Polymer reagents: preparation of polymer esters of thiocarboxylic acids based on crosslinked polystyrene

Summary The process of acylation of polymer thiols based on microporous poly (styrene-co-divinylbenzene) (crosslinking agent content 1–2%) with carboxylic acids was investigated depending of the degree of functionalization, on the crosslinking of the polymer carrier and on the structure of acids. In the presence of dicyclohexylcarbodiimide and 4-dimethylaminopyridine the acylation reactions can be conducted to high degrees of the transformation of SH groups already at room temperature. The extent of such refunctionalization reactions depends neither on the degree of functionalization of the starting polymer thiol nor on the structure of the acids. Reactions of polymer esters of thiocarboxylic acids with primary, secondary and tertiary alcohols activated with mercury (II) trifluoroacetate lead to low ester yields.     

Activation of solid polymer surfaces with bifunctional reagents

An original procedure is described which calls upon the heterogeneous grafting of bifunctional molecules onto a reactive polymeric surface, leaving one of the functions available for further exploitation. The principle of this strategy is to use reagents characterised by a rigid planar structure bearing the two active moieties at opposite sites of the molecule. The examples provided include the reactions of lignocellulosic fibres with 1,4‐phenyl diisocyanate and 1,2,4,5‐benzenetetracarboxylic anhydride, which give rise to their surface activation through the incorporation of covalently bound isocyanate or anhydride functions. © 2001 Society of Chemical Industry     

Esterification of cellulose with acyl-1H-benzotriazole

For the first time, the acylation of cellulose was realized by activation of carboxylic acid with 1H-benzotriazole. The reaction could be carried out under mild conditions. The acyl-1H-benzotriazole reacts with cellulose leading to cellulose acetate, butyrate, caproate, benzoate, myristate, and stearate with DS values between 1.07 and 1.89. The reaction proceeds completely homogeneously in dimethyl sulfoxide (DMSO)/TBAF × 3H₂O (tetrabutylammonium fluoride trihydrate) using acyl-1H-benzotriazole as acylation agent. The cellulose esters were characterized by means of ¹H NMR, GPC measurements, and solubility tests.     

HPLC法监控L-噻唑烷-4-甲酸乙酯生产中的酯化反应

研究了用HPLC法监控L-噻唑烷-4-甲酸乙酯合成关键步骤酯化反应。色谱条件:YMC-Pack Pro C18反相柱(4.6 mm×150 mm×5μm);0.01 mol/L磷酸二氢钠溶液(用磷酸调节pH为2.0)-甲醇为流动相,检测波长210 nm;流速1.0 mL/min。酯化反应液在0.158～1.278 mg/mL范围内线性关系良好(相关系数r=0.997 6);加标平均回收率为94.70%,重复进样的RSD为0.08%～1.62%,该方法的准确度高,精密度好,实际监测效果好。     

Solid-phase acylating polymer reagents. II. Amino acids acetylation in aqueous solution

Some amino acids have been acetylated in aqueous solution by an active polymeric reagent containing thiolester functions in yields depending upon the nature of the amino acids, and which increased with time and pH (until pH=12). The different reactivities of amino acids can be explained in terms of steric hindrance around the NH₂ group. An increase of the transfer yield in the presence of imidazole, BO₃H₂^? or Ag⁺ ions has also been demonstrated.     

Zur unverträglichkeit von polymergemischen. VII. Lichtstreuungsmessungen an quaternären und quintären polymer-systemen polymer(1)/polymer (2)/polymer(3)/benzol und polymer(1)/polymer(2)/polymer(3)/polymer (4)/benzol

A polystyrene of high molecular weight was investigated by means of light scattering in isoerefractive polymer/benzene mixtures. Two or three of the following polymers are used, which are isorefractive with benzene: polymethylmethacrylate (PMMA), polybutadienne (PB), and polyisobutene (PIB). It is possible to determine the degree of incompatibility of the ?unvisible”? polymers by a comparison of the ?-points of PS in the multi-component systems with the ?-points PS in the ternary systems PS/polymer(2)/benzene. In all cases it turned out, that the degree of compatibility of PS with the other polymers increased by a further addition of a chemical different polymer.     

Concave reagents. 31. A Merrifield bound concave pyridine for the selective acylation of polyols

The concave pyridine 2a has been synthesized in 61% yield in two macrocyclization steps. After deprotection to give 2b , the concave pyridine has been attached to a Merrifield resin, and the resulting polymer 10 containing 0.3 mmol 2 /g has been used as a selective acylation catalyst for the addition of propane‐1,2‐diol ( 11 ) and the glucose derivative 14a to diphenylketene ( 12 ) to form selectively 2‐hydroxypropyl diphenylacetate ( 13a ) (selectivity 13a / 13b : 11:1) and methyl 4,6‐0‐benzylidene‐2‐diphenylacetyl‐α‐D‐gluco‐pyranoside ( 14b ), (selectivity 14b / 13c : 29:1), respectively. After successful applications in batch reactions, the selective addition of 11 to 12 has also been carried out in a flow reactor filled with the polymeric catalyst 10 .     

N-[1-(Benzotriazol-1-yl)alkyl]amides,versatile amidoalkylation reagents. Part 4. A New Synthetic Route to 4H-1,3-Oxazines

A variety of 2,4,6-tri- and 2,4,5,6-tetrasubstituted 4H-1,3-oxazines ( 7a – i ) were synthesized in excellent yields by the reaction of acetylens ( 5 ) in the presence of aluminum chloride with N-[1-(benzotriazol-1-yl)alkyl]amides 4 , themselves readily prepared from benzotriazole (1) with amides (2) and aldehydes (3) .     

