Ultraviolet and visible spectra

UV/Visible Spectra of Substituted 3H-Pyrrolizin-3-ones and Related Derivatives 

Fi) 12.30 An artist s color wheel complementary colors are opposite each other on a diameter. The numbers correspond to wavelengths of hght in nanometers. 

31 The absorption spectra of chlorophylls a and b (Atlas R3), the main pigments in plants, in the visible region. Note that the chlorophylls absorb in the orange-red and blue regions and that green light is not absorbed significantly. 

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Ultraviolet and visible spectra arise from transitions between the electronic states in molecules. The terms electronic spectra and ultraviolet and visible spectra are synonymous and cover the range 200-800 mp.. The far-ultraviolet region 100-200 mp, only partially transmitted by quartz and appreciably absorbed by air, will not be considered. 

V NH band is present in the infrared spectra of both indanthrone and mono-A -methylindanthrone, (h) the infrared spectra of indanthrone and its mono- and di-A -methyl derivatives showed vC—O bands of approximately equal intensity, and (c) the ultraviolet and visible spectra of indanthrone and its A -methyl derivatives are similar. 

Addition of water across a C=N bond in a conjugated system breaks the conjugation and alters the electronic transitions. The ultraviolet and visible spectra of anhydrous and hydrated species are therefore usually dissimilar, and such differences have been used as the basis for much of the qualitative and quantitative work done on covalent hydration. 

Fig. 5.1. Typical format, absorbance versus wavelength, of ultraviolet and visible spectra. Peaks in these regions tend to be broad.

The ultraviolet and visible spectra are usually comprised of a few broad peaks at most. This is due to the fact that electronic transitions... 

The NMR spectra and dipole moments of l,2,4-triazole-3-thiones support their meso-ionic formulation (227). For example, the compound (227, R = Me, R = R = Ph) has a dipole moment of 9.1 D in dioxan solution. The effect of solvent polarity upon the ultraviolet and visible spectra of the triphenyl derivative (227, R = R = R = Ph) has been reported but no direct interpretation was made. The meso-ionic l,2,4-triazole-3-thiones (227) form hydrochlorides (234, R = H, X = Cl) and methiodides (234, R = Me, X = I) they yield 1,2,4-triazolidine-3-thiones by lithium aluminum hydride reduction. ... 

Triplet species absorb light to give higher excited triplets and thus have characteristic ultraviolet and visible spectra. This phenomenon was discovered for phosphorescent fluorescein in 1941 by Lewis and... 

Ultraviolet and visible spectra were recorded with a Beckman DK-2 or Cary 14 spectrophotometer. ESR spectra were measured with a Varian model 4500 ESR spectrometer with 100-kHz field-modulation and detection. The klystron frequency was measured with a transfer oscillator and a frequency counter. The magnetic field was measured by a proton gauss meter monitored by the same frequency counter. 

Ivancic and Rydholm 14) noted changes in lignosulfonate from a Mitscherlich cook upon various types of treatments by recording ultraviolet and visible spectra. Hydrochloric acid condensation of the lignosulfonate resulted in increased absorption throughout both spectra, and absorption increased with increased reaction time. Thus, the increase in color is reflected by structural changes recorded in the ultraviolet region. 

Resonance Energies. Resonance energies and the like have been calculated by various procedures for 1,5- and other naphthyridines.209,676,812,840 Ultraviolet and Visible Spectra. As well as those obtained from solution, such spectra of 1,5-naphthyridine have been measured in the vapor state830,1119 and the solid state.1094 Interpretation of the various bands has been proposed with assistance from magnetic circular dichroism data1153 and other sources.1016,1113,1336 Several types of calculation have been used to rationa-... 

The ultraviolet spectrum of pyrazine in cyclohexane shows maxima at 260 nm (corresponding to a tt-tt transition) and 328 nm (corresponding to a n-7r transition) in each case with vibrational fine structure the coefficients of molecular extinction are 5600 and 1040, respectively.78,79 Substitution of halogen has a bathochromic effect on the ultraviolet spectrum of pyrazine.80 A useful index of the ultraviolet and visible spectra of pyrazine derivatives is available for the period from 1955 to 1963.81 The far-ultraviolet spectrum of pyrazine... 

Charge-transfer complexes are mainly characterized by their ultraviolet and visible spectra. The ratio of their repeating units is almost unity. 

Studies carried out in solution provide strong evidence that the helical amylose-iodine complex also exists in such circumstances.11014 1141 The structure of the iodine-amylose complex has also received theoretical treatment,142 and a three-dimensional free-electron model was developed for quantum mechanical calculations. Ultraviolet and visible spectra simulated in this manner reached close agreement with experiment observations. 

The method used to observe the infrared spectra of the deposits is relatively simple. The optics of a single-beam infrared spectrometer have been modified so that light from the Nernst filament is incident nearly normally on the drum and the light that is reflected directly from the surface of the drum is focused on the slit of the spectrometer. Because of the nature of the optics and the detector it is not feasible to divide the deposit into two bands as for the ultraviolet and visible spectra. Thus a blank run in which no alkali metal is deposited has to be made to provide a reference spectrum. 

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