Synthesis and reactions of [tris(trimethylsilyl)methyl]ethyl dichlorosilane

The crowded dichlorosilane TsiSiEtCl₂, (1), (Tsi = (Me₃Si)₃C) was prepared from the reaction between EtSiCl₃ and TsiLi, then it was reduced with LiAlH₄ to give TsiSiEtH₂, (2). The hydride (2) was then treated with two equivalents of ICl/CCl₄ or Br₂/CCl₄ to produce TsiSiEtI₂, (3), and TsiSiEtBr₂, (4), respectively. The reaction of compound (2) with one equivalent of ICl/CCl₄ gives TsiSiEtHI, (5). This product reacted with H₂O/dioxane in the presence of AgClO₄ or with dry MeOH to produce TsiSiEtHOH, (6), and TsiSiEtHOMe, (7), respectively. The compound (3) reacted with H₂O in DMSO/CH₃CN to give TsiSiEt(OH)₂, (8), and the compound TsiSiEtIOMe, (9), was prepared from the reaction of the compound (7) with ICl/CCl₄. When the dichloride (1) was treated with NaOMe/MeOH it gave (Me₃Si)₂CHSiEt(OMe)₂. It is suggested that the reaction proceeds through an elimination-addition mechanism. The dichloride (1) was also treated with KSCN, NaN₃ or NaOCN in CH₃CN to give S_N2 substitution products. All the new products were characterized by FTIR, ¹H NMR, and ¹³C NMR spectroscopy, mass spectrometry and elemental analysis.     

A powerful, practical and chemoselective synthesis of 2-anilinoalkanols catalyzed by Bi(TFA)3 or Bi(OTf)3 in the presence of molten TBAB

A facile and efficient synthesis of β-amino alcohols by ring opening of epoxides with anilines in good to excellent yields in the presence of catalytic amounts of Bi(TFA)₃ or Bi(OTf)₃ via the use of molten tetrabutylammonium bromide (TBAB) as an ionic liquid is described. In addition, the observed chemoselectivity can be considered as a noteworthy advantage of this method.     

One-pot, novel chemical modification of glycidyl methacrylate copolymers with very bulky organosilicon side chain substituents

Glycidyl methacrylate (GM) random copolymers with styrene and methylstyrene (in a 1:1 and 1:3 mole ratio) were synthesized by solution free radical polymerizations at 70 ± 1 °C using α,α′-azoisobutyronitrile as an initiator. The copolymer compositions were obtained using related ¹H NMR spectra and the polydispersity indices of the copolymers determined using gel permeation chromatography (GPC). Both types of polymer could be modified by incorporation of the highly sterically demanding tris(trimethylsilyl)methyl substituent (Me₃Si)₃C-(Tsi = trisyl) through the ring opening reaction of the epoxy groups in copolymers. Chemical modification was determined by ¹H NMR and infrared spectroscopies. The glass transition temperature T_g of all copolymers was determined by differential scanning calorimetry (DSC). The T_g value of the copolymers containing bulky trisyl groups was found to increase with incorporation of trisyl groups in polymer structures. The presence of trisyl groups in the polymer side chain created new macromolecules with novel modified properties and potential use as membranes for fluid separation.     

Enhancement of Photocatalytic Efficiency of TiO2 by Supporting on Clinoptilolite in the Decolorization of Azo Dye Direct Yellow 12 Aqueous Solutions

Structure and physico‐chemical properties of a photocatalyst, especially surface area and absorption ability, were correlated to catalytic activities in photodegradation of dye pollutants in water. In this investigation photocatalytic degradation of azo dye Direct yellow 12 (Chrysophenine G) in water was studied. Titanium(IV) oxide was supported on Clinoptilolite (CP) (Iranian Natural Zeolite) using solid‐state dispersion (SSD) method. The results show that the TiO₂/Clinoptilolite (SSD) is an active photocatalyst. The maximum effect of photo degradation was observed at 10 wt.% TiO₂, 90 wt.% Clinoptilolite. A first order reaction with k = 0.0108 min^?1 was observed. The effects of some parameters such as pH, amount of photocatalyst, initial concentration of dye were examined.     

Glass transition temperature modification of acrylic and dienic type copolymers of 4-chloromethyl styrene with incorporation of (Me3Si)3C- groups

The new functional styrenic monomer, 4-trisylmethyl styrene (TsiMS) [Tsi=trisyl=tris(trimethylsilyl)methyl], was synthesized by reacting 4-chloromethyl styrene (CMS) with trisyllithium (TsiLi) in tetrahydrofuran (THF) solvent in the presence of copper chloride (CuCl). Attempt for the free radical polymerization of TsiMS by α,α^′-azobis(isobutyronitrile) (AIBN) as an initiator at 70 ± 1 °C failed for several periods of times. This result showed that the trisyl group is a highly sterically hindered substituent and, subsequently, TsiMS becomes resistant for polymerization. Therefore, for preparation of new methacrylic, acrylic and dienic copolymers of TsiMS, we firstly synthesized the copolymers of CMS with different monomers such as methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA), n-butyl acrylate (BA) and isoprene (IP) by free radical polymerization method in toluene solution at 70 ± 1 °C using AIBN initiator to give the copolymers I-VI in good yields. The copolymer compositions were obtained using related ¹H NMR spectra and the polydispersity indices of the copolymers determined using gel permeation chromatography (GPC). The trisyl groups were then covalently attached to the obtained copolymers as side chains by reaction between excess of TsiLi and benzyl chloride bonds of CMS units, to give the copolymers - in 80-92% yields. All the resulted polymers were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques. The solubility of all the copolymers was examined in various polar and non-polar solvents. The glass transition temperature (T_g) of all copolymers was determined by differential scanning calorimetry (DSC) apparatus. The T_g value of copolymers containing bulky trisyl groups was found to increase with incorporation of trisyl groups in polymer structures. The presence of trisyl groups in polymer side chains, create new macromolecules with novel modified properties.     

