Selenium absorption spectra

Hexahydrobenzoyloxodedelphonine acetate (VI) was dehydrogenated by selenium at 330° and gave as chief product a hydrocarbon, b.p. 90°/0-02 mm., whose composition, ultra-violet absorption spectrum and chemical properties, so far as examined, indicate that it may be a bicyclopentenobenzene and therefore in a different category from the phenanthrene hydrocarbons yielded by the atisine group of bases. 

The UV absorption spectrum of benzoisotellurazole is similar to those of its sulfur and selenium analogues, all absorption bands of the former being bathochromi-cally shifted relative to the latter compounds. The NMR signal of the H-3 proton... 

Beckmann, Zeitsch. physikal. Chem., 1910,70,1 also Ramsay, Bull. Soc. chim., 1890, [iii.], 3, 783. Por the absorption spectrum of selenium monoehloride vapour, see Gernez,... 

The absorption spectrum of selenium dioxide vapour contains groups of lines, particularly in the blue and violet.2... 

A photometric titration of selenium and S20eF2 established the oxidation state of the yellow species as + conductometric measurements showed that two fiuorosulfate ions are produced per four selenium atoms and the molecular weight of Se was established by cryoscopy. The absorption spectrum of the yellow 804 solution in HSOgF is shown in Fig. 4. 

The most important experimental fact, however, reported for any of the miscellaneous bases concerns the unnamed base recently (90) isolated, which accompanies delphinine and staphisine in D. staphisagria. This base, which may not be correctly formulated, on dehydrogenation over selenium jdelds a crystalline hydrocarbon (CisHie), the ultraviolet absorption spectrum of which indicates the presence of a phenanthrene structure. The fact that the presence of a phenanthrene system can be established both in this new base and in staphisine, i.e., in both minor alkaloids accompanying delphinine, whilst delphinine itself does not readily yield a phenanthrene derivative on dehydrogenation (70), should stimulate further research in this field. If the reason for this difference in behavior can be ascertained, it should permit a better imderstanding of the nature of the polycyclic skeleton present in the atisines and in the aconitines and result in a great advance towards the complete elucidation of the structures of the Aconitum and Delphinium alkaloids. 

Figure 8.30 Time-resolved absorbance spectrum of a human urine sample in the vicinity of the selenium absorption line at 196.026 mn (a) without correction (b) after subti-action...

Tile photolysis (A = 365 nm) of 42 alone resulted in a very slow conversion to the 1,4-dithiin 259, whereas the irradiation in the presence of nor-bornene quickly produced 260 in 95% yield (88CL657).Tlierefore, the conversion of 42 to 261 (or 262) and sulfur atom should be reversible. Tlie photolysis of 263 in 3-methylpentane at 77 K yielded a mixture of 261 and 262, as suggested by the electronic spectrum, which showed two absorption maxima at 580 and 370 nm (89TL2955). Similar results were also obtained for selenium species (88CL657 89TL2955). 

The UV spectral data of various A,B-diheteropentalenes are presented in Table 2. The systems containing only sulfur and/or selenium show more absorption maxima in their UV spectra than those molecules possessing one or two nitrogen atoms. The UV spectrum of the quinonoid thieno[3,4-6]thiophene is in marked contrast to the UV spectra displayed by thieno-[2,3-6]- and -[3,2-6]-thiophenes (67TL761). The analogous, known... 

Atomic selenium was monitored in flashed CSe2 by kinetic absorption spectroscopy, and its rate of reaction with ethylene was measured in the temperature range 302-412 K. The rate of appearance of a new spectrum in the far ultraviolet (intense bands at 2259 and 2208 A) was symmetrical with atomic decay, and was assigned to ethylene selenide, i.e. selenirane (1) (Equations (la) and (lb)). Absorption spectra of flashed CSe2 and alkene mixtures show band systems in the 2000-2300 A region which do not occur in flashed saturated-hydrocarbon and CSe2 mixtures. The band centers obtained from their spectra are listed in Table 4. 

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