Aqueous Hydrobromic Acid Research Articles

Osmotic coefficients and activity coefficients of aqueous hydrobromic acid solutions at 25�C

The osmotic coefficients ϕ and activity coefficients γ± of aqueous solutions of HBr depend largely on emf measurements utilizing the silver-silver bromide electrode. There is evidence, however, that side reactions between AgBr and bromide ion render this electrode unreliable when the HBr molality (m) exceeds 2 mol-kg−1. It is shown, however, that the isopiestic vapor-pressure technique is capable of yielding data for HBr at higher molalities. New emf measurements of cells with hydrogen and AgBr/Ag electrodes at 25°C have been combined with literature data to recommend values for the activity coefficients of HBr in the dilute range. These have been supplemented by isopiestic measurements vs. NaCl and CaCl2 reference solutions in the range of HBr molalities from 0.7 to 6.2m. A table of ϕ and γ± at 25°C at round molalities from 0.005 to 6.0 is presented.

The mean bond dissociation energy of the carbonmagnesium bond in bis(2,2‐dimethylpropyl)magnesium

AbstractThe standard enthalpy of formation of solid bis(2,2‐dimethylpropyl)magnesium (dineopentylmagnesium, Np2Mg) has been determined from its reaction enthalpy with aqueous hydrobromic acid and found to be ‐235.8 ± 5.5 kJ·mol−1. Using the experimentally determined sublimation enthalpy of Np2Mg and the enthalpies of formation of the 2,2‐dimethylpropyl radical and gaseous magnesium, the mean dissociation energy of the carbonmagnesium bond in the monomeric title compound is found to be 133.7 ± 5.0 kJ·mol−1. This value is discussed and compared with those of other reported carbonmagnesium bonds. In combination with the previously determined difference in enthalpy of formation of dimeric and monomeric Np2Mg, the bond energy of the bridging 2,2‐dimethylpropylmagnesium bonds in dimeric Np2Mg is calculated to be D̄B = 205 ± 3 kJ·mol−1, which is a remarkably high value.

Anion-exchange behaviour of a number of metal ions on DEAE-cellulose in hydrobromic and hydriodic acid media

The adsorption behaviour of 48 metal ions on DEAE-cellulose layers has been investigated in aqueous hydrobromic and hydriodic acid media. RF values are given as a function of the hydrobromic and hydriodic acid concentration over the ranges 0.01–6 mol dm−3 and 0.01–3 mol dm−3, respectively, and are compared with those obtained with Avicel SF. RF spectra are comparatively simple in both media, reflecting the strong affinity of the bromide and iodide ions to the DEAE-cellulose phase. Pd, Pt, Re, Au and Hg are distributed chromatographically in either system, while most other metal ions exhibit rather extreme RF values of near unity or zero. Therefore, the selectivity of the systems is particularly high for Pd, Pt, Re, Au and Hg, providing the possibility of their excellent selective separations.

Ionic dissociation of aqueous hydrobromic acid. V. Estimate from refractive index and density measurements

The refractive index of aqueous hydrobromic acid was measured up to 19.6m at 0.25 and 60°C. The density of dilute solutions, 0.0676 to 2.76m, was measured at 25°C to high accuracy. These and supplementary data from the literature yielded apparent molar volumes and refractivities. The latter showed the shallow maximum at low concentrations (less than 1.5m) and the gentle linear decline with increasing concentrations, characteristic of strong electrolytes up to about 8 m. The abrupt decline of the apparent molar refractivity with increasing concentrations is interpreted in terms of the association of hydrobromic acid. The apparent molar volumes can also be interpreted, though only quantitatively, in these terms. The results are related to the previously obtained proton nmr data, concerning the extent of association.

The structure and absolute configuration of heterophylloidine

The structure and absolute configuration of heterophylloidine, a new C 20-diterpenoid alkaloid isolated from Aconitum heterophylloides Stapf, have been determined with the aid of 13C NMR spectral data and single-crystall X-ray analysis of the product obtained by treatment of heterophylloidine with aqueous hydrobromic acid.

ChemInform Abstract: ORGANIC PHOSPHORUS COMPOUNDS. LXXI. PREPARATION, PROPERTIES, AND STRUCTURE OF F BIS(AMINOMETHYL)PHOSPHINIC ACID, (H2NCH2)2P(O)OH

AbstractDer Versuch, die Titelverbindung (X) mit Ammoniak direkt aus (V) darzustellen, führt unter Umlagerung zu (VI), so daß zur Herstellung von (X) der Umweg über (VIII) eingeschlagen werden muß.

