1.3- Dicyclopentadiene dimer

DICYCLOPENTADIENE DIMER (77-73-6) Forms explosive mi xture with air (flash point 20°F/—7°C oc). Violent reaction with strong oxidizers. Forms peroxides may polymerize unless inhibited. Decomposes above 338°F/170°C. Flow or agitation of substance may generate electrostatic charges due to low conductivity. 

Synonyms/Trade Names Bicyclopentadiene DCPD 1,3-Dicyclopentadiene dimer 3a,4,7,7a-Tetrahydro-4,7-methanoindene [Note Exists in two stereoisomeric forms.]... 

We have studied the same rearrangement directly by preparing the radical from 6-bromo-hex-l-ene in a suitable matrix, and observing the e.s.r. spectrum of the product radical. The cyclopentylmethyl radical (6) is formed predominantly in matrices of camphane, adamantane or dicyclopentadiene dimer (BCPD). 

Sulfur can be fully plasticized by using the modifiers dipentene, styrene, and dicyclopentadiene. Sulfur can be plasticized with dicyclo-pentadiene at two minimum concentrations, as indicated in Table III 13% at reaction temperatures of < 140°C and 6% at reaction temperatures > 140 °C. This effect probably results from cracking of the dicyclopentadiene dimer molecule, which doubles the molecules available for reaction. The higher percentage dicyclopentadiene mixture was initially flexible. Upon aging, both plasticized materials became brittle. The reaction is exothermic and very difficult to control above 140 °C. When uncontrolled, extreme viscosity increases were encountered. 

Aliphatic C-5—C-6. Aliphatic feedstreams are typically composed of C-5 and C-6 paraffins, olefins, and diolefins, the main reactive components being piperylenes cis-[1574-41 -0] and /n j -l,3-pentadiene [2004-70-8f). Other main compounds iaclude substituted C-5 and C-6 olefins such as cyclopentene [142-29-OJ, 2-methyl-2-butene [513-35-9] and 2-methyl-2-pentene [625-27-4J. Isoprene and cyclopentadiene maybe present ia small to moderate quaatities (2—10%). Most steam cracking operatioas are desigaed to remove and purify isoprene from the C-5—C-6 fraction for applications ia mbbers and thermoplastic elastomers. Cyclopentadiene is typically dimerized to dicyclopentadiene (DCPD) and removed from C-5 olefin—diolefin feedstreams duriag fractionation (19). 

Cycloaliphatic Diene CPD—DCPD. Cycloatiphatic diene-based hydrocarbon resias are typically produced from the thermal or catalytic polymerization of cyclopeatadieae (CPD) and dicyclopentadiene (DCPD). Upon controlled heating, CPD may be dimerized to DCPD or cracked back to the monomer. The heat of cracking for DCPD is 24.6 kJ / mol (5.88 kcal/mol). In steam cracking processes, CPD is removed from C-5 and... 

In the process of thermal dimerization at elevated temperatures, significant polymer is formed resulting in seriously decreased yields of dimer. Dinitrocresol has been shown to be one of the few effective inhibitors of this thermal polymerization. In the processing of streams, thermal dimerization to convert 1,3-cyclopentadiene to dicyclopentadiene is a common step. Isoprene undergoes significant dimerization and codimerization under the process conditions. 

Dicyclopentadiene exists ia two stereoisomeric forms, the endo and exo isomers. Commercial DCPD, 3a,4,7,7a-tetrahydro-4,7-methano-lH-iadene, is predominandy the endo isomer (exo endo 6 953 by capillary gas chromatography). The dimer is the form ia which CPD is sold commercially. 

The purity of a dicyclopentadiene stream may be expressed in terms of DCPD itself or in terms of available CPD monomer. Both analyses are deterrnined by gas chromatography (gc). The first analysis is capillary gc on a nonpolar column. The data from the analysis can be used to calculate the available CPD, assuming that all the DCPD and CPD codimers crack completely. In the second analysis the sample is charged to the gc equipment under temperature conditions (injection port 400°C) that cause essentially complete reaction of the dimers to monomers. 

The recovery of cyclopentadiene is based on the rapid dimerization rate of this compound to dicyclopentadiene, and the ease of separating heavy dimer from the feedstock. 

Cyclopentadiene was prepared2 by heating dicyclopentadiene (purchased from Eastman Organic Chemicals) and a pinch of hydro-quinone (1,4-benzenediol) under a column of glass helices or a Vigreux column at 175° and collecting the distillate in a receiver cooled with a 2-propanol-dry ice bath. The monomer was dried over Linde 4A Molecular Sieves at —20° and could be stored at this temperature for several weeks without excessive dimerization. 

AuCl(alkene)] (alkene = m-cyclooctene. norbornene, CHf/o-dicyclopentadiene ) complexes have been obtained by reaction of [AuCl(CO)] with the alkene.2280,2281 The structure of [AuC1(Ci0H12)] shows the ligand //2-bonded to gold via the C=C bond in the norbornene ring and the molecules are associated into dimers through Au Au interactions.2281... 

By contrast, m/fl-dicyclopentadiene forms a stable crystalline 1 1 complex with AuCl, which is a dimer in the solid state with short aurophilic contacts. The Au-C distances are 2.20(1) and 2.16(1) A (Scheme 77).314... 

