UV data

Table 3. Spectral (Uv) Data and Redox Potentials for Selected Quinones ...

Pyridazine-3(2//)-thiones exist in the thione form (14), as is evident from an X-ray structure analysis of pyridazine-3(2//)-thione. 6-Mercaptopyridazine-3(2//)-thione is predominantly in the monothiolmonothione form (15) in aqueous solution and in the solid state, 6-hydroxypyridazine-3(2//)-thiones are in the hydroxythione form (16) and 6-aminopyridazine-3(2//)-thiones exist in the aminothione form (17) for further details see (73HC(28)755). Cinnoline-4(l//)-thiones and phthalazine-l(2//)-thione have been shown on the basis of UV data and ionization constants to exist in the thione forms. 

Little information is available at the present time on these systems, but UV data 51JCS3204 indicate that the hydroxy forms rather than the vinylogous amide forms are favoured and these systems are true hydroxyquinoxalines and hydroxyphenazines . 

From UV studies of 4-phenyl-, 4-nitro- and 4-nitroso-pyrazoles, Habraken et al. (67RTC1249,72JHC939) conclude that the 4-pyrazolyl group acts as an electron-donating group. UV spectra of pairs of 1-aryl- and 2-aryl-indazoles and their utility in the determination of isomeric structures are discussed in (67BSF2619) many other UV data on indazole derivatives can be found in (71PMH(3)67). 

Comparison of UV data for 3-aminoisothiazoles with those of reference compounds confirms that they exist in the 3-amino form. A more recent investigation of 4-aminoisothiazole (76MI41701) using deuterium exchange experiments of the type described in Section 4.01.5.2, and analysis of the symmetric and antisymmetric NH2 stretching frequencies in its IR spectrum, show that this compound also exists in the 4-amino form. 

Compilations of UV data for 1-acyl- and 1-sulfonyl-l//-azepines are available.61 These systems display three major absorptions at 210-215, 240-247 and 285-330 nm. The weak, long wavelength band, which is thought to be due to interaction of the nitrogen lone pair with the triene system, often extends into the visible region and is responsible for the orange-yellow color of many 1-substituted 1//-azepines. 2,7-Disubstituted 1/7-azepines, in which the azepine ring is in the boat conformation, are colorless.61... 

UV data of other l//-62-63 and 3//-azepines,34,64-66 2//-azepin-2-ones,67 3-hydroxy-2//-azepin-2-ones and their methyl ethers48,52 are available. 

Llrlodenine from Fractions 33-40 - Crystallization of the residue of these fractions (118 mg) from chloroform yielded 85 mg of yellow needles, mp 280-281°. The melting point, IR, and UV data were consistent with that reported for the yellow alkaloid, llrlodenine, previously reported from the heartwood (9). Direct comparison (melting point, mixture melting point, IR, and UV) with an authentic sample of llrlodenine confirmed the identity. Antimicrobial assay showed llrlodenine to be the active component present in these fractions (Table II). 

In diaryl cyclopropenones, the UV data are not very characteristic and resemble those of diaryl cyclopropenones and stilbenes as well as diaryl cyclopropenium cations, as shown in Table 8. Recently a new long-wave absorption band was found164) in diphenyl cyclopropenone [362 nm, log e = 3.06 (cyclohexane)] which was assigned tentatively to an intramolecular charge-transfer. 

The UV data of the dialkylsubstituted species 182 and 193-195 can be regarded to be more specific for the triafulvene system. 

Some aspects of the UV spectroscopy of calicenes and quinocyclopropenes deserve attention. Thus, the UV data of the tetrachloro compound 184 and the thioketal 196 suggest93 that the absorption maximum of the parent pentatriafulvene (197) should Ue close to 300 nm ... 

Hydroxy-l,2,4-thiadiazoles can exist in 3-tautomeric forms (Scheme 1). Chemical evidence suggests that the OH form 4 predominates however, UV data suggest that the lactam form 5 is the major tautomer in ethanol <1996CHEC-II(4)307>. 

The ultraviolet spectrum of triprolidine hydrochloride in 0.1N HC1 was taken with a Beckman ACTA CIII UV spectrophotometer and is shown in Figure 3.4 Table III gives the UV data for triprolidine hydrochloride in various solvents. 

Ultraviolet (UV) data are seldom reported for new pyrrolizine derivatives. Flamini et al. <2001J(P1)3069> described the optical spectra of 5-amino-3-imino-l,2,6,7-tetracyano-3//-pyrrolizines 18, which exhibit an intense broad absorption band centered at ca. 580 nm. 

UV data for the non-ionic water-soluble polysilane 41 (see Section 3.11.4.2.1.(0) were recorded in 20 different solvents.149 Selected spectra are shown in Figure 17. 

UV data shown in Table 26 clearly support our expectations. For example, the mr transition energy for cis 1,2-dichloroethylene is 42300 cm-1 while the same quantity is 41700 cm-1 in the corresponding trans molecule. The same trend is observed in the 1,2-difluoroethylenes, as well as in the 1,2-dialkylethylenes, where a distinct hypsochromic shift is observed in the comparison of trans and cis isomers. 

Spectroscopic information on R3E other than NMR chemical shifts and coupling constant are hardly available. Some UV data are reported for MessE" cations (E = Si, Sn) in benzene solution. The UV absorption in these aryl-substituted... 

The reaction of 8 with oxygen (Scheme 1) leads to the bis-carbonyl-0-oxide 10 and can be seen either as a reaction of two carbene centers or as a reaction of two radical centers, giving a bis-peroxide. The IR and UV data suggest that there is little interaction between the two carbonyl centers via the linker. 

UV data for the parent compound are still lacking. Table V gives UV data for some 6-acyl substituted imidazo[2,l-h]thiazoles. 

IR and UV data have been reported repeatedly but no systematic investigations seem to have been carried out. 

Both the parent compound and the alkyl-substituted thiazolo[3,2-h][l,2,4]triazoles show UV absorption between 240 and 250 nm. Some UV data of other derivatives are given in Table XV. 

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