Controlled cationic polymerization of styrene using AlCl3OBu2 as a coinitiator: Toward high molecular weight polystyrenes at elevated temperatures

The controlled cationic polymerization of styrene using CumOH/AlCl₃OBu₂/Py initiating system in a mixture CH₂Cl₂/n‐hexane 60/40 v/v at ?40 and ?60 °C is reported. The number‐average molecular weights of the obtained polystyrenes increased with increasing monomer conversion (up to M_n = 85,000 g mol^?1) although experimental values of M_n were higher than the theoretical ones at the beginning of the reaction that was ascribed to slow exchange between reversible‐terminated and propagating species. The molecular weight distribution became narrower through the reaction and leveled of at the value of M_w/M_n = 1.8–2.0. A kinetic investigation revealed that the rate of polymerization was first‐order in AlCl₃OBu₂ concentration meaning that monomeric counteranion (AlCl₃OH^? or AlCl) involved in the initiation and propagation steps of the reaction. It was also found that the rate of polymerization decreased with lowering temperature, which could be attributed to a decrease in concentration of free Lewis acid (AlCl₃), the true coinitiator of polymerization, because of an increase in the tightness of its complex with dibutyl ether. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3736–3743, 2010     

Kinetic and mechanistic study of the quasiliving cationic polymerization of styrene with the 2-phenyl-2-propanol/AlCl3 · OBu2 initiating system

The cationic polymerization of styrene with the 2-phenyl-2-propanol (CumOH)/AlCl₃ · OBu₂ initiating system at various dibutyl ether concentrations in a mixture of 1,2-dichloroethane and n-hexane (55:45 v/v) at −15 °C was investigated. The experimental results showed that an increase in dibutyl ether concentration leads to a noticeable decrease in the polymerization rate as well as to the more controlled polymerization in terms of molecular weight (M_n) and molecular weight distribution (MWD) evolutions. The kinetic investigation revealed that the polymerization proceeds in two stages. The first stage is characterized by high polymerization rate and slow initiation relative to propagation. During this stage molecular weight decreases or does not change and MWD increases with conversion. In the second stage considerably slower quasiliving polymerization of styrene occurs. The quasiliving nature of the styrene polymerization by the CumOH/AlCl₃ · OBu₂ system is proved and mechanistic scheme of the polymerization is proposed.     

The cationic dimerization of 1,1-diphenylethylene. III. Kinetics of initiation by aluminum chloride

Kinetics of the reaction of AlCl₃ with 1,1-diphenylethylene (DPE) in CH₂Cl₂ solution have been investigated at low temperature by ultraviolet (UV) spectrophotometry. Initiation proceeds in three successive stages. The first, very fast and leading to a low and constant concentration of carbocations, is assigned to residual traces of cocatalyst. A second stage, slower but more extensive, yields about one carbocation for two aluminum in a reaction that is first order in AlCl₃ and first order in monomer (k_i = 2.5 10^?2 liter mole^?1 sec^?1 at ?30°; E_i = 10 kcal mole^?1). This stage, which takes place after consumption of residual cocatalyst, should be attributed to a direct initiation. In a proposed mechanism the cationic intermediate produced by reaction of DPE with AlCl₃ transfers a proton to DPE, thus leading to a stable diphenylethyl cation and to alkenyldichloroaluminum (Al-Cl₂CH?CPh₂). A third stage develops slowly and the yield in carbocations finally reaches 65–70% with respect to AlCl₃. This stage is tentatively assigned to a second direct initiation by the less active organoaluminum compound formed in the preceding stage.     

Application of chloroaluminate ionic liquid as catalyst and medium for the dealkylation of esters

Abstract  

Dealkylation of esters to carboxylic acids was performed using chloroaluminate ionic liquids (PyHBr/AlCl₃, PyHCl/AlCl₃, Me₃NHCl/AlCl₃, Et₃NHCl/AlCl₃) as catalyst and medium. The catalytic activity of PyHBr/AlCl₃ (X(AlCl₃) = 0.67) proved to be superior to the other three ionic liquids for the dealkylation of methyl benzoate with a conversion of 97% after 3 h at 140 °C. After easy separation from the products the ionic liquid PyHBr/AlCl₃ could be reused six times without loss of its activity.     

