Color formation system

A final electron transfer-based color formation system is an inorgaic one. In a series of patent publications, DoMinh of Eastman Kodak describes a high... 

Another initiator system that can operate using electron transfer pathways involvers the HABI s discussed above in connection with color formation systems (see Sect. 6). Lophyl radicals were shown to be able to oxidize various leuco dye species to their colored forms. Similarly, such radicals can extract an electron from an arylamine containing hydrogens on a carbon alpha to N to form a-amino radicals capable of initiation [Eqs. (21,22)] of... 

Powdered antimony pentoxide is used primarily in plastics. Stabilizers used to prevent the particles from growing are caustic, and can react with the halogen in the formulation. This can result in color formation and a lower flame-retarding efficiency of the system. 

For most color photographic systems, development is the rate determining step, and within that step the formation of semiquinone is the slow process (37). The fate of the highly reactive QDI is deterrnined by the relative rates of a number of competing processes (38). The desired outcome is reaction with ionized coupler to produce dye (eq. 3). Typically, the second-order rate constant for this process with ionized coupler is about 10 to 10 ... 

Schebor, C., Buera, M.P., Karel, M., and Chirife, J. 1999. Color formation due to nonenzymatic browning in amorphous, glassy, anhydrous, model systems. Food Chem. 65, 427-432. 

Two of these systems were studied as models—the acetylation of choline in brain to give acetyl choline (Hebb, Nachmansohn), and of sulfanilamide (the active component in prontosil, Chapter 3) in liver (Lipmann). Sulfanilamide is rapidly inactivated by acetylation on the p-amino group and then excreted. Sulfanilamide is easily diazotized the diazonium salt formed can be coupled with N-( 1 -naphthyl)ethylenedi-amine dihydrochloride to give a pink derivative (Bratton and Marshall, 1939). This formed the basis for an elegant colorimetric assay. Only the free p-amino group reacts, so that as acetylation proceeded color formation diminished. 

Reaction of the amine with p-dimethylaminobenzaldehyde (Ehrlich reagent) or p-diethylaminobenzaldehyde to produce a colored Schiff base [23—25]. The color formation is ascribed to a resonance hybrid between a protonated Schiff base and a quinoid system (Eq. (2)) ... 

Photo-oxidation of LCV by the Pyrene-Bonded Film. The surface properties and structure of these systems should be related to the sensitizer efficiency of pyrenyl groups. Pyrene is a good sensitizer for the oxidative color formation of LCV. The singlet excited state of Py acts as an electron acceptor bringing about one electron oxidation of LCV+. The unit processes are considered as... 

Extraction. A system has been devised which allows for performing successive liquid-liquid extractions followed by reagent addition and color formation. In one application the test substance in water, after being extracted into another solvent, is backwashed with color-forming reagent, and the solution is then passed into the colorimeter for reading and recording. 

In a series of experiments in which the sugar was increasingly replaced by 2-furaldehyde in the n-xylose-glycine system, color formation increased with the initial amount of the furan added. It was concluded that both the sugar and the furan contribute to browning.101 Other experiments also... 

MacLachlan continued to investigate the invention, and Dr. Charles Yembrick and Dr. Peter Strilko, who had joined our group recently, were assigned to optimize MacLachlan s system. They did a superb job and before long we had developed coatings, which functioned reliably. Of course, it was fortunate that we had access to leucodyes that were not oxidized by phenanthrenequinone, and that the spectra of the various components had minimum overlap in the critical spectral regions required for color formation and photodeactivation. 

Our deactivation, or fixing speed, was purposely low, so that the materials could be handled in ambient light. Could we speed it up During our discussion I suggested that as we needed plasticizer to permit color formation to occur at all, perhaps we needed to consider the rapid photochemical removal of the plasticizer as a route toward a higher speed. All of a sudden, an obvious approach appeared Use a monomer as plasticizer, and polymerization to fix the system. Cescon and Cohen immediately began to purify monomers, because they were excited to demonstrate new technology. 

The bulk composition of the SAN copolymer can be determined by ultraviolet spectroscopy. Absorbances consistent with conjugated systems such as Figures 13.1 and 13.2 have been observed. Studies usually compare the UV spectra of model systems with the actual absorbances seen in SAN copolymers. The models represent chemically reasonable species based upon the starting monomers, known reactivity ratios, and oxidation and rearrangement chemistry [2]. The data are self-consistent with these criteria however, identification of all chromophores responsible for color formation in SAN copolymers is still work in progress. One source of species with extended conjugation is the cyclization of acrylonitrile triads to form heteroaromatic structures (Figure... 

---