1,3-Dimethoxy-4-nitrobenzene

V in both methanol and acetonitrile. These values, combined with the doping density and the band gap of 1.12 eV for p-Si places the conduction band edge in methanol and acetonitrile at -0.85V (vs SCE). The supraband edqe redox couples chosen for the two electrolytes were 1,3 dimethoxy-4-nitrobenzene (8,=-l -0V vs SCE)for methanol, and 1 nitronaphthalene (E0=-l. 08), 1, 2 dichloro 4-nitrobenzene (E0= -0.95), and anthraquinone (Eo=-0.95) for acetonitrile. These redox couples lie from 0.IV to 0.24V above the conduction band edge of p-Si, and hence, in the conventional model, could not be photoreduced by p-Si. 

Figure 3. Photoreduction on p-Si or redox couples with redox potentials lying above the conduction band edge as determined by dark flat-band potential measurements. (a) Photoreduction of 1,3 dimethoxy-4-nitrobenzene in methanol (E0 = —1.0V vs. SCE) (b) photoreduction of anthraquinone in acetonitrile (E0 = —0.95 V vs. SCE) Ec for p-Si in both cases in the dark is —0.85 V vs. SCE (------------------------------) dark (---) light (5).

Figure 6. Wavelength dependence of the photoreduction current of 1,3 dimethoxy-4-nitrobenzene (20mMj in methanol (1M TMAC)...

The pH dependence of the regioselectivity for the nucleophilic photosubstitution of 3,4-dimethoxy-l-nitrobenzene by n-butylamine gives21 2-methoxy-5-nitro-Af-butylaniline as the major product at pH = 11 (equation 19). At pH = 12, the ratio of the major product to 2-methoxy-4-nitro-7V-butylaniline increases to 12 1 the increased selectivity is caused by hydroxide ion, which can either promote exciplex formation or act as a base catalyst in deprotonation steps following the cr-complex formation22. 

An attempt to combine electrochemical and micellar-catalytic methods is interesting from the point of view of the mechanism of anode nitration of 1,4-dimethoxybenzene with sodinm nitrite (Laurent et al. 1984). The reaction was performed in a mixture of water in the presence of 2% surface-active compounds of cationic, anionic, or neutral nature. It was established that 1,4-dimethoxy-2-nitrobenzene (the product) was formed only in the region of potentials corresponding to simultaneous electrooxidation of the substrate to the cation-radical and the nitrite ion to the nitrogen dioxide radical (1.5 V versus saturated calomel electrode). At potentials of oxidation of the sole nitrite ion (0.8 V), no nitration was observed. Consequently, radical substitution in the neutral substrate does not take place. Two feasible mechanisms remain for addition to the cation-radical form, as follows ... 

For the anode process at comparable conditions, the yield of l,2-dimethoxy-2-nitrobenzene depends distinctly on the electrical natnre of a micelle. Namely, the yields are equal to 30, 40, and 70% for the positively, negatively, and nentrally charged micelles, respectively. The observed micellar effect corroborates the mechanism that inclndes 1,4-dimethoxybenzene cation-radical and nitrogen dioxide radical as reacting species. 

Chloro-3, 5-dimethoxy-2,4,6-tri nitrobenzene or 5 -Chi oro-2,4,6-trinitroresorci nol Di methyl ether... 

For Hammett correlations for rate constants of substituted benzenes reacting with hydroxyl radicals under experimental conditions of pH 9, the elementary hydroxyl radical rate constants (l/m sec 108) containing toluene, dimethoxy-benzene, benzene, and nitrobenzene correlate with aresonance as follows ... 

Fig. 4-1. Examples of classical methods indicating a phenylpropanoid structure of lignin. (A) Permanganate oxidation (methylated spruce lignin) affords veratric acid (3,4-dimethoxybenzoic acid) (1) in a yield of 8% and minor amounts of isohemipinic (4,5-dimethoxyisophtalic acid) (2) and dehydrodiveratric (3) acids. The formation of isohemipinic acid supports the occurrence of condensed structures (e.g., /3-5 or y-5). (B) Nitrobenzene oxidation of softwoods in alkali results in the formation of vanillin (4-hydroxy-3-methoxybenzaldehyde) (4) (about 25% of lignin). Oxidation of hardwoods and grasses results, respectively, in syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde) (5) and p-hydroxybenzaldehyde (6). (C) Hydrogenolysis yields pro-pylcyclohexane derivatives (7). (D) Ethanolysis yields so-called Hibbert ketones (8,9,10, and 11).

C8H8CIN04 1-chloro-2,4-dimethoxy-5-nitrobenzene 119-21-1 495.45 43.447 1.2 13424 C8H802 2-hydroxy-4-methylbenzaldehyde 698-27-1 496.15 43.514 1,2... 

Anhydrous Cu-acetate added in small portions, with vigorous stirring, to a boiling soln. of 5-methoxy-6-(acetylamino) benzothiazole in nitrobenzene, stirring and boiling continued 2-3 min. —6,6 -diacetylamino-5,5 -dimethoxy-2,2 -dibenzothiazole. Y 75%. (P. Petitcolas et al., Bl. 1949, 108.)... 

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