Solutions azulene

Charge items 1 and 2 in a suitable mixing vessel and heat to 60°C. 

In a separate vessel, heat item 3 to 60°C and then add to step 1. Mix well for a clear solution. 

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Another probe of the local environment around the azulene solute molecule was the shift of the frequency of the S3 Sq absorption band, as a function of density. This solvachromic shift, or stabilization of the electronic states of the solute in the presence of the solute, was accurately described using the same radial distribution function used to reproduce the collisional deactivation rates. The applicability of the same radial distribution function to treat collisional deactivation and solvachromic frequency shifts suggests that both have a similar dependence on local density. 

The participation of higher excited singlet states (Sn, n > 1) of molecules in photophysical (Sn SQ fluorescence (FL)) or photochemical (photoinduced electron transfer (PET), isomerization, etc.) processes, which compete with radiationless deactivation, manifests itself in the dependence of the quantum yield (q>) and FL spectra on the wavelength of the exciting light (the violation of the Vavilov law). Such processes were first shown for the FL of azulene solutions due to the transition from the second excited level to the ground state S2 -> S0. ... 

Azulene (2) A mixture of 2-isopropyl-4,7-climethylindane 1 (200 g, 1.91 mol) and ethyl diazoacetate (50 g, 0.5 mol] was heated for 1 h at 130°C. Vacuum distillation and recovery ol 1 (160 g) gave a brown residue which was heated with 40% NaOH (40 mL) and EtOH (200 mL). The unreacled ester was extracted with Et20 and the aqueous solution was acidified to obtain crude 2, which after distillation afforded 24 g ol 2(52%), bp t60-185°C/ 2mm. 

Polycyclic aromatic hydrocarbons, naphthylamines After application of the sample solution place the TLC plate in a darkened iodine vapor chamber (azulene a few minutes, PAH several hours). Then remove the excess iodine at 60 °C. [20]... 

When azulene is heated with sulphuric acid and acetic anhydride a sulphonic acid, soluble in water, is formed. This acid forms a fine violet sodium salt. This sodium salt is not very stable when kept for three months it decomposes into a mixture of oil and resin. Its aqueous solution gives blue precipitates with calcium and barium salts. 

The chosen eluent can then be then used for the separation of the necessary components in the usual maimer in the elution chromatography stage. The solvent flow can be monitored by spotting a dilute solution of nonadsorbed dye (e.g., azulene in case of NP systems) to the adsorbent layer. 

Sometimes the hydrocarbon is blue, probably owing to traces of an azulene. The contaminant is easily removed by dissolving the hydrocarbon in an equal volume of hexane or petroleum ether and shaking this solution with an equal volume of 85% syrupy phosphoric acid until the color has been removed. The hydrocarbon is then obtained on evaporation of the solvent it does not need redistillation. 

The quasi-aromatic azulenes dissolve in 50-60% sulfuric acid, a property used in their isolation. The sulfuric acid solutions are yellow to orange rather than blue like the parent hydrocarbon, and they are... 

Photoreduction was quenched by high concentrations of biacetyl, slightly retarded by iodonaphthalene, but not affected by azulene or anthracene.113 These observations led to the unsatisfying conclusion that reduction proceeded via a triplet state which could be only selectively quenched. However, later work114 using flash photolysis showed that the benzophenone ketyl radical was generated upon irradiation of solutions of benzophenone and acridine, and that its predominant mode of disappearance was by reaction with... 

Azulene. The absorption spectrum of azulene, a nonbenzenoid aromatic hydrocarbon with odd-membered rings, can be considered as two distinct spectra, the visible absorption due to the 1Lb band (0-0 band near 700 nm) and the ultraviolet absorption of the 1L0 band.29 This latter band is very similar to the long wavelength bands of benzene and naphthalene CLb) and shows the same 130 cm-1 blue shift when adsorbed on silica gel from cyclohexane.7 As in the case of benzene and naphthalene, this blue shift is due to the fact that the red shift, relative to the vapor spectra, is smaller (305 cm"1) for the adsorbed molecule than in cyclohexane solution (435 cm"1). Thus it would appear that the red shifts of the 1La band are solely due to dispersive forces interacting with the aromatic molecule, in agreement with Weigang s prediction,29 and dipole-dipole interaction is negligible. 

