UV spectral data

The use of direct UV spectrophotometry to measure sample concentrations in pharmaceutical research is uncommon, presumably because of the prevalence and attractiveness of HPLC and LC/MS methods. Consequently, most researchers are unfamiliar with how useful direct UV can be. The UV method is much faster than the other methods, and this is very important in high-throughput screening. 

If samples are highly impure or decompose readily, the UV method is inappropriate to use. LC/MS has been demonstrated to be a suitable detection system 

TABLE 7.21 Approximate Intraplate Errors in PAMPA Measurement  

With surfactant-created sink condition in the acceptor compartment, the amount of propranolol reaching the acceptor wells is dramatically increased (Fig. 7.57d), 

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The melting points, optical rotations, and uv spectral data for selected prostanoids are provided in Table 1. Additional physical properties for the primary PGs have been summarized in the Hterature and the physical methods have been reviewed (47). The molecular conformations of PGE2 and PGA have been determined in the soHd state by x-ray diffraction, and special H and nuclear magnetic resonance (nmr) spectral studies of several PGs have been reported (11,48—53). Mass spectral data have also been compiled (54) (see Mass spectrometry Spectroscopy). 

Selected physical data for various quiaones are given ia Table 2 Table 3 gives uv spectral data and redox potentials (Fig. 2). References 19 and 20 greatiy expand the range of data treated. 

Similarly, 3- and 4-hydroxycinnolines and their derivatives exist predominantly in the 0X0 forms (7) and (8), as supported by both pjSTa values and UV spectral data. The oxo forms for 3-hydroxycinnolines have been further supported by IR data <76MI21200>. Phthalazin-4-ones exist in the oxo form and phthalic hydrazide in the monohydroxymonooxo... 

NMR data for 4-methyloxazole have been compared with those of 4-methylthiazole the data clearly show that the ring protons in each are shielded. In a comprehensive study of a range of oxazoles. Brown and Ghosh also reported NMR data but based a discussion of resonance stabilization on pK and UV spectral data (69JCS(B)270). The weak basicity of oxazole (pX a 0.8) relative to 1-methylimidazole (pK 7.44) and thiazole (pK 2.44) demonstrates that delocalization of the oxygen lone pair, which would have a base-strengthening effect on the nitrogen atom, is not extensive. It must be concluded that not only the experimental measurement but also the very definition of aromaticity in the azole series is as yet poorly quantified. Nevertheless, its importance in the interpretation of reactivity is enormous. 

Table 19 Experimental and Calculated UV Spectral Data for Indazole...

UV Spectral Data for Some Monosubstituted Thiophenes in Alcohol... 

The electronic transitions of 5//-dibenz[6,/]azepine have been calculated using self-consistent field (SCF) methods and the results compare favorably with experimentally determined UV spectral data.36... 

Ultraviolet (UV) spectral data of compound 2 are available and have been discussed in CHEC-II(1996) <1996CHEC-II(8)707>. 

The (Z)- and ( )-styrylpyrazine structures 20j and 20k were assigned on the base of the mass, NMR, and UV spectral data. The mass spectrum of Z isomer (20j) shows a base peak (the molecular ion) at m/z 210 with a peak at m/z 133 formed by the loss of a phenyl group firom 20j. The H-NMR spectrum shows the presence of five aromatic and two olefinic protons in addition to one heteroaromatic proton and two methyl groups attached to the heteroaromatic nucleus. Ozonolysis of the Z isomer (20j) yields 3-formyl-2,5-dimethylpyrazine (487) and benzaldehyde, confirming the styryl moiety in 20j. The ( )-styryl derivative (20k) is readily isomerized to the Z isomer (20j) on exposure to sunlight (Scheme 60). Extraction of the pyrazines from I. humillis in the dark indicates that E isomer 20k is the naturally occurring product 144,145). 

The UV spectral data for each of the six isomeric naphthyridines (l)-(6), measured in methanol as solvent, are shown in Table 3. They indicate that there are strong similarities in the spectra of (1) and (4) and those of (2) and (3), but the spectra of (5) and of (6) do not resemble those of any other isomer (60JCS1790). The main features of the spectra of (1), (2), (3) and (4) are three distinct bands similar to those in the spectra of quinoline and isoquinoline. 

Table 5 UV Spectral Data for Thietane and Thiete Derivatives...

The UV spectral data for several hydroperoxo complexes in aqueous solution are shown in Table II. Intense transitions appear for all the compounds at wavelengths that are well below the 270-290 nm maxima for the superoxo complexes. This feature is particularly useful in mechanistic studies of the complex reactions involving several forms of activated oxygen simultaneously (58). 

