Modellrechnungen zum Gegenioneneinfluß auf die kationische Polymerisation; Der Zerfall der gemischten Halogenoantimonate SbCl5Br− und SbClBr

Model Calculations on the Counterion Effect in the Cationic Polymerization; Decay of the Mixed Halogenoantimonates SbCl₅Br⁻ and SbClBr The decay of the halogenoantimonates SbCl₅Br⁻ and SbClBr according to SbCl₅Br⁻ → SbCl₅ + Br⁻ resp. SbCl₄Br + Cl⁻ and SbClBr → SbBr₅ + Cl⁻ resp. SbClBr₄ + Br⁻ has been investigated by the quantum-chemical CNDO/2 method including geometry optimization. The calculations show that the dissociation of the Sb Cl bond needs more energy (7,8 kcal/mol) than the dissociation of the Sb Br bond. Dissociation of the complex anions is facilitated with increasing Br content.     

Stereochemische Gesichtspunkte zu der Reaktion zwischen Cyclohexylidenacetaldehyden und Mercaptanen

Some Stereochemical Aspects of the Reaction between Cyclohexylidene Acetaldehydes and Thiols The reaction between cyclohexylidene acetaldehyde, 4-methyl-cyclohexylidene acetaldehyde resp. 4-tert.-butylcyclohexylidene acetaldehyde and thioglycolic acid thioglycolic acid methylester, benzylthiol resp. isopropylthiol and catalytical amounts of conc. HCl gave 60% cyclohexylidene acetaldehyde dimercaptales 1 – 3 . In addition to these compounds i t was also obtained in 40% a mixture of 46% cis and 54% trans forms of the cyclohexane derivatives 4–9. Double magnetic non equivalent methylenic protons were found in the compounds 2a – 2c and 3a – 3c and double magnetic non equivalent geminal methyl groups in the compounds 2d and 3d . ⁴J_H,H couplings were observed in 1–3. The reaction mechanisms of the formation of the compounds 4–9 as well as the ¹H-n.m.r. spectra of the compounds 1–9 were discussed.     

Zur Rolle von EDA-Komplexen bei kationischen Polymerisationen. IV. Untersuchungen an Modellsystemen in Lösung

On the Role of Charge-Transfer Complexes in Cationic Polymerization. IV. Investigation of Model Systems in Solution For the purpose of modelling the influence of donors on the cationic polymerization the complex formation between triphenylmethyl salts of the type (p-R C₆H₄)₃C⁺MtX and aromatic π-and n-donors was investigated. The position of the charge-transfer bands, the equilibrium constants as well as the enthalpies and entropies of complex formation were correlated with the acceptor strength of the cations resp. the basicity of the donors. The complex formation equilibrium was found to be strongly influenced not only by electronic but also steric effects. Strong π-donors like hexamethylbenzene and anthracene as well as n-donors like dialkylethers show a deviating behaviour.     

Selektivitätsstudien: OH-, NH- und SH-gruppenspezifische Reagentien – ihre Anwendung in der organischen Analytik und als Schutzgruppen in der Synthese

Selectivity: OH-, NH- and SH-Groupspecific Reagents. The Application in Organic Analysis and as Protective Groups Phosphylhalides and -pseudohalides R¹R²P(O)X (X = Cl, F, CN, N₃, OC₆H₄NO₂(p)) reactdepending on X- with a different selectivity with OHNH- and SH-groups. Vinylsulfones ArSO₂CH = CH₂ are SH-selective. Silanes R₃SiH are OH-selective. By exchange of one ligand bound on P, SO₂ or Si by the 5-dimethylamino resp. the 5-methoxynaphthalinogroup reagents are formed, which combine group selectivity with fluorescence. The fluorescence is quenched if a ligand or the leaving group is substituted by a NO₂-group. The fluorescence appears again if after the group selective fixation the ligand with the nitrogroup is split off. In serine enzymes (α-chymotrypsine, trypsin, butyryl- and acetylcholinesterase, subtilisine) and insuline (after the reductive opening of the S-S bridges) the primary OH-groups in the active site in the enzymes resp. the SH groups in the reduced insuline were substituted with fluorescing groups using group selective fluorescing reagents.     