Direct irradiation of the (CH)10 hydrocarbon triquinacene (26) in pentane solution gave five different (CH)10 isomers along with some naphthaline and azulene. The two major products were pentacyclo[4.4.0.02 4.03 i0.05,9]dec-7-ene (27), arising from an intramolecular [2 + 2] cycloaddition, and hexacyclo[4.4.0.02,4.03,10.05,8.07 9]decane ( barettane , 28), which is formed via a di-n-methane rearrangement (see Section l.A.2.2.) followed by an intramolecular [2 + 2] cycloaddition,50... 

More recently, photochemical reactions of 138 with cyclic and acyclic olefins have been described. When 138 is irradiated (Pyrex) with cyclo-heptatriene, [4 + 4]- and [4 + 6]-adducts (247-250, Scheme 16) are obtained in addition, photodimer 242 and o-dibenzoylbenzene (140) were isolated. The ratio of the [4 + 6]-adducts to the [4 + 4]-adducts [(249 + 250)/(247 + 248)] is increased in air-saturated benzene solutions compared with oxygen-free benzene solutions, and enhanced in heavy atom solvents (e.g., chloroform compared with cyclohexane) furthermore, this ratio is decreased in the presence of the triplet quencher azulene. These observations suggest that [4 + 6]- and [4 + 4]-adducts are formed by different mechanisms. 

Azulene has weak absorption in the visible region (near 7000 A) and more intense band systems in the ultraviolet. The first ultraviolet system, which commences at about 3500 A, has been examined in substitutional solid solution in naphthalene (Sidman and McClure, 1956) and in the vapour state (Hunt and Ross, 1962), and can be observed in fluorescence from the vapour (Hunt and Ross, 1956). Theory predicts that the transition is 1Al<-lAl(C2K), i.e. allowed by the electronic selection rules with polarization parallel to the twofold symmetry axis (see, e.g., Ham, 1960 Mofifitt, 1954 Pariser, 1956b). The vibrational analysis shows that the transition is allowed but does not establish the axis of polarization. The intensity distribution among the vibrational bands indicates a small increase in CC bond distance without change in symmetry. 

Figure 3. Regression line of the solution reduction potential versus the hmo-lumo energy (eLUM0, / negative) for a series of benzenoid hydrocarbons (Streitwieser Schwager 1962 Streitwieser 1962). The half-wave potentials for azulene (1), acepleiadylene (2), pyracyclene (3), and C60 are also shown (see text).

The well known anomalous fluorescence from S2 has been interpreted in terms of a much slower radiationless transition out of S2 than Si, such that for Si the fluorescence lifetime is severely shortened relative to the radiative lifetime. The anomaly is related to the unusual energy disposition of the two lowest excited singlet states. Hochstrasser and Li wished to ascertain whether the spectral linewidths were consistent with this interpretation and also whether the Si linewidths of azulene-ds were narrowed in comparison, as theoretically predicted. Their results are listed in Table 1. The spectral resolution was claimed to be <0.15 cm-1 as linewidths in the S2 system corresponding to the observed fluorescence lifetime are of the order of 10-4 cm-1, the linewidths of 0.50 cm-1 measured must be considered crystal-imposed. It is assumed that the maximum crystal inhomogeneity contribution to the Si linewidth is similarly 0.50 cm-1. This leads to a line broadening due to rapid nonradiative electronic relaxation of 1.61 (-hs) and 1.27 (-da) cm-1 as compared to 0.64 cm-1 (-hs) determined by Rentzepis 50> from lifetime studies of azulene in benzene solution at 300 K. 

Rate coefficients, DjO solvent isotope effects, and carbon-13 isotope effects in the decarboxylation of azulene-l-carboxylic acid and 2,4-dihydroxybenzoic acid in solutions of moderately concentrated strong acids... 

The constancy of k in the acidity region above 3.5 M HC1 indicates a change of the rate-determining step. In that region, the transition state formed by carbon—carbon bond cleavage in X contains as many protons as the main form of the substrate in the solution, HS, and consequently, the rate must be independent of [H30+] or h0. Additional evidence for carbon—carbon bond cleavage in the slow step in solutions with H0 values below —1.3 may be obtained from results of carbon-13 [247] (Table 22) and D20 solvent isotope effect [259] studies (Table 24). The value of h2o/ d2o decreases from 2.0 in 1 M HC1 to 1.3 in 4 M HC1, and remains constant if the HC1 concentration is increased further, in a very similar way as in the example of the decarboxylation of azulene-1-carboxylic acid. 

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