Copolymerization of isobutene with trans-1,3,5-hexatriene

Summary The cationic copolymerization of isobutene (I) and trans-1,3,5-hexatriene (HT) at low temperature occurs randomly (r_I=0.59, r_HT=1.57). The prevalent 1,6-opening of the triconjugated system of HT was ascertained mainly by ¹H- and ¹³C-NMR analysis. The formation of gelled products was avoided by working in a homogeneous medium and the cyclization of the triene units by copolymerizing I and HT in bulk.     

Synthesis of functional polyisobutene I. Copolymerization of isobutene with 4-vinylbenzyl N,N-diethyldithiocarbamate

Summary A special monomer 4-vinylbenzyl N,N-diethyldithiocarbamate (VBDC) was synthesized firstly, and then the cationic copolymerization of VBDC with isobutene was investigated. The results of ¹H-NMR, EA and GPC (with UV detector) indicated that VBDC could copolymerize with isobutene and form the copolymer, and the units of VBDC incorporated into copolymer chains increased with the increasing of the feed ratio of VBDC. However, there has apparent discrepancy between the VBDC in the monomer feed and the VBDC incorporated into the copolymer chain, which is probably due to the relatively lower reactivity of VBDC. In the presence of VBDC, the MWD is narrower than that of in absence of VBDC under the similar experimental conditions. For cumyl methyl ether/TiCl₄ initiating system, the M_w/M_n could be slightly narrowed from 1.55 (no VBDC) to 1.33 (with VBDC) in the mixed solvents of n-hexane and CH₃Cl (15/10,V/V), while cumyl chloride /TiCl₄ initiating system, the M_w/M_n is narrowed from about 5.0 (no VBDC) to about 1.5 (with VBDC) with n-hexane and CH₂Cl₂ (10/10,V/V) as the mixed solvents. When benzyl N, N-diethyldithiocarbamate (BDC) was used as the model compounds instead of the VBDC, the similar results of M_w/M_n were obtained. These results demonstrated that the VBDC functions as the monomer electron donor (ED) in this polymerization system. Received: 23 August 2001/Revised version: 29 October 2001/ Accepted: 2 November 2001     

合成类胡萝卜素关键中间体十碳烯醛的新方法

对类胡萝卜素关键中间体十碳烯醛的合成方法作出重要改进,新的合成路线包括以反式-1,4-二氯-2-丁烯为起始原料,经格氏反应、缩合反应与酸性水解反应合成2,7-二甲基-2,4,6-辛三烯-1,8-二醛（十碳烯醛）。反应选择性好,副产物少,工艺较简单,操作方便。     

Convenient synthesis of perhydroindene derivatives from 2,7-dimethyl-1,3,7-octatriene

Several perhydroindene derivatives were prepared from 2,7-dimethyl-1,3,7-octatriene ( I ) via Diels Alder reaction followed by cyclisation. For example, the Diels Alder reaction between I and methyl vinyl ketone ( II ) in the presence of Lewis acid afforded 4-acetyl-3-(3-methylbut-3-enyl)-1-methylcyclohexene ( IIIa ), which, upon treatment with phosphoric acid, was converted to a mixture of 2-acetyl-5,7,7-trimethyl-bicyclo [4,3,0]-non-1-(6)-ene ( IV ), 2-acetyl-5,7,7-trimethylbicyclo[4,3,0]-non-1-ene ( VI ) and 2-isopropyl-3,6-dimethylindene ( V ).     

Selective synthesis of isobutene trimers and hexamers with oxo acid catalysts

The reaction of isobutene (IB) with its dimers (IB₂) catalyzed by CF₃SO₃H yielded isobutene trimers (IB₃) in high yield in nonpolar solvents at 0°C. The initial feed of isobutene, in the presence of equimolar IB₂ or more, was selectively converted into IB₃ without loss or accumulation of IB₂. After complete consumption of the isobutene, however, the remaining IB₂ rapidly dimerized to isobutene tetramers (IB₄). ¹³C-NMR analysis of the products showed that the IB₃ was formed via addition of the t-butyl cation (protonated isobutene to 2,4,4-trimethyl-1-pentene (an IB₂ isomer); the trimer fraction was free from isomers arising from addition of the t-butyl cation to 2,4,4-trimethyl-2-pentene (another IB₂ isomer) or addition of the IB₂ cation to isobutene. The IB₃ thus obtained was further oligomerized with CF₃SO₃H catalyst in nonpolar media in the range of 0 to ?25°C to give a mixture of IB₅, IB₆, and IB₇ in high yield. With EtAlCl₂ as catalyst, reaction of isobutene with IB₂ and oligomerization of IB₃ both resulted in products with a broad molecular weight distribution containing higher oligomers and complex hydrocarbons formed via cracking of the intermediate carbocations.     

