Partial molal volumes of ions in organic solvents from ultrasonic vibration potential and density measurements. III. Dimethylsulfoxide

The partial molal volumes of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Cl^–, Br^–, I^–, and NO ₃ ^- in DMSO at 25°C have been determined from ultrasonic vibration potential data and density data for solutions of uni-univalent electrolytes. Hepler's semiemprirical equation has been used to split ionic partial molal volumes into geometric and electrostrictive contributions. The results obtained in this work confirm the conclusion of our previous studies, namely, that the contribution of electrostriction is essentially determined by the properties of that layer of atoms, 0.3 to 0.4 nm thick, in contact with the ion and by the degree of steric hindrance of the poles of the dipole of the solvent molecule. On the other hand, the geometric contribution depends on the size of the solvent molecule and also on the arrangement of the solvent molecules about the ions. It is shown that the geometric contribution to the partial molal volume of ions is largely increased when ions cannot come close enough to the poles of the solvent-molecule dipole, owing to steric hindrance.     

Relation between stability constants of metal ion cryptates in two solvents and the transfer activity coefficients of the metal ions

The extrathermodynamic assumption of Lejaille and Bessière that _1,2 log K (LM ⁿ⁺ )=–G _tr (M ⁿ⁺ ) in which K is stability constant and L is cryptand 2.2.2, 2 _B 2 _B 2, 2.2.1, or 2.1.1 has been tested in dipolar aprotic solvents for M ⁿ⁺ being Li⁺, Na⁺, K⁺, Ag⁺, Tl⁺, and Ba²⁺. The relation has been found generally acceptable for the dipolar aprotic solvents propylene carbonate, acetonitrile, N,N-dimethylformamide and dimethylsulfoxide, provided the size of the ion is equal to or smaller than the cavity of the cryptand. The relation does not hold for the hydrogen bonded donating solvents, water, and methanol.     

Cyano- and thiocyanato-derivatives of tetrahalophosphonium ions

Several cyano- and thiocyanato-derivatives of the ions PBr⁺₄ and PCl⁺₄, including some mixed species, have been obtained in solution by using liquid halogens as solvents, and identified by means of ³¹P NMR spectroscopy. The method of pairwise interactions has proved very valuable for assigning structures to the various species.     

The thermochemical characteristics of the solvation of amines and silver ions in methanol-dimethylformamide mixtures

The heat effects of solution of ethylenediamine, sodium perchlorate, and silver perchlorate in the nonaqueous methanol-dimethylformamide binary solvent were determined calorimetrically at 298.15 K. The suggestion of equal enthalpies of solvation of Ph₄P⁺ and PhB^? was used to calculate the enthalpies of transfer of the ClO ₄ ^? and Ag⁺ ions from methanol to dimethylformamide. The influence of the composition of methanol-dimethylformamide solvents on the energy characteristics of solvation of ethylenediamine, Ag⁺, and ClO ₄ ^? was considered.     

Microwave spectroscopy of molecular ions

In this paper a brief overview of the research in microwave spectroscopy of molecular ions done at the University of Wisconsin will be given, with major emphasis on work done in the past year. Five molecular ions (CO⁺, HCO⁺, HNN⁺, HCS⁺, and HOC⁺) have been studied in this work, and all of them have also been detected by radioastronomy. Molecular structures (r_s for HCO⁺, HOC⁺, and HNN⁺ and r_e for HCO⁺) have been determined and important dynamical information has been obtained from pressure broadened linewidths (Δν/P), Doppler shifts, and relative intensity data. In particular the Δν/P values have been shown to correspond to the Langevin cross-section, indicating the monopole-induced dipole interaction is the pertinent intermolecular force.     

Stability constants of diaza-crown-ether complexes of univalent metal ions and free energies of transfer of ligand and complexes from acetonitrile to several solvents

1:1 complexes of 1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (2,2) with Ag⁺ and T1⁺ have been determined by potentiometric pAg measurements in several polar nonaqueous solvents at 25°C. A comparison of the results with those for the cryptand (2,2,2) including alkali metal ions shows that interactions for a given ion with the two ligands are similar but differ considerably for different ions. The free energies of transfer of ligand (2,2) and its complexes have been determined from distribution measurements and are around zero between acetonitrile and aprotic solvents.     

