Weak reducing agents

The requirements of a developer moiety for incorporation into a dye developer are well fulfilled by hydroquinones. Under neutral or acidic conditions hydroquinones are very weak reducing agents and the weakly acidic phenoHc groups confer tittle solubility. In alkali, however, hydroquinones are readily soluble, powerful developing agents. Dye developers containing hydroquinone moieties have solubility and redox characteristics in alkali related to those of the parent compounds. 

Explain the observation that phosphorus acts both as a weak reducing agent and as a weak oxidizing agent. 

Nitrite is a weak reducing agent and is oxidized to nitrate by strong chemical oxidants or by nitrifying bacteria. It also oxidizes reduced substances. 

Tungsten is a weak reducing agent ( ow/wo3 = —0.09 V), which can be oxidized into WOj, W2O5, or WO3. Passivation is achieved in aqueous solutions by WO3 which is stable at pH lower than 4 except in the presence of HF, which forms fluorinated tungsten complexes. Never-therless corrosion is very low in diluted ammonia. 

The C-Si bonds of aryl-, heteroaryl-, vinyl-, and allylsilanes are stable towards alco-holates or weak reducing agents, but can be cleaved under mild conditions by treatment with acids or fluoride to yield a hydrocarbon and a silyl ester or silyl fluoride. Several linkers of this type have been tested and have proven useful for the preparation of unfunctionalized arenes and alkenes by cleavage from insoluble supports. Typical loading procedures for these linkers are sketched in Figure 3.42. 

Lewis base, an oxidizing agent, and a weak reducing agent hydrogen... 

Miscellaneous Activators. A variety of other weak reducing agents have been reported to reduce the excited states of some dyes. This section will briefly summarize what is known about the mechanisms of these interactions. 

Two factors are important in determining the relative values of kd and fce-the oxidation potential of the catalyst and its Lewis acidity. In general, the ease with which transition metal complexes catalyze the decomposition of hydroperoxides is related to their redox potentials (see Table V). Hydroperoxides are strong oxidants but weak reducing agents. Hence, reaction (312) is the slower,... 

The rifamycins have some remarkable chemical properties. Rifamycin SV can be obtained from the quinone rifamycin S by treating the latter with weak reducing agents such as ascorbic acid. It is fairly stable against oxidation by air and can form a stable sodium salt. This behaviour can be ascribed to the acylamino group in position 2. Unsubstituted naphthoquinone can only be reduced under much more drastic conditions, and once in the hydroquinone form it is very sensitive to oxidation. 

Reductions in tiifiuoroaeetie acid. Borane-pyridine in refluxing benzene is a rather weak reducing agent. When used in trifiuoroacetic acid it has much stron r reducing properties. It has been used to effect a number of useful reductions, such as those shown. ... 

Useful for salts of carbonates, some oxides and some sulphides. A weak reducing agent not generally used to dissolve organic matter... 

Sodium borohydride is a weak reducing agent and fragmentation (push by N and pull by C=0) is faster. The borohydride reduces the iminium salt to a methyl group and, at the other end of the molecule, the product is the keto form of a phenol. 

Reaction in THF-d8 reveals that solvent is the source of the two hydrogens in the final product. This reaction is especially significant since it shows that per-fluorocarbons without tertiary C-F bonds are also subject to defluorination chemistry [64].Remarkably,related transformations of perfluorocarbons can be carried out using solid sodium oxalate as the (rather weak) reducing agent [76] in a flow system at 425°C. 

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