Rhodizonates

Bromophenol blue 2, 7 -DichIorofluorescein Eosin, tetrabromofluorescein Fluorescein Potassium rhodizonate, C404(0K)2 Rhodamine 6G Sodium 3-aIizarinsuIfonate Thorin Dissolve 0.1 g of the acid in 200 mL 95% ethanol. Dissolve 0.1 g of the acid in 100 mL 70% ethanol. Use 1 mL for 100 mL of initial solution. See Dichlorofluorescein. Dissolve 0.4 g of the acid in 200 mL 70% ethanol. Use 10 drops. Prepare fresh as required by dissolving 15 mg in 5 mL of water. Use 10 drops for each titration. Dissolve 0.1 g in 200 mL 70% ethanol. Prepare a 0.2% aqueous solution. Use 5 drops per 120 mL endpoint volume. Prepare a 0.025% aqueous solution. Use 5 drops. 

Rhodizonic acid sodium salt (5,6-dihydroxycyclohex-5-ene-l,2,3,4-tetraone di-Na salt)... 

The four-, five-, and six-membered analogs (178,180, and 182) were also obtained from the diprotonation of squaric acid (3,4-dihydroxy-3-cyclobutene-l,2-dione, 177), tri-O-protonation of croconic acid (4,5-dihydroxy-4-cyclopentene-l,2,3-trione, 179), and tetra-O-protonated rhodizonic acid (5,6-dihydroxy-5-cyclohexene-l,2,3,4-tetraone, 181), respectively. These ions were prepared in either Magic Acid (1 1 FSOsH-SbFs) or fluorosulfuric acid at low temperature and characterized by NMR. Ab initio/IGLO calculations showed that di-O-protonated squaric acid (178) is planar and aromatic, whereas the polyprotonated croconic and rhodizonic acids (180 and 182) have more carboxonium ion character, and no indication was obtained for any significant contributing homoaromatic structures. 

Analysis. The bright scarlet flame color of Sr indicates that atomic emission and absorption methods wiU be good for its analysis. Sr is quantitatively determined by colorimetry down to 200 ppm using chloranrlic acid, by atomic absorption spectroscopy (AAS) to 100 ppb, to 1 ppb by electrothermal absorption spectroscopy (ETAS), and to 0.1 ppb by inductively-coupled plasma emission spectroscopy (ICPES) and inductively-coupled plasma mass spectroscopy (ICPMS). A spot test for Sr which extends to 40 ppm is provided by K2Cr04 and sodium rhodizonate. 

Infrared and Raman spectra of crystalline barium rhodizonatc have been reported.51 From an inspection of the data, the author concluded tint the rhodizonate ion, C6Oj. (Fig I6J5) probably has D, symmetiy Examine the data below (frequency m cm 1) and explain this conclusion. 

Synthesis. Benzenehexol is available only from laboratory reagent suppliers. The simplest laboratory preparation involves the aeration of the glyoxal—bisulfite addition product in sodium carbonate solution at 40—80°C, isolation of the sodium salt of tetrahydroxybenzoquinone, followed by acidification to obtain the free tetrahydroxy-p-benzoquinone in about 8% yield the latter is reduced with stannous chloride in boiling dilute hydrochloric acid solution to benzenehexol (77) in 77% yield (261). A similar procedure affords dipotassium rhodizonate (80) in good yield (262). 

Derivatives. A considerable number of compounds that contain the benzenehexol structure possess therapeutic activity. Esterification of benzenehexol with a pyridinecarbonyl chloride gives the corresponding hexaesters, which are antiatherogenics (267). Tetroquinone [319-89-1] (tetxahydroxy-/>-benzoquinone) is administered orally for the treatment of keloids. The dipotassium salt of rhodizonic acid (80) is useful as a remedy for diabetes mellitus (262). Compounds, eg (81) and (82), which are derived from rhodizonic acid, are useful as antiinflammatory agents and diuretics (qv) (268). 

Deltic acid Squaric acid Croconic acid Rhodizonic acid Tropolone... 

Carbon-13 NMR spectra of the H2C On series, such as deltic, squaric, croconic and rhodizonic acids, obtained in anhydrous solvents [304] display carbonyl shifts similar to those reported for quinones (Table 4.33). Considerable shielding of the carbonyl carbon of deltic acid diethyl ester is not only attributed to the three-membered ring but also to an electron releasing effect of the ethoxy groups. 

As shown above, di-tert-butoxyethyne 1s the only acetylenic diether prepared so far whose stability allows its use as a synthetic Intermediate. It has been used 1n the synthesis of all the members of the series of monocyclic oxocarbons (deltic, squaric, croconic, and rhodizonic acids), as well as in the synthesis of semisquaric acid, the parent compound of the natural mycotoxins, noniliforndna... 

H. S. Isbell, H. L. Frush, and Z. Orhanovic, Oxidation of sodium salts of alduronic and glyculosonic acids by sodium peroxide, Carbohydr. Res., 36 (1974) 283-291 Oxidation of certain cyclic carbonyl compounds with alkaline hydrogen peroxide, ibid., 43 (1975) 93-100 H. S. Isbell, Concurrent oxidation and reduction reactions of cyclohexanehexone, rhodizonic acid, and tetrahydroxy-l,4-benzoquinone with hydrogen peroxide, ibid., 39 (1975) C4-C7. 

Sodium rhodizonate Strontium (II), Sr2 Ammonium carbonate Dilute sulfuric acid Saturated calcium sulfate Potassium chromate Ammonium oxalate... 

The hydrogenation of rhodizonic acid 1,4-diimine and triaminophloro-glucinol has been reported to give 50% yields of an inosadiamine and an inosatriamine, respectively.233 No information about the configurations of the products has been published. 

In the final section of this chapter, we discuss the vibrational spectra of benzene, its isostructural species CeOg- (rhodizonate dianion), and dibenzene metal complexes. 

Benzene and the rhodizonate dianion (C6C>62-, structure shown above also see Section 20.4.4) are isostructural species. Hence all the symmetry arguments and results given in the previous section for benzene are applicable here. The results for C6C>62- are summarized in Table 7.3.5. 

Table 7.3.5. The normal modes of the rhodizonate dianion and observed frequencies...

The rhodizonate dianion C60g (Fig. 20.4.19) is a member of a series of planar monocyclic oxocarbon dianions C 0 (n = 3, deltate n = 4, squarate n = 5, croconate n = 6 rhodizonate) which have been recognized as nonbenzenoid aromatic compounds. However, this six-membered ring species... 

Projection along the b axis showing the hydrogen-bonding interactions within the puckered rhodizonate-bisurea-water layer of [(n-... 

Bond lengths (pm) of (a) D6tl (note that in this case the dianion is located at a site of symmetry) and (b) C2v valence tautomers of the rhodizonate dianion. 

Results indicated that in each case the diameter and density of the unburned propellant patterns were similar using the same gun but different ammunition. There were variations in the soot (blackening) deposits with different ammunition. Contact shots were very similar irrespective of the ammunition. All gave positive rhodizonate tests for lead. 

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