Tetraalkylammonium Halides Research Articles

Aluminum Chloride–Tetraalkylammonium Halide Complex as a Novel Catalyst in Friedel–Crafts Alkylation. Direct Construction of the Chroman Structure from 1,3-Diene

Abstract Tetrabutylammonium halides were found to accelerate Lewis acid-catalyzed Friedel–Crafts alkylation when trimethylhydroquinone and myrcene were used, followed by cyclization to give the chroman compound predominantly. For tetraalkylammonium salts which have long-chain alkyls and/or bromide, iodide counter anions promote the reaction in less-polar solvents. Phosphonium halides and sulfonium halide were also effective. The tetraoctylammonium bromide–aluminum chloride complex was an effective catalyst for the initial regioselective protonation of 7,11,15-trimethyl-3-methylene-1,6-hexadecadiene to give α-tocopherol in high yield.

Ein neuer Zugang zu ionischen Thionylimiden. Einkristallstruktur von N(CH3)4NSO / A New Access to Ionic Thionylimides. Single Crystal Structure of N(CH3)4NSO

Abstract Single crystals of N(CH3)4NSO have been prepared via ion exchange from RbNSO or CsNSO and tetraalkylammonium halides in liquid ammonia and investigated by X-ray single crystal techniques (I4̅, a = 1137.6(1), c = 1134.9(2) pm, Z = 8, T = -100 °C). The crystal structure of N(CH3)4NSO is related to the CsCl-type of structure. Using the same preparative route NMe3BzNSO has been obtained. Its lattice powder data (orthorhombic primitive; a = 896.3(2), b = 1235.4(3), c = 1070.7(4) pm).

Preparation, characterization, and application of fine metal particles and metal colloids using hydrotriorganoborates

The reduction of transition metal salts and oxides using hydrotriorganoborates in organic media allows the production of X-ray amorphous nanopowders of metals and alloys under mild conditions. For example, the reduction of needle-shaped iron oxides at 80°C in organic solvents leads to acicular iron-magnet pigments suitable for recording magnetic signals. The reduction of TiCl 4 with K[BEt 3H] gives an ether-soluble [Ti(0)·0.5THF] x which serves as a catalyst for the hydrogenation of titanium or zirconium sponges and related systems and as a powerful activator for heterogeneous hydrogenation catalysts. The use of tetraalkylammonium hydrotriorganoborates as reducing agents leads to colloidal transition metals in organic phases. These colloids may also be obtained using conventional reducing agents after first reacting the metal salts with the stabilizing tetraalkylammonium halide. Colloidal metals prepared in this way serve as sources for heterogeneous metal catalysts.

Facile Preparation of the C 60 Monoanion in Aprotic Solvents

A facile method of monoanion preparation in various aprotic solvents is presented and interpreted in terms of the Nernst electrochemical equilibria. The method consists of reduction of with mercury in the presence of tetraalkylammonium halide. The radical product, containing traces of , is detected and identified by electron spin resonance spectroscopy. The selectivity of the method is tuned by a proper selection of solvent, tetraalkylammonium halide, and its concentration.

The conformational stability of tactic poly(2‐hydroxyethyl methacrylate) in aqueous salt solutions

AbstractThe conformational stability of tactic poly(2‐hydroxyethyl methacrylate) (PHEMA) in aqueous salt solutions was investigated by measurements of swelling, surface‐free energy, and differential scanning calorimetry, as this polymer in water is sensitive in various electrolytes. In the case of inorganic salts, the major role for the salt effect is played by the anions, and the exposure of hydrophobic components at the PHEMA surface can be correlated with the increase of the degree of swelling. The influence of cations is considerably weaker. In the case of organic salts, tetraalkylammonium halides cause the chain extension more effectively with the increase of alkyl chain length in the cations. This result indicates that the breakdown of the hydrophobic parts in PHEMA provides an important clue on conformational stability. The amount of water molecules bound with the hydrophilic sites of tactic‐PHEMA mainly depends on the chain extension and the hydration of cations. Since the sites in tactic‐PHEMA influenced by the cation and the anion are different, their effects cause the conformational transition at a specific range of salt concentration. © 1993 John Wiley & Sons, Inc.

Near infrared spectral studies on interactions of CH3 groups with halide ions

Near infrared (NIR) spectra in the CH3 stretching first-overtone region for methyl iodide, acetonitrile, nitromethane and dimethyl sulphoxide are discussed in terms of normal mode and local mode descriptions. NIR spectra in this region for solutions of several alkali metal halides and tetraalkyl ammonium halides in these solvents are also reported. It is found that the relative intensity of the cooperative excitation band with respect to the pure overtone excitation band reduces considerably on increase in the concentration of the electrolytes in solution. The results are discussed in terms of the formation of anion-molecular complexes as well as intermode coupling due to kinetic energy and anharmonicity effects.

