Halogen absorption maxima

Figure 5 (a)-(c) shows the absorption spectra of some halogenated ketones in the near ultraviolet. In the case of acetone itself the absorption may be attributed to an n - tt transition associated with the carbonyl group. The substitution of halogen atoms leads to an increase in the molecular extinction coefficient and a shift of the absorption maximum toward the red. The ketones containing both chlorine and fluorine atoms show absorption curves with some fine structure but it is not possible to find any correlation between the structure and the shape of the absorption curve. 

Physicochemical characterization of the oxidized species was primarily made working with chemically generated ones. Usually, only parameters characterizing the main absorption maximum of the colored products obtained by the action of sulfuric acid were reported. In the case of halogenated phenothiazines, systematic determinations were carried out by Rupprecht and the dependence of the position of the absorption maximum upon the amount and nature of the halogen atoms may be obtained from the data in Table IV. 

Acetone has an absorption band in the near ultraviolet with a maximum near A 2800 A, and the substitution of halogen atoms leads to a shift of the maximum to longer wavelengths with an increase in the extinction coefficient. For continuous photolysis the 3130 A emission line in the merciuy spectrum is most frequently used, and hexafluoroacetone has an absorption maximum near this wavelength . 

K = absorption constant of optical absorption maximum). The diffusion of hydrogen was followed by the same method as was employed for the halogens, using as indicator metal potassium and following the movement of the boundary K-KH (blue to colourless) through the crystal. 

This polyatomic molecule has two halogen chromophores attached to it, so that in principle it is possible to excite one of them and determine which of the halogen bonds is broken. Lee and Bersohn (192) did just this experiment. The molecule has two absorption bands, one with a maximum at 213 nm and the other with... 

Photolysis of trifluoroacetyl fluoride and chloride results in cleavage of the carbon-halogen bond. The UV absorption band of CF3C(0)C1 starts at 315 nm, with a maximum at 260 nm, while that for CF3C(0)F is blue shifted97 this may suggest that photolysis of the chloride is more important in the troposphere, while photolysis of the fluoride occurs in the stratosphere. 

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