Dichromate spectrum

A compound is a cyclic ether of molecular formula C9H10O Its NMR spectrum is shown in Figure 16 10 Oxidation of the compound with sodium dichromate and sulfunc acid gave 1 2 benzenedicarboxylic acid What is the compound d... 

Alkaloid A. This forms a chloride, [CjoHjaONjJ+Cl", HjO, isomeric with the chlorides of toxiferine, C-eurarine I and C-curarine III the picrate has m.p. 269° (dec.). The chloride differs from the isomerides named, in potency, colour reactions and ultra-violet absorption spectrum. The chloride in 2N-sulphuric acid gives a carmine-red colour with potassium dichromate. 

The anaerobic oxidation of phosphines to their oxides by hydroxide ion has been shown to involve the liberation of hydrogen, possibly from the intermediate (21). These oxidations were studied with water-soluble phosphines, since solubility was found to be the main factor controlling the rate of oxidation. The preparation, and detailed n.m.r. spectrum, of PP-dimethyl-P P -diphenyldiphosphine disulphide (22) is a relatively rare example of a study of a mixed disulphide. Many examples of routine oxidation of phosphines to their oxides have appeared. These include the preparation of polyhalogenoarylphosphine oxides using dichromate... 

Figure 4 is a good example of satellite structure associated with a surface species. The chromium 2p /2,l/2 spectrum results from the reaction of the dichromate ion,, with galena to yield both... 

In neutral or weakly acidic solutions of dichromates and H2O2 the violet species CrOs(OH)-forms (equation 129) and explosive violet salts M[CrVI0(02)20H] (M = NH4, K, Tl) can be isolated.1433 The salt [Ph3MeAs][Cr0(02)20H] is more stable, and from the lack of an OH band in the IR spectrum it is believed that the anion contains a strong hydrogen bond related blue peroxohalochromates [Ph3MeAs][CrO(02)2X] (where X is Cl or Br) are, also known (Scheme 124).1432 Kinetic studies show that the blue and the violet anions are formed by similar... 

Color Plate 15a shows the spectrum of white light and the spectra of three different colored solutions. You can see that potassium dichromate, which appears orange or yellow, absorbs blue wavelengths. Bromophenol blue absorbs orange wavelengths and appears blue to our eyes. Phenolphthalein absorbs the center of the visible spectrum. For comparison, spectra of these three solutions recorded with a spectrophotometer are shown in Color Plate 15b. 

Spectroscopy has not proven to be very conclusive in solving this problem. Similarities between the visible spectrum of the calcined catalyst and that of bulk dichromates have been noted (5,12-14). In the end, however, there is always doubt about the interpretation of spectra because no adequate reference data exist for these surface bound species (76). Krauss and coworkers have carefully studied the luminescence of Cr/silica and concluded that at least a portion of the chromium is present as chromate (75). 

Comparison of the electrical conductivities of chromium penta-phenyl hydroxide, sodium hydroxide and ammonia in absolute methyl alcohol and in methyl alcohol-water solution, shows that the former is a very strong base. In aqueous methyl alcohol solution the chromium compound does not appear to approach the limiting value with increasing dilution. The ultra-violet absorption spectrum examined in absolute ethyl alcohol solution resembles that of chromic acid and the dichromates, but the absorption is noticeably greater in the case of the organic compound. 

Nuclear Magnetic Resonance. Taube (18) has shown that two different chemical shifts in the 170 NMR spectrum of C Ot2- solutions are observed, in the approximate ratio of non-bridging O to bridging O. However, 2M solutions of dichromate were used in water enriched to 1.4% H2017, and no shifts were observed in several other cases studied. 

The secondary alcohol was smoothly oxidized to a ketone in high yield with pyridinium dichromate in dimethylformamide (cf 36). The IR spectrum indicated the presence of a ketone group bonded to the a-carbon of a thiophene (absorption at 1660 cm 1). The 200 MHz XH NMR spectrum showed all the features expected of this structure (cf Figure 12) as did the mass spectrum (cf. 1). 

Another compound that has wide utility as an oxidizing agent is potassium dichromate, K2Cr207. This compound is an oxidizing agent that will oxidize a broad spectrum of materials in synthetic reactions, and it is used in redox titrations in analytical chemistry. 

In addition to these four main types of UV spectra of natural water, many more can be encountered. For memory, when the flow measurement of river, using dichromate, was formerly authorised, typical spectra of hexavalent chromium were obtained (see Chapter 9). In case of pollution, the UV spectrum shape is obviously dependent on the pollutant nature and concentration. In all cases, if the UV spectrum of natural water is flat and close to zero, the pollution probability is very low. On the contrary, a more or less important UV spectrum is always related to the presence of dissolved compounds or suspended solids. 

When heated with an acidic solution of sodium dichromate, compound A forms benzoic acid. Identify compound A from its NMR spectrum. 

Rode et al. (107) carried out an electron spin resonance study of the intermediate oxides formed in the thermal decomposition of chromic anhydride. Chromium decachromate, chromium dichromate, and chromium hydroxide at room temperature, as well as the ferromagnetic compounds chromium monochromate and chromium dioxide above their Curie points at 130°, give symmetrical absorption lines 130 to 160 gauss wide with a g factor of 1.97, Shnkin and Fedorovskaia (108) studied CrgOa containing lithium, and detected fine structure in the ESR spectrum. 

The absorption is slightly greater in the more dil. soln., and this points to slight dissociation with formation of some dichromate, which, however, is only produced in very minute quantity. H. Becquerel found that soln. of potassim chromate are transparent for the ultra-red rays and G. Massol and A. Faucon studied the transmission of ultra-violet rays. D. Brewster investigated the absorption spectrum of soln. of ammonium chromate and J. H. Gladstone, soln. of metal chromates. H. von Halban and H. Siedentopf found that a soln. of potassium chromate in 0-05A -KOH had the extinction coefE., e, for light of wave-length, A, when where C denotes the cone, in mols per litre. 

H. C. Jones and W. W. Strong found that the absorption spectra of cone. soln. of potassium chromate shows a stronger absorption than the value calculated from Beer s law. G. Rudorf discussed the applicability of Beer s law. F. Weigert, and H. von Halban and H. Siedentopf studied the absorption of light by mixed soln. of potassium chromate and copper sulphate. Observations on the absorption spectrum of soln. of potassium dichromate were made by H. Bremer, P. Gian,... 

D. Coster, and 0. Stelhng studied the X-ray spectrum and D. M. Yost, the absorption of X-rays. I. PlotnikofE and M. Karshulin measured the absorption spectrum and the region of photochemical sensitivity for soln. of potassium chromate in colloidion films—with methyl alcohol as acceptor. A. Kailan found that an aq. soln. of potassium chromate is reduced by radium rays more slowly than potassium dichromate. E. Montignie observed that after exposure to ultra-violet light, potassium chromate affects a photographic plate. 

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