Tetraalkylammonium Halides Research Articles

Tetraalkylammonium cations in electron impact mass spectrometry

AbstractTwenty‐five tetraalkylammonium halide salts were investigated by means of electron impact mass spectrometry. In all cases, corresponding ammonium cations have been detected at low electron energy. Moreover, [C+M]+ have been detected (where C and M denote ammonium cation and molecule, respectively) for both symmetrical salts and iodine salts. Quaternary ammonium salts are considered to be more stable than believed previously.

Time-resolved laser desorption mass spectrometry. I. Desorption of preformed ions

A laser desorption time-of-flight (LD-TOF) mass spectrometer has been used to study the time-resolved desorption of nonvolatile organic salts following a laser pulse. An electron beam, pulsed prior to the pulse which draws the ions from the source, can be used to examine the neutral species desorbed by the laser. Experiments on tetraalkylammonium halides indicate desorption rates for neutral decomposition products vastly different from those for intact ions and neutral clusters, so that the method can be used to resolve competing thermal processes.

Solvolytic behaviour and the solubilities of various inorganic compounds, lewis acids and bases in fused monobromo acetic acid solvent system—II

Abstract Solubilities and the solvolytic behaviour of various inorganic compounds, Lewis acids and bases in fused monobromoacetic acid at 60 ± 0.5°C are discussed. Ionic compounds are fairly soluble, iodides and thiocyanates being comparatively more soluble than chlorides and bromides. Tetraalkyl ammonium halides are highly soluble in this solvent. Conductometric and spectroscopic studies of various Lewis acids and bases in fused monobromoacetic acid indicate their solvolytic behaviour and their subsequent ionization. The solvolyses products BBr3·CH2BrCOOH and SbCl5·CH2BrCOOH have been observed to be the strongest Bronsted acids. Auto-ionization of this solvent has been supported by acid/base titrations.

A simple and convenient synthesis of β-haloketones

A new rapid quantitative method to synthesize β-halo-ketones is described (eqn 2) which utilizes the reaction of an enone with a tetraalkyl ammonium halide in anhydrous trifluoro acetic acid. The method is especially convenient for the preparation of β-iodoketones.

Conductances of some electrolytes in 2-methylpyridine-N-oxide at 55�C

Conductance measurements for fifteen uni-univalent salts in 2-methylpyridine-N-oxide (2-MPO) were made over the concentration range of 2−120×10−4 mol-dm−3 at 55°C. All conductance data were evaluated by the Lee-Wheaton equation. The results indicate that all of the salts studied are slightly associated in 2-MPO, which is, nevertheless, a reasonably good ionizing solvent compared to other solvents having a similar value for the dielectric constant. The tetraalkylammonium halides are weaker electrolytes than the tetraphenylborate salts in 2-MPO. Ionic limiting molar conductances were obtained by using as a reference electrolyte tris(iso-pentyl)butylammonium tetraphenylborate. Anions appear to be poorly solvated in this solvent but certain cations, particularly Na+ and K+, show evidence of specific ion-solvent interaction.

Isothermal transport properties in solutions of symmetrical tetra-alkylammonium bromides

Density, molar conductance, transference number, tracer diffusion (cation, anion, water) and mutual diffusion data are reported for aqueous solutions of the following symmetrical tetra-alkylammonium halides at 25 °C up to 2 mol kg–1 concentration: Me4NBr, Et4NBr, n-Pr4NBr and n-Bu4NBr. These data were used to obtain information on the interactions between pairs of species c, a, w (cation, anion, water) using Hertz's velocity-correlation formalism. Within this formalism the transport coefficients are related to time integrals over velocity cross-correlation functions between the various interaction partners. Results obtained for solutions of tetra-alkylammonium salts differ characteristically from those reported for alkali halides and reflect structural features such as hydrophobic hydration, cation–cation and anion–anion interactions.

Solute–solvent interactions in water + t-butyl alcohol mixtures. Part 11.—Enthalpies of transfer of ammonium and tetra-alkylammonium salts

Enthalpies of solution of tetra-alkylammonium halides (from ammonium to tetrapentylammonium) in mixtures of water and t-butyl alcohol (from 0 to 40% by weight) are reported.

