Aspects of tautomerism. Part 16. Influence of the y-keto function on the reactions of sulphonic acids

Reaction of sodium 2-formylbenzenesulphonate (1) with thionyl chloride or phosphorous pentachloride gives a mixture of pseudo (2) and normal (3) sulphonyl chlorides. Whereas ammonium 2-carboxybenzenesulphonate (6) gives only the normal sulphonyl chloride (7) on reaction with thionyl chloride, a mixture of normal (7) and pseudo (8) isomers are formed on reaction with phosphorous pentachloride. Sodium 2-benzoylbenzenesulphonate (15), on the other hand, gives the corresponding normal sulphonyl chloride (16) on reaction with both of the reagents mentioned above. Based on these observations it is concluded that γ-keto sulphonic acids are amenable to the influence of γ-carbonyl group as in the case of γ-keto carboxylic acids but to a lesser extent. © 1989 Indian Academy of Sciences.

Chemical potentials of oxygen for fayalite-quartz-lron and fayalite-quartz-magnetite equilibria

The oxygen potentials corresponding to fayalite-quartz-iron (FQI) and fayalite-quartz-magnetite (FQM) equilibria have been determined using solid-state galvanic cells: Pt,Fe + Fe2SiO4 + SiO2/(Y2O3)ZrO2/Fe + \r"FeO,\l"Pt and Pt, Fe3O4 + Fe2SiO4 + SiO2/(Y2O3)ZrO2/Ni + NiO, Pt in the temperature ranges 900 to 1400 K and 1080 to 1340 K, respectively. The cells are written such that the right-hand electrodes are positive. Silica used in this study had the quartz structure. The emf of both cells was found to be reversible and to vary linearly with temperature. From the emf, Gibbs energy changes were deduced for the reactions: 0.106Fe (s) + 2Fe0.947O (r.s.) + SiO2 (qz) → Fe2SiO4 (ol) δG‡= -39,140+ 15.59T(± 150) J mol-1 and 3Fe2SiO4 (ol) + O2 (g) → 2Fe3O4 (sp) + 3SiO2 (qz) δG‡ = -471,750 + 160.06 T±} 1100) J mol-1 The “third-law≓ analysis of fayalite-quartz-wustite and fayalite-quartz-magnetite equilibria gives value for δH‡298 as -35.22 (±0.1) and -528.10 (±0.1) kJ mol-1, respectively, independent of temperature. The Gibbs energy of formation of the spinel form of Fe2SiO4 is derived by com-bining the present results on FQI equilibrium with the high-pressure data on olivine to spinel transformation of Fe2SiO4.

Simulation of precipitation reactions in reverse micelles

Precipitation involving mixing of two sets of reverse micellar solutions-containing a reactant and precipitant respectively-has been analyzed. Particle formation in such systems has been simulated by a Monte Carlo (MC) scheme (Li, Y.; Park, C. W. Langmuir 1999, 15, 952), which however is very restrictive in its approach. We have simulated particle formation by developing a general Monte Carlo scheme, using the interval of quiescence technique (IQ). It uses Poisson distribution with realistic, low micellar occupancies of reactants, Brownian collision of micelles with coalescence efficiency, fission of dimers with binomial redispersion of solutes, finite nucleation rate of particles with critical number of molecules, and instantaneous particle growth. With the incorporation of these features, the previous work becomes a special case of our simulation. The present scheme was then used to predict experimental data on two systems. The first is the experimental results of Lianos and Thomas (Chem. Phys. Lett. 1986, 125, 299, J. Colloid Interface Sci. 1987, 117, 505) on formation of CdS nanoparticles. They reported the number of molecules in a particle as a function of micellar size and reactant concentrations, which have been predicted very well. The second is on the formation of Fe(OH)(3) nanoparticles, reported by Li and Park. Our simulation in this case provides a better prediction of the experimental particle size range than the prediction of the authors. The present simulation scheme is general and can be applied to explain nanoparticle formation in other systems.

Elastic Properties of Alkali Phosphomolybdate Glasses

Ultrasonic velocities at 10 MHz have been measured in two series of lithium, sodium, and potassium phosphomolybdate glasses with two fixed P2O5 concentrations. Elastic moduli, Poisson's ratio, and Debye temperature have been calculated. The composition dependence of most of the properties of lithium glasses exhibits a trend opposite to that of potassium glasses. Properties of sodium glasses lie between the other two alkali systems. Alkali oxide modification is suggested to be accompanied by ring reformation in lithium and sodium glasses. Ring size effects have been shown to account for all of the composition dependence.

Studies on optical absorption and photoluminescenceproperties of Pr3+ and Nd3+ doped mixed alkali chloroborate glasses

This article presents the optical absorption and emission properties of Pr3+ and Nd3+ doped two different mixed alkali chloroborate glass matrices of the type 70B(2)O(3)center dot xLiCl center dot(30 - x)NaCl and 70B(2)O(3)center dot xLiCl center dot(30 - x)KCl (x = 5, 10, 15.20 and 25). The variation of Judd-Ofelt parameters (Omega(2), Omega(4) and Omega(6)), total radiative transition probabilities (A(T)), radiative lifetimes (tau(R)) and emission cross-sections (sigma(p)) with the variation of alkali contents in the glass matrix have been discussed in detail. The changes in the peak wavelengths of the hypersensitive transition and intensity parameters with x are correlated to the structural changes in the host matrix. The estimated radiative lifetimes of certain excited states of Pr3+ and Nd3+ in these two glass matrices are reported. Peak stimulated emission cross-sections (sigma(p)) are reported for the observed emission transitions of Pr3+ and Nd3+ ions. Branching ratios (beta) of the observed emission transitions obtained from the Judd-Ofelt theory are compared with the values obtained from the emission spectra. (C) 2010 Elsevier B.V. All rights reserved.