Molecular and electronic structure,and stability of organic cations,dications and donor-acceptor complexes

The MNDO method with optimization of geometric parameters has been used to study the fragments of the potential energy surface for the acylium cation MeC⁺, radical dication MeCO^2+., and the (1 n) complexes of general formula MeCOCl ·nAlCl₃ (wheren=1, 2, 3). The stability of these complexes with respect to certain dissociation mechanisms has been studied. The calculations show that the the hitherto unknown RCOCl · 2AlCl₃ and RCOCl · 3AlCl₃ can actually exist. Moreover, it has been shown that there can be complexes where the charge on the strongly electrophilic carbon atom is greater than that of the carbon in the acylium cation. The result of the study provided an explanation for the superacidity of the RCOX · 2AlX₃ systems in reactions with saturated hydrocarbons.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 854–858, May, 1993.     

Synthesis of methyl 12-benzoyldehydroabietate in ionic liquid

In the presence of the ionic liquid [bmim]Br/AlCl₃ as green reaction medium, methyl 12-benzoyldehydroabietate was synthesized through Friedel-Crafts acylation reactions on the aromatic ring of methyl dehydroabietate. The optimum synthetic conditions of the target product were found to be as follows: molar ratio of methyl dehydroabietate to [bmim]Br to AlCl₃ to benzoyl chloride 1:4:8:8, reaction temperature 40°C, reaction time 2 h. The target product was analyzed and characterized by means of IR, MS, NMR and elemental analysis. The results show that this novel method has the advantages of mild condition, short reaction time and environmental benignity. __________ Translated from Chemistry, 2008, 71(2): 138–143     

Cryosynthesis,structure, and IR spectra of aluminum chloride—nitromethane molecular complexes

The products of codeposition of aluminum chloride and nitromethane were studied by low-temperature IR spectroscopy (80—200 K). Density functional (B3LYP/6-31G* and B3LYP/6-31+G**) quantum-chemical calculations of the geometry and vibrational frequencies of aluminum chloride, nitromethane, and AlCl₃·MeNO₂ and 2AlCl₃·MeNO₂ complexes were carried out. Comparison of the experimental and calculated IR spectra suggests that the preferred geometry of the 2AlCl₃·MeNO₂ complex is such that one AlCl₃ molecule is coordinated to an O atom of the nitro group, while the other AlCl₃ molecule forms an Al...Cl bridge.     

Versatile synthesis of cadalene and iso-cadalene from himachalene mixtures: Evidence and application of unprecedented rearrangements

From a mixture of α-, β- and γ-himachalenes extracted from waste wood of Atlas cedar (Cedrus atlantica), cadalene (1,6-dimethyl-4-isopropylnaphthalene) and iso-cadalene (1,6-dimethyl-3-isopropylnaphthalene) were produced in two steps with up to 71% ± 5% yield through the ar-himachalene intermediate using I₂ and/or AlCl₃ as reagents. The selectivity is shown to sharply depend on the operating conditions: while I₂/AlCl₃ in dichloromethane promotes the formation of cadalene, the formation of iso-cadalene is favored in the presence of AlCl₃ in cyclohexane. The bicyclic aromatic compounds were thus obtained through unique rearrangements involving sequential CC bond cleavage/formation and hydride transfer processes. In the absence of AlCl₃ or I₂, dihydrocurcumene was also found to be formed with up to 70% selectivity. A tentative mechanism is proposed and discussed.     

High-temperature gas-chromatography of some inorganic chlorides

Summary Electric-conductivity detector is used successfully for the detection of inorganic chlorides in high temperature gas chromatography (450–1000°C). Following mixtures can be separated by the carrier gas He (60 ml/min) on a 250 mm Pt-column with the packing constructed of a fused salt and Chromosorb WAW: BeCl₂/AlCl₃at 560°C; PbCl₂/SnCl₂at 780°C; BiCl₃/SbCl₃at 660°C; BiCl₃/PbCl₂ at 560°C; TlCl/FeCl₃, TlCl/BeCl₂, TlCl/AlCl₃, ThCl₄/AlCl₃ at 640°C; InCl₃/(AlCl₃+FeCl₃) at 660°C; ZnCl₂/PbCl₂ at 780°C; SnCl₂/(NaCl+KCl) at 830°C; and TlCl/PbCl₂ at 830°C.

