Quantitative analysis of cyclopentadiene compounds

A quantitative color reaction of cyclopentadiene was examined when cyclopentadiene was contained in a mixture of benzene, 1,3-cyclohexadiene, cyclohexene, cyclohexane, cyclopentene, or cyclopentane. It was found that cyclopentadiene could be determined in the following manner. A sample was weighed to 1.38 x 10^-5 mole in a test tube, while a mixture of 10 ml ethyl alcohol plus 4 ml sulfuric acid was cooled in an ice bath. The mixture was poured into the test tube and the tube was heated in a water bath at 95 C for 30 sec followed by immediate cooling. Then the absorbance at 580 nm was measured and the content of cyclopentadiene was calculated with a calibration curve. The color reaction was tested with ethyl linoleate cyclic monomer (11 cm), ethyl linolenate cyclic monomer (mem), and photoisomerized tung oil fatty acid ethyl ester cyclic monomer (βcm), which were prepared from each purified fatty acid or from photo-isomerized tung oil by cyclization with sodium hydroxide. It was found that cyclopentadiene compounds were formed from ethyl linolenate, but not from ethyl linoleate or from β-eleostearate, which was a main component of photo-isomerized tung oil.     

New Methods for the Preparation of Multiply Substituted Cyclopentadienes and Related Compounds

Substituents on cyclopentadienyl ligands significantly influence the reactivity and catalytic efficiency of their transition metal complexes. Therefore, development of synthetic methods for cyclopentadiene derivatives possessing different substituents has been in great demand. In this paper, we report new synthetic methods for multiply substituted cyclopentadienes recently developed in this group. In principle, three types of preparative methods are described. Firstly, zirconacyclopentadienes in the presence of Lewis acids react with aldehydes to afford multiply substituted cyclopentadienes, thus providing a one-pot procedure from two molecules of identical or different alkynes and one molecule of aldehyde; reaction of aluminacyclopentadienes with aldehydes also result in high-yield formation of multiply substituted cyclopentadienes. Secondly, 1,2,3,4-tetrasubstituted 1,4-dilithio- and 1,4-bis(magnesiobromo)-1,3-diene derivatives react with aldehydes or ketones via deoxygenation of the C=O moieties to afford cyclopentadiene derivatives. Thirdly, monolithio reagents, 1,2,3,4-tetrasubstituted 1-lithio-1,3-butadienes, and Grignard reagents, 1,2,3,4-tetrasubstituted 1-magnesiobromo-1,3-butadienes react with aldehydes or ketones to afford cyclopentadiene derivatives upon hydrolysis.     

环戊二烯阳离子聚合的研究--聚合反应条件对产物分子量的影响

随着石油化工和煤化工的迅速发展，环戊二烯的产量大幅度增加，其聚合物已用于聚丙烯等通用塑料的改性，赋予其热封性、气体阻隔性。本实验以TiCl4为引发剂，研究不同浓度、温度溶剂中引发环戊二烯的阳离子聚合。结果表明，溶剂对产物的分子量和分子量分布的影响最为显著，这与离子对的状态有密切的关系；并且用甲苯作溶剂时，^1HNMR结果表明甲苯作为聚合反应的链转移剂参与链转移反应。     

Pyrolysis–molecular weight chromatography–vapor-phase infrared spectrophotometry: An on-line system for analysis of polymers. IV. Influence of cis/trans ratio on the thermal degradation of 1,4-polybutadienes

The influence of the cis/trans ratio of 1,4-polybutadienes on the volatile products formed during temperature-programmed thermal degradation to 15% weight loss has been investigated using a mass chromatograph (a gas chromatograph which directly provides mass numbers of resolved components of a mixture) and an “on the fly” vapor-phase infrared spectrophotometer. In order of amounts, major volatile products were 4-vinyl-1-cyclohexene (dimer), 1,3-butadiene (monomer), cyclopentene, and 1,3-cyclohexadiene. With increasing trans content, the relative quantities of 4-vinyl-1-cyclohexene decreased strongly, cyclopentene increased strongly, 1,3-butadiene decreased moderately, and 1,3-cyclohexadiene increased moderately. For a high-trans polybutadiene, increasing the heating rate produced relatively more monomer and dimer but less cyclopentene. Mass chromatograms from 1,4-polybutadienes which had been heated to 15% weight loss in their prehistory were similar to those obtained from 1,2-polybutadiene, indicating that 1,4-polybutadiene undergoes isomerization prior to degradation. Mechanisms for the formation of the main volatile products of decomposition are discussed.     