Interaction of isobutene and methacrolein with silica-supported uranium and molybdenum oxide catalysts

The adsorption of isobutene (in the temperature range 309–341K) and methacrolein (in the temperature range 296–336 K) on a Mo/(Mo+U)=0.89 catalyst were studied. The equilibrium data were analysed according to Freundlich's model. The high coverages observed at lower temperatures suggest some participation of physical adsorption in the reversible adsorption. Entropy calculations showed that these adsorbed species are best described by a mobile model which assumes bidimensional translation and two rotational degrees of freedom. Isobutene is weakly chemisorbed, producing reversible species which were identified as a π-complex formed by interaction with surface OH groups through π-electrons (infrared bands at 1655, 1615, 1470 and 1375 cm^?1), and only a small fraction of isobutene interacts strongly via lattice oxygen forming intermediate species in the oxidation reaction. However, in the presence of oxygen at 523 K a majority of the surface species are strongly held by the surface (infrared bands at 1775, 1723, 1610, 1460 and 1350 cm^?1 associated to a methacrylic complex and bands at 1590 and 1538 cm^?1 of carbonate-carboxylate species).     

异丁烯氢甲酰化合成异戊醛的研究

以Rh(acac)(CO)_2/双亚磷酸酯体系为催化剂,提高异丁烯氢甲酰化反应的活性和选择性。在此基础上考察了温度、压力、溶剂、有机碱、催化剂套用等参数对异丁烯氢甲酰化反应的影响。结果表明,以Rh(acac)(CO)_2/双(2,4-二叔丁基苯基)季戊四醇二亚磷酸酯为催化体系,铑的溶液浓度为1.55×10~(-3)mol/L,异戊醛为溶剂,三苯基氧膦为有机碱,在110℃下2 MPa的合成气下反应6 h,异丁烯的转化率高达96.82%,选择性为99.75%,套用4次衰减很小。该催化剂体系显著提高了异丁烯氢甲酰化反应的活性和选择性,且具有良好的套用性能。     

异丁烯氢甲酰化合成异戊醛的研究

以Rh(acac)(CO)_2/双亚磷酸酯体系为催化剂,提高异丁烯氢甲酰化反应的活性和选择性。在此基础上考察了温度、压力、溶剂、有机碱、催化剂套用等参数对异丁烯氢甲酰化反应的影响。结果表明,以Rh(acac)(CO)_2/双(2,4-二叔丁基苯基)季戊四醇二亚磷酸酯为催化体系,铑的溶液浓度为1.55×10^(-3)mol/L,异戊醛为溶剂,三苯基氧膦为有机碱,在110℃下2 MPa的合成气下反应6 h,异丁烯的转化率高达96.82%,选择性为99.75%,套用4次衰减很小。该催化剂体系显著提高了异丁烯氢甲酰化反应的活性和选择性,且具有良好的套用性能。     

Preparation of 2,4,6-triaminotoluene and its salts with inorganic acids from 2,4,6-trinitrotoluene

The basics of the technological process of 2,4,6-trinitrotoluene hydrogenation on palladium catalyst at atmospheric pressure are described. A technology is developed for isolating 2,4,6-triaminotoluene from the reaction solution in the form of salts with inorganic acids stable in storage     

Copolymerization of styrene. IV. Copolymerization with esters of benzylidenecyanoacetic acid

Styrene was copolymerized in bulk with a number of esters of benzylidenecyanoacetic acid. The kinetic scheme of all pairs fitted the improved scheme of copolymerization, taking into account the effect of the penultimate unit. The Alfrey-Price Q and e values were calculated. Using the modified Taft equation, log (1/r₁) = ρ^*σ^* + δE_s, it was found that the relative reactivities of the ester monomers toward the polystyryl radical were correlated by the polar substituent constants σ^* of the ester alkyl groups (ρ^* = 0.14) and not by their steric substituent constants E_s (δ = 0.008).     

Equilibrium of the simultaneous etherification of isobutene and isoamylenes with ethanol in liquid-phase

The simultaneous etherification of isobutene and isoamylenes with ethanol has been studied using macroreticular acid ion-exchange resins as catalyst. Most of the experiments were carried out over Amberlyst-35. In addition, Amberlyst-15 and Purolite CT-275 were also tested. Chemical equilibrium of four chemical reactions was studied: ethyl tert-butyl ether formation, tert-amyl ethyl ether formation from isoamylenes (2-methyl-1-butene and 2-methyl-2-butene) and isomerization reaction between both isoamylenes. Equilibrium data were obtained in a batchwise stirred tank reactor operated at 2.0 MPa and within the temperature range from 323 to 353 K. Experimental molar standard enthalpy and entropy changes of reaction were determined for each reaction. From these data, the molar enthalpy change of formation of ethyl tert-butyl ether and tert-amyl ethyl ether were estimated. Besides, the chemical equilibrium between both diisobutene dimers, 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene, was evaluated. A good agreement between thermodynamic results for the simultaneous etherification carried out in this work and those obtained for the isolated ethyl tert-butyl ether and tert-amyl ethyl ether systems was obtained.     

