Complexes of Aluminum and Gallium Halides with Dibutylamine: Structures and Properties

The reactions of dibutylamine (DBA) with aluminum tribromide and gallium trichloride (MX₃) in a benzene solution were studied using calorimetric and dielectrometric titration. The formation of stable and highly polar molecular complexes DBA · M₂X₆, DBA · MX₃, 2DBA · MX₃, and 6DBA · MX₃ was established.     

One‐Pot,Four‐Component Reaction of Aryl Aldehydes,Aryl Ketones,Phosphorus Trichloride,and Acetonitrile Catalyzed by Acetyl Chloride: Synthesis of β‐Acetamido Ketones

The one‐pot, four‐component reaction of aryl aldehydes, aryl ketones, phosphorus trichloride, and acetonitrile, catalyzed by acetyl chloride, affords β‐acetamido ketones in good to excellent yields. Silicaphosphine (silphos), [P(Cl)_3‐n(SiO₂)_n], can also be used effectively as a solid‐supported reagent instead of phosphorus trichloride.     

The Synthesis of Pamidronic Derivatives in Different Solvents: An Optimization and a Mechanistic Study

The synthesis of pamidronic acid and sodium pamidronate dihydrate from β‐alanine and P‐reagents (phosphorus trichloride and phosphorous acid) was investigated at 75°C in different solvents, and the preparation was optimized. In sulfolane, the use of 2 equiv of phosphorus trichloride and phosphorous acid was found the optimum to lead to pamidronic acid in a yield of 63%. In methanesulfonic acid, 3.2 equiv of phosphorus trichloride was necessary without any phosphorous acid to give pamidronate dihydrate in the best yield (57%) after hydrolysis and pH adjustment. In the first case, the P‐nucleophile may be (HO)₂P–O–PCl–O–P(OH)₂ or (HO)₂P–O–PCl₂, whereas in the second case, the P‐reactant is probable Cl₂P–O–S(O)₂Me. It can be said that the mechanism proposed for the formation of pamidronic acid is highly influenced by the solvent used, as it determines the necessary P‐reagent(s). Our results promote the “on purpose” planning of the synthesis of dronates.     

Oxidation of alcohols by transition metal complexes part V. Selective catalytic monoalkylation of arylacetonitriles by alcohols

Selective catalytic monoalkylation of arylacetonitriles by primary alcohols can be achieved at ≤ 100° using a catalyst prepared in situ from rhodium trichloride, triphenylphosphine and sodium carbonate. RuH₂(PPh₃)₄ is a more effective catalyst for this process.     

Efficient Synthesis of 1,5‐Benzodiazepine Derivatives by Ytterbium Trichloride–Catalyzed Condensation of o‐Phenylenediamine and Ketones

1,5‐Benzodiazepines are synthesized in good to excellent yields by ytterbium trichloride (YbCl₃)–catalyzed condensation of o‐phenylenediamine and ketones under mild and solvent‐free conditions. The Lewis acid–type catalyst, ytterbium trichloride, is found to be water stable and reusable.     

Simulation of the Solid State Vibrational Spectra of Aminodichloroborane and Ammonia Boron Trichloride

This is the second part of a quantum chemical investigation on the reaction between boron trichloride and ammonia. In part I [9] we focused on the energetic course of successive chlorine substitutions which are relevant for the chemical vapor deposition of BN. In this work we analyze in detail the vibrational spectra of reaction products accessible at room temperature. Regarding an experimental IR spectrum of the condensation product of the reaction between BCl₃ and NH₃ [10], there are more signals than expected for monomeric aminodichloroborane. Since this molecule shows the tendency to oligomerize, we have studied whether the presence of aminodichloroborane dimers or trimers or an impurity of the ammonia boron trichloride complex – an intermediate from which aminodichloroborane is formed – can explain the shape of the measured spectrum. To this end we have calculated the vibrational frequencies of monomeric, dimeric, and trimeric BCl₂NH₂, H₃N · BCl₃, and several van der Waals complexes at the level of a Møller‐Plesset second order perturbation theory. For the verification of the methodology, the vibrational frequencies of the dimethylaminodichloroborane molecule have been determined, in good accord with experimental gas phase spectra. Also the solid state spectrum of H₃N · BCl₃ is well reproduced by the computed vibrational spectrum of the monomeric adduct and a hydrogen‐bonded aggregate. Our studies concerning the spectrum of the condensation product of the reaction of boron trichloride with ammonia indicate that the substance investigated by Kwon and McGee had contained, besides monomeric aminodichloroborane, also its trimer and ammonia boron trichloride.     

