Redox resin

Note 3 Use of the term redox resin is strongly discouraged. 

Treatment of the same sample with an indigocarmine-based redox resin resulted in mirrored peaks (Ir—8r) with [M + H] 16 mass units less and eluting slightly earlier than their respective N-oxide peaks. 

C-7 position will result in ions with the same m/z ratio, one of which wUl be protonated under the ESI conditions. The difference in molecular ion data between peak 4 and peaks 6 and 7 is consistent with an additional hydroxylation relative to sarracine-N-oxide and it is tentatively suggested that this extra hydroxylation is a result of hydration of the 1,2 olefinic center of triangularine-N-oxide to yield 2-hydroxysarracine-N-oxide. In support of this, the abundant presence of an ion at m/z 138 in the ESI-MS/MS spectra of peak 4, and its redox resin reduction product, can be rationalized as the 1,2-hydrated analog of the m/z 120 ion characteristically observed in the ESI-MS spectra of 1,2-dehydropyrrolizidine alkaloids [33]. In contrast to the proposed structure for peak 4, the MS/MS data for the minor, but isobaric, peak 2 clearly indicated the structural difference between the two (Figure 13.16) and suggested the extra hydroxylation of the C-9 esterifying add rather than in the necine base as with peak 4. 

Another type of redox resin comprises those obtained by loading cationic resins with ions such as Fe(III), Cu(II), or Sn(II) or by loading anionic resins with methylene blue, sulfite, or hydroquinone. Cerrai and Testa prepared columns from Kel-F powder (a porous organic material) and tetrachlorohydroquinone with a... 

Expertise in resin and polymer synthesis has made available materials which can function as solid, but insoluble, oxidizing or reducing agents they are sometimes called redox resins or electron exchangers . Their reactivity in the latter sense is due to the polymer matrix carrying functional groups which may be reversibly oxidized and reduced. Studies of these polymers have involved two main kinds of... 

Ergozhin, E.E., Mukhitdinova, B.A. Redox resins (Redoksionity), Nauka, Alma-Ata, 1983. 

The reaction rate of fumarate polyester polymers with styrene is 20 times that of similar maleate polymers. Commercial phthaHc and isophthaHc resins usually have fumarate levels in excess of 95% and demonstrate full hardness and property development when catalyzed and cured. The addition polymerization reaction between the fumarate polyester polymer and styrene monomer is initiated by free-radical catalysts, commercially usually benzoyl peroxide (BPO) and methyl ethyl ketone peroxide (MEKP), which can be dissociated by heat or redox metal activators into peroxy and hydroperoxy free radicals. 

Catalyst Selection. The low resin viscosity and ambient temperature cure systems developed from peroxides have faciUtated the expansion of polyester resins on a commercial scale, using relatively simple fabrication techniques in open molds at ambient temperatures. The dominant catalyst systems used for ambient fabrication processes are based on metal (redox) promoters used in combination with hydroperoxides and peroxides commonly found in commercial MEKP and related perketones (13). Promoters such as styrene-soluble cobalt octoate undergo controlled reduction—oxidation (redox) reactions with MEKP that generate peroxy free radicals to initiate a controlled cross-linking reaction. 

The action of redox metal promoters with MEKP appears to be highly specific. Cobalt salts appear to be a unique component of commercial redox systems, although vanadium appears to provide similar activity with MEKP. Cobalt activity can be supplemented by potassium and 2inc naphthenates in systems requiring low cured resin color lithium and lead naphthenates also act in a similar role. Quaternary ammonium salts (14) and tertiary amines accelerate the reaction rate of redox catalyst systems. The tertiary amines form beneficial complexes with the cobalt promoters, faciUtating the transition to the lower oxidation state. Copper naphthenate exerts a unique influence over cure rate in redox systems and is used widely to delay cure and reduce exotherm development during the cross-linking reaction. 

Organic peroxide-aromatic tertiary amine system is a well-known organic redox system 1]. The typical examples are benzoyl peroxide(BPO)-N,N-dimethylani-line(DMA) and BPO-DMT(N,N-dimethyl-p-toluidine) systems. The binary initiation system has been used in vinyl polymerization in dental acrylic resins and composite resins [2] and in bone cement [3]. Many papers have reported the initiation reaction of these systems for several decades, but the initiation mechanism is still not unified and in controversy [4,5]. Another kind of organic redox system consists of organic hydroperoxide and an aromatic tertiary amine system such as cumene hydroperoxide(CHP)-DMT is used in anaerobic adhesives [6]. Much less attention has been paid to this redox system and its initiation mechanism. A water-soluble peroxide such as persulfate and amine systems have been used in industrial aqueous solution and emulsion polymerization [7-10], yet the initiation mechanism has not been proposed in detail until recently [5]. In order to clarify the structural effect of peroxides and amines including functional monomers containing an amino group, a polymerizable amine, on the redox-initiated polymerization of vinyl monomers and its initiation mechanism, a series of studies have been carried out in our laboratory. 

Redox-sensitive resin 24 designed for solid-phase peptide synthesis (SPPS) [29] was prepared from commercially available 2,5-dimethylben-zoquinone in seven steps [30] and loaded to a support via a Wittig reaction. Release of the peptide occurs using two sequential mild conditions, reduction with NaBH4 followed by TBAF-catalyzed cyclic ether formation (Scheme 8) which provide orthogonality to acid sensitive reactions. 

OH redox-sensitive resin linker W (29) 0 x COOH NaBH , then TBAF COOH... 

Zheng A, Shan D, Wang B. A redox-sensitive resin linker for the solid... 

Primary driers like cobalt, lead and manganese napthenates or linoleates establish redox systems that lead to rapid auto-oxidation and cross-linking of resin. 

Another class of co-reactants leads to entirely different behavior, however. By providing a redox pathway to phthalocyanine (7), hydroquinone promotes a very different network structure, and this difference shows up clearly in Figure 4. This resin still shows the cryogenic damping peak, the +50°C peak which has been attributed to crosslinked structures is very prominent, but the Tg is hardly visible. 

Figure 9.1 Cross-sections of a typical inert or redox electrode, embedded (a) within glass, and (b) within epoxy resin. Type (b) is preferred if the metal is liable to melt or react when very hot.

Table 10.2 presents the total coke yields and the nonvaporized hydrocarbons produced over a spent catalyst obtained with different feedstocks. The catalyst used was deactivated for 20 hours, 30 ReDox cycles, and 50% steam. When the 100% vacuum gas oil (VGO) is replaced with a mixture of 5%w DMO-VGO and/or 30%w DMO-VGO an increase of 30% and 120% in the coke yields was observed. While the spent catalyst from VGO cracking does not have adsorbed hydrocarbons, the mixture with DM0 does, becoming almost 1% for the mixture with 30%w DM0. The SARA (saturates, aromatics, resins, and asphaltenes) analysis of these hydrocarbons showed a high concentration of asphaltenes. 

Np through Lr are all prepared artificially by bombardment with neutrons and/or light element ions (He-4, B-10, B-11, C-12,0-16,0-18, Ca-48, Fe-56). Some routes are presented in Table 18.1. The elements have been separated from the targets and other product species by redox reactions, ion exchange, and solvent extraction. In a typical separation, a sulfonic acid ion exchange resin is placed in a column, the tripositive ions of Am through Lr are poured into the column where they are taken up, then the column is eluted with a solution of ammonium a-hydroxybutyrate. As elution proceeds, the An+ ions come off in this order Lr-Md-Fm-Es-Cf-Bk-Cm-Am. They are detected by the distinctive energies of their radioactive emissions. 

---