Electrolytic aluminium plating in molten salt mixtures based on AlCl 3 I: Influence of the addition of tetramethylammonium chloride

The effect of additions of surface-active substances on the aluminium plating of iron (steel) in molten chloride electrolytes containing AlCl 3 as the electrochemically active component was investigated. Tetraalkylammonium halides were found to be the most effective additives. The addition of 0.5–2.0 wt% tetramethylammonium chloride to the base AlCl 3-NaCl-KCl electrolyte made it possible to decrease the concentration of the highly hygroscopic and volatile AlCl 3 to about 50 mol.% when almost all the AlCl 3 is bound in the form of the stable complex compound NaAlCl 4. In addition, the effect of the operational parameters of the electrolysis on the current efficiency and the morphology of the aluminium deposit was determined.

Dissociation equilibria of 1-1 electrolytes in acetylacetone

The dissociation equilibria of tetraalkylammonium and alkali metal salts have been studied by conductometry in acetylacetone as a new electrochemical solvent. The limiting molar conductivities and ion association constants of these 1-1 electrolytes have been calculated by the Shedlovsky method, and the dependence of ion association constants on cation and anion sizes has been discussed in connection with the properties of acetylacetone. In acetylacetone, as well as in acetone, alkali metal ions are not strongly solvated, and alkali metal salts form contact ion-pairs predominantly. On the other hand, the small anions such as chloride and bromide are solvated in this solvent to a considerable extent based on the enol form of the solvent, and the ion-pairs of tetraalkylammonium halides are solvent-separated as in alcohols.

Viscosities of solutions of electrolytes and nonelectrolytes inN-methylacetamide at 35� and 55�C

The viscosities of dilute solutions of a number of tetraalkylammonium and alkali metal halides, tetraphenylarsonium chloride, sodium tetraphenylborate, and tetrabutylammonium tetrabutylborate, as well as several nonelectrolytes have been measured in the high dielectric constant solvent N-methylacetamide (NMA) at 35 and 55°C. The relative viscosities were fitted to the extended Jones-Dole equation, ηГ = 1 + AηC1/2 + BηC + DηC2. The pattern of behavior of the Bη coefficients is roughly similar to that observed in H2O. However, the small ions have exceptionally large Bη values in this solvent due to strong solvation effects, while the large organic ions do not display the sharp crossing of the Einstein law, Bη=2.5 φV, characteristic in H2O of hydrophobic interaction. The Dη coefficients roughly parallel the Bη behavior and display remarkably regular ionic trends. This suggests that they arise largely from hydrodynamic origins. Nonelectrolytes have small or negative Bη coefficients showing that the Einstein law is not applicable at the molecular level and that nonelectrolytes are poor models for structurally similar ions. A simple mixture law is presented as an alternative to the Einstein law to explain the Bη coefficients.

Synthesis and 1H NMR studies of some pentacoordinate tin(IV) complexes derived from triphenyltin halides

Several anionic—cationic and neutral pentacoordinate tin(IV) complexes were prepared by the reaction of triorganotin(IV) halides, R 3SnX (R =Me and X =Cl; R =Ph and X =F, Cl, Br) with tetraalkylammonium halides and neutral ligands (pyridine, 4-(dimethylamino)pyridine, hexamethylphosphoramide and triphenylphosphine oxide). The complexes were examined in solution by 1H NMR spectroscopy and characterized as having trigonal bipyramidal geometry around tin where the phenyl groups occupy the equatorial sites and more electronegative ligands are at axial positions. The 1H NMR spectra of these complexes showed two distinct sets of aromatic multiplets arising from ortho-protons at low field, and meta- and para-protons at high field. A possible rationale has been offered for this observation. The upward shift of the tetraalkylammonium proton resonances in the phenyl-substituted complexes has been postulated to arise from shielding caused by the aromatic ring.

A CONVENIENT STEREOSPECIFIC ALKYLATION OF PHENYLACETYLENE BY ELECTROCHEMICAL REACTION OF ORGANOBORANES

Abstract The electrochemical reaction of phenylacetylene with trialkylboranes in a tetrahydrofuran solution containing tetraalkylammonium halide gives the corresponding alkynes via a retention of configuration with respect to the boron-carbon bonds. The reaction mechanism is also discussed.

