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Pyridine refining

Carbazole [86-74-8J M 167.2, m 240-243 , pK <0. Dissolved (60g) in cone H2SO4 (300mL), extracted with three 200mL portions of benzene, then stirred into 1600mL of an ice-water mixture. The ppte was filtered off, washed with a little water, dried, crystd from benzene and then from pyridine/ benzene. [Feldman, Pantages and Orchin J Am Chem Soc 73 4341 795/]. Has also been crystd from EtOH or toluene, sublimed in vacuum, zone-refined, and purified by TLC. [Pg.156]

A iD-Corticoids have been important intermediates since it was shown ° that substitution at C-9 enhances anti-inflammatory activity. These olefins are usually obtained from 11a- or 11)5-alcohols, and consequently several refined methods have been devised for effecting this dehydration. It is desirable that such methods be compatible with the presence of A" -3-ketone and 17-hydroxy functions. The first direct procedure for which high yields were claimed was described in a patent issued to Upjohn. According to this method, the alcohol (11a or )5) is treated first with A-bromoacetamide in pyridine, then with sulfur dioxide. Recently it has been claimed " that the A-haloamide/sulfur dioxide method gives results superior to other methods, although the methanesulfonyl chloride/sulfur dioxide procedure (see below) apparently was not compared (see also ref. 94). [Pg.323]

The CNDO method has been modified by substitution of semiempirical Coulomb integrals similar to those used in the Pariser-Parr-Pople method, and by the introduction of a new empirical parameter to differentiate resonance integrals between a orbitals and tt orbitals. The CNDO method with this change in parameterization is extended to the calculation of electronic spectra and applied to the isoelectronic compounds benzene, pyridine, pyri-dazine, pyrimidine and pyrazine. The results obtained were refined by a limited Cl calculation, and compared with the best available experimental data. It was found that the agreement was quite satisfactory for both the n TT and n tt singlet transitions. The relative energies of the tt and the lone pair orbitals in pyridine and the diazines are compared and an explanation proposed for the observed orders. Also, the nature of the lone pairs in these compounds is discussed. [Pg.150]

CT+-values may not differ too widely from ct-values. Since the charges in 2 and 4 actually reside in the ring, the pyridine system may, in addition, be particularly subject to the variability of cr-values, and consequently a careful analysis of some rather extensive material in the sense of some of the most refined methods might be very profitable... [Pg.217]

In solvent refining, coal is converted to a pyridine-soluble product after very short residence time at reaction conditions. [Pg.179]

Heterocyclic systems have played an important role in this historical development. In addition to pyridine and thiophene mentioned earlier, a third heterocyclic system with one heteroatom played a crucial part protonation and methylation of 4//-pyrone were found by J. N. Collie and T. Tickle in 1899 to occur at the exocyclic oxygen atom and not at the oxygen heteroatom, giving a first hint for the jr-electron sextet theory based on the these arguments.36 Therefore, F. Arndt, who proposed in 1924 a mesomeric structure for 4//-pyrone, should also be considered among the pioneers who contributed to the theory of the aromatic sextet.37 These ideas were later refined by Linus Pauling, whose valence bond theory (and the electronegativity, resonance and hybridization concepts) led to results similar to Hiickel s molecular orbital theory.38... [Pg.10]

Residua are the dark-colored nearly solid or solid products of petroleum refining that are produced by atmospheric and vacuum distillation (Figure 11.1 Chapter 3). Asphalt is usually produced from a residuum and is a dark brown to black cementitious material obtained from petroleum processing that contains very high-molecular-weight molecular polar species called asphaltenes that are soluble in carbon disulfide, pyridine, aromatic hydrocarbons, and chlorinated hydrocarbons (Chapter 3) (Gruse and Stevens, 1960 Guthrie, 1967 Broome and Wadelin, 1973 Weissermel and Arpe, 1978 Hoffman, 1983 Austin, 1984 Chenier, 1992 Hoffman and McKetta, 1993). [Pg.284]

