Simple Chromophoric Groups

Some of the simple chromophoric groups, together with the absorption maxima of simple compounds containing these groups, are collected in... 

A uv or visible absorption peak is caused by the promotion of an electron in one orbital (usually a ground-state orbital) to a higher orbital. Normally the amount of energy necessary to make this transition depends mostly on the nature of the two orbitals involved and much less on the rest of the molecule. Therefore, a simple functional group such as the C=C double bond always causes absorption in the same general area. A group that causes absorption is called a chromophore. 

Table 4.4. Characteristics of Simple Conjugated Chromophoric Groups...

Steroid hormones, especially those containing the A S-keto-chromophore group, are frequently marketed in the form of oily injections. Direct determination of the active ingredient content using the CD method is conveniently done by measuring the ellipticity of an aliquot of the injection after the very simple process of dilution with an appropriate solvent [22]. Problems that might arise in these analyses and the recommended method of examination are discussed in the case of an oily injection that contains testosterone phenylpropionate. 

The name phenylosazone formazan is suggested for this group of compounds, of which a few simple representatives have been known for some time, such as those where R = CH3 or R = CO2H however, these were not made from osazones, but by treatment of the corresponding a-keto-formazans with phenylhydrazine (as shown in the lower left of the above equation). For example, pyruvaldehyde phenylosazone formazan (C-acetyl-A, A -diphenylformazan phenylhydrazone) was prepared by Bamberger and Lorenzen as early as 1892 by condensation of acetyl-formazan with phenylhydrazine. The violet or brownish-black color characteristic of all known compounds of this group can be attributed to the three chromophoric groups present in the structure. 

The fact that the formazan is formed ehminates structures XVII, XVIII, and XXI, which do not meet the conditions for this reaction. This fimiishes dired evidence in place of the indirect evidence on which Hardegger and Schreier had discarded structures XVIII and XXI. The bicyclic structure XIX, and XX, proposed by Percival" can be dismissed on comparison of the ultraviolet spectra. This compound, after coupling, should contain the two chromophoric groups of the simple formazans, whereas osazone formazans contain three of them. Anhydro- D-glucose phenylosazone formazan and its diacetate display practically the same maxima (maxima at 335 and 405 ran and 340 and 405 m/x, respectively) as does the indisputably-acyclic pyruvaldehyde phenylosazone formazan (maxima at 335 and 410 m/t), and these peaks differ substantially from the values for the simple sugar for-... 

Dyes have many diverse structures since chromophore groups may be attached to all aromatic molecules. A comprehensive review of hepatic dye uptake and biliary dye excretion has been published (C12). A simple classification, based on the anionic or cationic nature of the dye and its chromophore group, is applied, but such a classification may not be... 

Photodegradation is a result of the absorption of UV light that leads to molecules in the excited states, which undergo reaction. When molecules are present that take over the energy from the excited polymer and release this energy in a harmless form, an increased stability can be expected. This can be represented by a simple mechanism in which an excited chromophoric group (P ) is deactivated by a stabilizer molecule (Q)... 

Radiative and Nonradiative Decay Processes - The use of cyclodextrins or surfactant dispersions to promote room-temperature phosphore ence from organic molecules is a particularly simple but elegant way in which to characterise triplet excited states. This field has been greatly extended by the synthesis of modified cyclodextrins bearing chromophoric groups that can be included into the cavity.Additional studies have reported binding constants for the... 

CD derivatives have wide applications in analogue enzyme and analysis chemistry. CD derivative with special functional group can be used as a simple enzyme model which is convenient for studying the action mode and functional groups of the enzyme. The fluorescent and chromophore groups linked to the CDs can be seen as an indicator or a probe which are beneficial for separating the isomers and enantiomers. 

Most of the methods commonly used for the characterization of the molecular structure of organic molecules can be applied to the identification of polymers—in particular, conventional absorption spectroscopies (NMR, IR, UV-visible). However, it is important to point out that the determination of the copolymer composition by UV spectroscopy can lead to erroneous values as a matter of fact, interactions between local chromophoric groups can modily the values of the overall molar extinction coefficients as compared to those of simple molecules taken as models. 

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