Solutions Of Alkali Metals Research Articles

Use of cryptates in anionic polymerization. II. Solutions of alkali metals and their complexes with polycyclic hydrocarbons

Use of cryptates in anionic polymerization. II. Solutions of alkali metals and their complexes with polycyclic hydrocarbons

Clivage réducteur des sulfonamides et des sulfonates par les métaux alcalins dissous dans le hmpt

Alkali metal solutions in hexamethylphosphotriamide effect the cleavage of various sulfonamides and sulfonates under mild conditions.Sulfonamides give amines in good yields: the presence of a protic cosolvent is not necessary. Sulfonates of all types (e.g. tosylate, benzylate, mesylate) give the alcohol always contaminated with a little of the corresponding hydrocarbon.

Solvated electrons in hexamethylphosphoramide. Part 1.—Conductivity of solutions of alkali metals

Apparatus for the preparation, and measurement of the conductance, of solutions of lithium, sodium and potassium in hexamethylphosphoramide is described. The time- and concentration-dependence of the conductance of these solutions have been measured and are discussed. The results of some e.s.r. measurements are also presented.

Solvated electrons in hexamethylphosphoramide. Part 2.—Density measurements, electrical properties of frozen solutions, electron emission from surfaces of solutions

The dissolution of alkali metals in hexamethylphosphoramide (HMPA) causes a decrease in density and a value of approximately 80 cm3 for the apparent molal volume of the solvated electron has been deduced. The change of electrical conductance of alkali metal solutions in HMPA on freezing has been studied. Surprisingly, while the conductance of sodium solutions falls almost to zero on freezing, that of lithium solutions increases by a factor of about one hundred. The solid lithium solutions have a peak conductance at about –19°C; possible reasons for this behaviour are discussed. Thermionic- and photo-emission of electrons have also been measured. The dependence of thermionic current on concentration is unexpected; for both lithium and sodium solutions there is a pronounced maximum at concentrations of about 10–3 mol dm–3 and the current decreases to about 1/40 of the peak value at a concentration of 0.4 mol dm–3. The thermionic emission energy has been calculated from the temperature dependence of the thermionic current, and is about 0.74 eV at c∼ 10–3 mol dm–3, and 0.98 eV at c∼ 0.4 mol dm–3. The threshold energy for photo-emission calculated from the long wavelength limit for photo-emission from a 0.4 mol dm–3 solution is 1.05 eV.

Pulse Radiolysis of Alkali Metal Solutions in Ethylamine

Pulse radiolysis of solutions of alkali metal ethylamides in ethylamine shows the formation of three distinct species; the solvated electron es−, the alkali metal anion M−, and a species considered to be the cation–electron pair with stoichiometry M. The three species coexist in equilibrium in accord with the equations[Formula: see text]Studies of these solutions as a function of temperature, alkali metal concentration, and added complexing agents ("crown" compounds) show that es− and M have distinct absorption spectra with the former having a maximum ≥ 1800 nm. The latter exhibit maxima at 1400 nm for Na and K, ~1400 nm for Cs, and 1600–1700 nm for Li. The corresponding M− species were observed in sodium, potassium, and cesium solutions with absorption maxima at 680, 890, and 1100 nm, respectively.Rate and equilibrium constants for the formation of M and M− vary markedly with the nature of the alkali metal. Estimates for these constants along with the extinction coefficients for the various species are summarized and compared with data obtained in alkali metal solutions.

Pulse radiolysis of solutions of alkali metals in liquid amines

Pulse radiolysis of solutions of alkali metals in methylamine and ethylamine shows the formation of three distinct species; the solvated electron e − s, the alkali metal anion M − and a species considered to be a metal—electron pair with stoichiometry M. Hitherto no kinetic or conclusive optical evidence has been obtained for the species M in amine solutions. The three species coexist in equilibrium according to the equation c − s + M + ⇌ M + e − ⇌ M − with the corresponding rate constants markedly dependent on the solvent and nature of the alkali metal.

Compressibility of Metal-Ammonia Solutions

The compressibility of solutions of several alkali metals in liquid ammonia has been calculated using a hard-sphere model. The constituents are solvated ions and free ammonia molecules. The calculation requires solvation numbers for the ions consistent with expectations based on chemical experience.

Conductivity and Phase Separation of Rb-NH3Solutions

The electrical conductivity of Rb-N${\mathrm{H}}_{3}$ solutions has been measured over the concentration range 2-27 MPM (mole percent metal) at temperatures between 190 and 240 K. The conductivity is lower than for any other alkali-metal solution. Evidence for phase separation below 205 K is given.