Not surprisingly, formalisms with very diffuse density functions tend to yield large electrostatic moments. This appears, in particular, to be true for the Hirshfeld formalism, in which each cos 1 term in the expansion (3.48) includes diffuse spherical harmonic functions with / = n, n — 2, n — 4,... (0, 1) with the radial factor rn. For instance when the refinement includes cos4 terms, monopoles and quadrupoles with radial functions containing a factor r4 are present. For pyridin-ium dicyanomethylide (Fig. 7.3), the dipole moment obtained with the coefficients from the Hirshfeld-type refinement is 62.7-10" 30 Cm (18.8 D), whereas the dipole moments from the spherical harmonic refinement, from integration in direct space, and the solution value (in dioxane), all cluster around 31 10 30 Cm (9.4 D) (Baert et al. 1982). [Pg.160]

Bis(pyridine)(meso-tetraphenylporphinato)iron(II), discussed in section 10.5.2, was reanalyzed to evaluate the importance of anharmonic motion in nitrogen-temperature transition metal studies. A number of different refinements are summarized in Table 10.13. It is striking that treating the Fe atom as spherical... [Pg.244]

Organonitrogen compounds are quite stable throughout most refining processes. Basic heteroatomic species such as pyridine and quinoline can be found as well as nonbasic pyrrole and indole compounds. [Pg.38]

The action of H202 on acidic dichromate solutions gives an unstable blue species which can be extracted into ether (equation 128).2,518,1428 On the addition of pyridine the blue compound Crvl0(02)2py crystallizes. The molecules are distorted pentagonal pyramids with sideways-bonded peroxo groups (298) 1429 some workers with less refined data have reported rather different bond distances.1430 In water the blue species is considered to be CrO(62)2(OH2), in ether it is Cr0(02)20Et2, and amines such as aniline, bipy and phen can replace the pyridine. With bidentate bipy the coordination sphere becomes essentially a pentagonal bipyramid (299),... [Pg.945]

Another level of refinement regarding in situ acyl group activations is reached when the activated hydroxycarboxylic acid A is converted into the corresponding IV-acylpyridinium salt B with / ara-(dimethylamino)pyridine, (Figure 6.9). Under these conditions macrocyclizations routinely succeed in yields well above 50%. [Pg.295]

Information regarding the physical and chemical properties of benzene is shown in Table 3-2. The major impurities found in commercial products are toluene, xylene, phenol, thiophene, carbon disulfide, acetylnitrile and pyridine (NIOSH 1974). Commercial refined benzene-535 is free of hydrogen sulfide and sulfur dioxide, but contains a maximum of 1 ppm thiophene and a maximum of 0.15% nonaromatics. Refined nitration-grade benzene is free of hydrogen sulfide and sulfur dioxide. Benzene is also commercially available as thiophene-free, 99 mole%, 99.94 mole% and nanograde quality (HSDB 1996). [Pg.274]

The benzols are treated with sulfuric add or by catalytic hydrorefining to remove compounds containing sulfur (thiophene, mercaptans), oxygen (phenols) and nitrogen pyridine, cyanidesi. The refined product is then distilled to ield crude benzene containing the following hydrocarbons . ... [Pg.194]


See other pages where Pyridine refining is mentioned: [Pg.45]    [Pg.8]    [Pg.603]    [Pg.26]    [Pg.388]    [Pg.32]    [Pg.181]    [Pg.38]    [Pg.244]    [Pg.245]    [Pg.162]    [Pg.108]    [Pg.235]    [Pg.431]    [Pg.8]    [Pg.952]    [Pg.135]    [Pg.527]    [Pg.528]    [Pg.159]    [Pg.178]    [Pg.180]    [Pg.92]    [Pg.67]    [Pg.169]    [Pg.108]    [Pg.235]    [Pg.99]    [Pg.515]    [Pg.158]    [Pg.485]    [Pg.243]   
See also in sourсe #XX -- [ Pg.395 ]




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