Benzene, pentaphenyl

Chromium pentaphenyl hydrogen carbonate,2 (C6H5)5Cr.HC03. 3H20, is formed when a methyl alcohol solution of the base is saturated with carbon dioxide. The crystals are orange-red and melt at 120° C. in a bath previously heated to 100° C. By suitably drying the product mono- and di-hydrates are isolated. The crystals are readily soluble in alcohols, sparingly soluble in water, insoluble in ether or benzene. 

Chromium pentaphenyl acid anthranilate, (C6H5)5Cr.O.CO. C6H4.NH2.NH2.C6H4.COOH, is formed by the action of anthranilie acid in chloroform on the hydroxide, the temperature of the reaction being 50° C. The salt melts at 141° to 142° C., is readily soluble in methyl alcohol, sparingly soluble in chloroform, insoluble in ether or benzene. Microscopic examination reveals the compound as bright reddish-orange columns. 

Chromium tetraphenyl iodide in methyl alcohol or moist chloroform is treated with silver oxide, or the iodide is subjected to electrolysis, using an alcohol solution with a platinum or mercury cathode and a rotating silver anode. One molecule of wTater is removed by drying over calcium chloride. The base forms orange-coloured plates, M.pt. 104° to 105° C. when placed in a bath previously heated to 95° C. It dissolves readily in water or alcohols, is sparingly soluble in chloroform, insoluble in benzene or ether. Measurements of its conductivity in aqueous solution show that it is comparable in strength with the alkali hydroxides, whilst comparative tests in methyl alcohol solution show that it is a stronger base than chromium pentaphenyl hydroxide. It may readily be converted into the chloride, bromide and iodide. 

Chromium tetraphenyl hydrogen oxanilate,1 (C6H6)4Cr.02C. C0.NH.C6H5.C6H5.NH.C0.C02H, from the pentaphenyl base and oxanilic acid, yields orange-red needles, M.pt. 1-11° C., very soluble in methyl alcohol, pyridine or chloroform, sparingly soluble in ethyl alcohol, insoluble in benzene. 

The most striking photocyclization of a 1,3-cyclohexadiene is one which occurs with concomitant shift of a hydrogen atom. Irradiation of 1,2,3,4,-5-pentaphenyl-l,3-cyclohexadiene (Formula 359) in the absence of oxygen in benzene solution gives l,2,3,5,6-pentaphenylbicyclo[3.1.0]-hex-2-ene (Formula 360) (158). 

Fig. 15. (a) Normalized pure-exchange CODEX intensities E(tm) as a function of tm for the aromatic ternary CH and the quaternary Cquat in Td-G2(-Me),6 dendrimer (T=363K). The fit curve for the ternary carbons is a stretched exponential cxp[—(rln/rcyi with /I = 0.51 and tc = 401 ms. The dotted line indicates the final CODEX exchange intensities, (b) Motional model of the localized, cooperative dynamics in polyphenylene dendrimers, including two-site jumps of all phenyl substituents of a pentaphenyl benzene building block. As indicated by X-ray analysis and computer simulations, the peripheral aromatic rings are inclined by 30° with respect to an axis normal to the face of the central benzene ring. For details, see ref. 44. 

Pentaphenylbenzene is formed in 99% yield when a mixture of l,2,3,4,5-pentaphenyl-l,3-hexadiene and chloranil in benzene is irradiated under nitrogen for 2.5 h by a mercury vapor lamp.130... 

The first product of the interesting pentaphenylation is o-phenylphenol (50). It was found that o-phenylphenol (50) undergoes not only monophenylation, but also diphenylation on treatment with iodobenzene at the C-2 positions to give 51 and 52 by the use of PdCb and CS2CO3. The fact that the monoarylated product 51 (25 %) and the diarylated product 52 (62 %) were obtained by the treatment of 2-phenylphenol (50) with 4 equivalents of iodobenzene shows that the arylation of benzene ring is faster than the arylation of ortho carbon of phenol under these conditions [16]. Similarly, when the reaction of bromobenzene with 50 in xylene was stopped after a short time, 2-(biphenyl-2-yl)phenol (51) was obtained in high yield, but 2,6-diphenylphenol was not formed [15]. 

The transfer constants (ox solvents vary by several orders of magnitude, from 2 X 10 for styrene in benzene to 5 700 for vinyl acetate in carbon tetrabromide. The constants increase with the number of transferable atoms per solvent molecule (series benzene-toluene-ethyl benzene), the weakness of the bond (carbon tetrachloride and carbon tetrabromide), and the resonance stabilization of the free radical produced (benzene-fluorene-pentaphenyl... 

The solvent transfer constants vary by several orders of magnitude (Table 20-7). The more readily transferable atoms that there are per molecule (H in the benzene, toluene, ethyl benzene series), the weaker the bond (carbon tetrachloride, carbon tetrabromide), and the more resonance-stabilized the resulting radical (triphenylmethane, fluorene pentaphenyl-ethane), the higher is the transfer constant. 

C5nHs9OP, 9-Oxo-1,2,3,4,9e-pentaphenyl-9H-tribenzo[b,d,f]phosphepine benzene solvate, 44B, 641... 

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