Codimerization of butadiene with dicyclopentadiene (example 8, Table II) was shown to proceed via a crotyl-nickel complex (62). Ring contraction of cyclooctadiene (example 10, Table II) appears to be a hydride promoted reaction. The hydride-promoted dimerization of norbomadiene to -toly 1 norbornene (example 9, Table II) appears to be quite different from dimerization via a metallacycle (see Table I, example 16). 

The 1 2 adducts in these examples were accounted for by dimerization of cyclopentadiene and subsequent hydrosilation of dicyclopentadiene. The 3-trichlorosilyl isomer is that expected from 1,4 addition of trichlorosilane. Unless isomerization occurred, the 4-isomer could arise only by 1,2 addition... 

Dicyclopentadiene is the Diels-Alder reaction dimer of cyclopentadiene. It is the thermodynamically stable form of cyclopentadiene at room temperature, and is also a byproduct in the olefin cracking process. Industrially, it is isolated by distillation, and currently is readily available in North America. 

The starting material is called dicyclopentadiene . Cyclopentadiene itself is not stable it dimerizes to dicyclopentadiene slowly at room temperature by a Diels-Alder reaction. It does this even though it is not an electron-deficient dienophile, demonstrating the enormous reactivity of cyclopentadiene as a diene in the Diels-Alder reaction. 

Biological. Cyclopentadiene may be oxidized by microbes to cyclopentanone (Dugan, 1972). Chemical/Physical. Dimerizes to dicyclopentadiene on standing (Windholz et al., 1983). 

Cyclopentadiene dimerizes rapidly at room temperature and should be used immediately (Note 5) or stored at Dry Ice temperatures. As obtained above, the product has a refractive index of about 1.433 at 25° and is quite satisfactory as a starting material for the following preparation (Note 6). The yield, which is determined by weighing the receiving flask plus product, depends upon the quality of dicyclopentadiene employed (Note 7). 

Commercial dicyclopentadiene (b.p. 170°) is placed in a flask and boiled to crack the dimer to the monomer. A 20-cm. glass-bead column permits taking relatively pure... 

The metathesis polymerisation of dicyclopentadiene, an inexpensive monomer (commercially available cyclopentadiene dimer produced by a Diels-Alder addition reaction containing ca 95 % endo and ca 5 % exo form), leads to a polymer that may be transformed into a technically useful elastomer [144-146, 179] and thermosetting resin [180,181]. The polymerisation has characteristics that make it readily adaptable to the reaction injection moulding ( rim ) process [182], The main feature of this process comes from the fact that the polymerisation is carried out directly in the mould of the desired final product. The active metathesis catalyst is formed when two separate reactants, a precatalyst (tungsten-based) component and an activator (aluminium-based) component, are combined. Monomer streams containing one respective component are mixed directly just before entering the mould, and the polymerisation into a partly crosslinked material takes place directly in this mould (Figure 6.5) [147,168,183-186],... 

Cyclopentadiene cannot be purchased because it is too reactive and dimerizes to dicyclopentadiene upon storage. If it is needed, it is prepared by heating dicyclopentadiene. Cyclopentadiene is produced in a reverse Diels-Alder reaction. It is distilled from the hoi reaction mixture as it is formed and used immediately. 

The dicyclopentadiene that is formed in the dimerization of cyclopentadiene has the ring of the dienophile in an endo orientation to the cyclopentadiene ring that acts as the diene. Usually, substituents on the dienophile are found to be endo in the adduct if the substituents contain pi bonds. Another example is provided by the reaction of cyclopentadiene and maleic anhydride illustrated in the following equation ... 

Because cyclopentadiene is fixed in the. v-cis conformation, it is highly reactive in the Diels-Alder reaction. It is so reactive, in fact, that at room temperature, cyclopentadiene slowly reacts with itself to form dicyclopentadiene. Cyclopentadiene is regenerated by heating the dimer above 200 °C. At this temperature, the Diels-Alder reaction reverses, and the more volatile cyclopentadiene monomer distills over into a cold flask. The monomer can be stored indefinitely at dry-ice temperatures. 

Cyclopentadiene featured in Chapter 35 as an important diene in the Diels-Alder reaction. If you try to buy cyclopen tadi-ene you will find that the catalogues list only dicyclopentadiene or cyclopentadiene dimer . The dimerization of cyclopentadiene is reversible the monomer dimerizes by a Diels-Alder reaction at room temperature to give the dimer and the reaction is reversed on heating. So the dimer is a good source of the monomer. 

Cyclopentadiene is a product of petroleum cracking. It dimerizes exothermically in a Diels-Alder reaction to dicyclopentadiene, which is a convenient form for storage and transport. Dicyclopentadiene plus cyclopentadiene demand in the United States amounted to 270 million lb in 1998. 

Aside from the carbonyl group, the Cp ligand and its analogs are probably the most common ligand systems in organometaUic chemistry. This is also reflected in the large number of cyclopentadienyl metal carbonyl dimers and their derivatives that have been studied. For molybdenum, direct reaction of molybdenum hexacarbonyl and dicyclopentadiene is one of several routes to [CpMo(CO)3]2 (equation 14). 

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