Radiolytic Formation of Ammoniated Electrons of Long Lifetime at Room Temperature

AbstractThe yields of the γ radiolysis of liquid ammonia at various pH are compared. In basic solutions, containing an alkali amide, the attack of hydrazine by H atoms is less important, since these species are transformed into ammoniated electrons which do not destroy N2H4. On the other hand, adding hydrogen to amide solutions increases the initial yield G(N2H4), so suggesting that the NH2 radicals may be scavenged by H2 and also transformed into eam−. Under those conditions the disappearance reactions of eam− are all hindered.Effectively, after irradiation, for an H2 pressure of 0.2 – 0.8 atm (5 ± 10−2 M KNH2) an absorption in near infra‐red with the same characteristics as for eam− is observed. This absorption increases first linearly with the dosis and the initial yield G(eam−) is independent of H2 pressure above 0.6 atm. After the end of irradiation, the decrease of absorption with time is of the first order and very slow (1/2 ± 2 hr) as in the spontaneous decomposition of alkali metal solutions.

Alkali Metal solutions Effect of Two Cyclic Polyethers on solubility and Spectra

AbstractAlkali metals can be made to dissolve in solvents in which they are normally insoluble or only slightly soluble, by using cyclic polyethers to complex the cations. Although the use of the cyclic polyether, dicyclohexyl‐18‐crown‐6 results mainly in the formation of M− as the reducing species, the bicyclic polyether, “cryptate” yields in addition, substantial concentrations of solvated electrons. It also increases the solubility compared with the “crown” compound.

Solvent Dependence of the Optical Absorption Spectrum of the solvated Electron

AbstractWith the recent application of fast infra‐red detection to pulse radiolysis studies of the solvated electron, the optical absorption spectrum has now been observed into the wavelength region beyond 2000 mμ. It has thus been possible to determine the spectrum in such weakly‐polar liquids as tetrahydrofuran, diethylamine and others, and in binary solvent systems of tetrahydrofuran with other liquids.Data now available for a variety of liquids cover an enormous range with the maximum of the absorption band at 580 mμ to 2100 mμ. In the following weakly‐polar liquids the band maxima are: tetrahydrofuran 2100 ± 50, diethylamine 1900 ± 80, dimethoxyethane 1900 ± 150 and diethyl ether 2050 ± 150mμ.It has been shown for such liquids as ammonia and ethylenediamine that results from pulse radiolysis of the pure liquid and from alkalimetal solutions lead to the same absorption band for the solvated electron. In all binary solvent systems studied, only a single absorption band is seen with λmax intermediate to the maxima observed for the pure components. Most of the data suggest that selective solvation in microscopic domains of the individual component does not occur, and the observations do not seem to support those models which propose that the optical properties are determined only by solvation with a small number of molecules. In tetrahydrofuran‐water solutions, however, the water is dominant in determining the optical properties, whereas the tetrahydrofuran is dominant in determining the dielectric properties.There thus appears to be some selective interaction with the water.The data now available for various liquids suggest that the spectral position of λmax is determined by the structural class of the molecule as well as by the dielectric properties of the liquid.

New absorption bands in solutions of alkali metals in amines

New absorption bands in solutions of alkali metals in amines

Platinum–oxygen electrode in moleten alkali-metal nitrates

Platinum metal immersed in a Cr2O72––CrO42– solution of molten alkali metal nitrates behaves as an electrode reversible to oxide ion concentration.

Pulse Radiolysis Studies. XVIII. Spectrum of the Solvated Electron in the Systems Ethylenediamine–Water and Ammonia–Water

The pulse radiolysis technique with fast infrared detection was used to determine the optical absorption spectrum of the solvated electron in the systems ethylenediamine–water and ammonia–water. These spectra, determined over the entire concentration range, show the following: In ammonia and in ethylenedamine, the bands at 1550 and 1350 nm, respectively, have the same shape and position as those attributed to the solvated electron in alkali metal solutions. In each of the two-component systems a single band is seen with the peak position intermediate to those in the pure solvents. For ethylenediamine–water mixtures, the band shape (normalized) and half-width (energy scale) are invariant with composition, while for ammonia–water mixtures the ratio of the peak position to the half-width is invariant. These observations suggest a delocalized electron with optical characteristics determined by the aggregate properties of the solvent. Models which require that the optical properties be strongly influenced by solvation with a small number of solvent molecules are not in accord with these observations. Kinetic data indicate that the decay of the solvated electron in ammonia and in ethylenediamine is a complex process. The rate constant for the reaction of the solvated electron in ammonia with ammonium ion was found to be at least four orders of magnitude lower than the diffusion-controlled limit.

