Cis-azobenzene

As shown in Figure 3, the change in Rg is non-linearly related to the cis content expressed by the increase in absorbance at 4.50 nm, a characteristic absorption band of cis-azobenzene. This nonlinearity is attributed to the intrinsic nature of phase transformation occurring at a critical condition. A sudden change in Rq commences when the cis content reaches the critical value which can trigger the transformation. 

F. W. Schulze, H. J. Petrick, H. K. Cammenga, H. Z. Klinge. Thermodynamic Properties of the Structural Analogues Benzo[c]cinnoline, trans-Azobenzene and cis-Azobenzene. Z. Phys. Chem. 1977, 107, 1-19. 

The addition of cis-azobenzenes to ketenimines gives 3-imino-l,2-diazetidines which cleave to give carbodiimides and imines upon thermolysis (Scheme 4) (67JHC155, 72JHC555, 74JHC409). l,2-Diphenyl-l,2-diazetidin-3-one has similarly been reported to fragment to isocyanate and imine (56AG71). 

In a dark room, to 50 ml of a 0.78 N solution of perbenzoic acid in chloroform is added with stirring, at room temperature, 1.5 gm (0.008 mole) of cis-azobenzene. The mixture is stirred for hr. Then it is extracted in turn with three 40 ml portions of 5 % aqueous sodium hydroxide solution and one 50 ml portion of water. The chloroform solution is rapidly dried with anhydrous sodium sulfate, filtered, and evaporated at room temperature under reduced pressure. The trans isomer is separated from the desired cis isomer by slurring and filtering the resulting solid six times with 20 ml portions of petroleum ether (b.p. 40°-60°C). The residue is the desired product yield approx. 0.75 gm (50%), m.p. 87°C. 

Cis azobenzenes have been oxidized with more concentrated hydrogen peroxide solutions, as illustrated in Procedure 3-4. 

Fig. 8-2.—The planar configuration of cis-azobenzene, drawn to scale using 1.0 A for the van der Waals radius for hydrogen. Steric interactions of hydrogen atoms prevent the assumption of this configuration.

Azinphos-methyl, see O, <9-Dimethyl-S- [(4-oxo-1,2,3-benxotriazin-3 [477]-yl)methyl] phosphorodithioate, 3301 cis-Azobenzene, 3478... 

Ammonium hexacyanoferrate(II), 2572 f Arsine, 0100 Azido-2-butyne, 1469 3-Azidopropyne, 1111 cis-Azobenzene, 3478 Azoxybenzene, 3479 Barium azide, 0214 Benzenediazonium nitrate, 2268 Benzotriazole, 2262 Borane, 0135 Bromine azide, 0256 f 3-Bromopropyne, 1087 f 1,2-Butadiene, 1475 f 1,3-Butadiene, 1476 f Buten-3-yne, 1419 f 1-Butyne, 1477 f 2-Butyne, 1478 Cadmium azide, 3951 Cadmium cyanide, 0585 Cadmium fulminate, 0586 Cadmium nitride, 3954 Calcium azide, 3930 t Carbon disulfide, 0557 Chlorine dioxide, 4036 Chloroacetylene, 0648... 

Monolayers representing two-dimensional arrays of membrane-mimetic assemblies, consisting of azobenzene (poly-L-lysine) with 43 % loading of the photoisomerizable units, were prepared.1441 The compressed trans-azobenzene polymer mono-layer exhibited a surface pressure of 7 mN m 1, whereas photoisomerization of the monolayer to the cis-azobenzene state by UV light decreased the surface pressure to... 

Figure 22. (a) Photoisomerization dynamics of trans- to cis-azobenzene, indicating torsional... 

In cis azobenzene, steric factors prevent the molecule being flat owing to the interference of the two hydrogen atoms in the ortho position, and the C—N—N system (the C being in a benzene ring) is not linear, with the result that a valence bond structure of the type VIII cannot contribute to the molecular resonance. The CN bond distance is found to be 1 46 A as in the single bond and the molecule is represented correctly by the formula IX. 

Since light could not be completely excluded in the dark adsorption experiments, cis-azobenzene was present at about 1 Vn. 

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