16-DPA

Most observations of SCRP have been from triplet preeursors, but Fiikuju et al [61] have observed smglet-bom SCRP upon photolysis of tetraphenylliydrazine in sodium dodeeyl sulfate (SDS) mieelles. The tetraphenylhydrazine (12) eleaves to fomi two diphenylamino (DPA) radieals, as shown below. 

Fig. 8. Ball powder batch process. NC = nitrocellulose, EA = ethyl acetate, DPA = diphenylamine, NG = nitroglycerine.

A commonly used measure of irradiation damage is displacements per atom (dpa). A unit of 1 dpa means that on the average, every atom in the irradiated volume has been displaced once from its equiUbrium lattice site. The approximated dpa in the implanted region is given by equation 16 where 0 (ions/cm ) is the dose, and (NJE)) is the damage function given by equation 14. 

The first detailed investigation of the reaction kinetics was reported in 1984 (68). The reaction of bis(pentachlorophenyl) oxalate [1173-75-7] (PCPO) and hydrogen peroxide cataly2ed by sodium saUcylate in chlorobenzene produced chemiluminescence from diphenylamine (DPA) as a simple time—intensity profile from which a chemiluminescence decay rate constant could be determined. These studies demonstrated a first-order dependence for both PCPO and hydrogen peroxide and a zero-order dependence on the fluorescer in accord with an earher study (9). Furthermore, the chemiluminescence quantum efficiencies Qc) are dependent on the ease of oxidation of the fluorescer, an unstable, short-hved intermediate (r = 0.5 /is) serves as the chemical activator, and such a short-hved species "is not consistent with attempts to identify a relatively stable dioxetane as the intermediate" (68). 

Diarylamines are compounds that have two aromatic groups and one hydrogen atom attached to nitrogen. Diphenyl amine (DPA), or... 

Selected physical properties for representative diarylamiaes are givea ia Table 1. The solubiUty of DPA ia water (1) is givea by ... 

Diphenylamine is a weak base, = 9 x lO ". Dilute acids are used to separate DPA from primary aromatic amines, such as aniline,... 

G-All lation. Siace para-alkylated derivatives of DPA are widely used ia large volumes as antioxidants (qv), the most important reaction of DPA is the acid catalyzed reaction with olefins (2,3). Alkylation is carried out by adding the olefin to a mixture of DPA and an acid catalyst, such as AIQ. ... 

Diphenylamine can be alkylated exclusively in the ortho positions by reacting with an olefin in the presence of aluminum diphenylamide (7), which can be readily obtained by heating DPA with powdered aluminum, or more easily by treating sodium diphenylamide with AIQ. - Ethylene is more reactive than propylene, which in turn is more reactive than isobutylene. Eor a typical reaction, a small amount of the amide is generated in a DPA melt and ethylene is introduced under pressure (5 —30 MPa) at 200—400°C. The absorption of ethylene stops after about 30 min and 2,2 -diethyldiphenylamine is obtained in 95% yield. With propylene only a 25% yield of the 2,2 -diisopropyldiphenylamine is obtained. 

Thus, W,W,W W -tetraphenylhydra2ine [632-52-0] 5,10-dihydro-5,10-diphenylphena2ine [3665-72-3] and W,W,Ar-triphenyl-l,2-ben2enediamine [29325-54-0] are oxidation products of DPA. The permanent stain caused by these compounds is in part due to the formation of the following highly conjugated, polymeric products which are insoluble ... 

Eor antioxidant activity, the reaction of aminyl radicals with peroxy radicals is very beneficial. The nitroxyl radicals formed in this reaction are extremely effective oxidation inhibitors. Nitroxides function by trapping chain-propagating alkyl radicals to give hydroxylamine ethers. These ethers, in turn, quench chain propagating peroxy radicals and in the process regenerate the original nitroxides. The cycHc nature of this process accounts for the superlative antioxidant activity of nitroxides (see Antioxidants). Thus, antioxidant activity improves with an increase in stabiUty of the aminyl and nitroxyl radicals. Consequendy, commercial DPA antioxidants are alkylated in the ortho and para positions to prevent undesirable coupling reactions. 

