Aluminum chloride-induced heteroarylation of arenes and heteroarenes. 2. A new synthesis of 4-substituted phthalazin-1(2H)-ones

We herein report the efficient syntheses of 4-(hetero)aryl-substituted 1-chlorophthalazines via heteroarylation of arenes/heteroarenes through AlCl(3)-induced C[bond]C formation reactions. A number of (hetero)arenes were reacted with 1,4-dichlorophthalazine to give aryl/heteroaryl-substituted phthalazines in good to excellent yields. Many of them were converted to the corresponding phthalazin-1(2H)-ones.     

Photochemical thallimetric oxidations-estimation of formic acid

A simple, rapid and convenient redox method has been developed for the estimation of formic acid. Formic acid is photochemically oxidized with thallium(III) in the presence of bromide as catalyst, and the thallium(I) formed is determined by titration with potassium bromate. The procedure can also be used for the estimation of thallium(III) with formic acid as reductant.     

Complexometric determination of thallium(III) in pure solution,alloys, and complexes using semicarbazide hydrochloride as a releasing agent

A simple and accurate complexometric method is proposed for the determination of Tl(III) using semicarbazide hydrochloride as a releasing agent. In the presence of diverse metal ions, thallium is complexed first with a known excess of EDTA, and the surplus EDTA is then titrated with standard zinc sulfate at pH 5.0–6.0 (hexamine) using xylenol orange indicator. An excess of 5% aqueous neutral solution of semicarbazide hydrochloride is then added and the released EDTA is titrated against standard zinc sulfate solution. The method works well in the range 2–50 mg of Tl(III) with relative errors < 0.5%, standard deviations 0.05mg and coefficient of variation 0.4%. The method is applied for the determination of thallium content in complexes and alloy compositions     

Kinetics of the 2,2′-bipyridyl catalyzed Cr(VI)?I? reaction

The kinetics of 2,2-bipyridyl catalyzed Cr(VI)–I^– reaction has been studied. The order with respect to Cr(VI) is one and fractional with respect to bipyridyl. The order in [I^–] changes from unity to zero. Plots of 1/k_obs vs. 1/[bipy] and 1/k_obs vs. 1/[I^–] are straight lines with positive slopes and intercepts.

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2,2-, Cr(VI)–I^–. Cr(VI) , -. [I^–] 1 0. 1/k_obs 1/[bipy] 1/k_obs 1/[I^–] .

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IICT Publication NO. 2586     

Properties of balanced and perfect matrices

In this paper we define wheel matrices and characterize some properties of matrices that are perfect but not balanced. A consequence of our results is that if a matrixA is perfect then we can construct a polynomial number of submatricesA _I,,A _n ofA such thatA is balanced if and only if all the submatricesA ₁,,A _n ofA are perfect. This implies that if the problem of testing perfection is polynomially solvable, then so is the problem of testing balancedness.Partial support under NSF Grants DMS-8606188, ECS-8800281 and DDM-8800281.     

Tin(II) sulphate as a new reductimetric titrant--direct titration of thallium(III) with use of ion-pair and redox indicators

The use of tin(II) sulphate as a direct reductimetric titrant for thallium(III) has been investigated, with potentiometric and visual detection of the end-point. Some azure dyes are used as redox indicators and Methylene Blue is used as both a redox and an ion-pair indicator.     

Kinetics of stepwise oxidation of manganese(II) by peroxodisulphate in phosphoric acid medium

Summary The oxidation of Mn^II by S₂O₈ ^2– to Mn^VII in phosphoric acid medium proceeds via a stable Mn^III and Mn^IV species. The reaction is catalysed by Ag⁺ and exhibits first order dependence on [S₂O₈ ^2–], [Ag⁺] and, is independent of [Mn^II]. The [H⁺] has no significant effect on the reaction. It is observed that the PO₄ ^3– ion stabilises the transient manganese(III) and manganese(IV) species by forming a stable and soluble phosphato-complexes. The activation parameters for the two stages of oxidation, namely Mn^II Mn^IV and Mn^IVMn^VII at 25° C are E_a=52 ±4 kJ mole^–1, S^*=–57±2 JK^–1 mole^–1 and E_a =56±4 kJ mole^–1, S^*=–44±2 JK^–1 mole^–1, respectively. A mechanism consistent with the experimental observations is proposed.Presented at the National Symposium on Reaction Kinetics and Mechanism, Department of Chemistry, University of Jodhpur, Jodhpur, India, Nov. 15–18, 1986.     

Four spectrophotometric methods for determination of nitrofurazone in pharmaceutical formulations

Four simple and sensitive visible spectrophotometric methods (A-D) for the determination of nitrofurazone in bulk samples and pharmaceutical formulations are described. They are based on the formation of colored species by treating either its reduction product with 3-methylbenzothiazolin-2-one hydrazone in the presence of ferric chloride (method A: _max 600 nm) or its hydrolysis product with thiobarbituric acid (method B: _max 520 nm, 440 nm) or barbituric acid (method C: _max 400 nm) or by oxidizing it with excess N-bromosuccinimide and determining the consumed NBS using metol-isonicotinic acid hydrazide (method D: _max 620 nm).     

Structural and electronic properties of compound metal clusters

The equilibrium geometries, relative stabilities, and vertical ionization potentials of compound clusters involving Li _n , Na, Mg, and Al atoms have been calculated using ab initio self-consistent field linear combination of atomic orbitals — molecular orbital (SCF-LCAO-MO) method. The exchange energies are calculated exactly using the unrestricted Hartree-Fock (UHF) method whereas the correlation correction is included within the framework of configuration interaction involving pair excitations of valence electrons. While the later correction has no significant effect on the equilibrium geometries of clusters, it is essential for the understanding of relative stabilities. Clusters with even numbers of electrons are found to be more stable than those with odd numbers of electrons regardless of their charge state and atomic composition. The equilibrium geometries of homo-nuclear clusters can be significantly altered by replacing one of its constituent atoms with a hetero-nuclear atom. The role of electronic structure on the geometries and stabilities of compound clusters is discussed.