31P-NMR-Untersuchungen N-Aryl-substituierter Iminotriphenylphosphorane: Hammettbeziehung zwischen 31P-Verschiebung und Substituentenkonstanten

³¹P-NMR Investigation of N-Aryl-substituted Iminotriphenylphosphoranes: Hammett Relationship between ³¹P Chemical Shift and Substituent Constants The ³¹P chemical shifts of p- and m-substituted N-arylimino-triphenylphosphoranes reflect the electronic influence of the substituents and can be correlated by a Hammett relationship. This new correlation was used for the estimation of σ- resp. σ-values for p-(CH₃)₂N-, p-C₆H₅CO- and p-C₆H₅ N  N-groups as well as for β-naphthyl- and pyridyl(4)-rings. The applicability of a similar Hammett equation for the o-substituted compounds is not possible.     

Pyryliumverbindungen. XXVII. Spezifisch deuterierte Carbo- und Heterocyclen via 2,4,6-Triaryl-[3,5-2H2]pyryliumsalze

Pyrylium Compounds. XXVIII. Specifically Deuterated Carbo- and heterocycles via 2,4,6-Triaryl[3,5-²H₂]pyrylium Salts On heating with catalytic amounts of bases(e.g. triethyl amine) in deuterated alcohols such as methan[²H]ol or ethan[²H]ol pseudobases of 2, 4, 6-triarylpyrylium salts 1 undergo fast¹H/²H isotopic exchange reaction affording 1, 3, 5-triaryl[2, 4, 4-²H₃]pent-2-ene-1,5-diones which with [²H] perchloric acid give highly deuterated 2, 4, 6-triaryl-[3, 5-²H] pyrylium perchlorates 8 . These salts are obtainable also directly from 1 through a one-pot procedure by ring opening of the latter with deuterium oxide under the above-mentioned¹H/²H isotopic exchange conditions followed by recyclization of the formed 1, 3, 5-triaryl[2, 4, 4-²H₃]pent-2-ene-1, 5-diones with [²H]ClO₄. Ring transformations of 2, 4, 6-triphenyl[3, 5-²H²]pyrylium perchlorate (8a) to 2, 4, 6-triphenyl[3, 5-²H₂]nitrobenzene (9) 2, 4, 6-triphenyl[3, 5-²H₂]pyridine (10) , 1, 2, 4, 6-tetraphenyl[3, 5-²H₂]pyrydinium perchlorate (11) , 2, 4, 6-triphencyl[3, 5-²H₂]thiopyrylium perchlorate (12) , 2-benzoyl-3, 5-diphenyl[4-²H]furan (13) , and 3, 5, 7-triphenyl-[4, 4, 6-²H₃]4H-1, 2-diazepin (14) demonstrate the usability of pyrylium salts of type 8 as starting materials for syntheses of specifically deuterated carbo- and hetrocycles.     

On the anode effect in cryolite-alumina melts—II the initiation of the anode effect

Polarization curves obtained with graphite anodes in cryolite-alumina melts by steady state, potential sweep and galvanostatic measurements exhibited three steps at low alumina concentrations, due to the formation of CO₂ and CF₄, prior to the anode effect (AE), and probably of F₂ after the occurrence of the AE. Formation of CF₄ started at ~2·8 V positive to the aluminum electrode, while the potential and the critical current density (ccd) at which the AE occurred were 3·5 V and 0·11 A/cm² resp. in purified cryolite and 2·7 V and 2·1 A/cm² at 1 wt per cent Al₂O₃. The proportion of CF₄ in the gas reached 40 per cent in purified melts, but decreased sharply on the addition of alumina. At > 2 wt per cent Al₂O₃ the ccd decreased when the external pressure was lowered approximately in proportion to the volume of escaping gas. It is concluded that the AE occurs when the melt adjacent to the anode is depleted with respect to oxygen-containing ions, and the rate of fluoride ion discharge exceeds the rate of CF₄ formation.     

