Catalytic Systems Containing p-Toluenesulfonic Acid for the Coupling Reaction of Formaldehyde and Methyl Formate

The coupling reaction of formaldehyde(FA)and methyl formate(MF)to form methyl glycolate(MG)and methyl methoxy acetate(MMAc),catalyzed by p-toluenesulfonic acid(p-TsOH)as well as assisted by different kinds of solvents or Ni-containing compounds,had been investigated.The results showed that when the reaction was carried out at 140℃,with a molar ratio of FA to MF of 0.65:1, molar fraction of p-TsOH to total feedstock of 11.0%,and reaction time of 3 h,the yield of MG and MMAc was 31.1% and 17.1%,respectively,p-TsOH catalyzed the coupling reaction by means of the synergistic catalysis of protonic acidity and soft basicity.Adding extra solvents to the reaction system was unfavorable for the reaction.The composite catalytic system consisting of p-TsOH and NiX_2(X=Cl,Br,I)exhibited a high catalytic performance for the coupling reaction,and NiX_2 acted as a promoter in the reaction,whose promotion for the catalysis increased in the following order:NiCl_2相似文献   

Organometallic derivatives of 2,6-di-tert-butylphenols as specific inhibitors of methyl oleate oxidation

2,6-Di-tert-butylphenols containing the Pt—SnCl₃ and Pt—GeCl₃ groups in the para position exert a dual effect on the oxidation of methyl oleate by molecular oxygen. Initially, these compounds act as antioxidants producing the corresponding phenoxyl radicals whose decomposition is accompanied by elimination of SnCl₂ and GeCl₂, which are oxidation promoters.     

Preparation and characterization of star ABC triblock copolymer of ethylene oxide,styrene and methyl methacrylate

A universally significant method,which combines the anionic polymerization with photoinduced charge transfer polymerization,for preparation of soluble star ABC triblock copolymer of ethylene oxide,styrene and methyl methacrylate,was described.The poly(ethylene oxide) (PEO) block was formed by initiation of phenoxy an-ions using p-aminophenol protected by Schiff's base as the parent compound Then the charge transfer system composed of PEO chains with deprotected-amino end groups and benzophenone initiated the polymerization of styrene and methyl metnacrylate sequentially under UV irradiation.The formed star triblock copolymer of styrene,ethylene oxide and methyl methacrylate could be purified by thin-layer chromatography (TLC) and characterized by IR,1H NMR,GPC (gel permeation chromatogrphy) and PGC (pyrolysis gas chromatography).     

Packed-column hydrodynamic chromatography using 1-μm non-porous silica particles

150×3 mm I.D. columns, packed with 1-μm non-porous spherical silica particles, were used to separate soluble synthetic polymers by hydrodynamic chromatography. The columns exhibited a plate height of about 1.4 μm allowing very fast and efficient separations of polymers in the molecular mass range 10³−2·10⁶ g/mol. The migration behaviour of polymers could be well described by a simple theoretical model. The applicability of packed bed HDC for the fast separation of polymers was illustrated with separations of polystyrene and poly(methyl methacrylate) mixtures.     

Pinacone reduction of methyl trifluoropyruvate

Methyl trifluoropyruvate (1) enters into reductive dimerization during UV irradiation in the presence of isopropyl alcohol or of a sensitizer and during reaction with sodium in the presence of trimethyldichlorosilane, giving dimethyl 2,3-bis(trifluoromethyl)-2,3-dihydroxysuccinate. Unlike hexafluoroacetone, compound 1 does not form the reductive dimerization product after prolonged standing over sodium but is converted into the cyclic dimer 2-methoxycarbonyl-4-methoxy-2,4-bis(trifluoromethyl)-1,3-dioxolan-5-one.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1408–1411, June, 1992.     