Asynchronous behaviour in some three-atom linear concerted radical-exchange reactions

A few simple three-atom thermoneutral radical exchange reactions (i.e. A + BC --> AB + C) are examined by ab initio SCF methods. Emphasis is laid on the detailed analysis of density matrices rather than on energetics. Results reveal that the sum of the bond orders of the breaking and forming bonds is not conserved to unity, due to development of free valence on the migrating atom 'B' in the transition state. Bond orders, free valence and spin densities on the atoms are calculated. The present analysis shows that the bond-cleavage process is always more advanced than the bond-formation process in the transition state. Further analysis shows a development of the negative spin density on the migrating atom 'B' in the transition state. The depletion of the alpha-spin density on the radical site "A" in the reactant during the reaction lags behind the growth of the alpha-spin density on the terminal atom "C" of the reactant bond, 'B-C' in the transition state. But all these processes are completed simultaneously at the end of the reaction. Hence, the reactions are asynchronous but kinetically concerted in most cases.

Bicyclic Phosphazenes Derived from (Amino) Cyclotetraphosphazenes

Amination reactions of 2,6-bis(primary amino)cyclotetraphosphazenes yield not only the expected (amino)cyclotetraphosphazenes but also novel trans-annular bridged bicyclic phosphazenes by an intramolecular substitution pathway. In addition, resins are formed in some reactions by an intermolecular condensation. The effect of substituents attached to the phosphazene ring, the attacking nucleophile and solvent on the formation of the trans-annular P-N-P bridge is considered in detail in relation to plausible reaction mechanisms. Analytical separation of bicyclic phosphazenes by high performance liquid chromatography (HPLC) on a reverse phase silica column is demonstrated. Structural features of bicyclic phosphazenes and salient aspects of their NVR spectroscopic data are discussed.

Reactions of coordinated bivalent tetradentate schiff-base chelates of nickel (II) and palladium (II)

Reactions of N,N′-n-propylene-bis(acetylacetoneimino) metal (II), M[n-P-(AI)2], where M=Ni(II) or Pd(II), with nitrosating reagents have been investigated. Mono- and di-nitrosated complexes were obtained selectively, depending upon the concentration of the nitrosating reagents and the reaction time. In both the cases, the γ-CH group is transformed to an ambidentate isonitroso group (>C=NOH), which coordinates to the metal ion by dislodging the already coordinated carbonyl group. The factors influencing the mode of binding of the isonitroso group have been discussed. The bromination reactions of the mono-nitrosated products of M[n-P-(AI)2] and Pd (II) complexes, Pd [E/i-P-(AI)2], where E/i-P-(AI)2 is a dianion of ethylene/i-propylene-bis (acetylacetoneimine), are also reported. The reaction products have been characterized by elemental analyses, electrical conductivity molecular weight determination, and ir, pmr and electronic spectral data.

Attaching chelating ligands to polybenzimidazole via epoxidation to obtain metal selective sorbents

Microporous polybenzimidazole of 250–500 μm spherical bead size from Celanese has been reacted with epichlorohydrin and sodium hydroxide and the resulting product with pendant epoxy groups has been reacted with various chelating ligands in order to augment the metal sorption capacity and selectivity of the resin. The chelating ligands used include ethylenediamine, diethylenetriamine, diethanolamine, dimethylglyoxime, L-cysteine, thiourea, dithiooxamide, glyoxal-bis-2-hydroxyanil, salicylaldehyde-ethylenediimine, and glyoxal-bis-2-mercaptoanil. The aminolysis of the pendant epoxy groups with the oligoamines has been performed in pyridine under reflux conditions, while the addition reactions with the other ligands which are alkali soluble have been carried out at room temperature in a mixture of dioxane and aqueous KOH using tetra-n-butylammonium iodide as the phase transfer catalyst. The products are found to possess high capacity and selectivity in metal sorption depending on the ligand attached.

Copper(I) promoted C---C bond forming reactions: direct activation of allyl alcohols

Allylic alcohols, acetates, carbonates and chlorides can be activated by copper(I) salts towards nucleophilic substitution by carbon nucleophiles under relatively mild conditions.

A Novel Synthetic Route For The Preparation Of Ammonium And Alkali-Metal Tetrafluoroborates And Alkyl Substituted Ammonium Tetrafluoroborates Using Pyridinium Tetrafluoroborate As The Precursor

Ammonium and alkali metal tetrafluoroborates have been prepared by the cation exchange reaction of pyridinium tetrafluoroborate with the corresponding hydroxides/halides. The reaction of pyridinium tetrafluoroborate with primary, secondary and tertiary alkyl amines at room temperature gives rise to mono-, di- and tri-alkylammonium tetrafluoroborates, respectively. The yields are good and the samples are of high purity. The products have been characterised by elemental analysis, IR and PMR spectroscopy. The spectral data for most of the compounds are reported for the first time.

Catalytic Reactions of Titanium Alkoxides with Grignard Reagents and Imines:A Mechanistic Study

The reactivity of Grignard reagents towards imines in the presence of catalytic and stoichiometric amounts of titanium alkoxides is reported.Alkylation, reduction, and coupling of imines take place. Whereas reductive coupling is the major reaction in stoichiometric reactions, alkylation is favored in catalytic reactions. Mechanistic studies clearly indicate that intermediates involved in the two reactions are different. Catalytic reactions involve a metal alkyl complex. This has been confirmed by reactions of deuterium-labeled substrates and different alkylating agents. Under the stoichiometric conditions, however, titanium olefin complexes are formed through reductive elimination, probably through a multinuclear intermediate.