Synthesis of fluorocyclohexadienes by the electrochemical fluorination of p-difluorobenzenes on a preparative scale

Fluorine containing-cyclohexadienes (FCHDs), 3,3,6,6,-tetrafluoro-1,4-cyclohexadiene (1a), 1-chloro-3,3,6,6-tetrafluoro-1,4-cyclohexadiene (3a) and 1-bromo-3,3,6,6-tetrafluoro-1,4-cyclohexadiene (4a), were isolated in pure states with high yields (ca. 80%) by the preparative scale electrochemical fluorination of 1,4-difluorobenzene (1), 1-chloro-2,5-difluorobenzene (3) and 1-bromo-2,5-difluorobenzene (4), respectively, in Et₄NF · mHF (Et = C₂H₅: m = 4.0, 4.45 and 4.7) at a platinum anode, followed by extraction and fractional distillation. The electrochemical fluorination of 1,2,4-trifluorobenzene (2) yielded both 1,3,3,6,6-pentafluoro-1,4-cyclohexadiene (2a) and 2,5,5,6,6-pentafluoro-1,3-cyclohexadiene (2b) with high yield (ca. 90%). Some of (2a) was also isolated in a pure state by fractional distillation. Each substrate compound (1–4) was fluorinated to the corresponding FCHDs with an almost quantitative yield when 2.0–2.1 faraday (per mol of substrate) of electricity was passed.     

Synthesis of porphyrin-end-functionalized poly(p-phenylene) as a leaf-green-colored soluble semiconducting polymer: Control of π–π interactions for visible-light absorption

The synthesis of tetraphenylporphyrin (H₂TPP)-end-functionalized poly(p-phenylene) (H₂TPP-PPP) as a leaf-green-colored soluble semiconducting polymer with a well-controlled and defined polymer chain structure was achieved for the first time. Chloromethyl-end-functionalized poly(1,3-cyclohexadiene) (CM-PCHD) was prepared by the living anionic polymerization of 1,3-cyclohexadiene and the post-polymerization reaction of poly(1,3-cyclohexadienyl)lithium and chloro(chloromethyl)dimethylsilane. H₂TPP-end-functionalized PCHD (H₂TPP-PCHD) was then prepared by the addition of 5-(4-hydroxyphenyl)-10,15,20-triphenylporphyrin to CM-PCHD. The dehydrogenation of H₂TPP-PCHD with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone was performed under ultrasonic irradiation, and H₂TPP-PPP was obtained as a target polymer in almost quantitative yield. The –Si(CH₃)₂–CH₂–O– bond in H₂TPP-PPP effectively inhibited the coordination of the H₂TPP end-group onto the PPP moiety, and the aggregation of H₂TPP-PPP with the accumulation of the H₂TPP end-group was formed. H₂TPP-PPP exhibited a leaf-green color and had a very broad absorption band overlapping the visible-light region, similar to chlorophyll a.     

Poly(1,3-cyclohexadiene-1,4-diyl)

Summary Dehalogenation polycondensation of 1,4-diiodo-1,3-cyclohexadiene with zerovalent nickel complex gives a new -conjugated polymer, poly(1,3-cyclohexadiene-1,4-diyl) PCyh. A copolymer constituted of 1,3-cyclohexadiene-1,4-diyl and 1,4-cyclohexadiene-1,4-diyl is also obtained by a similar method. The black color of PCyh indicates the presence of extensive -conjugation along the polymer chain presumably due to takings-trans conformation of PCyh. PCyh is unstable and oxidized under air. IR and CP-MAS¹³C-NMR spectra of PCyh are reasonable for the structure.     

Stereoselective polymerization of butadiene by a new dicationic nickel complex

The new dicationic nickel complex [dppfNi(MeCN)₄][BF₄]₂ (dppf = 1,1′-bis(diphenylphosphino)ferrocene) in the presence of diethylaluminium chloride (AIEt₂CI) exhibited high activity on the 1,3-butadiene polymerization. Reaction time, temperature and aluminium/nickel molar ratio were optimized in order to achieve maximum activity and selectivity. Conversions higher than 90% were obtained in contrast to other nickel-based systems using phosphine ligands, the resulting polybutadiene showed high cis-1,4 (<80%) content and only small amount of 1,2-units (2%). All polymers presented low molecular weights (M_w > 11 800).     

