Benzene transition energies

Solvent — The transition energy responsible for the main absorption band is dependent on the refractive index of the solvent, the transition energy being lower as the refractive index of the solvent increases. In other words, the values are similar in petroleum ether, hexane, and diethyl ether and much higher in benzene, toluene, and chlorinated solvents. Therefore, for comparison of the UV-Vis spectrum features, the same solvent should be used to obtain all carotenoid data. In addition, because of this solvent effect, special care should be taken when information about a chromophore is taken from a UV-Vis spectrum measured online by a PDA detector during HPLC analysis. 

A calculated transition energy used to assess the polarity of a solvent. The solvent ionizing capability directly affects the position of a peak, easily measured, in the ultraviolet region of the spectrum of the complex of an iodide ion with 2-methyl- or l-ethyl-4-carbomethoxypyridinium ion. Water has a Z value of 94.6, ethanol has a value of 79.6, dimethyl sulfoxide s value is 71.1, and benzene has a value of 54. A similar polarity scale, known as x(30) values, is related to the Z value scale Z = 1.41 t(30) -E 6.92. See Solvent Effects... 

The CD of a series of eight differently-substituted analogues of 9,10-ethano-9,10-dihydroanthracen-ll-one (142 and 143) was studied experimentally and theoretically329. Alteration of the substituent(s) on the benzene ring(s) affects the transition dipole magnitude and the transition energy of the aromatic chromophore without much change in the polarization direction. 

The case of benzene is treated in the same way starting from an antisymmetrized orbital formed on an LCAO MO basis. The value obtained for the transition energy, 2687 A, is slightly greater than the experimental value, 2550 A. It is possible that the value chosen for the parameter S, namely 0.218, is slightly low. 

Exactly the same trend is obtained for the second isomerization route. An important consequence of this is that the activation energy barrier for the isomerization via methoxy and benzene transition state is found to be = +... 

Transition Energies and Spectrum. The results of the PPP calculations on the transition energies and oscillator strengths of phenyl-azide are shown in Fig. 1 -e-. The spectrum in EPA at 77 K has the same peak at 40000 cm-1 as that in n-hexane. solutions at room temperature without the remarkable vibrational structure near 35000 cm in the former. The vibrational structure corresponds to that of B2u state of benzene in the number of peaks and the Intervals as was shown in Fig. 1ft Therefore, it is considered that the transition arises from the B2u transition of benzene. The MIM calculation justified the estimation as was shown in Table 1, where the contribution of the LE function of B2u is 84 % in the Si state. The forbidden 82 transition becomes a weakly allowed one by the perturbation of azide. 

Figure lb. The comparison of the calculated values with the emerimental ones on the electronic transition energies and oscillator strengths of phet lazide. TTie Si transition has a vibraticmal structure corresponding to the five peaks of of benzene. The absorption spectrum lower than 45,000 cm was measured at 77°K in EPA. The Sj absorption is that of neat phenylazide (thin layer). 

Figure 3 Resonance energy of benzene transition from a fictitious system with three separated n bonds to the delocalized ground state.

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