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Hochtemperatur-Gas-Chromatographie einiger anorganischer Chloride

Zusammenfassung Zum Nachweis anorganischer Chloride bei der Hochtemperatur-Gas-Chromatographie (450–1000°C) wird mit gutem Erfolg ein Leitfähigkeitsdetektor verwendet. Es wird eine 250 mm-Pt-Säule benutzt, gefüllt mit einem geschmolzenen Salz (Alkaki oder Erd-alkalichloride) auf Chromosorb WAW. Als Trägergas dient Helium (60 ml/min). Folgende Gemische können getrennt werden: BeCl₂/AlCl₃ bei 560°C; PbCl₂/SnCl₂ bei 780°C; BiCl₃/SbCl₃ bei 660°C; BiCl₃/PbCl₂ bei 560°C; TlCl/FeCl₃, TlCl/BeCl₂, TlCl/AlCl₃, ThCl₄/AlCl₃ bei 640°C; InCl₃/(AlCl₃ + FeCl₃) bei 660°C; ZnCl₂/PbCl₂ bei 780°C; SnCl₂/(NaCl+KCl) bei 830°C; TlCl/PbCl₂ bei 830°C.

     

Study on the mechanism of catalytic synthesis of dimethyldichlorosilane by AlCl3/MIL‐53(Al)@γ‐Al2O3

Dimethyldichlorosilane, one of the most consumed organosilicon monomers in the industry, can be prepared in a highly efficient and environmentally friendly synthesis method of disproportionating methylchlorosilanes. However, the internal mechanism of the reaction remains unclear. In this paper, the mechanism catalyzed by AlCl₃/MIL‐53(Al) and AlCl₃/MIL‐53(Al)@γ‐Al₂O₃ catalysts was calculated at B3LYP/6‐311++G(3df, 2pd) level by using the density functional theory (DFT). The results showed that although the two catalysts had similar active structures, the catalytic effects were significantly different. The Lewis acid center on the surface of γ‐Al₂O₃ in the core‐shell catalyst is complementary to the classic Lewis acid AlCl₃ through the spatial superposition effect, which greatly improves the Lewis acid catalytic activity of AlCl₃/MIL‐53(Al)@γ‐Al₂O₃.     

Biphasic ethylene polymerisation using ionic liquid over a titanocene catalyst activated by an alkyl aluminium compound

1-n-Butyl-3-methylimidazolium tetrachloroaluminate ([BMIM]⁺[AlCl₄]⁻) was applied to biphasic ionic liquid/hexane ethylene polymerisation as a medium of the Cp₂TiCl₂ titanocene catalyst activated by alkylaluminium compounds (MAO, AlEt₂Cl, AlEt₃). The best results were obtained using AlEt₂Cl. The results show that catalyst recycling, higher ethylene pressure, and greater Al/Ti molar ratio along with a greater volume of the ionic liquid phase enhance catalyst activity. The polyethylene gathered from the hexane phase is characterised primarily by its high purity. Its physical properties remain polyethylene obtained over a heterogeneous metallocene catalyst. Thus, biphasic ionic liquid polymerisation using a metallocene catalyst is possible and offers interesting technological implications.     

Effects of Salts Containing Mono-, Di-, and Trivalent Ions on Electrical and Rheological Properties of Oil-Water Interface in Presence of Cationic Surfactant: Importance in the Stability of Oil-in-Water Emulsions

Many industrial applications of oil-in-water emulsions involve salts containing ions of different valence. The properties of the oil-water interface (e.g., interfacial tension, zeta potential and interfacial shear viscosity) are strongly influenced by the presence of these salts. This work investigates the role of NaCl, CaCl₂ and AlCl₃ on these properties of the hexane-water interface in presence of a cationic surfactant, viz., hexadecyltrimethylammonium bromide. Addition of salt enhanced the adsorption of surfactant molecules at the hexane-water interface, which increased the interfacial charge density, and consequently, the zeta potential. Interfacial shear viscosity significantly decreased in the presence of salt. The effectiveness of salt at a given concentration was in the sequence: AlCl₃ > CaCl₂ > NaCl. The hexane-in-water emulsions coarsened with time due to the coalescence of hexane droplets. The increase in droplet size with time was analyzed by a model based on the frequency of rupture of the thin aqueous film. The rate constants for coalescence were determined. The rate of coalescence increased in presence of salt.      