Synthesis,characterization and thermal properties of phenylene–disiloxane polymers obtained from catalytic cross‐dehydrocoupling polymerization of bis(dimethylsilyl)benzene isomers and water

Phenylene–disiloxane polymers were prepared from 1,4‐bis(dimethylsilyl)benzene and 1,3‐bis(dimethylsilyl)benzene with water in various ratios by catalytic cross‐dehydrocoupling polymerization. Each isomer showed almost equal reactivity in the polymerization as verified by the analysis of the composition by ¹H NMR. Crystallinity observed in the polymer obtained from the 1,4‐isomer was removed by incorporating a small amount of 1,3‐isomer. © 2001 Society of Chemical Industry     

Pyrolyse-Gaschromatographie von Dien-Polymeren III. Polyisoprene

The pyrolysis of polyisoprenes with 1,4 and 3,4-units occurs in an analogous way as the pyrolysis of polybutadienes with 1,4 and 1,2 units.     

Polymerization of 1,3‐dienes containing functional groups: 8. Free‐radical polymerization of 2‐triethoxysilyl‐ 1,3‐butadiene

The presence of a bulky substituent at the 2‐position of 1,3‐butadiene derivatives is known to affect the polymerization behavior and microstructure of the resulting polymers. Free‐radical polymerization of 2‐triethoxysilyl‐1,3‐butadiene ( 1 ) was carried out under various conditions, and its polymerization behavior was compared with that of 2‐triethoxymethyl‐ and other silyl‐substituted butadienes. A sticky polymer of high 1,4‐structure ( ) was obtained in moderate yield by 2,2′‐azobisisobutyronitrile (AIBN)‐initiated polymerization. A smaller amount of Diels–Alder dimer was formed compared with the case of other silyl‐substituted butadienes. The rate of polymerization (R_p) was found to be R_p = k[AIBN]^0.5[ 1 ]^1.2, and the overall activation energy for polymerization was determined to be 117 kJ mol^?1. The monomer reactivity ratios in copolymerization with styrene were r ₁ = 2.65 and r_st = 0.26. The glass transition temperature of the polymer of 1 was found to be ?78 °C. Free‐radical polymerization of 1 proceeded smoothly to give the corresponding 1,4‐polydiene. The 1,4‐E content of the polymer was less compared with that of poly(2‐triethoxymethyl‐1,3‐butadiene) and poly(2‐triisopropoxysilyl‐1,3‐butadiene) prepared under similar conditions. Copyright © 2010 Society of Chemical Industry     

Effect of α-tocopherol on the volatile thermal decomposition products of methyl linoleate hydroperoxides

α-Tocopherol and 1,4-cyclohexadiene were tested for their effect on the thermal decomposition of methyl linoleate hydroperoxide isomers. The volatiles generated by thermolysis in the injector port of a gas chromatograph at 180°C were analyzed by capillary gas chromatography. In the presence of either α-tocopherol or 1,4-cyclohexadiene, which are effective donors of hydrogen by radical abstraction, volatile formation decreased in all tests, and significant shifts were observed in the relative distribution of products in certain hydroperoxide samples. When an isomeric mixture of methyl linoleate hydroperoxides (cis, trans andtrans, trans 9- and 13-hydroperoxides) was decomposed by heat, the presence of α-tocopherol and 1,4-cyclohexadiene caused the relative amounts of pentane and methyl octanoate to decrease and hexanal and methyl 9-oxononanoate to increase. A similar effect of α-tocopherol was observed on the distribution of volatiles formed from a mixture of thetrans,trans 9- and 13-hydroperoxides. This effect of α-tocopherol was, however, insignificant with purecis,trans 13-hydroperoxide of methyl linoleate. The decrease in total volatiles with the hydrogen donor compounds, α-tocopherol and 1,4-cyclohexadiene, indicates a suppression of homolytic β-scission of the hydroperoxides, resulting in a change in relative distribution of volatiles. The increase in hexanal and methyl 9-oxononanoate at the expense of pentane and methyl octanoate in the presence of hydrogen donor compounds supports the presence of a heat-catalyzed heterolytic cleavage (also known as Hock cleavage), which seems to mainly affect thetrans,trans isomers of linoleate hydroperoxides.     