Inhibition of near-infrared photoinduced electron transfer between free hexacyanoferrate(II) and hexacyanoferrate(III) by tetramethylammonium ions

A recently reported weak 800-nm intervalence absorption band in mixtures of potassium hexacyanoferrate(III) and -(II) was interpreted as photoinduced electron transfer between the free hexacyanoferrate ions. We have investigated the effect of replacing potassium ions by tetraalkylammonium ions on this band using mixtures of the appropriate hexacyanoferrates rather than by adding tetraalkylammonium halides to the potassium hexacyanoferrates. The intervalence band appears to vanish on full replacement. This suggests that the phototransition is likely to be in an ion pair bridge configuration

Cathodic carbonylation of 1-halogenopentanes

Reaction conditions for electroreductive conversion of 1-halogenopentane into hexanal using [Fe(CO)5] have been investigated in detail. The use of acetonitrile as solvent containing tetraalkylammonium halides or toluene-p-sulfonate and a divided cell gave good results. Under the conditions, the best results were obtained with the bromide as starting halide.

Structural and spectroscopic studies of halogenocuprate(I) complexes

Reaction of tetraalkylammonium halides, PPh3 and copper(I) halides in a 1 : 1 : 1 mole ratio in dichloromethane yields complexes [NR4][Cu(PPh3)X2](R = Et, X = Cl or Br; R = Pr, X = Br, I; R = Bu, X = Br) and [NEt4]2[Cu2(PPh3)2I4]. These have been characterized by infrared and cross polarization magic angle spinning (CP MAS)31P NMR spectroscopy, and the structures of most have been determined by single-crystal X-ray diffraction. The compounds [NR4][Cu(PPh3)X2] in the first group above contain mononuclear anions [Cu(PPh3)X2]– with essentially trigonal planar PCuX2 co-ordination. The P–Cu–X and X–Cu–X angles are all within 5 ° of the ideal trigonal angle of 120 °. The compound [NEt4]2[Cu2(PPh3)2I4] contains the centrosymmetric binuclear anion [Cu2(PPh3)2I4]2–{a dimer of [Cu(PPh3)I2]–} in which the two copper atoms are bridged by two iodine atoms, and each copper atom is also bound to a terminal iodine atom and PPh3 molecule. The FIR spectra of the mononuclear complexes [Cu(PPh3)X2]– show strong bands at 264, 195 and 175 cm–1 for X = Cl, Br and I respectively, which are assigned to the asymmetric v(CuX) stretching mode of the bent X–Cu–X units, and weak bands at 194, 150 and 128 cm–1 due to the symmetric v(CuX) mode. In addition, the X = Cl complex shows a strong band at 126 cm–1 which is assigned as the δ(CuCl2) bending mode. The dimer [Cu2(PPh3)2I4]2– shows a remarkably simple spectrum in the v(CuI) region: a partially resolved doublet at 113 and 126 cm–1. The above vibrational frequencies are compared with those of the species [CuX2]– and [Cu2I4]2–, from which the present species can be considered to be derived by addition of one PPh3 molecule per copper atom. The solid state CP MAS 31P NMR spectra generally consist of asymmetric quartets due to coupling of the 31P nucleus to the quadrupolar copper nucleus, and the splitting patterns are interpreted in terms of the copper co-ordination environment.

Kubanartige Molybdän-Halogen-Schwefel-Clusterdithiophosphinate / Cubane Type Molybdenum-Halogen-Sulfur Clusterdithiophosphinates

Diamagnetic clusters [Mo3X-μ-(S2)3-μ3(S)(R2PS2)3] 2-4 (2: X = Cl; 3: X = Br; 4: X = I; 2-4: a: R = Et; b: R = Pr; c: R = Bu) are conveniently obtained by reaction of [Mo3S7(R2PS2)3]+(R2PS2)- 1 either with alkyl halides RX or with tetraalkylammonium halides R4NX. Between halogen X and one of the S atoms of each disulfido bridge there exist bonds which seem to be mainly of covalent character. Thus X is incorporated into the cluster core leading to a cubane type structure. [Mo3ClS7(Et2PS2)3] forms orthorhombic crystals with space group Pnma, Z = 4, a = 1931.9(7), b = 1551.2(6), c = 1286.5(4) pm. Isostructural substructures of 3b, 4a and 4b (space group P21) were also studied. All these cluster molecules reveal similar core geometries with distances S—Cl 239.4(4), S—Br 305(1) and S—I 322.5(3) pm much less than the sum of the van der Waals radii. The results of structural and spectroscopic investigations are discussed.

