Ultraviolet-visible spectroscopy table

Table 7.9 Electronic Absorption Bands for Representative Chromophores Table 7.10 Ultraviolet Cutoffs of Spectrograde Solvents Table 7.11 Absorption Wavelength of Dienes Table 7.12 Absorption Wavelength of Enones and Dienones Table 7.13 Solvent Correction for Ultraviolet-Visible Spectroscopy Table 7.14 Primary Bands of Substituted Benzene and Heteroaromatics Table 7.15 Wavelength Calculation of the Principal Band of Substituted Benzene Derivatives...

TABLE 7.13 Solvent Correction for Ultraviolet-Visible Spectroscopy... 

The section on Spectroscopy has been retained but with some revisions and expansion. The section includes ultraviolet-visible spectroscopy, fluorescence, infrared and Raman spectroscopy, and X-ray spectrometry. Detection limits are listed for the elements when using flame emission, flame atomic absorption, electrothermal atomic absorption, argon induction coupled plasma, and flame atomic fluorescence. Nuclear magnetic resonance embraces tables for the nuclear properties of the elements, proton chemical shifts and coupling constants, and similar material for carbon-13, boron-11, nitrogen-15, fluorine-19, silicon-19, and phosphoms-31. 

Fourier transform methods have come into their own as a means of studying the optical spectra of gas-phase radicals. Both infrared (FTIR) and ultraviolet/visible spectroscopy (FTUV/VIS) are now used to scrutinize these reactive molecules. We discuss the underlying principles of Fourier transform spectroscopy (FTS) with particular emphasis on the advantages and drawbacks of FTIR and FTUV/VIS measurements. Extensive tables are presented of metastable molecules that have been studied by Fourier transform methods. 

Most physical properties of oxazoles have now been extensively explored. This chapter serves as an overview of the most important areas and updates the previous edition, in which the spectroscopic chapter remains relevant in aU details. NMR (surely now the single most important technique to the practicing organic chemist) is covered first and in the most detail, followed by a review of mass spectrometry, infrared and ultraviolet/visible spectroscopy, microwave spectroscopy, and other techniques. This order parallels that used in the previous edition, with some changes the proton and carbon NMR tables have been expanded, oxygen and fluorine NMR are now covered, as are microwave spectroscopy and other methods, such as photoelectron spectra. 

There have been relatively little ultraviolet-visible (UV-Vis) spectroscopic data for 1,4-oxazines, but selected data are presented in Table 8. UV spectroscopy is important for photochromic compounds, such as spirooxazines. The UV spectra of 33 spirooxazines in five different solvents are collected in a review <2002RCR893>, and the more recently reported examples of photochromic oxazines 65, 66, 101, and 102 are shown here. It can be seen from Table 8 that both adding methoxy substituents to the oxazine and changing to a more polar solvent give a UV maximum at a higher wavelength. This solvent effect can also be seen in the case of 102, which also has important fluorescence properties, discussed in Section 8.06.12.2. 

The spectroscopy experiments are further subdivided into atomic spectroscopy found in Table XII, infrared and Raman spectra found in table XIII, visible and ultraviolet absorption spectroscopy found in table XIV, and luminescence spectroscopies found in table XV. 

Table XIV. Visible/Ultraviolet Absorption Spectroscopy Experiments...

Ultraviolet-visible (UV-Vis) spectroscopy was used to monitor synthesis and decomposition of dithiiranes 25a with an absorption maximum at 442 nm, and 25b with an absorption maximum at 438 nm <1995TL1867>. The UV-Vis spectra of dithiiranes 21, 8, 23a, and 22 reveal the absorption maximum in a range of450-455 nm due to the S-S bond <2003JOC1555>. UV-Vis spectroscopic data for dithiiranes are collected in Table 1. 

It is perhaps surprising not that the values vary, but that they are as close as they are. Values of DH° for a small number of specific bonds have been determined with difficulty using such techniques as mass spectrometry, and ultraviolet and visible spectroscopy. On the whole, however, accurate values are rather few and far between, and as there are far more bonds than there are chemical compounds, the prospect for complete tables of DH° is slight indeed. 

Time-resolved spectroscopy (stopped-flow ultraviolet-visible (UV-vis) spectroscopy at -90° C, proprionitrile or acetonitrile, [O2] S> [complex]) has been used to characterize intermediates and evaluate the mechanism of the peroxo complex formation (see Fig. 16) (196). Based on the similarity of the spectral features with known superoxo copper(lI) and peroxo-dicop-per(ll) complexes (262, 268, 281) the mechanism shown in Scheme 17 was proposed, and the spectra of the superoxo copper(II) and peroxo-dicop-per(II) complexes were determined (see Table XI). For steric reasons and in... 

Table 2.1 summarizes the regions of the spectmm and the types of energy transitions observed there. Several of these regions, including the infrared, give vital information about the stmctures of organic molecules. Nuclear magnetic resonance, which occurs in the radiofrequency part of the spectrum, is discussed in Chapters 3,4,5,6 and 10 whereas ultraviolet and visible spectroscopy are described in Chapter 7. 

Some transitions require more energy than others, so we must use radiation of the appropriate frequency to determine them. In this chapter, we will discuss three types of spectroscopy that depend on such transitions. They are nuclear magnetic resonance (NMR), infrared (IR), and ultraviolet-visible (UV-vis) spectroscopy. Table 12.1 summarizes the regions of the electromagnetic spectrum in which transitions for these three types of spectroscopy can be observed. We will begin with NMR spectroscopy and nuclear spin transitions, which require exceedingly small amounts of energy. 

Sets of buffers that are nearly transparent down to 240 nm have been developed for use in ultraviolet and visible spectroscopy (Perrin, 1963). Their low and constant ionic strength of 0.01 and pH range (2.2 to 11.6) make them suitable for spectrophotometric pAa determinations because only small, constant corrections are needed to convert experimental pAa values to thermodynamic ones. Buffer compositions are given in Table 3.8. Other buffers suitable for ultraviolet spectroscopy include those based on 77-ethyl-... 

For detailed consideration of the relationships between chemical constitution and the absorption of visible/ultraviolet radiation, textbooks of physical chemistry or of spectroscopy should be consulted.12-17 A table of Amax and max values is given in Appendix 10. 

In addition to the IR, Raman and LIBS methods previously discussed, a number of other laser-based methods for explosives detection have been developed over the years. The following section briefly describes the ultraviolet and visible (UV/vis) absorption spectra of EM and discusses the techniques of laser desorption (LD), PF with detection through resonance-enhanced multiphoton ionization (REMPI) or laser-induced fluorescence (LIF), photoacoustic spectroscopy (PAS), variations on the light ranging and detecting (LIDAR) method, and photoluminescence. Table 2 summarizes the LODs of several explosive-related compounds (ERC) and EM obtained by the techniques described in this section. 

Solvents used for visible-ultraviolet spectroscopy may be used only for wavelengths greater than some ultraviolet cutoff wavelength Xc, below which the solvent absorbs strongly. These cutoff wavelengths /,c are listed with some other useful data in Tables 11.3 and 11.4. 

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