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Glyoxal fluorescence

Peptides containing a tryptophan residue at the N-end can be determined by pre-column derivatization with glyoxal and RP-HPLC-FLD, as shown in reaction 9, giving single fluorescent peaks LOD 0.55-3.82 nM (SNR 3) for 100 pL injection volume221. [Pg.1080]

The lowest excited triplet states of a-dicarbonyl compounds are considerably less energetic than those of simple carbonyls. For instance the energy of the vibrationally relaxed triplet of glyoxal is 55 kcal,366 as compared to 72 kcal for formaldehyde. Irradiation of glyoxal at 4358 A populates the lowest vibrational levels of the first excited singlet, 30% of which fluoresce and 70% of which cross over to the triplet manifold.388 Almost all of the triplet molecules then decompose to formaldehyde and carbon monoxide, the phosphorescence yield being only 0.1%. [Pg.108]

Fluorination and chlorination cause a large decrease in the nonradiative decay rates. The intersystem crossing rate constant drops from 4 x 10 s for acetone to 1.5 x 10 s- - for hexafluoroacetone. For the cyclobutanone/perfluorocyclobutanone pair, the rates are 4.2 x 10 s- - and 1 x 10 s l, respectively. A similar decrease is likely for the glyoxal/oxalyl fluoride pair, where zero-pressure tp values of 2.4 ps and 24 ps, respectively, have been measured (19,25,26). The fluorescence yields of these compounds must be measured before the true extent of this effect is known. Mixed chlorofluoroacetones exhibit nonradiative rates of intermediate value, with k jR increasing at low energy excitation with increasing chlorination from 2.7 x 10 s l for chloropentafluoroacetone to 3.9 x 10 s l and 8.0 x 10 s l for dichlorotetrafluoroacetone and trichloro-trifluoroacetone, respectively (94). [Pg.46]

Radiationless Processes. There were several studies of the fluorescence and phosphorescence (253) of glyoxal at much lower pressures than were used previously, which showed that the photochemistry observed by Parmenter was primarily collision-... [Pg.50]

Fluorescence quantum yields from 12 SVLs of the glyoxal (A "Ay) state have been recently reported by B. G. MacDonald and E. K. C. Lee [J. Chem. Phys., 71, 5049 (1979)]. (After Section III.C.)... [Pg.96]

Acetaldehyde, henzaldehyde, formaldehyde, and glyoxal Rain water 5 mM Na3PO4-10 mM Na2B407, pH 8.0, 20% acetonitrile Laser-induced fluorescence 325 and 442 nm ... [Pg.651]

A tandem Kornblum ox/daf/on/imidazole formation reaction was used during the preparation of new fluorescent nucleotides by B. Fischer and co-workers.The adenosine monophosphate free acid was mixed with 10 equivalents of 2-bromo-(p-nitro)-acetophenone and dissolved in DMSO. The required pH value was maintained with the addition of DBU which also served as a base. The Kornblum oxidation of the alkyl halide yielded the glyoxal, which reacted in situ with the aromatic amine to form the desired imidazole derivative. [Pg.251]

Unlike the case of collision-induced vibrational energy transfer, collision induced rotational energy transfer seems to be free of strong restrictions on the changes in the rotational quantum numbers. When account is taken of the spectral widths of the excitation sources used, the nature of the rotation-vibration structure in the fluorescence and absorption spectra, and the possibility of resonant ener f transfer in the collision, it is concluded that the studies of Bj aniline are the weakest, those of B2 benzene better, and those of glyoxal the best available. With this hierarchy of quality of information kept in mind, the following weaker conclusions can also be obtained from the studies cited. [Pg.259]

Systematic measurements of the fluorescence quenching rates as a function of the collision partner have been carried out for a number of diatomic and small polyatomic molecules glyoxal, propynal, ... [Pg.368]

In a diatomic molecule, the s-l coupling strength is no longer proportional to the gas pressure but attains its limiting value, when collisionally broadened / levels form a statistical quasi-continuum. This corresponds to a nonzero fluorescence yield at the high pressure limit, i.e., to a deviation from the Stern-Volmer law, a phenomenon actually reported for glyoxal (Parmenter, 1976). Relatively low rates of the lattice-induced internal conversion and vibrational relaxation of diatomic fragments in rare-gas matrices may be treated in the same way (Bondybey, 1977). [Pg.386]

In 440 nm photodissociation of glyoxal using vacuum ultraviolet laser-induced fluorescence and resonance enhanced multiphoton ionization, Li et al. (2006) have confirmed the occurrence of process (III) by observing directly the internal energy in the H2 product. The v = 1 vibration level of the H2 product was the highest populated with rotational states from /= 0 to 9. Of the energy available to the H2 + 2CO products, they found 3.1% appears as rotational energy (in v = 1 state), 17.8% appears as the H2 (v = 1) vibration, and 46.8% appears as H2 (v = 1) translation. [Pg.1061]


See other pages where Glyoxal fluorescence is mentioned: [Pg.1058]    [Pg.1058]    [Pg.552]    [Pg.407]    [Pg.49]    [Pg.123]    [Pg.713]    [Pg.45]    [Pg.49]    [Pg.289]    [Pg.299]    [Pg.72]    [Pg.107]    [Pg.121]    [Pg.122]    [Pg.238]    [Pg.292]    [Pg.342]    [Pg.360]    [Pg.372]    [Pg.372]    [Pg.111]    [Pg.567]    [Pg.126]    [Pg.246]    [Pg.247]    [Pg.248]    [Pg.249]    [Pg.383]    [Pg.384]    [Pg.35]    [Pg.334]    [Pg.1057]    [Pg.246]   
See also in sourсe #XX -- [ Pg.371 ]




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