顺丁橡胶装置丁二烯回收单元的改造

介绍了顺丁橡胶装置丁二烯回收单元的技术改造情况，改造后回收了放火炬燃烧的1．3-丁二烯，其收率可达85％，回收的1，3-丁二烯的质量满足设计要求，并可直接作为顺丁橡胶聚合的单体。     

Theoretical investigation of the mechanism of cis-trans regulation for the allylnickel(II)-catalyzed 1,4 polymerization of butadiene

In this Account we summarize the recent progress in the computational modeling of the transition-metal-catalyzed 1,3-diene polymerization. We present a comprehensive and theoretically well-founded view of the cis-trans regulation mechanism of the intriguing C-C coupling for the allylnickel(II)-catalyzed 1,4 polymerization of butadiene. The crucial elementary reactions of the entire polymerization process were theoretically explored for typical trans-1,4- and cis-1,4-regulating catalysts. As a result, the catalytic structure-activity relationships are deduced, which are responsible for opening that reaction channel which yields trans-1,4 and cis-1,4 polymer units.     

Evaluation of monomers derived from resorcinol as eluents of bisphenol A glycidyl dimethacrylate for the formulation of dental composite resins

The objective of this work was to synthesize two bio-based monomers, using the resorcinol as raw material, and its effect as bisphenol A glycidyl dimethacrylate (Bis-GMA) eluents on different chemical–physical and biological properties of experimental photopolymerizable composite resins. The acrylic 1,3-phenylen diacrylic (1,3-FDA) and methacrylic 1,3-phenylen dimethacrylic (1,3-FDMA) monomers were synthesized and fully characterized through FTIR and ¹H-NMR spectroscopies. Experimental photopolimerizable composites were formulated using Bis-GMA/1,3-FDA or Bis-GMA/1,3-FDMA as organic matrix. The materials were compared with a Bis-GMA/TEGDMA resin-based composite used as control. Polymerization kinetics was evaluated by means of FTIR spectroscopy. Polymerization stress was directly measured through a polymerization stress tester. The cell viability of the composites was evaluated using the MTT assay. One-way analysis of variance and Tukey's test were used for statistical analysis. The materials formulated with the 1,3-FDA monomer showed higher Rp_max values and lower polymerization stress values (p < 0.05), while the flexural strength, water sorption, and solubility remained similar to the TEGDMA composite. Conversely, the materials formulated with the 1,3-FDMA monomer showed a lower degree of conversion and statistically lower flexural strength (p < 0.05). All materials exhibited a cellular viability close to 100%. Concerning the study conditions, the acrylic 1,3-FDA monomer could be considered an alternative to TEGDMA in the formulation of photopolymerizable dental composite resins. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48576.     

Properties of the methylene group in 1,4-Dienes. I. Catalytic polymerization of 1,4-Pentadiene

Summary Attempts to obtain 1,3-pentadiene from the uncatalyzed or catalyzed isomerization of 1,4-pentadiene at 200–250° were not successful. Dimers and higher polymers were formed, presumably by conjugation and addition reactions. The activity of several catalysts was measured by the yields of polymer. Sodium hydroxide was most effective, followed by sulfur dioxide,beta-chloroanthraquinone, anthraquinone-beta-carboxylic acid, and anthraquinone in order of decreasing activity. In 1,4 and 1,3-pentadiene mixtures, anthraquinone and sulfur dioxide catalyze slightly the formation of high polymers, but sodium hydroxide catalyzes both total polymer and dimer. The quinones are believed to function in 1,4 to 1,3-diene isomerization by a free radical mechanism, sulfur dioxide and sodium hydroxide by polar mechanisms. These results are related to the polymerization of non-conjugated drying oils. Presented before the Organic Chemistry Division, American Chemical Society, Atlantic City, September, 1952.     