AlCl<Subscript>3</Subscript>/amide ionic liquids for electrodeposition of aluminum

AlCl₃/amide (acetamide, propionamide, butyramide) ionic liquids were used as the electrolytes to study the electrodeposition behavior of aluminum on a tungsten electrode. Cyclic voltammograms on the tungsten electrode indicate that Al(III) ions can be reduced to aluminum only within the molar ratio range of 1.1 to 1.5 and the reduction potentials of Al(III) ions strongly depend on the molar ratio of AlCl₃/amide. Raman spectra results reveal that the electroactive specie of AlCl₃/amide ionic liquids is Al₂Cl₇ ^?. Aluminum coatings were prepared at ?0.25 V (vs. Al/Al³⁺) and at 313 K in AlCl₃/amide ionic liquids with the molar ratio of 1.3. The SEM and cross-sectional SEM images show that all the obtained aluminum films are silver-colored, thick, and adherent. The EDS and XRD analysis confirm that the obtained deposits are pure aluminum. The present results can provide a new route for aluminum electrodeposition under ambient conditions.     

In Situ Formation of Al(Fe)/Cl Metal Chloride Complexes and Evaluation of Their Catalytic Properties in the Reaction of Ethylene Oligomerization

According to FT-IR and UV spectroscopic data, the interaction of the Al/Fe alloy with tert-butyl chloride results in that AlCl₄^–, Al₂Cl₇^–, and FeCl₂⁺ ion complexes, Fe³⁺ ions, and AlCl₃ molecular form are produced in situ in the reaction medium. Ethylene was oligomerized in n-hexane on metal chloride complexes produced in situ from Al/Fe alloys and tert-butyl chloride.     

Influence of AlCl<Subscript>3</Subscript> on aggregation stability of aqueous dispersions of kraft lignin according to filtration through track membranes

The influence of AlCl₃ (0–10⁻³ M) and pH (9.5–2.0) on the aggregation of dilute (10 mg/l) aqueous dispersions of kraft lignin is studied by filtration through several track membranes with pore diameters of 50–2500 nm. AlCl₃ is shown to have markedly higher coagulating ability than NaCl and CaCl₂. In a pH range of 4.1–7.0, which corresponds to the significant hydrolysis of AlCl₃, the concentration inversion of AlCl₃ coagulating ability is observed when passing from 10⁻⁴ to 10⁻³ M, which is caused by the charge reversal of negatively charged kraft lignin particles under the action of AlCl₃ hydrolysis products.     

In situ study of the interaction between <Emphasis Type="Italic">tert</Emphasis>-butyl chloride and aluminum activated with liquid In-Ga eutectic

The interaction between tert-butyl chloride and activated aluminum was studied by attenuated total reflectance Fourier transform infrared spectroscopy near room temperature (18–25°C). A long induction period of ∼240–260 min was observed. The ionic aluminum chloride complexes [Al _n Cl_3n+1]⁻ (n = 1, 2) and the molecular species AlCl₃ were identified at the activated aluminum/tert-butyl chloride interface during the reaction. The formation of the ion in the AlCl₄⁻ ion in the liquid medium and the presence of the same ion and a molecular AlCl₃-tert-butyl chloride complex in the resinous products of the reaction were confirmed by ²⁷Al NMR spectroscopy. The reaction products were analyzed qualitatively by GC/MS. The reactivities of activated aluminum and anhydrous aluminum chloride toward tert-butyl chloride under the same conditions were compared. A distinctive feature of the interaction activated aluminum and tert-butyl chloride is the dominant formation of the AlCl₄⁻ ion. By contrast, the interaction between aluminum chloride and tert-butyl chloride yields the polynuclear ion Al₂Cl₇⁻ and, likely, Al₃Cl₁₀⁻.     