The only collection of UV spectral data for derivatives of compound 1 show the effect of a 3-acyl or 3-aroyl substituent.23 A bathochromic shift of the longest wavelength absorption band can reach 20 nm with an aroyl substituent. The spectra of 2-phenyl-,1" 2-benzyl-, 2-benzoyl-, and 2-benzhydryl[l,2,4]triazolo[l,5-fl]pyridines,42 and of the mesoionic compounds 42-44,56 and 109200 are reported. On the triazolopyridine 3, substitu-... 

Near- and Far-UV Spectral Data for Cytosine, Uracil, and Thymine... 

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... 

The NMR spectrum for the parent unsubstituted heterocycle gives absorptions at S 8.17 (H-4), 9.78 (H-5), 9.88 (H-3) and 10.20 (H-8), /3,4 = 6Hz (73JHC1081). H NMR, IR and UV spectral data have also been reported for several pyridazino[4,5-c]pyridazine derivatives (67JHC393). Hiickel MO calculations have been made for this ring system (66JSP(19)25). 

IR and UV spectral data have been reported for 6H- 1,2,3,4-tetrahydropyrimido-[1,6-a ]pyrimidine-4,6-dione (64JOC1762). Hiickel MO calculations have also been made for this ring system <66JSP(19)25). 

A great amount of UV spectral data for a wide variety of pyrimido[4,5-selected derivatives of this ring system are shown in Table 4. 

Visible and UV spectral data have been reported for the parent unsubstituted heterocycle (62JCS493). The apparent pKa values of several derivatives of this system were determined using spectrophotometric methods. The parent heterocycle has a pKt of 2.51. Values of 1.14, -0.25, -0.53 and -0.02 were obtained for the pKa of the 2-methyl, 2,3-dimethyl, 2,3,6-trimethyl and 2,3,6,7-tetramethyl derivatives of this ring system, respectively (63JCS4304). ESR data for the parent heterocycle have also been reported (71JA5850). 

The structure of 3-arylazo-4-hydroxycoumarin (246) has been investigated (78IJC(B)295). The authors stated that IR and UV spectral data indicate (246) to exist as such in the solid state and in solution the presence of the other possible tautomers (247) and (248) was discounted. 

In spite of the proliferation of isolated UV spectral data for individual pyrroles, relatively few attempts have been made toward a systematic study of the effects of substituents upon the positions and intensities of the absorption bands. The detailed spectra of alkyl,192 409 phenyl410-414 acyl,415-417 formyl,378,418,418a and their oximino419,420 and Schiff s base421 derivatives, cyano,177,378 car-... 

All UV spectral data were obtained by measurement using a conventional UV / vis spectrometer (HP8458) with either aqueous or acetonitrile solutions of the benchmark chemicals. The spectrum of DBP was assumed to be the same as the spectrum of 2,6-di-t-butyl-4-methylphenol. Since DBP differs from this compound by only a para methyl group, the assumption of identical spectra is a good approximation and the absence of absorbance above 300 nm quite certain. Values of were calculated from the absorption at the wavelength centers X (shown in Table 15.1, and the concentration using Equation (2). 

A fourth possibility, which arose from our collaborative structural work on both models and cobalamins, is mechanism (4), an alteration in the dmbim position or Co—N (dmbim) bond length [119], UV spectral data have been used to suggest that the Co-dmbim bond is broken during catalysis, giving the so-called base-off (benzimidazole-unhydronated) form of the coenzyme [163]. Furthermore, some unconfirmed evidence exists that axial base-free Ado-Cbi+ is still a partially active cofactor [76]. 

The UV spectrum of camphor in chloroform (Fig.2) was scanned from 200 to 1+00 nm using DMS 90 Varian spectrophotometer. It exhibited a Amax at 290 nm. Also it was scanned in methanol from 200 to 1+00 nm using Varian Carry 219, and exhibited a Amax at 289 nm. Other reported UV spectral data... 

Other UV spectral data of saccharin have also been reported (lk). 

Unfortunately, ultraviolet (UV) spectral data for most of the 1,2-dioxetanes prepared over the last decade have not been reported. In the previous version of this chapter, it was highlighted that the absorption maximum (Alna 4) of 1,2-dioxetanes occurs around 280-300 nm with very small extinction coefficients tailing up as far as 450 nm. Consequently, many 1,2-dioxetanes are pale yellow in color. 

Unfortunately, UV spectral data have not been reported for 1,2-oxathietanes, /3-sultincs, /3-sultones, 1,2-oxathietes, 1,3-oxathietanes, and their S-oxides. 

The UV spectral data of known parent A,B-diheteropentalenes are summarized in Table 9. The analogous thienothiophenes and selenolothiophenes show more absorption maxima in their UV spectra than the other systems. The known progressive shift of absorption to longer wavelengths which is observed in the simple five-membered heterocycles in the sequence furan < pyrrole < thiophene < selenophene is missing since the rings are fused. 

Table 27 UV spectral data for iodine complex of li/-pyrrolo[2,3-6]pyridine (1).

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