Preparation of tris(trimethylsilyl)methyl (“trisyl”) derivatives of silicon

Treatment of (Me₃Si)₃CLi (“trisyl”lithium, TsiLi) with appropriate silicon halides has given a range of compounds of the type (Me₃Si)₃CSiRR′X; e.g., TsiSiCl₃, TsiSiMeCl₂, TsiSiMe₂X (X = Cl, OMe), TsiSiPh₂X (X = F, Cl, OMe), and TsiSiPhMeH. The trisyl group causes very large steric hindrance to nucleophilic displacements at the silicon to which it is attached, so that (unless one or more hydride ligands are present) most of the common displacements at silicon do not occur. However, halides can be reduced to hydrides by LiAlH₄, and the hydrides can be converted into halides in electrophilic displacements by hallogens. The presence of even one hydride ligand markedly reduces the hindrance, so that, for example, TsiSiPhHI reacts with refluxing methanol to give TsiSiPhH(OMe).     

Using TiO<Subscript>2</Subscript> supported on Clinoptilolite as a catalyst for photocatalytic degradation of azo dye Disperse yellow 23 in water

In this investigation photocatalytic degradation of azo dye Disperse yellow 23 in water was studied. Titanium (IV) oxide was supported on Clinoptilolite (CP) (Iranian Natural Zeolite) using the solid-state dispersion (SSD) method. The results show that the TiO₂/Clinoptilolite (SSD) is an active photocatalyst. The maximum effect of photo degradation was observed at 10 wt % TiO₂, 90 wt % Clinoptilolite. A first order reaction with k = 0.0119 min^?1 was observed. The effects of some parameters such as pH, amount of photocatalyst, and the initial concentration of dye were examined.     

Solution of nonlinear weakly singular Volterra integral equations using the fractional‐order Legendre functions and pseudospectral method

In this article, our main goal is to render an idea to convert a nonlinear weakly singular Volterra integral equation to a non‐singular one by new fractional‐order Legendre functions. The fractional‐order Legendre functions are generated by change of variable on well‐known shifted Legendre polynomials. We consider a general form of singular Volterra integral equation of the second kind. Then the fractional Legendre–Gauss–Lobatto quadratures formula eliminates the singularity of the kernel of the integral equation. Finally, the Legendre pseudospectral method reduces the solution of this problem to the solution of a system of algebraic equations. This method also can be utilized on fractional differential equations as well. The comparison of results of the presented method and other numerical solutions shows the efficiency and accuracy of this method. Also, the obtained maximum error between the results and exact solutions shows that using the present method leads to accurate results and fast convergence for solving nonlinear weakly singular Volterra integral equations. Copyright © 2015 John Wiley & Sons, Ltd.     

Using generating functions to convert an implicit (3,3) finite difference method to an explicit form on diffusion equation with different boundary conditions

In this article, our main goal is to develop an idea to convert an implicit (3,3) ??-scheme finite difference method to an explicit form for both linear and nonlinear diffusion equations and also for nonlinear advection-diffusion equation with different boundary conditions. Accordingly, we assist power series generating functions which are a routine method in discrete mathematics. Also, the stability analysis of ??–scheme to implement in nonlinear advection–diffusion equation has been investigated. Finally, the new approach has been implemented for Fisher, reaction–diffusion, Burgers and coupled Burgers equations as test problems to verify the ability and efficiency of the method proposed in this paper.     

Speciation analysis of mercury contaminants in water samples by RP-HPLC after solid phase extraction on modified C18 extraction disks with 1,3-bis(2-cyanobenzene)triazene

A highly sensitive and accurate method for preconcentration and determination of ultra trace amounts of inorganic mercury and organomercury compounds in different water samples is proposed. The preconcentration is achieved using octadecyl silica (C₁₈) extraction disks modified with 1,3-bis(2-cyanobenzene)triazene (CBT). The retained analytes as their triazenide complexes on the solid phase was eluted with 10 ml acetonitrile and measured by reversed-phase high-performance liquid chromatography (RP-HPLC). Type and amount of eluent, pH, amount of CBT, flow rates of sample solution and eluent have been optimized in order to obtain quantitative recovery of the analytes. The effect of interfering ions, such as Cu²⁺, Mn²⁺, Fe²⁺, Al³⁺, Zn²⁺, Cd²⁺, Ca²⁺, Mg²⁺, Ba²⁺, Pb²⁺, K⁺ and Na⁺ usually present in water samples on the recovery of the analytes has also been investigated. The enrichment factor of 100 was obtained for all mercury species and the analytical detection limits of phenylmercury, methylmercury and Hg²⁺ were found as 0.8, 1.0 and 1.3 ng l^− 1, respectively. Stability of mercury species after extraction on the modified disks was studied and the results showed that complexes collected on the disks were stable for at least 5 days. The proposed method has been applied to the quantitative determination of mercury species in natural and synthetic water samples with recoveries more than 90%.