Physical and Spectroscopic Properties

The He(I) photoelectron, 14N-NMR, and high-resolution H-NMR spectra of indoxazene have been measured and are reproduced in references 33, 34, and 35, respectively. 

A study has been made of the chemical shifts of the methyl group in a comprehensive series of quaternized azoles and their benzologs, N-methyl-indoxazenium perchlorate being one of the compounds reported.36 

Analysis of metastable ion abundancies and shape has demonstrated that indoxazene isomerizes into o-cyanophenol prior to fragmentation in the mass spectrometer.37 

Calculations, by variable integral methods, of n-n transitions for indoxazenes are in good agreement with experimental data.38 Ultraviolet spectra of 3-hydroxyindoxazenes and of several indoxazene-3-carboxylic acids are available.8,23 On the basis of ultraviolet studies it is concluded that indoxazenes are weaker bases than the corresponding isoxazoles.39 Similar 

Vincent, J. Chim. Phys. Physicochim. Biol. 69, 860 (1972). 

Investigations of physical properties in solution as well as in the solid state have been predominantly carried out on C q, and to a minor extent on C70, since these are the most abimdant fullerenes. Currently, little material is available for the higher fullerenes or endohedrals, because it takes about 250 h to produce 1 mg of any of these [269]. 

To chemically modify fullerenes, in most cases it is necessary that they are in the solution. For extractions or chromatographic separations the solubility also plays a crucial role. The solubility of Cjq in various organic solvents has been investigated systematically (Table 1.5) [286-289]. 

In polar and H-bonding solvents such as acetone, tetrahydrofuran or methanol CgQ is essentially insoluble. It is sparingly soluble in alkanes, with the solubility increasing with the number of atoms. In aromatic solvents and in carbon disulfide, in general appreciable solubilities are observed. A significant increase of the solubility takes place on going from benzenes to naphthalenes. Although there are trends for the solution behavior of Cjq, there is no direct dependence of the solubility on a certain solvent parameter like the index of refraction n. When the solubility is 

The fullerenes, in particular Cgg, exhibit a variety of remarkable photophysical properties, making them very attractive building blocks for the construction of photosynthetic antenna and reaction center models (Table 1.6) [292-295], 

Solid CgQ forms a face-centered-cubic (FCC) structure at room temperature [244, 297, 298]. The density in the solid state is 1.72 g cm [299]. Four equivalent molecules are contained in a unit cube with edge length a = 14.17 A, at the origin 

The pyrazine ring may be represented as a resonance hybrid of the following canonical structures. 

Interatomic distances as calculated from the analysis of the rotational fine structure of the ultraviolet spectrum are C-C, 1.395 A C-N, 1.341A and C-H, 1.085 A.66 These are very similar to the bond lengths for pyridine which are C-2-C-3, 1.3945 A C-3-C-4, 1.3944 A and C-2-N, 1.3402 A. The C-N-C bond angle in pyrazine is 115° and the C-C-N bond angle 122.5°.56,67 A delocalization energy for pyrazine of ca. 18 kcal/mole is indicated from heats of combustion data.68 The C=N bond energy in 2,2,5,5-tetramethyl-2,5-dihydropyrazine has been calculated to be 130.3 kcal.58a 

The 7r-electron density distribution in the pyrazine ring has been calculated,59-61 and compared with that of the pyridine ring.3 These figures indicate an increase in 7r-electron density at the nitrogen atoms and a depletion of 7r-electron density at the carbon atoms. The values for charge distribution vary slightly with the method of calculation 

Palmer, The Structure and Reactions of Heterocyclic Compounds, p. 66. Arnold, London, 1967. 

Calculations by the self-consistent field LCAO-MO method for the ground state wave function of the pyrazine molecule indicate that the lone pairs are quite different. The lower lone pair is little delocalized (1.88 electrons on nitrogen), but the second lone pair is as delocalized as the lone pair in pyridine with 1.37 electrons on nitrogen, 0.22 electrons on hydrogen, and 0.40 electrons on carbon.63 

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The unique chemical, physical, and spectroscopic properties of organosiUcon compounds are reflected in the analytical methodology used for the detection, quantification, and characterization of these compounds. Several thorough, up-to-date reviews dealing with analytical methods appHed to siUcones have beenpubhshed (434—436). 

The review by Takeuchi and Ferusaki is quite encompassing and, in addition to synthesis and reactivity, the physical and spectroscopic properties of isoxazolidines are discussed in detail. Additional spectral studies on the parent and derivatives include H NMR (68MI41600, 77H(7)201, 78IZV850). 

Tire purpose of this chapter is to review the chemistry of the nitro-1,5-, -1,6-, -1,7-, and -1,8-naphthyridines (1) [nitro-2,6- and nitro-2,7-naph-thyridines (2) are unknown], with special attention to the results obtained in the laboratories of both authors. Tliis article mainly refers to the synthesis and reactivity of the nitronaphthyridines their physical and spectroscopic properties and biological activity are only covered briefly. For the convenience of the reader a table listing melting points of (di-)nitronaph-thyridines and some derivatives is included (Table III). Tire literature to about 1998 has been covered. 