Copolymerization of polyvinylpyridine macromonomers with styrene

Summary Free radical Copolymerization of ( -methylstyryl) poly (2-vinylpyridine) macromonomers with styrene was performed. After separation of residual macromonomer the graft copolymers were submitted to a careful characterization.The copolymers were generally of rather low molecular weight and the average number of grafts per backbone chain was found close to unity. Nevertheless, these polymeric species tend to give aggregates and/or emulsions in selective solvents of the grafts, a typical behaviour of graft copolymers.     

Alkylation of isobutene with 2-butene using composite ionic liquid catalysts

A composite ionic liquid was used as an acid catalyst for the liquid phase alkylation of isobutane and 2-butene. The main product obtained was trimethylpentane (>85 wt.%) and the research octane numbers of the alkylates was 98–101. In the ionic liquid sample, a composite anion [AlCl₄CuCl]⁻ was detected by means of ESI-MS. This new species was also confirmed by ²⁷Al NMR and FT-IR characterizations. The effects of anion composition on the product distribution have been investigated. The composite anion plays important roles in improving alkylate quality.     

Copolymerization of caprolactam with polyoxybutylene diamine

Nylon 6-polyoxybutylene block copolymers were prepared by reacting polyoxybutylene diamine with caprolactam in the presence of phosphoric acid. The copolymerization was carried out in a Helicone-type reactor and the effect of time, temperature, and caprolactam concentration on the properties of the products was recorded. Differential Scanning Calorimetry studies of the products suggest the presence of both the ABA and AB types of sequences, where A and B represent nylon 6 and polyether blocks, respectively. Dynamic mechanical measurements of typical copolymers revealed the presence of at least two different nylon moieties. The melt rheology data reflect a general increase in the pseudoplasticity of the copolymer with the increase of the polyether content. Increases of the polyether content in the copolymer result in an increased elongation and a decreased tensile strength and modulus.     

Copolymerization of elemental sulfur with styrene

Copolymerization of elemental sulfur with styrene in the presence and absence of metallic sodium was studied at 120°C and 138°C. Propagation of the reaction was followed by gel permeation chromatography (GPC). Glass transition temperatures of all samples were obtained by differential scanning calorimetry (DSC). Reaction products were fractionated with a preparative-type GPC, and each fraction was characterized by DSC, vapor pressure osmometry, infrared spectrophotometry, and both proton and carbon-13 nuclear magnetic resonance spectrometry. Results indicate that the product is a true copolymer of styrene and sulfur. Kinetics of the copolymerization were studied using GPC to monitor styrene and sulfur concentrations. The initial rate of copolymerization (as followed by the consumption of styrene and sulfur) decreases with increasing initial styrene to sulfur ratio. From kinetic analyses, ratios of the rate constants of homo- and copolymerization were determined. Copolymerization of the reactants is more spontaneous than homopolymerization. The reactivity ratios obtained are 0.2 for styrene and 0.6 for sulfur.     

淀粉与二甲基二烯丙基氯化铵的接枝共聚研究

以过硫酸铵一尿素为引发剂,可溶性淀粉为原料,实现了淀粉与DMDAAC、丙烯酰胺的三元接枝共聚,着重考察了单体配比、引发剂浓度、反应温度、反应时间等因素对接枝共聚的影响,得到了该聚合反应的适宜条件:(NH4)2SO8浓度为0.33 mmol/L,淀粉与单体总量的质量比为1:9,AM与DMDAAC摩尔比是12:1,反应温度40℃,反应5 h.接枝率可达89%,并用红外光谱、核磁共振谱图对接枝物进行了结构表征.     

Graft Copolymerization of Pectin with Polyacrylamide

In the present study, an attempt has been made to modify pectin by grafting polyacrylamide using ammonium ceric sulphate as initiator. The effect of various variables like initiator concentration, monomer concentration, temperature and time has been studied. The grafted copolymer was characterized by Fourier transform infrared spectroscopy (FT-IR), organic elemental analysis, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). FT-IR studies indicated incorporation of amide group. Rheological behavior of pectin solution was compared with that of the grafted copolymer. The comparative rheological properties of pectin and grafted copolymer indicated change in the property of the product. Differential scanning calorimetry and XRD suggested formation of the grafted copolymer.