The specific adsorption of halides on mercury in non-aqueous acetonitrile

The adsorption behaviour of various tetraalkylammonium halides R 4NX (R = Et, Bu; X = I −, Br −) and sodium iodide at the mercury/acetonitrile interphase has been investigated employing capacity measurements and measurements of the potential of zero charge at variable ionic strength. The results indicate strong specific adsorption of halide ions in the range between negative and positive electrode charges. For NaI, a more detailed study of the adsorption process based on the virial isotherm was performed including the evaluation of the standard Gibbs energy of adsorption and the interaction parameter. Moreover, the distance ratio ( x 2 − x 1/ x 2 and the Esin-Markov coefficients could be estimated. From differences between the Esin-Markov coefficients determined for all salts under investigation, a counter-ion effect with respect to the halide adsorption could be deduced. The specific adsorption of halide ions in acetonitrile will be discussed, particularly with regard to the influence of solvent and ion association.

Homogenization of Water/Chloroform and Water/n‐Butanol Mixtures with Tetraalkylammonium Halides. Phase Diagrams and Properties of the Homogeneous Phases

AbstractWe report on two ternary systems with a ternary miscibility gap. They consist of two immiscible solvents (water and chloroform or water and n‐butanol) and salts which can close the miscibility gap. These salts are unsymmetrical tetraalkylammoniumhalides R3R'N+X− (X− = Cl−, Br−, I−). We determined the binodal curves in the ternary phase diagrams. In the homogeneous region, we measured densities, kinematic viscosities, and electrical conductivities. At constant mole fractions of salt, the viscosities increase and reach constant values while the conductivities decrease monotonously with increasing mole fractions of the organic solvent. Addition of salt to a given mixture of the solvents leads to a monotonous increase of the viscosities while the conductivities first increase, then go through maxima and decrease again. By X‐ray analysis we determined the crystal structure of methyl‐tri‐n‐propylammonium iodide. The lattice is triclinic, space group P1. A ternary compound, containing the salt together with chloroform and water could also be prepared. The crystal is disordered at room temperature, a skeleton of tetraalkylammonium ions is present which contains channels. In these channels, chloroform and water molecules seem to be mobile. The X‐ray analysis shows no special positions for these solvent molecules. The structure of this compound does not indicate heteroselective solvation. This concept therefore should not be used in the discussion of the homogenization by these salts.

Hydrogen bonding Part 36. NMR study of 14N to CH coupling as a measure of hydration of tetramethylammonium and tetrapropylammonium halides

Correlation of development of 14N to CH NMR coupling with cation mobility has been used to study hydration behaviour of tetramethylammonium and tetrapropylammonium halides in the range between saturated solutions and the point where full ion mobility is attained. The tetramethylammonium ion in solutions of the chloride forms an initial tightly bound clathrate with 4 moles H 2O per mole of cation (H 2O/salt=4), and a larger, looser hydration shell with an additional 3 moles H 2O. The tetramethylammonium ion presumably also forms an initial clathrate with H 2O/salt=4 in solutions of the fluoride; however, the salt binds water so tightly that ion mobility does not commence until H 2O/salt = 7.5, and full mobility is not reached until H 2O/salt≈10. Tetramethylammonium bromide shows full ion mobility in the saturated solution with H 2O/salt= 8.75. The larger tetrapropylammonium ion forms an initial clathrate with H 2O/salt=9; both the chloride and bromide show development of a larger hydration shell. Comparison with previously studied tetraalkylammonium halides demonstrates that the formation or lack of formation of a larger hydration shell is not a function of hydration type (normal type A or hypobarogenic type B) of the tetraalkylammonium halide; rather, it is a combined function of cation size and anion electronegativity.