The completion of the total synthesis only requires a few deprotection steps. It was gratifying to find that the final deprotections could be conducted smoothly and without compromising the newly introduced and potentially labile trisulfide residue. In particular, exposure of intermediate 101 to the action of HF pyridine results in the cleavage of all five triethylsilyl ethers, providing 102 in 90% yield (Scheme 23). Finally, hydrolytic cleavage of the ethylene ketal with aqueous para-toluenesulfonic acid in THF, followed by removal of the FMOC protecting group with diethylamine furnishes calicheamicin y (1) (see Scheme 24). Synthetic calicheami-cin y, produced in this manner, exhibited physical and spectroscopic properties identical to those of an authentic sample. 

Carbonyl (Physical and Spectroscopic Properties) (see also Table 19)... 

The focus is on the primary formation of bonds, not on subsequent reactions of the products to form other bonds. These latter reactions are covered at the places where the formation of those bonds is described. Reactions in which atoms merely change their oxidation states are not included, nor are reactions in which the same pairs of elements come together again in the product (for example, in metatheses or redistributions). Physical and spectroscopic properties or structural details of the products are not covered by the reaction volumes which are concerned with synthetic utility based on yield, economy of ingredients, purity of product, specificity, etc. The preparation of short-lived transient species is not described. 

Treatment of 41 with diethyl fumarate under similar conditions gave 50, which displayed physical and spectroscopic properties similar to those of 49. 

The physical and spectroscopic properties of /V-acyloxy-A-alkoxyamides confirm pyramidality at nitrogen and the disconnection of the nitrogen lone pair from the amide carbonyl. The presence of an acyloxyl and an alkoxyl group at nitrogen also results in an anomeric interaction between the oxygens, which is facilitated by the sp3-hybridised nitrogen. Experimental observations, including X-ray analysis are fully supported by results from computational chemistry. 

The binuclear unit also confers characteristic physical and spectroscopic properties to the complexes. Electronic spectra reveal a strong (e - 3000-4000 M-icm l) absorption band at 3(X)-400 nm with a characteristic low energy shoulder, both associated with the presence of an 0x0 bridge weaker (e 300-600 M lcm" ) features in the 400-550 nm region associated with the (p,-oxo)bis(p.-carboxylato)-diiron(in) core and d-d bands in the near IR region (Hgure 2a) (5,10). Laser excitation into the visible and near UV bands results in the observation of enhanced Raman features due to Fe-O-Fe vibrations (5,11) (see Chapter 3 for a more detailed discussion into the Raman spectra of these complexes). 

Before plunging into a discussion of how such complexes are prepared, it is perhaps worthwhile to consider explicitly the rationale for such activity. The synthesis and characterization of accurate model complexes for a given metal site in a protein or other macromolecule allows one to (l) determine the intrinsic properties of the metal site in the absence of perturbations provided by the protein environment or (il) in favorable cases, deduce the structure of the metal site by comparison of corresponding physical and spectroscopic properties of the model and metalloprotein (3). The first class of model complexes has been termed "corroborative models" by Hill (4), while the second are termed "speculative models" (4). To date, virtually all the major achievements of the synthetic model approach have been in development of corroborative models. 

The submitters recrystallized the sample from EtOAc-hexanes and obtained a yield of 93%. The checkers yield is based on combined product from two successive crops, although additional product weis observed in the remaining mother-liquor (2 g of cmde materieil) which could be used, as obtained, for subsequent reactions. The physical and spectroscopic properties of 3 are as follows mp 104-106°C (material isolated by column chromatography alone) mp 110-112°C [a]p°-24.6° (EtOAc, cl.O) (after a single crystallization from EtOAc/hexane) mp 119-121 C [a]Q°-24.1° (EtOAc, cO.8) (after two... 

The submitters obtained 8.68 g (96%). The aldehyde 4 should be used immediately after preparation. It cannot be purified by chromatography. The checkers observed the following physical and spectroscopic properties of 4 [a]p° (EtOAc, c 1.0)... 

This article deals with the chemistry of carbazoles, and except for their formation from carbazoles as illustrations of the chemistry of carbazoles, it specifically excludes that of 1,2,3,4-tetrahydro-, 1,2,3,4,4a,9a-hexahydro-, 1,2,3,4,5,6,7,8-octahydro carbazoles, etc., because from the viewpoint of chemical reactivity, these are indoles, anilines, pyrroles, and so on. This article also excludes carbazoles with additional fused aromatic or heteroaromatic rings, again except for the formation of such systems as illustrations of carbazole reactivity. The physical and spectroscopic properties are not covered. 

A. NOMENCLATURE ANL) SELECTED PHYSICAL AND SPECTROSCOPIC PROPERTIES OF PAHs AND PACs 437... 

A. NOMENCLATURE AND SELECTED PHYSICAL AND SPECTROSCOPIC PROPERTIES OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) AND POLYCYCLIC AROMATIC COMPOUNDS (PACs)... 

A. NOMENCLATURE AND SELECTED PHYSICAL AND SPECTROSCOPIC PROPERTIES OF PAHs AND PACs 457 TABLE 10.8 Sum of the Particle-Associated (Filter) and Gas-Phase (Solid Adsorbent, PUF Plugs or Tenax Cartridges8) Concentrations of EPA Priority PAH Pollutants and the Percentage of Each PAH in the Particle Phase ... 

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