Approximation of Potentiometric Titration Curves by Logarithmic Functions: Titration of a Mixture of Two Monobasic Acids

The approximation of titration curves by logarithmic functions was described for the titration of a mixture of two monobasic acids. It was demonstrated with the titration of a mixture of CHCl₂COOH, CH₂ClCOOH, C₆H₅COOH, and H₃BO₃ that this method can be used for the precise determination of equivalence points. The relative error in the determination of titration end-points depends on the values of the corresponding jumps and, to some extent, on the choice of a weight function and lies in the range from 0.1 to 1%.     

Halogen exchange reactions of silicon tetrafluoride with phosphorus trichloride and phosphoryl chloride

Silicon tetrafluoride undergoes halogen exchange reactions with both phosphorus trichloride and phosphoryl chloride at temperatures of 500–600°C yielding mixed chlorofluorides of silicon and phosphorus. It is interesting to note that, at these high temperatures, PCl₃ undergoes complete exchange to form PF₃ while POCl₃ reacts only with partial substitution, the major products being phosphorus chloride difluoride and silicon trichloride fluoride.     

Organophosphorus Synthesis Without Phosphorus Trichloride: The Case for the Hypophosphorous Pathway

Abstract

The vast majority of organophosphorus compounds is currently synthesized from phosphorus trichloride (PCl₃), even though the final consumer products do not contain reactive phosphorus–chlorine bonds. In order to bypass phosphorus trichloride, significant interest has been devoted to functionalizing elemental phosphorus (P₄, the precursor to PCl₃), red phosphorus (P_red), or phosphine (PH₃). Yet, other industrial-scale precursors are hypophosphorous derivatives (H₃PO₂ and its alkali salts), but their use as phosphorus trichloride replacements has been completely overlooked. Here, the case is made for an alternative approach to the industrial synthesis of organophosphorus compounds based on hypophosphites.     

Polymer-Supported Lewis Acid Catalysts. I. Polystyrene-Gallium Trichloride Complex

Polystyrene-divinylbenzene (5-7%) copolymer beads are combined with anhydrous gallium trichloride in CS₂ to form a stable complex containing 3.06% Cl (equivalent to 0.287 mmol GaCl₃/g complex beads). The complex showed good catalytic activity in organic synthetic reactions such as acetalation, esterification, ketal formation, etherification, and Friedel-Crafts alkylation. The catalyst can be reused several times without losing its activity and can be easily separated from the reaction mixtures.     

Diastereoselective Aldol Addition Using Boron Trichloride or Alkoxydichloroborane

Under carefully controlled conditions, boron trichloride or alkoxydichloroborane/ethyldiisopropylamine in CH₂Cl₂ can be used to effect diastereoselective aldol additions of ethyl ketones to saturated, α, β-unsaturated, or aromatic aldehydes. The C? C bond formation takes place with relative topicity ul (‘syn,’ configuration of the aldols), in selectivities ranging from 90 to 99% ds (Tables 1–3). Mechanistic aspects of the reaction are discussed.     

ESR study on SiO2-supported half-titanocene catalyst for syndiospecific polymerization of styrene

Monocyclopentadienyltitanium trichloride (CpTiCl₃) was directly immobilized on silica surface. The resulting CpTiCl₃/SiO₂-MAO was investigated in view of its suitability for syndiospecific polymerization of styrene using ESR spectroscopy. Polymerization results show that both the syndiotacticity and the activity decrease upon immobilization. A possible explanation is that the active sites may become aspecific after immobilization and part of the immobilized active sites can be leached into the solution in the presence of MAO.     

Iodine trichloride as an analytical reagent for determination of some organic compounds

Procedures are described for the determination of organic compounds with iodine trichloride under Andrews's titration conditions. Samples are directly titrated with iodine trichloride or first reacted with an excess of iodine monochloride, with subsequent titration of the iodine formed. The direct titration is done initially in feebly acid medium, then the acidity is raised (biotin, methionine, cystine and thiomersal). Pre-oxidation with iodine monochloride is used if the organic compound reacts slowly [tryptophan and arsenic(III) compounds] or is determined in bicarbonate medium (hydroxylamine and thiosemicarbazide). The ferrocyanide formed by the reduction of ferricyanide (by thiourea and allylthiourea) can also be titrated. Arsenic(V) compounds are determined after reduction to arsenic(III), and iodine in organic compounds is converted into iodide by alkaline fusion into iodide and the iodide titrated.     

On the Existence of the Trimer of Gallium Trichloride in the Gaseous Phase

The dependence of the gallium trichloride saturated and unsaturated vapor pressures on temperature was studied by the static method using a quartz membrane zero‐manometer and taking into account the volume of its working chamber and substance mass. Conclusions about the presence of a distinguishable amount of trimeric molecules along with dimeric and momomeric molecules in the vapor were drawn on the basis of the obtained data. The following rough thermodynamic characteristics of a gaseous trimer of gallium trichloride were calculated: Δ_fH° (Ga₃Cl₉, gas, 298 K) = –1466 kJ · mol^–1. S°(Ga₃Cl₉, gas, 298 K) = 654 J · mol^–1 · K^–1. These data were used to elucidate the composition of the gaseous phase at a total pressure of 1 atm in the temperature range of 400–750 K. The suggested existence of trimeric molecules was not contradicted by vibrational spectroscopic analysis of gallium trichloride saturated vapor.     