129Xe NMR spectroscopy on molecular sieves SAPO-37, AIPO4-5, SAPO-5 and SSZ-24

Xe NMR spectroscopy is used to study SAPO-37, NaY, AlPO₄-5, SAPO-5, and SSZ-24. Of these samples, those with FAU topology show that the¹²⁹Xe chemical shift is dependent upon framework composition while the materials with API topology do not. Values of the¹²⁹Xe NMR chemical shifts at zero xenon pressure cannot be correlated with the size of the framework void space.     

Polymer supported reagents. III. Kinetic study of synthesizing n‐octylacetate using insoluble titanium tetrachloride

Insoluble poly(4‐vinylpyridine‐co‐styrene) beads are prepared using divinylbenzene as the crosslinking agent. These polymer beads are converted into poly(4‐vinylpyridine‐N‐oxide) (PVPNO) under peracetic acid conditions. The resulting polymer is functionalized with titanium tetrachloride (TiCl₄) to afford the corresponding PVPNO‐TiCl₄ complex. This complex shows good catalytic activity for esterification reactions. The kinetics of formation of n‐octylacetate from acetic acid and n‐octanol is reported. The effects of stirring speed, reactant concentration, catalyst amount, percent crosslinking, particle size, and temperature on the conversion is investigated. The rate constants are found to increase with an increase in the stirring speed, concentration of n‐octanol, catalyst amount, and temperature and decrease with an increasing percentage of crosslinking and the mesh size of the polymer beads. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2075–2080, 2000     

催化合成水杨酸酯的工艺研究

芳基磺酸（ＡＳＡ） 催化水杨酸（２ 羟基苯甲酸） 和Ｃ４ ～Ｃ５ 醇的酯化反应,性能优于磷钨酸等其他４ 种催化剂。探讨并找到了ＡＳＡ催化合成水杨酸丁酯、戊酯的优化反应条件：原料配比ｎ（Ｃ７Ｈ６Ｏ３）∶ｎ（ＲＯＨ）＝１∶１－８,催化剂ＡＳＡ的用量为酸质量的５ ％ ～７％ ,反应温度１１０ ～１４０ ℃,反应时间４～７ ｈ,转化率达９２％ ～９７％ ,产品纯度大于９９％ 。     

Bioactive polymers: Synthesis,release study and antimicrobial properties of polymer bound Ampicillin

Matrices of poly(styrene-co-maleic anhydride) with surface containing functional anhydride groups of different percentage was prepared by solution polymerization. Ampicillin was bound on the surface of this matrix by chemical bonding in organic medium. The amount of Ampicillin chemically bound to the matrix was spectroscopically characterized and the in vitro release rate of Ampicillin in weakly basic medium was established along with the determination of its antimicrobial activity. This prodrug allows a prolonged release (6–8 days) of the drug.     

Reactions of 4-Benzylidene-3-methyl-5-oxopyrazoline,pyrazole blue,and rubazoic acid with GRIGNARD reagents

While 4-benzylidene-3-methyl-5-oxopyrazoline 1 and pyrazole blue 2 with GRIGNARD reagents gave 1,4-addition, rubazoic acid 3 gave 1, 2-addition on both sides with ethylmagnesium bromide.     

Polymer modified grass fiber,part 1: Characterization of grass fiber and assessment of properties of polymer modified fiber

Natural fibers are used for reinforcement of ecofriendly green composites. These grass fibers have wide range of applications for the preparation of various domestic goods and handicraft items. But the chemical composition of the grass fiber has not been reported; therefore composition analysis of grass fiber was carried out. Morphology of the dry grass was studied by using scanning electron microscopy. Since the grass fiber contains around 22% water‐soluble matters, we have studied its influence on the tensile strength and aging characteristics. The tensile strength of the grass fiber was measured before and after water leaching. This study has shown a definite scope for the suitability of grass fiber in composite applications. To improve the strength of grass fiber, modification with various polymers such as P‐F resin, polyurethane and acrylamide was carried out. Moisture absorption property of unleached, water‐leached and different polymer modified fiber was also evaluated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1095–1103, 2007     

Polymer fibre composites, basic types, principles of fabrication, and properties. Part 3. Basic types of polymer fibre composites, properties, and use

The basic types of polymer composite materials (PCMM) made from different kinds of reinforcing fibre fillers: short-cut fibres, paper, yarns, tow, sliver, fabrics, and nonwovens, and their properties and use are examined. Information on the fabrication and properties of the different kinds of composites are reported: extruded fibre plastics, getinaxes, textolites, unidirectional composites, honeycomb plastics, and others. New kinds of composites with ultrahigh mechanical and thermal characteristics are also examined. Some of the reported information was previously covered very sparely in the literature. Based on the examination, the features of polymer fibre composites are summarized in comparison to other materials, and they can be summarized as the following basic points: 1) combining different kinds of fibre fillers and matrices (binders) allows fabricating PCM with a wide range of properties by selecting the optimum indexes for articles with a broad spectrum of applications; 2) articles made of fibre PCM are not very materials-intensive and are technologically effective for processing in comparison to many traditional materials, metals and ceramics in particular; 3) with respect to the specific mass characteristics, fibre PCM can be many times superior to articles made of traditional materials—metals, etc., so that the mass (weight) characteristics of articles made of fibre composites can be significantly reduced, which is especially important for using them in vehicles, aircraft, rescue equipment, and sporting goods; 4) articles made of composites have high performance reliability, are almost immune to corrosion, and do not require special protection or periodic painting of the surface. Due to the features of the properties and use, fibre PCM have a great future in the most varied areas of application. See No. 4, 7–12 (2005) for Part 1; No. 5, 54–69 for Part 2. __________ Translated from Khimicheskie Volokna, No. 1, pp. 41–50, January–February, 2006.