Solubility of methane in aqueous solutions of triethylenediamine

The solubilities of methane were measured in water and aqueous solutions of triethylenediamine (TED), triethylenediamine hydrochloride (TED·HCl), and HCl at several concentrations up to 1M at 5° intervals from 5 to 25°C. Methane solubilities in solutions of TED·HCl and HCl are lower than those in water and decrease with increasing cosolute concentration. In contrast, the solubilities in TED solutions are greater than those in water and increase with increasing TED concentration. The order of methane solubilities at 25°C in water and in 0.5M aqueous solutions is TED>H2O>HCl>TED·HCl with Ostwald coefficients of 3.57×10−2, 3.44×10−2, 3.26×10−2, and 3.19×10−2, respectively, and with an experimental precision of about ±0.2×10−3. Thermodynamic functions for the transfer of methane from water to 0.25, 0.50, and 0.75M aqueous solutions have been calculated on the molar concentration scale. The free energies of transfer are compared with previous results for methane in aqueous solutions of tetraalkylammonium halides.

The recirculation of Q + used to activate anions

Phase transfer catalysis is one method to activate anions. In this method the amount of catalyst used is usually equivalent to one percent of the anion to be activated. In almost every case a better yield is obtained by increasing the amount of catalyst to a full equivalent. One example of this is found in the process extractive alkylation which I have presented on several occasions. Another example can be found in reactions performed in the absence of an aqueous layer. In such a process as well as in the extractive alkylation process it is often essential for the economy of the method that the catalyst can be readily recovered and recirculated. Due to the outstanding selectivity and simplicity of ion pair extraction methods this recovery is very simple and complete in most cases. The principle used will be demonstrated by reductions with diborane generated from a tetraalkylammonium boranate and an alkyl halide in dichloromethane. Sodium boranate is a versatile reducing agent which has taken an important step towards a big scale use by its introduction as a bleaching agent in the pulp industry. The big scale use of sodium boranate for the generation of diborane has been limited since expensive ether solvents such as tetrahydrofurane have been needed. This problem is however readily circumvented by the use of tetra-alkylammonium boranates in dichloromethane. Solutions of tetrabutylammonium or tributylethylammonium boranate in dichloromethane ready for direct preparation of diborane solutions are prepared from sodium boranate by extractions in a practically quantitative yield. With acetonitrile as the extracting solvent it is even possible to extract tetraethylammonium boranate in an excellent yield. A solution of tetraalkylammonium boranate in dichloromethane gives diborane on the addition of an alkyl halide. These solutions of diborane in dichloromethane can be used in the same way as a solution of diborane in an ether. In fact it is in some cases still more reactive and useful. A tetraalkylammonium halide is obtained as a byproduct which is readily recovered and reconverted to the tetraalkylammonium boranate. Several examples will be given.

Aqueous solutions of azoniaspiroalkane halides. VI. Apparent molal volumes and apparent molal heat capacities of chlorides and iodides

Densities and heat capacities of aqueous solutions of azoniaspiroalkane halides, (CH2)nN+ (CH2)nX− (where X=Cl, I andn=5,6), have been measured at 25°C using a flow densimeter and a flow microcalorimeter. The limiting apparent molal volumes (ov∘) and apparent molal heat capacities (ocp∘) obtained from these data are compared with those of the azoniaspiroalkane bromides and the corresponding tetraalkylammonium halides. The concentration dependence of ov and ocp are examined for clues on the influence of solute hydration, structure, and conformational flexibility on the excess functions of quaternary ammonium halides.