Simultaneous determination of total homocysteine, cysteine and methionine in hypothyroid patients’ plasma by liquid chromatography using platinum/poly(methyl violet) modified electrode

The fabrication and application of a novel electrochemical detection (ED) system with the platinum/poly(methyl violet) (Pt/MV) chemically modified electrode (CME) for high performance liquid chromatography (HPLC) were described. The Pt particles deposited on the poly-MV film were characterized by atomic force microscope (AFM). It was found that the Pt/MV CME exhibited efficiently electrocatalytic effect on the current responses of cysteine (Cys), homocysteine (Hcy) and methionine (Met) with relatively high sensitivity, stability and long-life of activity. In HPLC-ED, these three amino acids had good and stable current responses at the CME and their linear ranges were over three orders of magnitude (R ≥ 0.9996) with the detection limits being 7.5 × 10⁻⁸ mol L⁻¹ for Cys, 1.0 × 10⁻⁷ mol L⁻¹ for Hcy, 5.0 × 10⁻⁷ mol L⁻¹ for Met. The application of this method coupled with microdialysis sampling for the determination of Cys, Hcy and Met in plasma from patients with hypothyroidism was satisfactory.     

Synthesis and characterization of new polymer systems containing very bulky tris(trimethylsilyl)methyl substituents as side chains

The 4-chloromethyl styrene (CMS) was copolymerized with different styrenic monomers such as methyl styrene, 4-methoxy styrene and α-methyl styrene by free radical polymerization method at 70 ± 1 °C using α,α^′-azobis(isobutyronitrile) (AIBN) as an initiator and the copolymers I, II and III collected respectively. The very bulky tris(trimethylsilyl)methyl {trisyl} substituents were covalently attached to the obtained copolymers with replacement of all the chlorine atoms in CMS units. The polymers, obtained in quantitative yields, were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopy; differential scanning calorimetry (DSC) and GPC studies. All the polymers containing trisyl groups showed a high glass transition temperature (in the range 150-190 °C) in comparison with copolymers I-III (in the range 90-95 °C). The increase of the glass transition temperature reflects the substantial increase in rigidity of new polymers bearing very bulky substituents in side chains.     

（—）—莰烷磺内酰胺法合成（S）和（R）切叶蚁警戒信息素

本文以樟脑衍生物(-)-莰烷磺内酰胺(2)为原料,经N-烷酰基莰烷-2,10-磺内酚胺(3)与碘代烷的不对称烷基化反应,用二锂代乙基苯基砜取代磺内酰胺助剂以及铝汞还原性脱硫反应等三步合成(S)和(R)一切叶蚁警戒信息素(1),其光学纯度高达95％e.e以上。     

Hg(Ⅱ)-SCN- -甲基紫三元络合物光度法测定牛奶中痕量的汞

用Hg(Ⅱ)-SCN~- -甲基紫三元络合物光度法测定牛奶中痕量的汞,该法灵敏度高,络合物的摩尔吸光系数ε=5.015×10~5 L/(mol·cm),汞浓度在0～8μg(50 mL)时与吸光度呈线性关系,线性回归方程为A=0.04693c 0.01816,相关系数r=0.9928,汞的回收率为97.0％～98.5％,检出限为0.0068μg/mL。     

Laser‐induced decomposition of 2,2‐dimethoxy‐2‐phenylacetophenone and benzoin in methyl methacrylate homopolymerization studied via matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

Pulsed laser polymerization (PLP) experiments were performed on the bulk polymerization of methyl methacrylate (MMA) at ?34 °C. The aim of this study was to investigate the polymer end groups formed during the photoinitiation process of MMA monomer using 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA) and benzoin as initiators via matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry. Analysis of the MALDI‐TOF spectra indicated that the two radical fragments generated upon pulsed laser irradiation show markedly different reactivity toward MMA: whereas the benzoyl fragment—common to both DMPA and benzoin—clearly participates in the initiation process, the acetal and benzyl alcohol fragments cannot be identified as end groups in the polymer. The complexity of the MALDI‐TOF spectrum strongly increased with increasing laser intensity, this effect being more pronounced in the case of benzoin. This indicates that a cleaner initiation process is at work when DMPA is used as the photoinitiator. In addition, the MALDI‐TOF spectra were analyzed to extract the propagation‐rate coefficient, k_p, of MMA at ?34 °C. The obtained value of k_p = 43.8 L mol^?1 s^?1 agrees well with corresponding numbers obtained via size exclusion chromatography (k_p = 40.5 L mol^?1 s^?1). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 675–681, 2002; DOI 10.1002/pola.10150