Orthoamide. LI. Push-Pull-Butadiene und Heterocyclen aus CH2-aciden Verbindungen und Orthoamiden von Alkincarbonsäuren

Orthoamides. LI. Push-Pull-Butadienes and Heterocycles from Alkyne Carboxylic Acid Orthoamides and CH₂-acidic Compounds The acetylides 4b, 4f react with N,N,N′,N′,N″,N″-hexamethylguanidiniumchloride ( 5 ) to give the orthoamides 6b, 6f , resp. From CH₂-acidic compounds and the orthoamides 6a, c, e can be obtained the push-pull-substituted butadienes 8a–8aj . The 2,3,5-trimethyl-thiadiazolium salt 9 does not condense with 6e , as other CH₂-acidic compounds do, instead the vinylogous guanidinium salt 10a is produced. On heating, the ketenaminals 8d, aa cyclize to give the pyridone-carbonitriles 11a, b , resp. From 4-amino-coumarins 12 and the orthocarboxylic acid amideacetals 13a, b and the ketenaminal 16 resp., the amidines 14a–c and the heterocyclic compounds 15a–c resp., are formed. The enamines 17a–c, 19a, b react with the orthoamides 6a–f to give the pyridine derivatives 18a–1, 20a–h and 21a, b , resp. Analogously, from 6-aminouracil 22 and 6a, b, e, f are formed the pure 7-dimethylaminopyrido[2,3-d] pyrimidines 23a, b or mixtures of compounds 23c, d and the isomeric 4-dimethylamino-pyrido[2,3-d]pyrimidines 24a, b resp., which can be separated via their salts 25a,b/26a,b . The heterocyclic compounds 30a–d, 32a,b can be prepared from the pyrazole derivatives 28, 31 resp. and the orthoamides 6a–f .     

Isomerisierung von (Z)-But-2-en-1,4-diol zu 4-Hydroxybutyraldehyd in Gegenwart von Palladium-(O)-komplexen mit tert. Phosphin- und tert. Phosphitliganden

Isomerization of (Z)-But-2-ene-1,4-diol to 4-Hydroxybutyraldehyde by Means of Palladium-(O)-complexes with tert. Phosphine and tert. Phosphite Ligands Catalysts of the type Pd(C₂H₄)(PR₃)₂ transform Z-but-2-ene-1.4-diol 1 to 4-hydroxy-butyraldehyde 2 in good to excellent yields. Analogous results are obtained by in situ preparations of catalysts from bis-(dibenzylideneacetone)-palladium and the phosphines and phosphites, resp., or even from the latter and palladium black. Velocity and selectivity of the reaction decrease in the order R:Cy > n-Bu > Et ≫ o-Tol > Ph ≫ O-o-tol. These results lead to the conclusion that mainly the electronic and not the steric properties of the ligands PR₃ determine the catalysts properties.     

Electrical Aspects of Adsorbing Colloid Flotation. X. Pretreatments,Multiple Removals,Interferences, and Specific Adsorption

Abstract

The compatibility of the adsorbing colloid flotation of Cu(II) with Fe(OH)₃ and sodium lauryl sulfate with a variety of precipitation pretreatment techniques was studied. Procedures were developed which permitted precipitation pretreatment and effective foam flotation polishing. The interferences of glycerol, ClO₄ ^?, NO₃ ^?, C1^?, CN^?, CNS^?, F^?, SO4₄ ^2?, HPO₄ ^2?, HAsO₄ ^2?, C₂O₄ ^2?, (PO₃)₆ ^6?, and EDTA with the precipitate flotation of ferric hydroxide by sodium lauryl sulfate were studied. The simultaneous adsorbing colloid flotation of Cu(II), Pb(II), and Zn(II) with Fe(OH)₃ and sodium lauryl sulfate was found to be effective in the pH range 6 to 7 at ionic strengths below 0.1 mole/l. A model was analyzed for calculating surface potentials for floe surfaces having the charge distributed at discrete sites in the presence of electrolytes. Plots of surface potential versus adsorbable ion concentration were calculated for various values of the model parameters.     