Alkali metal solutions in organic solvents obtained in the presence of polyethylene oxide

AbstractAlkali metals dissolve not only in liquid ammonia but also in ethers, such as tetrahydrofuran (THF), 1.2‐dimethoxyethane (DME), and dimethyl ether of diethylene glycol (diglyme), blue solutions being obtained1,2. “Blue” solutions can be obtained only with rigorously purified reagents in full absence of moisture and oxygen, usually at low temperature. They are not very stable systems, especially at room temp., and discoloration begins shortly after the removal of the metal. The concn. of the metal dissolved is as low as 10‐4 to 10‐3 mole/1. The electrical conductivity of the “blue” solutions is in the range of 10‐5 to 10‐6 ohm‐1 cm‐1 and that of the discolored solution is 10‐8 to 10‐9 ohm‐1 cm‐1.Obviously the solvation ability of the solvent plays a very important role in the formation of metal solutions. DAINTON et al.1,3 presented arguments that the predominant species in the “blue” solutions are pairs of electrons (e2) with coupled spins, whereas TUTTLE and WEISSMAN4 observed at ‐80°C a weak singlet in the ESR spectrum of the potassium solution in DME, and CAFASSO and SUNDHEIM2 revealed a weak ESR signal in a rubidium solution in bis‐2‐(2‐methoxyethoxy) ethyl ether as well as in a frozen potassium solution in DME.“Blue” alkali metal solutions can be easily obtained in hexamethylphosphoramide but it is not still clear whether they are solutions of alkali metals5 or of anion‐radicals of the solvent6.It was established that potassium solutions in THF and DME initiated polymerization of acrylonitrile (conversion about 4%) and of styrene (conversion up to 100%), but not of methyl methacrylate and acrylamide3.

Reactions involving electron transfer. II. Reductions of enones with alkali metal solutions

Reactions involving electron transfer. II. Reductions of enones with alkali metal solutions

Optical Constants of Metal-Ammonia Solutions

An ellipsometric technique has been used to determine the optical constants of sodium-, lithium-, and calcium-ammonia solutions between 0.6 and 2.3 eV in the temperature range of 213 to 233 K. The sodium-ammonia data span the range of the metal-nonmetal transition. The alkali metal solutions of concentration $x\ensuremath{\ge}8$ mole percent metal (MPM) are clearly free-electronlike, whereas, the solutions of concentration \ensuremath{\le} 4 MPM strongly indicate the presence of the solvated electron. In the intermediate concentration range ($4lxl8$ MPM), the solutions are undergoing the metal-nonmetal transition; and the species governing the optical properties cannot be unambiguously determined, but probably involve both bound and free electrons. The temperature dependence of the optical constants of concentrated ($x\ensuremath{\ge}6$ MPM) alkali metal-ammonia solutions was found to be negligibly small, while that of less concentrated solutions was consistent with that observed in the dilute alkali metal solutions. Concentrated solutions of calcium in ammonia (g6 MPM) deviated considerably from the Drude model but still appeared to be free-electronlike, as evidenced by the lack of structure in the absorption. They differed somewhat from the alkali metal solutions of similar electron concentration.

Photochemistry and Structure of Metal Amine Solutions

AbstractThe photochemistry of the 670 nm band in fluid sodium amine solutions is investigated by applying flash (optical detection) or steady state (ESR detection) irradiation techniques. The photoregeneration of faded alkali metal solutions induced by exciting the amide decomposition product, is also submitted to flash investigation. In both cases the primary act appears to be the generation of solvated electrons. The available photochemical data are examined in light of a recent spectroscopic study which attributes the 670 nm band to a sodium anion (Na−) and the 850, 920 and 1030 metal bands to K−. Rb− and Cs−, respectively. It is concluded that the photochemical observations provide new evidence for the model involving the alkali metals negative ions. Electron photoejection in a rigid amine glass at −196°C produces a (IR) band which is red shifted relative to that present in an equilibrium liquid solution, frozen to the same low temperature glass. The effect is attributed to two, physically distinguishable, solvated electrons in glasses or, alternatively, to an additional (unidentified) IR species present in the dark equilibrium solutions.

Metal-ammonia solutions

Abstract In dilute solutions of alkali metals in ammonia electrons are localized in cavities in the solvent, and thermodynamic and transport properties are very similar to those found for dilute solutions of strong electrolytes. At higher concentrations the properties deviate markedly from those of electrolyte solutions and approach those of a liquid metal. In this paper we propose an explanation for cavity formation, and discuss the metal-non-metal transition in the light of recent information about the transition in vanadium oxides and doped semiconductors.

Effect of some co-dissolved inorganic groups on the photodecomposition of aqueous nitrates

The rate of nitrite formation, in UV-irradiated aqueous solutions of alkali metals, is found to depend on co-dissolved chemical compounds and on their reactivities. The effect of some common and simple components of the atmospheric aerosol is investigated in the laboratory.