Ionic dissociation of aqueous hydrobromic acid. Part 2.—Estimate from proton magnetic resonance data at 6–60° C

Proton nuclear magnetic resonance measurements have been made on aqueous hydrobromic acid solutions at 6–60°C and over a concentration range ≈ 1–20 mol kg–1. The data have been interpreted according to the Gutowsky and Saika method, considering several options for the limiting slopes at low and high concentrations. The chemical shift of hydronium ions relative to water, SH3O+, can be obtained from extrapolation of data to zero concentration [option (a)], or from a correlation of data on other acids with the anion volume [option (b)]. The chemical shift of the undissociated acid, sHBr, can be equated with that of liquid hydrogen bromide [option (c)], or can be obtained from the data at the highest aqueous acid concentrations [option (d)]. The combination of options (a) and (d) is preferable to the other combinations of options. The data yield a mean degree of association over the temperature range studied of 2% at 4 mol kg–1, of 6% at 8 mol kg–1, of 11% at 12 mol kg–1, of 20% at 16 mol kg–1 and of 34% at 20 mol kg–1(with a relative uncertainty of ±25%).

Participation of 19-substituents in electrophilic additions to 6,7-unsaturated 5α-cholestane and B-homo 5α-cholestane derivatives; A case of competition between the participation of an ambident neighboring group and external nucleophile attack

Hypobromous acid action upon the 6,7-unsaturated 19-substituted 5α-cholestans Va-Vc results in the formation of two types of products, the cyclic ethers IX as products of 5(O)n participation of the 19-substituent, and the bromohydrins X. All these compounds are formed from the 6α,7α-bromonium ions Va'-Vc'. Under the same conditions the B-homo-5α-cholestane derivatives VIIa-VIIc afforded solely the cyclic ethers XIV as products of 5(O)n participation of the 19-substituent in the cleavage of the bromonium ions VIIa'-VIIc'. Acid cleavage of the 6α,7α-epoxides VIb and VIc with aqueous perchloric acid or hydrobromic acid gave two types of products, i.e. the cyclic ethers XI and the diols XII or bromohydrines XIII. The cyclic ethers XI arise by 5(O)n participation of the 19-substituent. The B-homo-6α, 7α-epoxide VIIIc on cleavage with aqueous perchloric acid have solely the cyclic ether XVc and by treatment with hydrobromic acid VIIIc afforded the mixture of XVc, as the main product, and of the bromohydrin XVIc. Discussed is the similarity of the bromonium ion cleavage with the fission of the corresponding epoxides, the mechanism of these reactions and the difference in the behaviour of the isomeric olefins Ia-c, IIIa-c, Va-c and VIIa-c and epoxides IIb,c, IVb,c, VIb,c and VIIIb,c. The competition between ambident neighbouring group participation and external nucleophile attack is discussed as well as the dependence of the products ratio on the nucleophilicity of the attacking species.

Participation of 19-substituents in acid cleavage of steroidal 3α,4α- and 4α,5α-epoxides

Participation of the 19-methoxy and 19-acetoxy group in 3α,4α- and 4α,5α-epoxides IIIc, IVb,c on treatment with aqueous perchloric or hydrobromic acid is investigated and compared with acid treatment of structurally similar 19-substituted 6α,7α- and 5α,6α-epoxides V and VI and with the behavior of analogous 3α,4α- and 4α,5α-bromonium ions. The 3α,4α-epoxides III react readily with 5(O)n participation. The reaction is practically quantitative on perchloric acid treatment. Under the same conditions, the 19-methoxy-4α,5α-epoxide IVb suffers mainly external attack leading to the diol XIb. The neighboring group participation is solely a 5(O)n process giving rise to the cyclic ether X. The 19-acetoxy-4α,5α-epoxide IVc reacts predominantly with participation of the ambident acetoxy group. This reaction is exclusively a 6(O)π,n process affording the diol XVI. External attack proceeds to a limited extent to give the isomeric diol XIc. In this respect the latter compounds react quite analogously to 5α,6α-epoxides VI and 4α,5α- and 5α,6α-bromonium ions bearing 19-acetoxyl.

