1.1- Bisphenols, oxidation

A three-level switching device has been demonstrated in which photochromic properties are used to control electrical properties, and vice versa. Such a system has been realized in the form of thiophene bisphenol [90, 91]. Conversion of the open (8a) to the closed (8b) form of the thiophene was achieved by absorption of 312 nm light, and revered by absorption of 600 nm light. The bisphenol oxidation occurs at +0.735 V (vs. SCE), forming the closed-ring bisquinone, compound 8c. This species has large absorptions at 400 and 534 nm. The optical properties of the quinone phenol couple have previously been used in a bianthrone-based system [87]. The bisquinone (8c) cannot be converted to the open thiophene, and locks the system in the closed form. The thiophene has also been incorporated as a component in two-level molecular switches [99, 128] and switchable molecular wires [30]. 

TetrabromobisphenoIA. Tetrabromobisphenol A [79-94-7] (TBBPA) is the largest volume bromiaated flame retardant. TBBPA is prepared by bromination of bisphenol A under a variety of conditions. When the bromination is carried out ia methanol, methyl bromide [74-80-9] is produced as a coproduct (37). If hydrogen peroxide is used to oxidize the hydrogen bromide [10035-10-6] HBr, produced back to bromine, methyl bromide is not coproduced (38). TBBPA is used both as an additive and as a reactive flame retardant. It is used as an additive primarily ia ABS systems, la ABS, TBBPA is probably the largest volume flame retardant used, and because of its relatively low cost is the most cost-effective flame retardant. In ABS it provides high flow and good impact properties. These benefits come at the expense of distortion temperature under load (DTUL) (39). DTUL is a measure of the use temperature of a polymer. TBBPA is more uv stable than decabrom and uv stable ABS resias based oa TBBPA are produced commercially. 

The Brominated Flame Retardants Industry Panel (BFRIP) was formed ia 1985 within the Flame Retardant Chemicals Association (FRCA) to address such concerns about the use of decabromodiphenyl oxide. Siace 1990 the BFRIP has operated as a Chemical Self-Funded Technical Advocacy and Research (CHEMSTAR) panel within the Chemical Manufacturers Association (CMA) (64). As of 1993, members of BFRIP are Ak2o, Amerihaas (Dead Sea Bromine Group), Ethyl Corp., and Great Lakes Chemical. Siace its formation, BFRIP has presented updates to iadustry on a regular basis (65,66), and has pubhshed a summary of the available toxicity information on four of the largest volume brominated flame retardants (67,68) tetrabromo bisphenol A, pentabromodiphenyl oxide, octabromodiphenyl oxide, and decabromodiphenyl oxide. This information supplements that summarized ia Table 11. 

Decafluorobiphenyl [434-90-2] C F C F (mol wt, 334.1 mp, 68°C bp, 206°C), can be prepared by I Jllmann coupling of bromo- [344-04-7] chloro- [344-07-0] or iodopentafluorobenzene [827-15-6] with copper. This product shows good thermal stabiHty decafluorobiphenyl was recovered unchanged after 1 h below 575°C (270). Decafluorobiphenyl-based derivatives exhibit greater oxidative stabiHty than similar hydrocarbon compounds (271). Therm ally stable poly(fluorinated aryl ether) oligomers prepared from decafluorobiphenyl and bisphenols show low dielectric constant and moisture absorption which are attractive for electronic appHcations (272). 

Benzene is alkylated with propylene to yield cumene (qv). Cumene is catalytically oxidized in the presence of air to cumene hydroperoxide, which is decomposed into phenol and acetone (qv). Phenol is used to manufacture caprolactam (nylon) and phenoHc resins such as bisphenol A. Approximately 22% of benzene produced in 1988 was used to manufacture cumene. 

The acetone supply is strongly influenced by the production of phenol, and so the small difference between total demand and the acetone suppHed by the cumene oxidation process is made up from other sources. The largest use for acetone is in solvents although increasing amounts ate used to make bisphenol A [80-05-7] and methyl methacrylate [80-62-6]. a-Methylstyrene [98-83-9] is produced in controlled quantities from the cleavage of cumene hydroperoxide, or it can be made directly by the dehydrogenation of cumene. About 2% of the cumene produced in 1987 went to a-methylstyrene manufacture for use in poly (a-methylstyrene) and as an ingredient that imparts heat-resistant quaUties to polystyrene plastics. 

