P-phenylene diamines

White crystals, m.p. 114" C. Manufactured by reacting aniline with excess ethanoic acid or ethanoic anhydride. Chief use is in the manufacture of dye intermediates such as p-nitro-acetanilide, p-nitroaniline and p-phenylene-diamine, in the manufacture of rubber, and as a peroxide stabilizer. 

The most noteworthy reaction of azo-compounds is their behaviour on reduction. Prolonged reduction first saturates the azo group, giving the hydrazo derivative (C NH-NH C), and then breaks the NH NH linkage, with the formation of two primary amine molecules. If method (1) has been employed to prepare the azo-compound, these two primary amines will therefore be respectively (a) the original amine from which the diazonium salt was prepared, and (6) the amino derivative of the amine or phenol with which the diazonium salt was coupled. For example, amino-azobenzene on complete reduction gives one equivalent of aniline, and one of p-phenylene diamine, NHaCeH NH benzene-azo-2-naphthoI similarly gives one equivalent of aniline and one of... 

Respiratory sensitizers Isocyanates proteolytic enzymes p-phenylene diamine complex salts of platinum cyanuric chloride. ... 

Fibers in which the basic chemical units have been formed by chemical synthesis, followed by fiber formation, are called synthetic fibers. Examples include nylon, carbon, boron fibers, organic fibers, ceramic fibers, and metallic fibers. Among all commercially available fibers, Kevlar fibers exhibit high strength and modulus. (Kevlar is a DuPont trademark for poly [p-phenylene diamine terephthalamide].) It is an aromatic polyamide (aramid) in which at least 85% of the... 

If one wants to modify an existing polyester without losing its high order, copoly-merizing it with diamide units is an option. PBT can be modified with a diamide based on 1,4-butane diamine or p-phenylene diamine and PET with 1,2-ethylene... 

The azastyryl dyes result from the condensation of 2-formylthiazolium salt either on N,N-dimethyl-p-phenylene diamine or aromatic nitroso derivative. 

This mechanism is based on the fact that the ozone uptake of elongated rubber containing a substituted p-phenylene diamine type of antiozonant is very fast initially and then decreases rather rapidly with time and eventually stops almost completely. The film has been studied spectroscopically and shown to consist of unreacted antiozonant and its ozonized products, but no ozonized rubber is involved [64], Since these ozonized products are polar, they have poor solubility in the rubber and accumulate on the surface. 

The addition of a 2-methyl-2-penten-4-yl radical to the QDI (based on p-phenylene diamines [PPDs] thus producing the corresponding PPD radical) is highly exothermic. The reaction not only stabilizes the relatively unstable alkenyl radical, but also results in the aromatization of the diimino-cylcohexadienyl ring. The enthalpy of reaction for this reaction is calculated (using MOPAC/AMl Hamiltonian ) to be about —40 kcal/mol. 

FIGURE 16.1 Lowest unoccupied molecular orbital (LUMO) representations of QDI and p-phenylene diamine (PPD). 

DOPPD Dioctyl-p-phenylene diamine fluorophenyl)-dithiocarbamate... 

When p-ethylaminobenzoate and N,N-dimethyl-p-phenylene diamine sulfate were similarly treated with the dibromosulfone (I) for 2 h, the yield was only 32% and 15% respectively (Figure 1). A possible explanation is that the nucleophilicity of these monosubstituted anilines is weaker than that of aniline while a Na2C03 1,4-HBr elimination reaction could be competing with the substitution reaction, leading to the lower yield (18). 

Sediment Trap hydrogen sulfide in sodium hydroxide sulfide reacts with AW-dimethyl-p-phenylene-diamine to from methylene blue. Colorimetry 0.01 pmol/gram NR Allen et al. 1994... 

Antiozonant additives are employed with unsaturated rubbers such as natural rubber, nitrile rubber, styrene-butadiene rubber, etc., to minimise the atmospheric ozone degradation reaction. Common antiozonant types include the parapheny-lene diamines such as N-(l,3-dimethylbutyl)-AT-phenyl-p-phenylene diamine (6PPD) and N-isopropyl-N7 phenyl-p-phenylene diamine (IPPD). Both these antioxidants can be identified and quantified using GC- or LC-based techniques. 

Figure 5. Single crystal structures of (A) Tetrakis- and (B) N,N -Bis(trimethylsilyl))-p-phenylene-diamine with essential bond lengths, bond angles and non-bonded distances as well as van der Waals contours.

Imines 268 (Ar = phenyl, p-anisyl, p-chloro-phenyl) are dimerized on heating in aprotic solvents to give the yellow tetraphenyl p-benzoquinone imines 267 and (or) their reduction products, the colorless p-phenylene diamine derivatives 270ss ... 

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