ChemInform Abstract: IONIC DISSOCIATION OF AQUEOUS HYDROBROMIC ACID. PART 1. ESTIMATE FROM VAPOR PRESSURE AND ACTIVITY COEFFICIENT DATA

Chemischer InformationsdienstVolume 10, Issue 40 Physical Inorganic Chemistry ChemInform Abstract: IONIC DISSOCIATION OF AQUEOUS HYDROBROMIC ACID. PART 1. ESTIMATE FROM VAPOR PRESSURE AND ACTIVITY COEFFICIENT DATA Y. MARCUS, Y. MARCUSSearch for more papers by this author Y. MARCUS, Y. MARCUSSearch for more papers by this author First published: October 2, 1979 https://doi.org/10.1002/chin.197940017AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume10, Issue40October 2, 1979 RelatedInformation

Organic phosphorus compounds : LXXI. Preparation, properties, and structure of bis(aminomethyl)phosphinic acid, (H 2NCH 2) 2P(O)OH

Bis(aminomethyl)phosphinic acid, (H 2NCH 2) 2P(O)OH · HCl, was prepared by debenzylation of (C 6H 5CH 2NHCH 2) 2P(O)OH · HCl with hydrogen using 5% Pd on C as catalyst, and from bis(t-butylaminomethyl)phosphinic acid, (t-C 4H 9NHCH 2) 2P(O)OH, by isobutylene elimination in concentrated aqueous hydrobromic acid at 175°C in sealed tube. Interaction of bis(chloromethyl)phosphinic acid with ammonia in an autoclave produced methylaminomethylphosphinic acid, CH 3NHCH 2P(O)(OH) 2. A mechanism for the formation of this product is proposed. Several derivatives of (H 2NCH 2)P(O)OH such as (RNHCH 2) 2P(O)OH, R = C 6H 5CO, CICH 2CO, [H 2NHNC(=NH)NHCH 2] 2P(O)OH and [(CH 3) 3SiNHCH 2] 2P(O)OSi(CH 3) 3 were prepared.

Participation of the methoxyl group in the cleavage of some 19-substituted steroid epoxides. A case of competition between internal and external nucleophile attack

Acid cleavage of two steroid epoxides III and IV, bearing a methoxy group in position 19, with aqueous perchloric acid or hydrobromic acid gives two types of products, i.e. diols or bromohydrins VI, VII, IX and X as products of the normal reaction course and cyclic ethers V and VIII formed by participation of the 19-methoxy group. Discussed is similarity of these reactions with electrophilic additions to the related 19-methoxy olefins I and II, the mechanism, and the difference in behavior of both epoxides III and IV. Also discussed is the dependence of product ratios on the nucleophility of the attacking species.

Participation of 19-ester groups in the cleavage of 2α,3α- and 5α,6α-steroid epoxides. A case of competition between participation and external nucleophile attack

Acid cleavage of the acetoxy epoxide IIIa with aqueous perchloric acid or hydrobromic acid gave two types of products, i.e. the diol Va or the bromohydrin VIa, and the cyclic ether VIII. The latter compound arises by participation of ether oxygen of the ester group. On reaction with perchloric acid the epoxide IVa gave the diol XIIIa as a product of a normal reaction and the isomeric diol Xa as a product arising by intramolecular participation of the carbonyl oxygen of the 19-acetoxy group. Participation of the 19-ester group is confirmed by the formation of the cyclic carbonate XI when the 19-carbonate IVb is treated analogously. On reaction with hydrobromic acid, the epoxide IVa gave solely the bromohydrin XIVa as a product of the normal reaction course. Discussed is the similarity of these reactions with electrophilic additions to the related 19-acetoxy olefins I and II, the mechanism, the difference in behavior of both epoxides III and IV, the dependence of the product ratio on the nucleophility of the attacking species, and the competition between participation of an ambident neighboring group and an external nucleophile attack.

Ionic dissociation of aqueous hydrobromic acid. Part 1.—Estimate from vapour pressure and activity coefficient data

The dissociation constant on the molal scale of a strong acid HX is usually evaluated from log K′a(m)= 2 log ms+ 2 log γs+ log f°HX– log pHX– log 55.51, where ms and γs are the stoichiometric molality and mean molal activity coefficient, f°HX the fugacity of the pure liquid acid and pHX the partial vapour pressure of the aqueous acid, all at a given temperature. This quantity is only an apparent dissociation constant, however, since it contains as a factor the transfer activity coefficient of HX from the pure liquid HX under pressure p°HX to the infinitely dilute aqueous HX standard states. The data available for HX = HBr are examined, and lead to log (K′a(m)/mol kg–1)= 8.60 ± 0.06 at 25°C, compared with 8.56 ± 0.07 for HI, 6.07 ± 0.03 for HCl and 3.65 ± 0.05 for HNO3. The apparent standard enthalpy of dissociation is ΔH′a/kJ mol–1=– 61 ± 3 for HBr compared with – 46 ± 4 for HCl. The degree of dissociation α of hydrobromic acid is estimated from a comparison of γs with the estimated activity coefficient of the ionized part, γ±. It falls below unity at ms > 7.5 mol kg–1, reaches ≈ 0.7 in the azeotropic acid (≈ 11 mol kg–1), and as low as ≈ 0.3 in nearly saturated acid, 20 mol kg–1. These estimates will be subject to revision when spectroscopically based values become available.