Determination of Strong Acid in Air-Borne Matter

Abstract

A titration variant for determination of strong acid in air-borne matter with Gran's plot method is proposed. The procedure can be applied to the titration of non sufficiently acidic samples containing weak acids as NH₄ ⁺, HSO₄ ^? and protolyzable ions. Interferences due to the presence of these species are evaluated.     

Modeling and Graphic Presentation of Acid–Base Titration Curves. Presentation of an Alternative Method

Titration curves for the acid—base–titration of polyvalent acids and bases and their mixtures can be created in a simple way and presented graphically. The method, an alternative to the existing procedures, shall be presented here for discussion. With the described method it is possible in an easy manner and for didactic purposes to show how the boundary conditions, such as concentrations, pK_a values, K_w values (temperature–dependent), and mixing ratios influence the shape of titration curves.The method comes from closed mathematical formulas, which can be developed in the form: titration degree, T = f(pH). An increase in the titration volume is, therefore, not considered. It can be neglected in practice by choice of suitable volumes and concentrations. The graphic presentation can be realized with the help of a customary mathematic program, such as MathCAD 7. The titration curves are derived in the familiar form of pH = f(T). During the derivation of the equations for the titration of polyvalent acids and bases, difficult expressions appear and approximations are suggested with only small deviations from the exact formulas, which nevertheless are both simple and manageable.The procedure is presented in a series of practical examples where computed and measured titration curves are compared. When using polyvalent acids, such as malonic acid or citric acid, the appropriate activity coefficients have to be considered. If the ionic strength is constant, which can be accomplished by addition of electrolytes like KCl, this is easily accomplished and is demonstrated by examples.     

Synthesis of trichlorophosphazo-trifluoromethane and - pentafluoroethane

The trichlorophosphazo compounds CF₃NPCl₃ and C₂F₅NPCl₃ could be obtained by reacting the corresponding perfluoroalkyl dichloroamines and phosphorous trichloride.     

Heterometric microdetermination of cobalt using nitron as titrant

Small amounts of cobalt (0.1–0.25 mg in 15 ml solution) were determined heterometrically in the presence of potassium thiocyanate by titration with nitron acetate solution. A strong electrolyte (Na₂SO₄) must be added to obtain a clear end point. The titration can be carried out in the presence of a number of diverse ions e.g., Cd²⁺, Ni²⁺, Pb²⁺, Mn²⁺, Cr³⁺, MoO₄^2?, WO₄², CrO₄^2?, NO₃^?, Au³⁺, Pt⁴⁺ without interference; Fe³⁺ can be masked with NaF. Copper and zinc interfere and must be absent. The titration takes about 2–3 min. and the maximum error was 1.5%.     

Electrochemical behaviour of organotin compounds: Part IV. Phenyltin trichloride

The electrochemical behaviour of phenyltin trichloride has been studied using various electrochemical techniques including polarography, coulometry and cyclic voltammetry. Phenyltin trichloride has been found to show a single major polarographic wave corresponding to a three-electron reduction process to form phenyltin free radicals which rapidly polymerise. Slow hydrolysis of phenyltin trichloride to stannoic acid has been observed to be the major cause of the time-dependence of the limiting current. Analytical methods for the determination of PhSnCl₃ at formulation and trace levels and in the presence of di- and triphenyltin compounds have also been developed.     

$^{1}_{\infty}\rm [Ho_{2}Cl_{6}\{1,3-Ph(CN)_{2}\}_{3}]$ – Eine zu Doppelsträngen kondensierte Variante der PaCl5‐Struktur in einem Selten‐Erd‐Benzodinitril‐Koordinationspolymer

– A Variant of the PaCl₅ Structure Condensed to Double Strands in a Rare Earth Benzodinitrile Coordination Polymer Single crystalline transparent pink (1,3‐Ph(CN)₂ = 1,3‐benzodinitrile, C₆H₄(CN)₂) was obtained by the reaction of anhydrous holmium trichloride with a melt of 1,3‐benzodinitrile at 175 °C. The trichloride structure is broken up by the dinitrile ligands and re‐arranged to double strands of edge connected pentagonal bipyramids of chlorine and nitrogen atoms. The structure can be deduced from the PaCl₅ structure type by condensation of two PaCl₅ strands and exchange of two chlorine atoms with nitrile groups. The double strands exhibit ligand free cavities of 600–800 pm diameter.