Electrophilic substitution reactions of diarylamines are easily accompHshed since the amino group activates the aromatic ring. Thus, DPA reacts with bromine or chlorine to form the 2,2H,4 tetrahalo derivative nitration usually produces the trinitro compound. 

Diarylamines do not react with carbon disulfide, whereas dialkylamines readily form dithiocarbamates. However, N,Ar-diaryldithiocarbamates can be prepared from metal salts of diarylamines and carbon disulfide (15). They are more stable than diaLkyldithiocarbarnic acids, eg, N,N -diphenyldithiocarbamic acid [7283-79-6] mp 142°C. Similarly, various metal salts of DPA react with carbon dioxide and an epoxide to give the P-hydroxyalkyldiphenylcarbamates (16). 

Thermodynamic analysis of this reaction shows favorable energy relations (18). The standard free energy of formation of DPA is 310.5 kj /mol (74.2 kcal/mol) (19). 

The vapor-phase conversion of aniline to DPA over a soHd catalyst has been extensively studied (18,22). In general, the catalyst used is pure aluminum oxide or titanium oxide, prepared under special conditions (18). Promoters, such as copper chromite, nickel chloride, phosphoric acid, and ammonium fluoride, have also been recommended. Reaction temperatures are usually from 400 to 500°C. Coke formed on the catalyst is removed occasionally by burning. In this way, conversions of about 35% and yields of 95% have been reported. Carba2ole is frequently a by-product. 

The second major route to diarylamiaes is the condensation of an aromatic amine with a phenol. Aniline [62-53-3] phenol [108-95-2] and 3.5% phosphoric acid at 325°C gives a 50% yield of DPA (23). Apparently, this reaction iavolves the addition of aniline to the keto form of the phenol. Thus, naphthols and hydroquiaone are more reactive and give higher yields of product. This is the preferred route to A/-phenyi-2-naphthyiamiQe, 4-hydroxydiphenyiamiQe, and diphenyl- -phenylenediamine (24). 

A process for the production of DPA from phenol and ammonia has been reported (25). Typically, the reaction is carried out continuously ia a fixed-bed reactor usiag an acidic alumiaa catalyst at 300°C—420°C. The first product formed is aniline which is subsequently converted to DPA. Consequently, the reaction can be carried out to simultaneously produce DPA and aniline, ia any desired ratio, simply by varyiag the molar ratios of phenol (and aniline) ia the reactor feed stream. 

Diarylamiaes fuactioa as mbber antioxidants by breaking the peroxidative chain reactions leading to mbber deterioration. Nearly all commercial synthetic mbbers (see Elastomers, synthetic), including neoprene, butyl, styrene—butadiene, and the acrylonitrile—butadiene mbbers, can be protected with about 1—2% of an alkylated diphenylamine. DPA itself is not used as a mbber antioxidant. An objectionable feature of these antioxidants is that they cause discoloration and staining which limits their use to applications where this is not important. 

The addition of 2,2, 4,4, 6-pentanitro-6 -methyldiphenylamine [64653-47-0] to seawater precipitates potassium (38). Aromatic amines, especially aminotetrahydronaphthalenes and their A[-aryl derivatives, are efficient flotation agents for quartz. The use of DPA for image formation in films has been patented (39,40). Diarylamines are used as intermediates (41) for azo, sulfur, oxidative base, triaryhnethane, oxazine, nitro, and safranine dyes (see Dyes and DYE INTERLffiDIATES). 

As discussed earlier, the first wall materials in next generation machines will receive from 0.005 to 30 displacements per atom. At the lower end of this range (<0.01 dpa) there are essentially no mechanical property changes expected in graphite materials. However, even at these low doses thermal conductivity and stored energy are of concern. For displacement levels >0.01 dpa other property... 

To illustrate the usefulness of such an algorithm, and the seriousness of the issue of thermal conductivity degradation to the design and operation of PFCs, the algorithm discussed above has been used to construct Fig. 9 [34], which shows the isotherms for a monoblock divertor element in the unirradiated and irradiated state and the "flat plate" divertor element in the irradiated state. In constmcting Fig. 9, the thermal conductivity saturation level of 1 dpa given in Fig. 8 is assumed, and the flat plate and monoblock divertor shown are receiving a steady state flux of... 

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