Solvation of ions. XXVII. Comparison of methods to calculate single ion free energies of transfer in mixed solvents

Free energies of transfer of ions from water to mixtures of water with acetonitrile (AN), with dimethylformamide (DMF), with dimethylsulfoxide (DMSO), and with ethylene glycol have been determined using both the tetraphenylarsonium tetraphenylboride [TATB] and the negligible liquid junction potential [E _j ] assumptions. By making use of ΔG _tr (Ag⁺)[TATB]=12 kJ-mol^?1 for transfer from DMSO to AN and by assuming negligible liquid junction potential in the cell $${\text{Ag|AgNO}}_{\text{3}} {\text{(0}}{\text{.01}}M{\text{),S}}\parallel {\text{Et}}_{\text{4}} {\text{NPic(0}}{\text{.1}}M{\text{),AN}}\parallel {\text{AgNO}}_{\text{3}} {\text{(0}}{\text{.01}}M{\text{),AN|Ag}}$$ single ion free energies of transfer of silver ion ΔG _tr (Ag⁺)[E _j ] from DMSO to 35 pure and mixed solvents show a standard deviation of only 2 kJ-mol^?1 when compared with ΔG _tr (Ag⁺) calculated from the TATB assumption that ΔG _tr (Ph ₄ As⁺)=ΔG _tr (Ph ₄ B^?). The ferrocene assumption [Fc] also gives acceptable agreement with ΔG _tr (Ag⁺)[TATB] provided that the solvents are not highly aqueous. Other cells with other junctions give less acceptable agreement between the E _j and TATB assumptions. It is essential that the salt bridge is always tetraethylammonium picrate in AN, if the E _j assumption is assumed. Because of the ease of making potentiometric measurements compared with the difficulty of measurements required for the TATB assumption, the negligible liquid junction potential method in the cell shown is recommended for estimating transfer free energies of single ions. The ferrocene assumption is acceptable only for non-structured aprotic solvents.     

Thin layer chromatography of 57 metal ions on an inorganic ion-exchanger in mixed solvent systems

Summary Thin layers of stannic arsenate have been used to study the chromatographic behaviour of 57 metal ions in different mixed solvents. Au³⁺, Hg²⁺, UO ₂ ²⁺ , Be²⁺ and Al³⁺ and others can be easily separated from numerous metal ions. Fast quaternary, ternary and binary separations have been also achieved. Important separations are discussed. The effect of pH, duration of heating of ionexchanger plates and layer thickness on the R_f values has been studied and discussed. It is shown that Lederer's equation is also obeyed by thin layers of stannic arsenate, if instead of concentration of Na⁺ ion its activity is taken into consideration.     

Thermoplastic urethane elastomers. VI. Dilute solution properties in various solvents

A thermoplastic urethane elastomer prepared from a polycaprolactone diol, 4,4′-diphenylmethane diisocyanate, and 1,5-pentanediol was fractionated and the solution properties of the fractions were characterized in terms of viscosity and sedimentation. Mark-Houwink relations were established for data obtained at 30° in various solvents: In dimethylacetamide, tetramethylurea, and N-methyl pyrrolidone, the value of K_θ increased systematically in the range (1.7 to 2.0) × 10^?3. Lower values of K_θ were obtained in dimethylformamide (0.8 × 10^?3) and meta-cresol (0.9 × 10^?3). The molecular expansion coefficients in the various solvents were approximated from the experimental viscosity data. Short-range interactions between the solvent molecules and polymer chains are suggested as possible causes for differences in the hydrodynamic parameters.     

Proton transfer reactions from H3+ ions to N2, O2, and CO molecules

The rate constants for proton transfer from H₃⁺ ions to N₂, O₂, and CO have been measured as function of hydrogen buffer gas partial pressure. The rate constant for proton transfer from H₃⁺ to N₂ shows a very large pressure dependence, increasing from 1.0 × 10^?9 cm³/s at low H₂ partial pressures to 1.7 × 10^?9 cm³/s at high H₂ partial pressures. The rate constants for proton transfer from H₃⁺ to O₂ and CO are constant with partial pressure of H₂; giving values of 6.4 × 10^?10 cm³/s and 1.7 × 10^?9 cm³/s, respectively. The roles of excess vibrational energy in H₃⁺ ions and of equilibrium between forward and back reaction are discussed. Back reaction is observed only for the reaction of H₃⁺ ions with O₂, and an equilibrium constant of K = 2.0 ± 0.4 at 298 K has been determined. From these data the proton affinity of O₂ is deduced to be 0.47 ± 0.11 kcal/mole higher than that of H₂.     