Distribution of isomeric structures in polyisoprenes

The ¹³C-n.m.r. spectra of polyisoprenes were investigated. Polyisoprenes were prepared with $\text{n-Buli}\text{Et}{}_2\text{O}$, radical (emulsion polymerization), and Alfin catalysts. Poly(isoprene-4,4-d₂)s were also prepared with $\text{n-BuLi}\text{Et}{}_2\text{O}$ catalysts for the signal assignments. ¹³C-n.m.r. signals were assigned for dyad or triad sequences of cis-1,4-, trans-1,4-, and 3,4- units. Signals due to head-to-head (4,1-1,4) and tail-to-tail (1,4-4,1) linkages were also assigned. On the basis of signal assignments it was revealed that cis-1,4-, trans-1,4-, and 3,4-units were distributed almost randomly in $\text{n-BuLi}\text{Et}{}_2\text{O}$ catalysed polyisoprenes. It was confirmed that radical and Alfin polyisoprenes contained about 15% of each of head-to-head and tail-to-tail linkages. It was found that radical polyisoprene had cis-1,4- and trans-1,4-units distributed randomly along the polymer chain regardless of the head and tail arrangements.     

Cyclohexadiene-linked clusters: synthesis and molecular structure of [{Os4(CO)8(MeCCMe)(η6-C6H6)}2(μ2-η2:η2-C6H8-1,3)]

The reaction of [Os₄(CO)₉(RCCR)(η⁶-C₆H₆)] (R=Me, Ph) with Me₃NO in the presence of 1,3-cyclohexadiene or 1,4-cyclohexadiene yields the clusters [{Os₄(CO)₈(RCCR)(η⁶-C₆H₆)}₂(μ₂-η²:η²-C₆H₈-1,3)] and [{Os₄(CO)₈(RCCR)(η⁶-C₆H₆)}₂(μ₂-η²:η²-C₆H₈-1,4)], respectively. The molecular structure of [{Os₄(CO)₈(MeCCMe)(η⁶-C₆H₆)}₂(μ₂-η²:η²-C₆H₈-1,3)] has been determined by single crystal X-ray diffraction, and represents the first example of two osmium cluster fragments linked by 1,3-cyclohexadiene through a μ₂-η²:η²-bridge.     

Soluble polyphenylene homopolymers with controllable microstructure and properties: Optical and electrical characteristics of completely dehydrogenated poly(1,3-cyclohexadiene) as a π-conjugated polymer semiconductor

The optical and electrical characteristics of soluble polyphenylene (PPH) homopolymers obtained by the complete dehydrogenation of poly(1,3-cyclohexadiene) (PCHD) are reported for the first time. The optical properties were strongly affected by the molar ratios of 1,2-/1,4-phenylene (Ph) units. The HOMO and LUMO energy levels were approximately −5.2 and −2.0 eV, and the microstructure did not influence those energy levels or the band gap energies. The generation of carriers (both electron and hole) in the polymer films was observed, and the drift mobility of electrons and holes was affected by the molar ratios of 1,2-/1,4-Ph units in the polymer chain. The drift mobility of electrons in PPH homopolymers with a high content of 1,4-Ph units was in the order of 10⁻⁴ to 10⁻⁵ (cm²/Vs). The I-V characteristics of soluble PPH homopolymers were controllable by the microstructure of PPH. The 1,2-Ph unit imparted appropriate solubility and toughness to the PPH homopolymers.     

UV curable,liquid diacrylate monomers based on (<Emphasis Type="Italic">cis,trans</Emphasis>)-1,3/1,4-cyclohexanedimethanol

Novel, liquid cycloaliphatic diacrylate monomers based on (cis,trans)-1,3/1,4-cyclohexanedimethanol have been synthesized for use in ultraviolet (UV)- and electron beam (EB)-cured coatings, inks, and adhesives. Diacrylate monomers prepared from this unique diol, and containing less than 15 wt% trans-1,4-cyclohexanedimethanol diacrylate, are liquid at room temperature and readily soluble in other acrylate monomers and oligomers (in contrast to diacrylates prepared from 1,4-cyclohexanedimethanol, which are solid). More importantly, UV-cured coatings based on (cis,trans)-1,3/1,4-cyclohexanedimethanol diacrylates (1,3/1,4-CHDMDA) show superior hardness, scratch resistance, and chemical resistance as compared to common diacrylate monomers used in the UV coating industry such as tripropylene glycol diacrylate, hexanediol diacrylate, dipropylene glycol diacrylate, and propoxylated neopentyl glycol diacrylate. Thus, this new monomer appears to be a promising material for enhancing the performance of radiation-cured coatings, inks, and adhesives applied to a variety of substrates, including plastic, paper, wood, metal, and glass. This paper will summarize the synthesis of liquid diacrylates from (cis,trans)-1,3/1,4-cyclohexanedimethanol, as well as the performance properties of the corresponding UV-cured coatings.