Intramolecular Kinetic Isotope Fractionation in the Decomposition of Alkaline Earth Carbonates by 47% Aqueous Hydrobromic Acid. Part II.

Intramolecular Kinetic Isotope Fractionation in the Decomposition of Alkaline Earth Carbonates by 47% Aqueous Hydrobromic Acid. Part II.

Preparation, crystal structure and enthalpy of formation of dicaesium hexabromoneptunate

Cs 2NpBr 6 has been prepared by precipitation from a saturated aqueous hydrobromic acid solution. X-ray powder diffraction patterns showed that the compound is face-centred cubic and isomorphous with the corresponding uranium compound. The lattice parameter is 11.082 ± 0.002 Å at 296 ± 2 K and the crystal contains four molecules per unit cell. The enthalpy of solution in 1M HCl at 298.15 ± 0.05 K has been measured as − 107.3 ± 0.4 kJ mol −1. Combination of this value with other thermodynamic data yield − 1682.5 ± 1.9 kJ mol −1 for the standard enthalpy of formation of the compound at 298 K.

Synthese von bromosubstituierten Butenoliden II

Synthesis of Bromosubstituted Butenolides II.Methyl 4,4′‐dibromosenecioate (2) was prepared by double N‐bromosuccinimide bromination of methyl senecioate (1) and converted to methyl 4,4′‐diiodo‐senecioate (3) with sodium iodide and to 3‐bromomethyl‐2‐buten‐4‐olide (4) with aqueous hydrobromic acid. A mixture of methyl (Z)‐ and (E)‐4‐bromosenecioate (8 and 9) yielded 3‐methyl‐2‐butenolide (5) with aqueous hydrobromic acid and a mixture of (Z)‐and (E)‐4‐methoxy‐senecioic acid (10 and 11) with methanolic potassium hydroxide. N‐Bromosuccinimide treatment of the butenolide 5 afforded 4‐bromo‐3‐methyl‐2‐buten‐4‐olide (6) and 4,4‐dibromo‐3‐methyl‐2‐buten‐4‐olide (7).

Preparative investigations of bromoantimonates(III)

In aqueous hydrobromic acid the reaction between antimony tribromide and amine hydrobromides gives rise to only one type of bromoantimonate(III), irrespective of the initial ratio of the reactants. Different types of bromoantimonates containing the same protonated amine cation have been prepared by the interaction of antimony tribromide with the amine hydrobromide, in appropriate ratios, at higher temperatures in the absence of solvent and also by a metathetical reaction between an amine hydrobromide and bromoantimonate of another amine in acetone. Conductimetric titrations of antimony tribromide with amine hydrobromides in isopropanol were used to establish the stoichiometry of these reactions.

Distribution coefficients and cation-exchange behaviour of elements in hydrobromic acid-acetone media

Cation-exchange distribution coefficients with Bio-Rad AG50W-X8, a sulphonated polystyrene cross-linked with divinylbenzene are presented for 54 cations in hydrobromic acid-acetone media, ranging from 0.1 to 3.0 M acid and 0 to 95% acetone. The elements are arbitrarily arranged according to their coefficients in aqueous hydrobromic acid. Some possible separations are pointed out and aspects of the elution behaviour of various elements are discussed. The versatility of hydrobromic acid-acetone mixtures as eluting agents for cation-exchange separations are demonstrated by sequential elution of the mixtures Hg(II). Cd, In, Zn, Cu(II) and Co(II); Bi(III), Pb, Zn, Fe(III) and Mn(II); and Au(III), Cd, In, Ga, Al and Sc.

Determination of thermoelectric powers in aqueous hydrobromic acid using hydrogen electrodes

The initial thermoelectric power (t.e.p.) has been determined for hydrogen electrodes in aqueous HBr solutions as a function of molality from 0.0004 to 0.11 mol kg–1 and as a function of temperature for a 10°C temperature difference at mean temperatures of 15, 25, and 35°C. For each mean temperature the thermoelectric powers have been analyzed by fitting the data to a linear equation. Comparison of each linear coefficient has been made with a value calculated from a heat-of-transport theory, which was modified so that each theoretical linear coefficient of the thermoelectric power was calculated. The theoretical and experimental values for the linear coefficient at each temperature are in agreement to within 7 %.