Studies concerning the growth of cadmium dendrites. II. Morphology in acidic media

The morphology of cadmium deposits formed during potentiostatic deposition onto etched cadmium substrates in a range of cadmium sulphate solutions with 0.5 mol dm^?3 sulphuric acid as supporting electrolyte has been investigated. The deposit morphology and induction time was found to be both concentration and overpotential dependent. At 10^?1 mol dm^?3 CdSO₄ for an overpotential range ?20 to ?80 mV, large crystalline aggregates were observed and large dendrites resulted after longer deposition times. The induction time was less than 1 min and the current time curves linear, indicating instantaneous rather than progressive initiation. At 10^?2 mol dm^?3 CdSO₄ the morphology varied from fine, 2D-fern dendrites atη=?75 mV to needle dendrites atη=?150 mV. The morphology at 10^?3 mol dm^?3 CdSO₄ closely resembled that at 10^?2 mol dm^?3 CdSO₄ but, showed finer structural detail with less filling in of the main skeletal structure. The induction time was an order of magnitude greater at 10^?3 mol dm^?3 CdSO₄ than at 10^?2 mol dm^?3 CdSO₄, and the time taken to grow dendrites of the same length was also increased.     

Voltammetric study of the cyanide complexes of osmium—II. The behaviour of lower oxidation state cyanide complexes of osmium on a platinum rde

It was found that the product of the reduction of the cyanide complex of hexavalent osmium, OsO₂(OH)₂(CN)^2?₂ is the Os(OH)₄(CN)^3?₄ complex and the product of the reduction of the OsO₂(CN)^2?₄ complex is the Os(OH)₂(CN)^2?₂ complex. Further reduction of the Os(OH)₄(CN)^3?₄ complex of trivalent osmium is complicated by a follow-up chemical reaction and the stable reduction product is a complex of divalent osmium, Os(OH)₂(CN)^4?₄ which forms a reversible redox system with the Os(OH)₂(CN)^3?₂ complex with a formal redox protential (1 M KOH, 0.1 M KCN) of ?760 mV/sce. The Os(OH)₄(CN)^3?₂ and Os(OH)₂(CN)^4?₄ complexes are stable only in solutions with at least a ten-fold excess of OH^? ions over the concentration of CN^t- ions. At greater cyanide concentrations, the chemical reactioins, Os(OH)₄(CN)^3?₂ → Os(OH)₂(CN)^3?₄ and Os(OH)₂(CN)^4?₄ → Os(CN)^4?₆, occur. The reaction rate for the latter reaction was found to be ?₄ = 1.87 × 10^t-4 l mol^?1 s^?1 in solutions with pH = 11.8. The characteristics of the individual forms of the cyanide complexes of osmium are also discussed.     

α-Substituierte Phosphonate. 39. Methandiphosphonsäureester durch UV-induzierte Michaelis-Becker-Reaktion

α-Substituted Phosphonates. 39. Methane-diphosphonic Esters by U.V.-Induced Michaelis-Becker-Reaction Dibromomethane resp. chlorbromomethane reacts with sodium dialkyl phosphite in heptane-/liq.NH₃ or in liq. NH₃ by u.v. irradiation at low temperatures to give in good yields methane diphosphonic acid tetraalkylesters 1 . In the same manner with sodium diethyl thionophosphite the corresponding methane-bis-thiophosphonic acid tetraethylester 4 is obtained.     

Die Reaktion von α,β-Dihalogen-propionitrilen mit monosubstituierten Hydrazinen - einfache Synthese 1-substituierter 3- bzw. 5-Amino-pyrazole