An attempt to parameterize the structuredness of solvents

An attempt has been made to parameterize the structuredness of solvents from the viewpoint of intermolecular interactions, and the structuredness parameter S _p has newly been proposed. The enthalpy of vaporization H _vap ^/o of various solvents has been considered to consist of donor-acceptor interaction energy (DA), which can been estimated from Gutmann's donor and acceptor numbers, some other interaction energies (VDW), which may not be fully described in terms of the donor-acceptor interactions and may be related to the electronic distribution, the volume and shape of the molecule, the polarizability and ionization potential of atoms in the molecule, the energies of these interactions being usually considered to be of Van der Waals type and possibly evaluated from the enthalpy of vaporization ofn-alkanes, and the intermolecular interaction energy (STR) due to the three-dimensional molecular ordering in the liquid: H _vap ^/o =DA+VDW+STR. The STR term obtained as the difference between H _vap ^/o and (DA+VDW) is defined as the structuredness parameter S _p , which is a dimensionless quantity by dividing the value with the (kJ-mol^–1) unit. The entropies of formation S ₁ ^o and S ₄ ^o of [MX]⁺ and [MX₄]^2– complexes, respectively, of divalent metal ions (Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Hg²⁺) with halide and thiocyanate ions in aqueous and nonaqueous solvents could be represented as an almost linear function of the structuredness parameters S _p .     

Kinetic isotope effect in the protonation of anthracenide salts by MeOH and MeOD role of counterions and solvents

Kinetics of protonation of Li⁺, Na⁺, K⁺, and Cs⁺ salts of anthracene radical anions (A^?_·,Cat⁺) and dianions (A^2?, 2Cat⁺) by MeOH and MeOD in tetrahydrofuran (THF) and dimethoxyethane (DME) led to the determination of the isotope effect (k_H/k_D) in the following reactions: Studies of cation and solvent influence on the rate constants of these reactions and on the magnitude of the isotope effect permitted us to draw some conclusions about the structure of the pertinent transition states. It seems that only the tight A^?·,Na⁺ pairs participate in the protonation, and on this basis the fraction of tight ion paris of A^?·,Na⁺ in DME was estimated. Our results have been compared with data reported in the literature.     

Chromatographic behaviour of metal ions on tin(IV) and titanium(IV) antimonate papers

Summary The chromatographic behaviour of 49 metal ions has been studied on papers impregnated with Sn(IV) and Ti(IV) antimonates in aqueous HNO₃ and mixed solvent systems containing dimethyl sulphoxide. Numerous separations have been achieved and the Alberti equation, for Sn(IV) and Ti(IV) antimonate papers, in the modified form: –nloga K⁺=R_M + constant (a K⁺=activity of K⁺), has been verified. The effect of the concentration of impregnating reagents on these papers has been determined and compared with other papers. The effect of pH on R_f, R_i, log R_f and R_M values of metal ions has also been examined in aqueous systems.     

Cation exchange, interlayer spacing, and thermal analysis of Na/Ca-montmorillonite modified with alkaline and alkaline earth metal ions

Na-montmorillonites were exchanged with Li⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺, while Ca-montmorillonites were treated with alkaline and alkaline earth ions except for Ra²⁺ and Ca²⁺. Montmorillonites with interlayer cations Li⁺ or Na⁺ have remarkable swelling capacity and keep excellent stability. It is shown that metal ions represent different exchange ability as follows: Cs⁺?>?Rb⁺?>?K⁺?>?Na⁺?>?Li⁺ and Ba²⁺?>?Sr²⁺?>?Ca²⁺?>?Mg²⁺. The cation exchange capacity with single ion exchange capacity illustrates that Mg²⁺ and Ca²⁺ do not only take part in cation exchange but also produce physical adsorption on the montmorillonite. Although interlayer spacing d ₀₀₁ depends on both radius and hydration radius of interlayer cations, the latter one plays a decisive role in changing d ₀₀₁ value. Three stages of temperature intervals of dehydration are observed from the TG/DSC curves: the release of surface water adsorbed (36?C84?°C), the dehydration of interlayer water and the chemical-adsorption water (47?C189?°C) and dehydration of bound water of interlayer metal cation (108?C268?°C). Data show that the quantity and hydration energy of ions adsorbed on montmorillonite influence the water content in montmorillonite. Mg²⁺-modified Na-montmorillonite which absorbs the most quantity of ions with the highest hydration energy has the maximum water content up to 8.84%.     

An algorithm for estimating the enthalpies of formation of amine molecular ions and immonium fragment ions

A method of estimating the enthalpies of formation of amino molecular ions, ΔH^? ([C_nH_2n+1NH₂]⁺˙) and of immonium ions ΔH([C_nH_2n+1N]⁺) is reported. It is based on the fact that CH₃ is isoelectronic with NH₂, CH₂ with NH and CH with N. Some calculated values of the enthalpies of formation of amine molecular ions and immonium ions are reported and estimates are made of the accuracy of such calculation.     