Synthesis of three-co-ordinate mono-, bis-, and tris-olefin complexes of platinum with dimethyl or diethyl fumarate, dimethyl maleate, or maleic anhydride ligands

Bis(cyclo-octa-1,5-diene)platinum, [Pt(cod)2], reacts with dimethyl or diethyl fumarate (dmf or def) or maleic anhydride (ma) to give the complexes [Pt(cod)(olefin)](olefin = dmf, def, or ma). Dimethyl or diethyl maleate (dmm or dem) yield the fumarate complexes [Pt(cod)(olefin)](dmf or def). In the presence of 1 mol equivalent of ButNC or PPh3, complexes of the type [PtL(olefin)2](L = CNBut or PPh3; olefin = dmf, def, dmm, or ma) are produced. With an excess of ButNC the complexes [Pt(CNBut)2(olefin)] are formed. The latter species can also be obtained from the triplatinum complex [Pt3(CNBut)6] and the respective olefin. Addition of tricyclohexylphosphine to [Pt(CNBut)(dmf)2] gives [Pt(CNBut)(dmf){P(C6H11)3}]. The tris(olefin) complexes [Pt(C2H4)(olefin)2](olefin = dmf or dmm) and [Pt(olefin)3](olefin = dmf or def) are formed by treating [Pt(C2H4)3] with the respective olefin. Tetra-alkylammonium halides react with a mixture of [Pt(cod)(dmf)] and dmf to give ionic complexes [NR4][PtX(dmf)2](X = Cl, Br, or I). Protonation of [Pt(cod)(dmf)] with trifluoroacetic acid gives selectively the platinum(II)σ-bonded complex [Pt{CH(CO2Me)CH2(CO2Me)}(O2CCF3)(cod)].

Interionic potential energy studied by far-infrared spectroscopy

Ionic potential models for tetra-alkylammonium halides are proposed, the repulsive energy being evaluated from crystal properties. By assuming a CsCl type structure, such potentials give a qualitative agreement with far-infrared (FIR) spectroscopic data (lattice bands and ion-pair vibration in solution) for a series of salts. For Pr 4NBr, the true structure is known and a more realistic potential has been elaborated. It is shown that the ionic potential is largely determined by the number of first neighbours and the shortest anion-cation distance in the solid. A possible way to estimate the repulsive energy for any R 4N X salt is suggested by using ion-pair dipole moment and vibration frequency data.

Freezing points, osmotic coefficients, and activity coefficients of some salts in ethylene carbonate: A high dielectric constant solvent without hydrogen bonding

The freezing points, conductivities, and densities of NaI, KI, CsI, Bu4NCl, Bu4NBr, Bu4NI, Et4NBr, and Pr4NBr (where Et = ethyl, Pr = propyl, and Bu =n-butyl) in ethylene carbonate have been measured. Osmotic and activity coefficients were calculated from the results. All of the salts studied are strong electrolytes. The trends in the osmotic coefficients of the alkali metal iodides are NaI>KI>CsI, showing that Na+ is more solvated by ethylene carbonate than Cs+. For the tetraalkylammonium halides, the order of osmotic coefficients are Et4NBr≃Pr4NBr≃Bu4NCl>Bu4NBr>Bu4NI. This is the same order as observed in two other high-dielectric-constant solvents, water andN-methylacetamide. The results indicate that the smaller anions are more solvated than the larger anions in ethylene carbonate in contrast to the usual behavior of dipolar aprotic (basic) solvents, such as dimethyl sulfoxide.

The electrochemistry of carbon monoxide reductive cyclotetramerization to squarate anion

The electrochemical reduction, of carbon monoxide to C 4O 2− 4 squarate anion is investigated. Particular attention is devoted to the influence that solvents, electrolytes, electrodes and carbon monoxide pressure have on the yields. The main feature appears to be that strictly controlled conditions are not necessary for cyclotetramerization. In dmf — Bu 4NBr the following yields vs reacted CO and circulated charge were obtained with different cathodes: Pt(49%, 34%); Au(48%, 29%); Al(47%, 38%); stainless steel (36%, 33%); graphite (39%, 31%). A distinct influence of the supporting electrolyte (inorganic and tetraalkylammonium halides) was however observed.

ChemInform Abstract: ELECTROCHEMICAL REACTION OF ORGANOBORANES IN THE PRESENCE OF PROPENOIC ACID ESTERS. A CONVENIENT CARBOXYLIC ESTER SYNTHESIS FROM ORGANOBORANES

Electrolysis of trialkylboranes using two platinum electrodes in the presence of α,β-unsaturated esters in an acetonitrile solution containing tetraalkylammonium halide as a supporting electrolyte, produces the corresponding alkylated carboxylic acid esters in good yields.