The Reaction of α,β-Dihalogeno-propionitriles with Monosubstituted Hydrazines — A Simple Synthesis of 1-Substituted 3- or 5-Amino-pyrazoles In methanol hydrazines 3 , and α,β-dihalogeno-propionitriles 1, 2 even at 0°C irreversibly yield 3 · HX, and α-halogenoacrylonitriles 4, 5 (A₁). Fast addition of alkyl- and aralkyl- hydrazines 3 to 4, 5 (C) gives 1-substituted 1-(2′-halogeno-2′-cyan-ethyl)-hydrazines 6 , the addition of arylhydrazines 3 to 4, 5 (D) 1-aryl-2-(2′-halogeno-2′-cyan-ethyl)-hydrazines 8 . In methanol 6 spontaneously cyclise (E) to hydrogen halides 7 · HX of 1-alkyl- and 1-aralkyl-3-amino-pyrazoles, 8 with 2 moles of acids (F) to salts 10 · 2HY of 1-aryl-4-halogeno-5-imino-pyrazolidines, and the free 10 spontaneously (G) to hydrogen halides 9 · HX of 1-aryl-5-amino-pyrazoles. Mechanisms (A₁), (C), (D), (E), (F), and (G) are proved by t.l.c., ¹H-n.m.r., and isolation of intermediates, the structures of 7 resp. 9 , using the significant ¹H-n.m.r.-parameter Δ. Simple general syntheses are described for 3-amino-pyrazoles 7 (R = H, alkyl, aralkyl) or 5-amino-pyrazoles 9 (R = aryl) starting with α,β-dihalogeno-propionitriles 1, 2 , and for α-bromo-acrylonitrile 5 .     

A chemically regenerative redox fuel cell. II

Our previous paper [1] has described an unconventional chemically regenerative redox fuel cell, including a modest amount of performance data, and has pointed out a number of problem areas. This paper describes additional work and some attempts that have been made to improve the cell performance in several of the problem areas described in the first paper. Two different redox fuel cell systems employing the V²⁺/V³⁺ and Mo³⁺Mo⁴⁺ redox couples as the anolyte, and a new NO ₃ ^–/NO catalyst system for VO²⁺ oxidation were explored and described. The reduction of Na₂MoO₄ to Mo⁴⁺ and Mo³⁺ by H₂ in concentrated H₂SO₄ solution was studied in small scale laboratory experiments and discussed. The performance of a redox cell in which H₂ was obtained from the Pd-catalysed decomposition of formic acid, HCOOH, is described and the results of experiments with different membranes are reported. The results of experiments using WC as a hydrogenation catalyst at a temperature of 70–90° C with mixed molybdo-tungsto-silicic acids are reported and discussed.     

Anodic substitution in emulsions under phase transfer catalysis conditions. II. Acetoxylation of dimethoxybenzenes

The anodic acetoxylation of 1,2-dimethoxybenzene in H₂O-CH₂Cl₂ emulsions with different phase transfer agents (nBu₄N⁺HSO ₄ ⁻ ,nBuP⁺ φ ₃Br⁻, Aliquat 336, Hyamine 1622 and CTAB) has been investigated. The conversion rates and the electrochemical efficiencies are mainly governed by two parameters: (a) the anode wetting by an organic layer which varies with the nature of the catalyst as shown by the preparative polarization curves; (b) the competitive oxidation of the counter-ions present in the organic phase (CH₂C1₂). The latter point is very important in the case of bromide salts. On the basis of these observations, the use ofnBu{4}N⁺HSO ₄ ⁻ appears to be the best compromise for the case of anodic acetoxylation of aromatic substrates in the media studied.     

Electrodeposition of catalytically active nickel powders from sulphate baths. I. Effect of bath constituents

A detailed study was made of the influence of the sulphate bath constituents: 0.3 - 0.0125 NiSO₄·7H₂O (I), 0.05 – 0.23 (NH₄)₂SO₄ (II), 0.1 – 0.4 H₃BO₃ (III) and 0.07 – 0.35 mol l^?1 Na₂SO₄·10H₂O (IV) on the electrodeposition of nickel powder. The cathodic polarization, current efficiency, growth morphology, crystallite size and catalytic activity of the electrodeposited nickel powders were affected to different extents by the bath constituents. A highly pure nickel powder characterized by a small crystallite size (776 Å) and moderate catalytic activity was obtained from a bath containing: 0.0125 (I), 0.23 (II), 0.1 (III) and 0.07 mol l^?1 (IV) at a current density of 10 A dm^?2 and electrolysis time 60 min. at 25 °C. Structural studies with a scanning electron microscope are given and a reaction mechanism for the electrolytic powder deposition is discussed.     