Formation and fragmentation of gas-phase ion-molecule complexes of transition-metal ions with organic molecules containing two functional groups

A mass spectrometer fast atom bombardment source has been used to synthesize, in the gas phase, the ion-molecule complexes of transition-metal ions (Ni⁺, CO⁺, Fe⁺, and Mn⁺) with α- or β-unsaturated alkenenitriles, RCH=CHCN (R=H, CH₃, and C₂H₅) and CH₃CH=CHCH₂CN, and 2-methyl glutaronitrile. The metastable ion fragmentations of the complexes are monitored in the first held-free region by B/E linked scans. Surprisingly, an intense HCN loss via an intermediate (C _n H_2n ?2)?M⁺?(HCN) is observed for the complexes of the alkenenitriles. The metal ions significantly affect the fragmentation processes. The coexistence of both end-on and side-on coordination modes is suggested to explain the fragmentations.     

Production of negatively charged fragments in collisions of swift positive hydrogen ions with molecules

A first detection and analysis of negatively charged fragments produced in collisions of fast (20–150 keV) positive hydrogen ions (H⁺, H ₂ ⁺ and H ₃ ⁺ ) with gas-phase molecules is presented. The fragments and their abundances were determined by means of a time-of-flight mass spectrometer. Negative ions did emerge from every investigated target molecule species, such as halomethanes, sulfur hexafluoride, propane and propene, but in all cases with distinctly lower probability (cross sections in the range 10^?20?10^?18 cm²) than positively charged fragments (approximately on the scale 10^?3 or even less). Another essential result is that stable collisionally induced negative fragments are mostly monatomic ions, whereas positive fragments are in their majority more complex polyatomic ions. Furthermore, we observed a direct electron capture from a positively charged but not totally stripped projectile (here: H ₂ ⁺ and H ₃ ⁺ ) into stable or very longlived states of the molecular ions SF ₆ ^? and O ₂ ^? , the latter with the largest cross section (10^?18?10^?17 cm²) found up to now.     

Selective transport of zinc and copper ions by synthetic ionophores using liquid membrane technology

This work highlights the role of synthetic carrier (ionophore) in the separation of heavy metal ions. A new series of ionophores; 4,4′-nitrophenyl-azo-O,O′-phenyl-3,6,9-trioxaundecane-1,10-dioate (R₁), bis[4,4′nitro-phenylazo-naphthyl-(2,2-dioxydiethylether)] (R₂) 1,8-bis-(2-naphthyloxy)-3,6-dioxaoctane (R₃), 1,11-bis-(2-naphthyloxy)-3,6,9-trioxaunde-cane (R₄), 1,5-bis-(2-naphthyloxy)-3-oxa-pentane (R₅) have been synthesized and used as extractant as well as carrier for the transport of various metal ions (Na⁺, K⁺, Mg²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) through liquid membranes. Effect of various parameters such as metal ion concentration, ionophore concentration, liquid–liquid extraction, back extraction, comparison of transport efficiency of BLM and SLM and different membrane support (hen’s egg shell and PTFE) have been studied. In BLM ionophores (R₂–R₅) transport Zn⁺ at greater extent and the observed trend for the transport of Zn²⁺ is R₂?>?R₄?>?R₃?>?R₅ respectively. Further transport efficiency is increased in SLM. In egg shell membrane ionophores (R₂–R₅) transport Zn⁺ due to their non-cyclic structure and pseudo cavity formation while ionophore R₁ transports Cu²⁺ ions at greater extent due to its cyclic structure and cavity size. Among the membrane support used egg shell membrane is found best for the transport of zinc ions because of its hydrophobic nature and exhibits electrostatic interactions between positively charged zinc ions and –COOH group of egg shell membrane. Thus structure of ionophores, hydrophobicity and porosity of the membrane support plays important role in separation of metal ions.     

A photoionization study of [C4H7]+ ions in the gas phase

The ionization and [C₄H₇]⁺ appearance energies for a series of C₄H₇CI and C₄H₇Br isomers have been measured by dissociative photoionization mass spectrometry. Cationic heats of formation, based on the stationary electron convention, are derived. No threshold ion is observed with a heat of formation corresponding to the trans-1-methylallyl cation, although there is evidence for formation of the less stable cis isomer. A 298 K heat of formation of 871 kJ mol^?1 is obtained for the cyclopropylcarbinyl cation, with the cyclobutyl cation having a higher value of 886 kJ mol^?1. At the HF/6-31G^** level, ab initio molecular orbital calculations show the 2-butenyl, isobutenyl and homoallyl cations to be stable forms of [C₄H₇]⁺, being less stable than the trans-1-methylallyl cation by 101 kJ mol^?1, 159 kJ mol^?1 and 164 kJ mol^?1, respectively. However, threshold formation is not observed for any of these ions, the fragmentation of appropriate precursor molecules producing [C₄H₇]⁺ ions with lower energy structures.