Azobenzene, reactant

Figure 23. (a) Schematic representation of an anionic surfactant azobenzene derivative monolayer film at the air-water interface. (i>) Schematic representation of the stable monolayer film formed from the polyion complex of anionic surfactant azobenzene derivatives with a cationic polymer. Note the difference in free volume around the reactant chromophores in the two monolayers. 

Oxidation of arylamines, nitroso compounds, and azobenzenes. Several 2,6-di-haloanllines have been oxidized successfully to the nitroso compounds with 30% hydrogen peroxide in acetic acid at room temperature. When a solution of the reactants is let stand for a time, crystals of the (dimeric) nitroso compound begin to... 

Phenylhydrazine as a reducing agent. Walther, at Dresden in 1895-96, ° observed by chance that phenylhydrazine reacts energetically with azobenzene at an elevated temperature. He heated a mixture of 0.1 mole of each reactant in abathat 125-130° and noted that evolution of nitrogen continued for about 1 hr. and then ceased. Crystallization of the residual material from an equal volume of absolute ethanol afforded white plates of pure hydrazobenzene in nearly quantitative yield. Nitrogen evolved amounted to 2.7 g. the amount expected for the following reaction is 2.8 g. ... 

In a reversible photoreaction (Scheme 3.2), such as the photoisomerization of azobenzene (Section 6.4.1), the differential rate for the disappearance of the reactant A is given by Equation 3.26, where dnVyA and drapB are the amounts of light absorbed by A and B, respectively, as defined by Equation 3.19. 

Reactions suitable for the kinetics aiming at the purpose mentioned above needs to satisfy one condition. The TST must be valid for a fairly wide range of pressure and temperature. Furthermore it is desirable that the reactant can be generated in situ and the reaction can be followed spectroscopically to obtain reliable rate constants. As the first set of reactions, thermal ZfE isomerization of three N-benzylideneanilines (benzaldehyde anUs), i.e. N-[4-(dimethylamino) benzylidene]-4-nitroaniline (DBNA), N-[4-(dimethylamino)benzylidene]-4-ethoxy-carbonylaniline (DBEA), and N-[4-(dimethylamino)benzylidene]-4-bromoaniline (DBBA), and two push-pull substituted azobenzenes, i.e. 4-(dimethylamino)-4 -nitroazobenzene (DNAB) and 4 -(dimethylamino)-2-methoxy-4-nitroazobenzene (DMNAB) as shown in Scheme 3.2 were selected. 

In particular, Russell and co-workers (37) have made extensive ESR studies on electron transfer from carbanions and nitranions to various acceptors including azobenzenes, diaryl ketones, and nitroaromatics. Some one-electron transfer processes have been investigated using a combination of electrochemical and ESR techniques (26). In these experiments, radical anions were produced electrochemically and introduced into a mixing chamber containing an aromatic electron acceptor. Electron transfer was indicated by the formation of the ESR spectrum of the resultant radical anion. It was verified that the direction of transfer between two reactants could be predicted from E0f values derived from polarographic data. 

In 1955, Terent ev and Mogilyanskii reported the catalytic oxidative coupling of aniline to azobenzene with a yield of 88%, mediated by copper chloride in pyridine (which acts as both a metal ligand and solvent) in the presence of molecular oxygen [1]. This system was subsequently used for the generation of various conjugated and nonconjugated main-chain aromatic azo polymers from primary aromatic diamines [2]. In contrast, the use of CUCI-O2 with phenol produces tars [3] as a result of the inherent properties of this reactant. Indeed, while the metal salt produces iV-centered aniline radicals that dimerize to form azobenzene... 

Azobenzene (138) and diphenylacetylene (139) (2 mol) gave 8-(l,2-diphenyl-vinyl)-2,3,4-triphenyl-2,3-dihydrocinnoline (140) [reactants mixed together at 85°C Co(N2) (PPh3)3j, portionwise (gasj) then 85°C, 2 h Such... 

Terentev and Mogilyansky [171] first reported that the air oxidation of aniUne catalyzed by cuprous chloride in pyridine gave good yields of azobenzene. Kinoshita [172,173] found that the actual oxidant was produced by air oxidation for a cuprous chloride pyridine complex. Table 8 lists some representative reactants and yields of azo compounds formed. Reaction occurs at room temperature when air or oxygen is bubbled into the reaction mixture. 

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