Aldehydes ultraviolet spectroscopy

These structural problems are also insoluble by physical methods alone. The infrared spectrum often gives an unambiguous decision about the structure in the solid state the characteristic bands of the carbonyl or the hydroxyl group decided whether the compound in question is a carbinolamine or an amino-aldehyde. However, tautomeric equilibria occur only in solution or in the liquid or gaseous states. Neither infrared nor ultraviolet spectroscopy are sufficiently sensitive to investigate equilibria in which the concentration of one of the isomers is very small but is still not negligible with respect to the chemical reaction. 

Some of the cuticular lipids are also suitable for spectroscopic analysis. )3-Diketones absorb at 273 nm so that ultraviolet spectroscopy can be used (Tulloch, 1976). The functional groups of various fractions obtained by TLC can be confirmed by infrared analysis. Aldehydes and )8-diketones give useful shifts when examined by nuclear magnetic resonance and this technique can be made considerably more sensitive by the application of C-NMR for some wax components (Tulloch, 1976). 

Several batches of each type of aminopolystyrene functionalized with nitroform-alddiyde P-naphthylhydrazone were prepared and charactmzed by infrared and ultraviolet spectroscopy. In a typical experiment aminopolystyrene was diazmized with an excess of sodium nitrite in hydrochloric acid and then coiq>lcd with nitroform-aldehyde P-naphthylhydrazone to give a polymer-supported diarylnitroformazan (Figure 5) following the reaction pathway described earlier for synthesis of unsymmetrical... 

The concentrations of the different intermediates are determined by the equilibrium constants. The observation of immonium ions [Eq. (5)] in strongly acidic solutions by ultraviolet and NMR spectroscopy also Indicates that these equilibria really exist (23,26). The equilibria in aqueous solutions are of synthetic interest and explain the convenient method for the preparation of 2-deuterated ketones and aldehydes by hydrolysis of enamines in heavy water (27). 

If a soluble reagent containing an ultraviolet (UV)-active group or dye can be used, then it may be possible to estimate the reaction yield from the amount of unreacted reagent stiU remaining in the supernatant solution at the end of the reaction. For example, the derivatization of aldehydes and ahphatic ketones with dansylhydrazine has been monitored by fluorescence spectroscopy of the supernatant solution, and has been used to quantify the amount of supported aldehyde or ketone. 

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