DCC/AlCl_3体系引发异丁烯正离子聚合

研究以对-二枯基氯(DCC)/AlCl3体系引发异丁烯在CH2Cl2/Hex(40/60,V/V)混合溶剂中进行正离子聚合,探讨了DCC用量、给电子试剂,如三苯胺(TPA)、2,6-二甲基吡啶(DMPy)对异丁烯正离子聚合转化率、产物分子量及其分布的影响.结果表明,在无给电子试剂存在时,DCC和体系中微量水均可与AlCl3产生络合竞争引起相继的引发竞争,聚合产物GPC谱图呈双峰分布,分子量分布宽,需要大量的引发剂DCC(DCC/H2O=5.3)来减少体系中微量水的不可控引发;在少量上述给电子试剂存在下,可提高DCC的引发效率,减少向单体链转移反应,提高聚合产物的分子量和使分子量分布呈较窄的单峰分布,即使在较低DCC用量下也可基本抑制体系中微量水的不可控引发,达到DCC定量引发,并得到分子量分布相对较窄(Mw/Mn≈2.3)的聚异丁烯产物.     

The polymerization of isobutylene by AlCl3 in CH2Cl2 and the role of CH2Cl2 in the initiation reaction

A solution of AlCl₃ in CH₂Cl₂ prepared in advance was used 18 days after the mixing of the components as an initiation system in the polymerization of isobutylene performed in CH₂Cl₂ in the temperature range between ?10 and ?20°C. The ¹H-NMR analysis of polyisobutylene (PIB) samples synthesized to low and high conversion showed that it is the initiation reaction and not the transfer reaction to dichloromethane that is responsible for the ? CH₂Cl endgroup in the polymer chain. In case of the transfer to monomer formation of PIB with internal terminal unsaturation [PIB? CH?C(CH₃)₂] is preferred to external unsaturation [PIB? CH₂(CH₃)C?CH₂]. The solutions of AlCl₃ in CH₂Cl₂ showed an absorption band at λ_max = 302 nm.     

Mechanism on The Disproportionating Synthesis of Dichlorodimethyl- silane by ZSM-5(5 T)@γ-Al2O3 Series Core-Shell Catalysts

In view of the wide application of organosilicon bifunctional structure in industry, the most effective disproportionation solution is used by the new catalyst to prepare the largest and the most versatile organic silicon monomer dimethyldichlorosilane. However, there are still remaining doubts on the disproportionation mechanism of the catalyst. The Density Functional Theory (DFT) was used to theoretically calculate the disproportionation mechanism of 5 T clusters ZSM-5@γ-Al₂O₃ series catalysts at the B3LYP/6–311++G(3df, 2pd) level. The properties were verified and the catalytic effects of different active sites pre- and post- modified by AlCl₃ were calculated and compared. The active center of HZSM-5@γ-Al₂O₃ was proton, and that of AlCl₃/ZSM-5@γ-Al₂O₃ changed to lewis acidic center. The presence of the lewis acid center enhances the total activity of the catalyst to some extent. The catalytic activity of the 5 T cluster ZSM-5@γ-Al₂O₃ catalyst modified by AlCl₃ was higher, which was the same as the experimental results.     

金属卤化物促进糖类催化转化制备5-羟甲基糠醛

研究了碱金属卤化物对AlCl₃催化葡萄糖转化制备5-羟甲基糠醛（HMF）的促进作用. 结果表明,NaF对反应有显著抑制作用,而NaI和NaBr对反应有显著促进作用,而且NaI比NaBr的促进效果更明显. 在N,N-二甲基乙酰胺（DMAC）中,以NaI为添加剂,130 ℃反应15 min,AlCl₃催化葡萄糖转化制备HMF,葡萄糖转化率由71%提高到86%,HMF收率由36%提高到62%. AlCl₃-NaI-DMAC体系也可用于果糖、甘露糖等单糖,蔗糖、麦芽糖、纤维二糖等二糖,以及菊粉等多糖的转化. 以蔗糖为原料,HMF收率可达63%.