Biochemie und Chemie
Refine
Document Type
- Article (4)
Has Fulltext
- yes (4)
Is part of the Bibliography
- no (4)
Keywords
- Chemiluminescence (4) (remove)
Institute
- Biochemie und Chemie (4)
- Physik (1)
The reactions of diluted aqueous solutions of SO2 resp. HSO3-ions with MnO4-or Ce4+ ions in the pH range 1-4 produce chemiluminescence in the spectral region of 450-600 nm. Measurements of the time course of the light emission and their simulation on an analog computer led to a reaction scheme in which a recombination product of primarily formed HSO3 radicals -of a lifetime of about 1 second -appears as precursor of electronically excited SO2 molecules. The participation of singlet oxygen can be excluded because at least the reaction with Ce4+ ions proceeds also in the absence of oxygen.
The thermal decomposition of 1,2-diadamantyldioxetane was studied by kinetic and spectroscopic methods. Spectra of the chemiluminescence emitted during the thermally induced decomposition of 1,2-diadamantyldioxetane, tetramethyldioxetane and trimethyldioxetane were obtained and the influence of quenchers and radical-scavengers, and the presence of "heavy atoms" in the surrounding of the emitting species was investigated. The kinetics of the decay mechanism was followed by measuring the time dependence of the chemiluminescence. The influence of radical-scavengers, quenchers and "external heavy atoms" on the kinetics was assessed. Experimental results were discussed in terms of a biradical decay mechanism.
Exposite produce chemiluminescence when heated to 50 - 70 °C or treated with nucleophilic substances at room temperature. Initiation by Piperidine in Dimethylsulfoxide allows to determine 5 nmol of Phenyloxirane in 5 ml samples.
During photooxidation of polycyclic aromatic hydrocarbons (PAH) products can be formed which develop chemiluminescence on treatment with bases. Flash photolysis experiments show that this is the case only after previous formation of cation radicals, e.g. in the presence of CCl4 as solvent or of e-acceptors in aprotic solvents. These radicals react with oxygen to peroxy-radicals which can combine to several kinds of peroxides. Primary and secondary peroxides are the sources of chemiluminescent activity.
Chemiluminescent peroxides can also be obtained by irradiation of PA H carbonyl com pounds in protic solvents under nitrogen. It is assumed that two excited CO groups combine exceptionally with their O-atom s thus creating a peroxide bond. 24 aromatic aldehydes, ketones, dicarboxylic acid anhydrides and coumarines develop chemiluminescence after illumination with wavelengths ≥ 320 nm with intensities varying 4 magnitudes of order.
The sensitivity of the photochemiluminescent method is sufficient to detect amounts of PA H and their CO derivatives in the ppb to ppm range.