibitors specific for HDACsl, 2 with potency superior to that of MS-275. Isoform-specific inhibitors should aid in dissecting the roles of HDACs in normal cellular fundioning and cancer. 

As is shown in Figure 3 the highest occupied energy level is found to parallel well the oxidation potential in aniline and p-phenylenediamine derivatives. To elucidate the existence of the optimum oxidation potentials for antioxidation and antiozonization, the reactivity indices Sr and S for radical and nucleophilic reactions have been used. These are ... 

The spirotetraaza silane 231 was prepared by treatment of the corresponding o-phenylenediamine derivative with SiCU. When 231 (X = H) was treated with bromotrichloromethane and AIBN, the monocyclization product 232 was isolated in low yield as a mixture of stereoisomers (Scheme 39). This radical-induced cyclization process was explored with respect to the impact of Si on the chemo- and regioselectivity <2002JOC8906>. 

Kidani, Y. Asano, Y. Noji, M. Synthesis of platinum(II) complexes of 4-substituted o-phenylenediamine derivatives... 

The electrochemistry of both NAD+ and NADH at clean electrodes occurs at high overvoltages (of the order of 1V) and hence causes imwanted side reactions, which tend to foul the electrode [142-144]. One way around this problem is to use mediators (two electron-proton acceptor/donors) such as o-quinone [145-147] or p-phenylenediamine derivatives [148], arylnitro derivative such as 2-nitro-9-fluorenone [149], PQQ with Ca " [150] and polyaromatic dye molecules, i.e., phenazine, phenoxazine and phenothiazine derivatives [11] that substantially lower the voltage for needed NADH oxidation. 

The influence of molecular structures and substituents on the antiozonant properties of a series of related aromatic diamine compounds was studied. The relative effectiveness of the compounds was determined by viscometric techniques and by comparison of the rate of degradation of protected vuicanizates. Results indicate that unsymmetrical p-phenylenediamine derivatives are less effective than analogous symmetrical compounds as antiozonants. The protective capacity of the antiozonants decreases as the size or number of the N-hydrogen substituents, or the distance between the amine groups, increases. The comparative stability of the free radicals of aryl diamines, in terms of the theory of resonance, is utilized to explain the relative inhibiting properties of the chemicals examined. 

Examination of postulated reactions 8) of p-phenylenediamine derivatives with ozone reveals that the antiozonant depletion is characterized by the intermediate formation of intensely colored products, or Wurster s salts (5), which are considered... 

Dialkyl or diaryl group substituents hold the molecule more rigidly out of the plane of the benzene ring than corresponding monosubstituted amine groups. The free radicals produced from unsymmetrical p-phenylenediamine derivatives should react more slowly with ozone than those formed from analogous symmetrical compounds. 

The reaction of o-phenylenediamine derivatives with quadrivalent selenium, which affords 2,1,3-benzoselenadiazoles, has been used as a very sensitive analytical method for the detection of selenium in water, food, and animal tissue. The 2,1,3-benzoselenadiazoles have also been... 

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