Concentrated Sulphuric Acid Solutions Research Articles

Proton magnetic resonance spectra of steroids in sulphuric acid

1 H N.m.r. spectra are presented of ten steroids in concentrated sulphuric acid solution. The bands are assigned to various features of the steroid molecule or to structures in carbonium or oxonium ions produced by reaction with the acid. The contribution made by the spectra to an understanding of steroid–acid colour reaction mechanisms is discussed.

The mechanism of the anodic formation of the peroxodisulphate ion on platinum—I. establishment of the participating anion

Abstract From the correlation of the current efficiency for peroxidisulphate (persulphate) formation in solutions of sulphuric acid, of K2SO4 and (NH4)2SO4 with the actual SO42− concentration, the conclusion is drawn that exclusively SO42− ions are involved in the persulphate formation. The discharge of HSO4− ions in concentrated sulphuric acid solutions leads to the formation of peroxomonosulphuric acid (Caro's acid).

Conversion of indones to quinoline and isoquinoline derivatives—IV : Schmidt reaction with 2-( o-carboxyphenyl)3-phenylindone and with 2-( o-carbomethoxyphenyl)-3-phenylindone

The Schmidt reaction with 2-( o-carboxyphenyl)3-phenylindone (VI) in a mixture of sulphuric and acetic acid affords 12-phenyl-5 H-[2]benzopyrano[3.4- b]quinoline-5-one (VII) as the main product. The methyl ester of V, which is almost unreactive towards hydrazoic acid in acetic-sulphuric acid solution, is converted mainly into 2-phenyl-3-( o-carbomethoxyphenyl)4--hydroxyquinoline (XVI) when the reaction is carried out in concentrated sulphuric acid solution.

The acid catalysed reactions of transition metal complexes—VI: The acid catalysed hydrolyses of cis and trans chloro- and cis isothiocyanato-nitrobisethylene-diaminecobalt (III) salts and the subsequent reactions in hydrochloric acid

The acid catalysed replacement of the nitro-group from cis and trans[Coen 2Cl(NO 2)] + salts has been studied in a series of aqueous solutions of strong acids. In hydrochloric acid the initial product is a mixture of cis and trans[Coen 2(H 2O)Cl] 2+ salts which are subsequently anated to yield cis and trans[Coen 2Cl 2] +. This anation and the rearrangement between the cis and trans dichloro-species have been studied independently in hydrochloric acid-lithium chloride solutions. The mechanisms of these reactions are discussed. The aquation of [Co(NH 3) 5NO 2] 2+ ions in concentrated sulphuric acid solutions is reported also.

The diazotisation of 3,4,5,6-tetrachloroanthranilic acid: a convenient synthesis of 2,3,4,5-tetrachlorophenol

Diazotisation of 3,4,5,6-tetrachloroanthranilic acid in concentrated sulphuric acid solution and subsequent steam distillation of the diazonium sulphate solution gives 2,3,4,5-tetrachlorophenol in 77% yield and 3,4,5,6-tetrachlorosalicylic acid as a minor product. Diazotisation in glacial acetic acid solution gives a mixture of 1,2,3,4,5,6,7,8-octachloroacridone, 3,4,5,6,2′,3′,4′,5′-octachlorodiphenylamine-2-carboxylic acid, and 2,3,4,5-tetrachlorophenyl acetate. Mechanisms are suggested for the formation of these products.

The electron-spin resonance spectra of 1,4-dithiin radical-cations and the nature of the carbon-sulphur ?-bond

The radical cations of 1,4-dithiin, 1,4-benzodithiin and thianthrene have been prepared and their electron-spin resonance spectra measured at room temperature in concentrated sulphuric acid solution. Spin densities for these radicals have been calculated using McLachlan's extension of the Huckel molecular orbital method with neglect of overlap and using two models for the sulphur atom, one with and the other without the participation of the 3d-orbitals. It is concluded that the 3d-model gives significantly better results although qualitatively a similar distribution is predicted by both models. Appropriate values for the sulphur atom parameters are those used by Longuet-Higgins in his discussion of thiophene. Owing to the probable non-planarity of these radicals the improvement arising from the inclusion of d-orbitals may in fact be due, at least in part, to interaction of the carbon 2pzorbitals with the antibonding carbon-sulphur σ orbitals.

