Molecular interaction in a mixed α-hydroxyoxime-sulfonic acid solvent extraction system

The molecular interaction between dinonylnaphthalenesulphonic acid (HDNNS) and 5,8-diethyl-7-hydroxy-6-dodecanone oxime (HOx) was examined based on variations in the critical micelle concentration (CMC) of HDNNS in the presence of HOx. The CMC values were obtained from interfacial tension vs concentration isotherms measured at the hexane/aqueous interface. The interaction appears to involve hydrogen bonding between the HOx and HDNNS polar functional groups to form a dimeric structured complex.     

Ab initio calculations on large molecules using molecular fragments. Preliminary investigation of ethyl chlorophyllide a and related molecules

Ab initio SCF calculations using the molecular fragment method are reported for four molecules related to chlorophyll a, i.e., free-base porphine, magnesium porphine, magnesium chlorin, and ethyl chlorophyllide a. Molecular orbital structure, the “four-orbital model”, reactivity sites, and Mg···N interactions are discussed.     

Selective reagents for solvent extraction of metals—II. Bis-quinaldic acids

Bis-quinoline-2-carboxylic acids in which the quinoline rings were joined via ether linkages to the 8-position have been synthesized and tested for metal extraction. The reagents extracted Cu²⁺ and Zn²⁺ selectively in the presence of Fe²⁺ and Fe³⁺ from aqueous sulphate solution.     

Surface crossing in interaction of atomic hydrogen with a lithium metal cluster

Interaction of atomic hydrogen with a (4,1,4) lithium cluster, simulating the (100) metal surface, is studied using the diatomics-in-molecules method. Ground-and excited-state potential curves for normal approach ofH to some attack positions on the surface intersect or pseudo-intersect. The results reveal possible non-adiabatic character of the absorption process.     

A 19F NMR study of the transmission of electronic effects in triarylantimony and triarylbismuth compounds. A comparison with the nitrogen- and carbon-containing analogues

A ¹⁹F NMR study of the transmission of electronic effects has been made for the systems Ar₂EC₆H₄F-4 (E = Sb, Bi, CH, N). The fluorine chemical shifts obtained are correlated with the polar constants (Σσ^o and Σσ) of the substituents, suggesting that electronic effects are transmitted through the SbC_ar, BiC_ar and CC_ar bonds predominantly by an inductive mechanism, whereas the transmission through the NC_ar bonds is contributed to significantly by classical resonance effects due to competitive conjugation of the lone pair with the aromatic rings, and the substituents therein. A dual parameter correlation of the fluorine chemical shifts with the inductive (σ_I) and resonance (σ^o_R and σ_R) parameters of the substituents in the aromatic rings has led to similar conclusions. The inductive transmission through the bridging Sb and Bi atoms has been assigned to the absence of conjugation of lone pair and vacant d-orbitals of the metals with π-electron systems of the aromatic rings. On the basis of the values of the ? coefficients for the correlation equations obtained it has been established that the transmitting ability of the BiC_ar bonds is close to that of the C_alC_ar bonds and considerably lower than the transmitting ability of the NC_ar bonds.     

Electrochemical cleavage of sulphones: Part III. Cathodic elimination study of some β-substituted sulphones as a function of the acidity of the solvent

The sulphones, substituted in the β-position by a group capable of leaving are electrochemically reduced with olefin formation in weakly protic solvents. When the proton concentration is too high, the protonation of the carbanion produced after the 2-electron step reduction of the sulphonyl group is fast and cathodic elimination does not occur. On the other hand, in aprotic media, the instability of the substrate in contact with the electrogenerated bases leads to the retrocondensation reaction (β-hydroxysulphone) or to a basic elimination reaction (β-acetoxysulphone) with formation of the corresponding electrolysis products. The range of proton availability for obtaining olefins in good yields is consequently rather narrow and will depend on the structure of the starting material.     

Solvent effects on the electronic spectrum of the hexathiocyanatochromate (III) anions. A revised octahedral crystal field splitting parameter for the thiocyanate ion

An early report on the solvent dependence of the electronic spectra of complex ions considered the electrostatic effect of solvent molecules in the second coordination sphere, on the position of the absorption bands.¹ Solvent effects on the ligand field bands for solutions of K[Cr(NH₃₂(NCS)₄] have been discussed by Adamson² who emphasised a correlation between the solvent shifts in the spin-allowed bands and the shifts in the quartet-doublet bands. This work describes the effects of various solvents on the electronic absorption spectra of [Cr(CNS)₆]^3?.     

Ligand effects on the redox potentials of metal carbonyls : Relationship to co force constants in manganese(I) derivatives

The reversible oxidation potentials E^o of a single series of methylcyclopentadienyldicarbonylmanganese(I) derivatives η⁵-MeCpMn(CO)₂L are measured for a wide variety of ligand types, including L = alkyl and aromatic amines, alkyl cyanide and isocyanide, alkene, alkyl and aryl phosphines and phosphites. The relationship of E^o with the carbonyl force constants evaluated by the Cotton-Kraihanzel method is presented.     

The influence of solvent polarity on the tetrahedral-octahedral equilibrium of Co(II)complexes with 3,5-dimethylpyrazole

The configuration equilibrium:

(where DMPz = 3,5-dimethylpyrazole), has been studied spectrophotometrically in various non-aqueous polar solvents. The influence of solvent polarity on the K value has been investigated. Solvation studies have also been carried out on the tetrahedral species Co(SCN)₂(DMPz)₂, and the results are interpreted in terms of the polarity of the various solvents.     

The weiss constant: A probe for the molecular packing of monomeric copper(II) complexes?