THE EXTRACTION BY N.N'TETRABUTYLGLUTARAMIDES II. EXTRACTION OF U(VI), Pu(IV) AND SOME FISSION PRODUCTS

The extraction of U(VI) and Pu(IV) from aqueous nitrate solutions by N,N'-tetrabutylglutaramide (TBGA) has been investigated. At low acidities, the extraction takes place via the formation of respectively UO₂(NO₃)₂. TBGA and Pu(NO₃)₄. TBGA which seem to be linked with additionnal molecules of TBGA in the second coordination sphere of the metal. When the saturation of TBGA by UO₂ ²⁺solutions is reached, the uranyl complex reorganizes to give a polymer (UO₂(NO₃)₂ TBGA)_x.

At high acidities, the anionic complexes : [UO₂(NO₃)₃, ^?] [HTBGA⁺] and probably [HPu(NO₃)₆?] [HTBGA+] are observed.     

Corrosion of nickel in sodium sulphate-sodium chloride melts. Part I

The corrosion behaviour of Ni in molten Na₂SO₄, NaCl, and in mixtures of these two salts, at 900° C, in laboratory air and under O₂+SO₂/SO₃ atmospheres has been examined by electrochemical curves and topochemical analysis of corrosion products.Ni passivity in pure Na₂SO₄ was observed under potentiodynamic and potentiometric conditions, the passive film corresponding to NiO. Passivity was not so easy to achieve in chloride melts as in sulphate alone, but once a thick oxide film forms on the specimen, the Cl^– addition is accompanied by an increase in the film stability. The inhibiting role of NaCl on Ni in the passive-transpassive area was also evidenced. In opposition, halide additions (especially those up to 25%) increased the dissolution current densities of Ni in the active region. These higher dissolution rates are represented by the equation Ni₃S₂+4NaCl+1/2 O₂ = 2NiCl₂+2Na₂S + NiO which is also suggested as a critical factor in the Ni passivation.The passive capability found for Ni in Na₂SO₄/NaCl melts, in air, is destroyed by SO₃ atmospheres. This corrosion-stimulation is due to the SO₃ role in promoting reactions such as NiS + 3O^2– = Ni²⁺+SO₃+8e which would be potential-determining at the Ni surface until Ni²⁺ precipitates or the conjugate oxygen cathodic reduction process takes place. Microprobe analysis also evidenced S penetration which might be the reason for the Ni embrittlement.The polarization curves for Ni in pure NaCl showed the lack of a passive region; occurrence of extensive intergranular attack was also indicated by metallographic observation. The observed dissolution must occur at the expense of the Ni interactions with the species which intervene in the reaction equilibrium between O₂ and molten NaCl (O₂, Cl^–, Cl₂ and O^2–) as well as with the Na⁺ cations, as has been discussed elsewhere. Its self-sustaining nature is enhanced by the continuous reduction of the nickel ion content of the melt by NiCl₂ evaporation.     

Cellulose phosphates as biomaterials. I. Synthesis and characterization of highly phosphorylated cellulose gels

The present study concerns the investigation of a material expected to be biocompatible and able to promote bone regeneration. For this purpose, cellulose was chemically modified by phosphorylation. Once implanted, phosphorylated cellulose could promote the formation of calcium phosphates, thus having closer resemblance to bone functionality. In a previous investigation, the obtention and the preliminary characterization of cellulose phosphate gels were reported. In the present study, the synthesis by the H₃PO₄/P₂O₅/Et₃PO₄/hexanol method was optimized in terms of reaction parameters. The structure of materials was investigated by FTIR, Raman, and solid‐state ³¹P– and ¹³C–NMR spectroscopic studies, and X‐ray diffraction. Water swelling and stability to sterilization by gamma‐radiation were also assessed. It was demonstrated that the present method allows highly phosphorylated cellulose derivatives to be obtained. Cellulose triphosphates gels are described here for the first time. Products obtained were poorly crystallized monoesters, apparently not significantly affected by gamma sterilization and showed a high water swelling capability. Chemical bonding was confirmed by FTIR, Raman, and both ³¹P– and ¹³C–NMR spectroscopies. It was also shown that the H₃PO₄/P₂O₅/Et₃PO₄/hexanol method provides a versatile and interesting alternative route to some of the more widely used techniques for the phosphorylation of cellulose. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3341–3353, 2001