Electrolyte solutions that unmix. Hydrophobic ions in water

Simple models for the solvent-averaged ion-ion pair potentials for aqueous solutions of tetraalkylammonium halides were previously treated under the HNC (hypernetted chain) approximation to find the parameters needed to fit osmotic coefficient data of the corresponding real solutions. Here the model Pr4NI is modified by changing the A+− Gurney parameter to give the ‘Pr4NX’ model which exhibits the unmixing (separation into two solution phases of different concentrations) that has been reported for several real aqueous tetraalkylammonim salt solutions. The models used here are established at the McMillan-Mayer (MM) or solvent-averaged level, so careful attention is given to the choice of the thermodynamic potential from which we may derive the condition of material stability (stability with respect to separation into two phases of slightly different composition), and calculate the required thermodynamic coefficients from the MM pair correlation functions. The emphasis is on the study of the hydrophobic unmixing in terms of thermodynamic coefficients derived from the pair correlation functions calculated for the Pr4NX model under HNC. In the temperature-concentration (T-cS) plane we can locate the ‘solvability line’ (which separates states for which the HNC equation can be solved from the rest) and portions of the coexistence line. To locate the coexistence line in regimes in which the double tangent method is not effective we use a method based on the osmotic pressure and the solute chemical potential isotherms. Our results suggest that for the Pr4NX model in the T-cS plane the spinodal line lies within the solvability line which, in turn, lies within the coexistence line for the states where the latter could be determined. The role of the thermodynamic inconsistency implicit in the HNC correlation functions is given special attention, as is the remarkable role of the 1/r4 cavity term in the model pair potential. Single-ion activity coefficients and DELα functions are calculated for some of the states studied.

Fluorescence study of the weak interaction between pyrene and quaternary ammonium groups

Systems containing pyrene and tetraalkylammonium halides (R4NX) were investigated using time-resolved and steady state fluorescence techniques. The existence of a previously suggested weak interaction between pyrene and quaternary ammonium groups is confirmed and is further verified by solubility measurements. The quenching of pyrene fluorescence by R4NBr is a synergistic effect, requiring Br− and enhanced by the simultaneous presence of the quaternary ammonium ion. The presence of tetraalkylammonium halides also affects the efficiency of pyrene excimer formation.

Investigations of the transitions of some tetraalkylammonium halides by DSC, NMR, and X-ray diffraction

The transitions of several symmetric tetraalkylammonium halides were studied by differential scanning calorimetry (DSC), solid-state nuclear magnetic resonance (NMR) and X-ray diffraction. The reversibility of the transitions of Bu 4NI is investigated by cycling of the samples in the DSC. A plastic-crystalline phase is found and characterized. A glass transition is observed for Bu 4NCl at 230 K. Solid-state CP-MAS 13C NMR is performed on Hex 4NI in order to reveal the large-amplitude molecular motion. The DSC transitions are confirmed by changes in the chemical shifts, but additional, more continuous changes are seen. Condis-crystalline phases are probable for the latter two salts. Room-temperature X-ray diffraction on various iodides shows that the appropriate d-spacings increase linearly with size of the alkyl groups.

Transference numbers of lithium chloride and tetraalkylammonium halides in 1-butanol at various temperatures

Transference numbers of lithium chloride and some tetraalkylammonium halides have been measured in 1-butanol at 298.15, 308.15, and 318.15 K up to concentrations of 11.84×10 −2 mol dm −3

Nuclear magnetic resonance studies of supercooled aqueous electrolyte solutions

The dynamic properties of water molecules coordinated to simple ions (alkali and alkali-earth halides) and hydrophobic ions (tetraalkylammonium (TAA) halides) in supercooled solutions have been investigated with NMR. The study of spin-lattice relaxation rates and self-diffusion coefficients as functions of temperature, pressure Larmor frequency and concentration reveals characteristic features of molecular motions close to the low-temperature limit of the metastable phase (percolation transition and glass transition) and provides certain details of the local arrangement of water molecules in the coordination sphere of these ions. The intramolecular flexibility of the alkyl chains of the hydrated TAA cations has been investigated also. The dynamics of the methyl group reorientation provide a sensitive probe of structural differences in these solutions.

ChemInform Abstract: Some Novel Phosphoranides Containing Pentafluorophenyl Groups.

AbstractThe formation of the phosphoranides (I) and (II) from the corresponding phosphines (C6F5)PX2 and (C6F5)2PX and an excess of tetraalkylammonium halides or isothiocyanate is observed by means of 31P NMR spectroscopy.

Study of the influence of tetraalkylammonium salts on the dissolution of aluminium in aqueous NaOH solutions

Tetraalkylammonium halides decelerate the reaction of aluminium in aqueous NaOH solutions. Their effect depends on the alkyl group, on the anion, and on their concentration; and it is additive with the effect of Ca2+ ions. The inhibition effects under study and the shift of the stationary potentials to more anodic values are shown to be related with the influence on the cathodic process, resulting in a retardation of the whole corrosion process.