Magnetic properties of the complexes Cu(pn)₂WO₄1.8H₂O, Cu(pn)₂I₂, Cu(pn)₂Br₂ 1.6H₂O and Cu(pn)₂Cr₂O₇ (ph = 1,2-diaminopropane) have been studied by ESR, magnetic balance (Gouy method) and PA techniques. Curie constants C were obtained from ESR spectra, temperature independent paramagnetism N∝ from PA spectra, and Weiss constants from magnetic susceptibility data. Isotropic factors r were calculated, describing reduction of the orbital angular momentum and the spin-orbit coupling constant from their free-ion values. From the measured crystal g values we conclude that there is axial elongation in all the coordination polyhedra, corresponding to the ground state d_x2-y2. The different line shapes in the ESR spectra depend on the alignment of the pseudo-tetragonal axes, induced by the counterion. The counterions have a clear effect on both the magnetic parameters and the reduction factors. The alignment of the pseudotetragonal axes is also reflected in the value of the Weiss constant. A correlation is proposed between the Weiss constant and molecular packing.     

The reactions between tetrachloroplatinate(II) anion and bidentate sulphur-nitrogen chelating agents: A direct route for the synthesis of the neutral dichloro species

A direct route for the synthesis of the neutral dichloro complexes [Pt(NS)Cl₂], (NS = 2-[(ethylthio)methyl]pyridine and 2-[(phenylthio)methyl]pyridine) in dimethylformamide, which avoids the formation of bis-chelate cations, is reported.     

Study of the complexes of Np(V) with organic ligands by solvent extraction with TTA and 1, 10-phenanthroline

Complex formation constants of Np(V) with 22 organic ligands, 7 hydroxycarboxylic acids, 4 dicarboxylic acids, 4 aminocarboxylic acids, 3 pyridinecarboxylic acids, 8-hydroxyquinoline-5-sulfonic acid, IDA, NTA and EDTA, have been determined in 1M NaClO₄ at 25°C by using the solvent extraction method with TTA and 1, 10-phenanthroline. The factors influencing the stabilities of Np(V) complexes are discussed in connection with the linear structure of NpO₂⁺.     

Spectrophotometric determination of saccharin in different materials by a solvent extraction method using Nile Blue as reagent

In a slightly acidic medium (sodium acetate-acetic acid buffer, pH 4) saccharin and Nile Blue form an ion-association compound which is extractable into methyl isobutyl ketone and allows the spectrophotometric determination of saccharin. At 630 nm Beer's law is obeyed over the saccharin concentration range 0.1-3.5 microg/ml in the aqueous phase and the apparent molar absorptivity is 5.8 x 10(4) l.mole(-1).cm(-1). The method shows good selectivity and can be applied to the determination of saccharin in artificial sweeteners, soft drinks and toothpastes.     

Kinetics and mechanism of the interaction of hexaaquochromium(III) with octacyanomolybdate(IV) ions

The kinetics of the interaction of hexaaquochromium(III) ion with potassium octacyanomolybdate(IV) have been studied using conductance and spectrophotometric data. The mechanism of the reaction is discussed and the effect of H⁺ ion and the ionic strength on the rate of the reaction determined. The reaction is found to be pseudo-first order with respect to potassium octacyanomolybdate(IV) and inverse first order with [H₃O⁺]. The rate of the reaction increases with increase in ionic strength and temperature. Activation parameters have been calculated using the Arrhenius equation and have the values ΔE^* = 1.3 × 10² kJ mol^?1, ΔH^* = 129 kJ mol^?1, ΔS^* = ?315 e.u., ΔF^* = 2.3 × 10² kJ and A = 1.5 × 10^?3. The mechanism proposed is based on ion-pair formation and the rate equation obtained is given by: k_obs=$\text{[}{}_{\mathrm{kK}}{}_{\mathrm{<mtext>E</mtext>}}\text{[H}{}_3\text{O}{}^{\mathrm{+}}\text{]+}\text{k′K′k}{}_{\mathrm{E}}\text{k}{}_{\mathrm{h}}\text{][Mo(CN)}{}_8{}^{\mathrm{4?}}\text{]}\text{[H}{}_3\text{O}{}^{\mathrm{+}}\text{]+}\text{k}{}_{\mathrm{<mtext>h</mtext>}}\text{+[}\text{K}{}_{\mathrm{<mtext>E</mtext>}}\text{[H}{}_3\text{O}{}^{\mathrm{+}}\text{]+}\text{K′}{}_{\mathrm{E}}\text{k}{}_{\mathrm{h}}\text{][Mo(CN)}{}_8{}^{\mathrm{4?}}\text{]}$     

A Calometric study of steric effects in the reactions of phosphorus ligands with Ni(COD)2

A calometric study of the reactions of various phosphorous ligands (and t-BuNC) with di-1,5-cycloocatadienenickel shows that both the extent of reaction and mean Ni-P bond strengths tend to decrease with increasing ligand size. The steric strain energies in various NiL₄ complexes and ΔG for their formation from nickel metal are estimated.     

An ab initio SCF and CI study of ketene imine

The electronic structures of the ground and excited states of ketene imine (_H^HCCNH) have been studied by ab initio SCF and CI calculations. The nucleophilic nature of the β carbon with respect to nitrogen has been discussed using calculated electrostatic potentials and by calculated energy differences between the parent and protonated species. The electronically excited ¹A″ and ³A″ states are found to be almost degenerate.     

Dependence of the closed-shell repulsive interaction on the overlap of the electron densities

The relationship between the closed-shell repulsive interactions and overlap of the electron densities is investigated. It is found that the repulsive interactions vary in almost direct proportion to the absolute size of the density overlaps.