Colored compounds, interaction

The red pigment isolated in crystalline form from the reaction products of 1-methyl-3,4-benzoquinone and 4-hydroxyproline ethyl ester was identified as 4-(4 -hydroxy-2 -carbethoxy-l -pyrrolidyl)-5-methyl-l,2-benzoquinone (115).283 This highly colored compound should probably be formulated as a zwitterion (116). Similar pigments can be obtained by the interaction of o-benzoquinone with proline, hydroxyproline, pyrrolidine, and glycine. Suzuki has shown... 

The TLC plate is then placed in a glass container with a solvent filled to approximately 1 cm from the bottom. The solvent will move to the top of the TLC plate as a result of capillary action. Since each compound in the mixture will have a unique way of interacting with the matrix and the solvent, some compounds will move faster towards the top of the TLC plate than others. The it /-value is the ratio of the distance of the compound has migrated divided by the distance the solvent has migrated, and has by definition a maximum value of 1. The -value tends to be constant for a given combination of compound, solvent, and matrix so that comparisons can be made between separations performed at different times. If a given compound is colored, it is easy to determine the / -value. For non-colored compounds staining methods are available (see section 1.3). 

Colored Compounds Formed by the Interaction of Glycine and Xylose... 

The final paper (44) reported the finding that nitro compounds such as trinitromesitylene and tetranitromethane give colors with aromatic hydrocarbons and amines. Saturated aliphatic compounds give no color with tetranitromethane, but unsaturated aliphatic compounds act like hydrocarbons as long as the ethylene link does not adjoin a carboxyl group. Werner concluded that the colored compounds result from the interaction of subsidiary valencies associated with the nitro group on one hand, and... 

Parallels have been proposed between the dissolution of the alkali metals in nonaqueous solvents and the interactions of alkali metals with zeolites.The sorption of sodium or potassium vapor into dehydrated zeolites produces intensely colored compounds, ranging from burgundy red to deep blue, depending upon the metal concentration. A combination of EPR,... 

Iodine forms insertion compounds with large-pore zeosils, as evidenced by X-ray diffraction and by the characteristic colors of the substances. These compounds are, however, much less stable than those of medium-pore zeosils. This hampers their further characterization. The colors indicate that, in most of the insertion compounds, interactions between the iodine molecules are present. The Raman spectrum of SSZ-24 further verifies the presence of such interactions. 

FIGURE 8.13 A representation of the melanophore lawn assay. A lawn of receptors is grown on a petri dish. Library beads are spread across the surface of the assay plate. The compounds interact with receptors on the cell lawn after photocieavage. Active compounds generate a color change on the cell lawn. The active beads are identified, isolated as single beads, and the code on each bead is chemically cleaved and analyzed by mass spectrometry. Each code is determined and associated with the compound s structure. 

Drawing Conclusions Identify the six solutions by relating your data and observations to the predicted colors and interactions. Assume that the color of an aqueous solution is generally the same as that of the corresponding solute compound, except that solutions of white compounds are colorless. 

Notice in the photo the colorful compoimds of transition metals. When placed in solutions, these compounds absorb different wavelengths of light. Visible spectroscopy uses light absorption at specific wavelengths to measure the concentration of colored compounds in solution. This method of analysis uses the interaction of valence electrons of transition elements and visible light. Because many transition element compounds are colored, this technique can be used in transition element analysis. 

Color from Transition-Metal Compounds and Impurities. The energy levels of the excited states of the unpaked electrons of transition-metal ions in crystals are controlled by the field of the surrounding cations or cationic groups. Erom a purely ionic point of view, this is explained by the electrostatic interactions of crystal field theory ligand field theory is a more advanced approach also incorporating molecular orbital concepts. 

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