The cycloahphatic products are generally Hquids of lower viscosity than the standard glycidyl ether resins. The peroxidized resins contain no chlorine and low ash content and their ring-contained oxirane group (cyclohexene oxide type) reacts more readily with acidic curing agents than the bisphenol A-derived epoxy resins. 

To obtain maximum lifetime, the oxidants must not be lost during service. A major potential source of loss is the evaporation of the antioxidant. Evaporation is often observed with BHT (butylated hydroxytoluene), a monomeric phenol, and to avoid evaporation less volatile, higher molecular weight antioxidants are used (i.e. bisphenols). 

Antioxidants. A good antioxidant should be added to CR adhesives to avoid oxidative degradation and acid tendering of substrates. Derivatives of diphenyl amine (octylated diphenyl amine, styrenated diphenyl amine) provide good performance but staining is produced. To avoid staining, hindered phenols or bisphenols can be added. 2 phr antioxidant is sufficient in solvent-borne CR adhesives formulations. 

Dehydrofluorination by primary and secondary aliphatic amines occurs at room temperature and is the basis of diamine cross linkmg, which occurs by dehydrofluonnation and subsequent nucleophihc substitution of the double bond The locus of dehydrofluonnation is a VDF unit flanked by two perfluoroolefin units This selectively base-sensitive methylene group also undergoes elimination as the first step in phase-transfer-catalyzed cross-hnking with quaternary ammo mum or phosphomum salts, bisphenols, and morganic oxides and hydroxides as HF acceptors [31, 32]... 

Polyphosphonates are well-known flame-retardant materials [110] and are generally prepared by melt [111,112], interfacial [113-115] and solution polycondensation methods [116]. A typical example of synthesis is the polycondensation of bifunctional organophosphorus compounds, such as dichlorophenylphosphine oxide, with bisphenols [117,118]. 

Hexa-fluorobisphenol A (HFBPA) based polysulfone and poly(arylene ether phosphine oxide) were prepared by nucleophilic aromatic substitution similar to that of bisphenol-A-based polysulfone and poly(arylene ether phosphine oxide).11... 

The degradation of bisphenol-A involves a rearrangement—analogous to those described for compounds with qnaternary carbon atoms in Chapter 7, Part 1—followed by oxidative fission of the stilbene prodnced (Lobos et al. 1992 Spivack et al. 1994) (Figure 8.38). 

The anthors also snccessfnlly catalysed the formation of PC with 39-R via oxidative carbonylation of bisphenol A [47], Under similar conditions with 39- Bu, a PC with = 24000 and = 9400 was obtained in 80% yield. The... 

Recently, several reports of the flame-retardant properties of boron-containing bisphenol-A resins have appeared from Gao and Liu.89 The synthesis of a boron-containing bisphenol-A formaldehyde resin (64 and 65) (Fig. 42) from a mixture of bisphenol-A, formaldehyde, and boric acid, in the mole ratio 1 2.4 0.5, has been reported.893 The kinetics of the thermal degradation and thermal stability of the resins were determined by thermal analysis. The analysis revealed that the resin had higher heat resistance and oxidative resistance than most common phenol-formaldehyde resins. 

Montaudo and co-workers have used direct pyrolysis mass spectrometry (DPMS) to analyse the high-temperature (>500°C) pyrolysis compounds evolved from several condensation polymers, including poly(bisphenol-A-carbonate) [69], poly(ether sulfone) (PES) and poly(phenylene oxide) (PPO) [72] and poly(phenylene sulfide) (PPS) [73]. Additionally, in order to obtain data on the involatile charred residue formed during the isothermal pyrolysis process, the pyrolysis residue was subjected to aminolysis, and then the aminolyzed residue analysed using fast atom bombardment (FAB) MS. During the DPMS measurements, EI-MS scans were made every 3 s continuously over the mass range 10-1,000 Da with an interscan time of 3 s. 

XH NMR was as fast as 300000 times a second. It is interesting if the shuttling speed can be controlled by light or an electrochemical method [96]. Bissell et al. [97] obtained the molecular shuttle shown in Fig. 29, in which benzidine and bisphenol units act as the stations. At 229 K the tetracation bead was found to stay on the benzidine side at a probability of 86%, but when the compound was treated with an acid or oxidized electrochemically it turned out that the bead can move to the bisphenol side at a higher probability. 

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