Spectroscopic studies on reactive intermediates of esterification of aromatic carboxylic acids

Ultra-violet absorption spectra were measured with a total of nine benzoic acid derivatives under various conditions, with special reference to the behavior of the intramolecular charge-transfer (CT) bands, which are caused by the conjugation of the benzene ring with the carboxyl group and therefore are expected to be sensitive to the steric hindrance. In fact, it was observed that the CT band, which appears with high intensity at 228 mμ with the aqueous solution of benzoic acid, becomes weak for the aqueous or n-heptane solution of mesitoic acid [(CH 3) 3C 6H 2CO 2H)], evidently because of the resonance inhibition caused by the steric requirement of the o-methyl groups. On the other hand, in concentrated sulphuric acid solutions strong CT bands were observed with both benzoic acid (262 mμ) and mesitoic acid (282 mμ). Furthermore, the latter band was found to be very similar to those observed with mesitoic acid-trifluoroacetic anhydride and mesitoyl chloride-stannic chloride systems which contain typical acylating reagents. This means that the 282 mμ band observed with the concentrated sulphuric acid solution of mesitoic acid is due to the mesitoyl cation [(CH 3) 3C 6H 2CO +)], which may be regarded as the intermediate state of acid catalysed esterification of mesitoic acid. Concerning the 262 mμ band of benzoic acid in sulphuric acid, its origin was ascribed to protonated benzoic acid cation. Further, it was demonstrated from the measurement of Raman spectra that in the protonated benzoic acid cation a proton is attached to the carbonyl oxygen atom. Detailed quantitative analyses of equilibria were made for the interaction of sulphuric acid with benzoic acid and with mesitoic acid by the use of the new method devised by the present authors. It was, then, clearly shown that, in strongly acidic media, mesitoic acid ionizes in the following two steps as suggested by Schubert et al.: ▪

Chemistry of polynuclear compounds. II. The behaviour in concentrated sulphuric acid solution and absorption spectra of some polynuclear quinones

In an investigation into the coking mechanism of coal, polynuclear quinones were adopted as models. The electronic absorption spectra of dibenzanthrone (I) ; 16,17-dimethoxydibenzanthrone (II) ; 16,17-diethoxydibenzanthrone (III) ; 16-methoxy-17-ethoxydibenzanthrone (IV) ; 16-methoxy-17-hydroxydibenzanthrone (V) ; and 16-ethoxy-17-hydroxydibenzanthrone (VI) in chlorobenzene and dioxane solution were measured and are discussed. Nan-planar configurations are proposed for II-VI and the possibility of the same for I considered. The electronic absorption spectra in concentrated sulphuric acid of I, II, V, and VI were measured and are discussed. IV, V, and VI are new vat dyes ; V is produced by the action of concentrated sulphuric acid on II and IV, and VI is produced by the same reaction with III. IV is prepared by the methylation of VI. The electronic absorption spectra of anthraquinone and some derivatives were measured in concentrated sulphuric acid and are discussed in conjunction with some of the above spectra. The infra-red spectra of IV, V, and VI confirm the identification of these compounds as 16,17-disubstituted dibenzanthrones and establish the nature of the alkoxyl substituents ; the quinonoid-carbonyl frequencies are discussed.

Thermodynamic data on concentrated sulphuric acid solutions

The first page of this article is displayed as the abstract.

The absorption and fluorescence properties, in the visible spectral region, of certain steroids in sulphuric acid solutions.

The absorption and fluorescence of steroids dissolved in concentrated sulphuric acid, and the changes in these properties on adding ethanol to the concentrated acid solutions, have been examined for: cholesterol, pregnandiol, α-estradiol, dehydroisoandrosterone (D.H.A.), dehydroisoandrosterone acetate, desoxycorticosterone acetate, (D.O.C.A.), testosterone propionate, and progesterone. At 57° C. or less, in concentrated sulphuric acid solution a colored compound was formed only if an hydroxyl group was present in the steroid molecule; the keto group formed a colored compound with sulphuric acid only in the presence of a hydroxyl group in the same steroid molecule. As the concentrated sulphuric acid solutions were diluted with alcohol, absorption maxima appeared which were characteristic of specific hydroxyl and keto groups. Irradiation of the solutions by light of the spectral regions corresponding to the absorption maxima produced related fluorescent bands.