1.3- Pen tadiene

Ethyl ( , 7-1,3-pen tadiene-l-carbamate, 59,8 3-Ethyl-3-pentanol, 58, 25, 26, 27, 31 3-Ethyl-3-pentyl alcohol, 58, 78 3-Ethyl-3-pentyl fluoride, 58, 78... 

Does the delocalized tt system of 1,3-pen tadiene stabilize the molecule relative to 1,4-pentadiene Each molecule reacts with two molecules of H2 to give a common product, pentane. Thus, a comparison of their energies of hydrogenation allows us to determine the relative stabilities of two delocalized tt bonds compared with two isolated tt bonds. The hydrogenation of 1,4-pentadiene releases 252 kJ/mol, but the hydrogenation of... 

Other reactions of dienes with metal atoms are only of a limited synthetic use. Dibenzylideneacetone (PhCH=CH—CO—CH=CHPh DBA) reacts with palladium vapor to afford Pd2(DBA)3, a complex in which the coordination is through the two C=C units and does not involve the C=0 (5, 92). Cobalt vapor undergoes an extremely complicated reaction with 1,4-pentadiene, producing pentenes, C5H6, and various polymers as well as the organometallic product, HCo( 1,3-pen tadiene)2, which involves isomerization from a nonconjugated to a conjugated diene (104, 110). 

Natta, G., L. Porri, A. Carbonaro, and G. Lugli Phenomena of isomorphism and polymorphism in trans-1,4-copolymers of 1,3-butadiene with 1,3-pen-tadiene. Makromol. Chem. 53, 52 (1962). 

Wiberg and coworkers published relative rate constants and the products of reaction of silene 6 with a number of alkenes and dienes in ether solution at 100 °C6 106-108. These data are listed in Table 2 along with an indication of the type of product formed in each case. As is the norm in Diels-Alder additions by more conventional dienophiles, the rate of [2 + 4]-cycloaddition of 6 to dienes increases with sequential methyl substitution in the 2- and 3-positions of the diene, as is illustrated by the data for 2,3-dimethyl-1,3-butadiene (DMB), isoprene and 1,3-butadiene. The well-known effects of methyl substitution at the 1- and 4-positions of the diene in conventional Diels-Alder chemistry are also reflected with 6 as the dienophile. For example, lruns-1,3-pen tadiene reacts significantly faster than the f/.v-isorrier, an effect that has been attributed to steric destabilization of the transition state for [2 + 4]-cycloaddition. In fact, the reaction of c/s-l,3-pentadiene with 6 yields silacyclobutane adducts, while the trans-diene reacts by [2 + 4]-cycloaddition108. No detectable reaction occurs with 2,5-dimethyl-2,4-hexadiene. The reaction of 6 with isoprene occurs regioselectively to yield adducts 65a and 65b in the ratio 65a 65b = 8.5 (equation 50)106,107. 

Imaizumi et al. studied the hydrogenation of l,4-dialkyl-l,3-cyclohexadienes over the nine group VIII (groups 8-10) metals and copper in ethanol at room temperature and atmospheric pressure.122 The selectivity for monoenes formation at 50% conversion increased in the order Os-C, Ir-C < Ru-C, Rh-C, Pt < Pd-C, Raney Fe, Raney Co, Raney Ni, Raney Cu (= 100%). The selectivity for 1,4-addition product increased in the order Os-C, Ir-C < Ru-C, Rh-C, Raney Cu, Raney Fe, Raney Ni < Raney Co, Pd-C, Pt. Extensive formation of 1,4-dialkylbenzenes (more than 50% with the 1,3-dimethyl derivative) was observed over Raney Ni and Pd-C, while they were not formed over Raney Cu, Os-C, and Ir-C. In the hydrogenation of 4-methyl-1,3-pen -tadiene (39) (Scheme 3.15) over group VIII metals in cyclohexane at room temperature and atmospheric pressure, high selectivity to monoenes was obtained with iron, nickel, cobalt, and palladium catalysts where the amounts of the saturate 2-methylpen-... 

Formations of 6-dimethylamino-2,4-hexadiene (163) from 1,6-dimethyl-3-piperideine,87 5-dimethylamino-4-methyl-1,3-pen tadiene (164) from l,3-dimethyl-3-piperideine,82 5-dimethylamino-3-methyl-1,3-pentadiene (165) from l,4-dimethyl-3-piperideine,83 and 6-di-methylamino-2,4-heptadiene (166) from l,2,6-trimethyl-3-piperi-deine94 may serve as further examples of the Hofmann exhaustive methylation in the 3-piperideine series. 

OSH4P3Z1C34H43, Zirconium, bis(l,l(T )-cyclopentadienyl]tris(dimethylphenyl-phosphine-2KP)-tri- j-hydrido-hydrido-Ipfr-osmium-, 27 27 OSOP2SC42H34, Osmium, carbonyl(5-thioxo-1,3-pen tadiene-1,5-diyl-C, C yS)bis(triphenylphosphine)-, 26 188... 

An alternative approach to preparing i-PP standard reference materials has been suggested by Fetters etal [37], using narrow-distribution atactic polypropylenes, a-PP. The anionic polymerization of 2-methyl-1, 3-pen-tadiene with s c-butyl lithium occurs exclusively by 1,4-addition to produce poly(l,3-dimethyl-l-butenylene). The polymers are monodisperse in molecular mass distribution. Hydrogenation transforms them into a-PP. Light scattering and osmometry were carried out, as well as viscosity measufements in tetrahydrofuran and 2-octanol, a 0-solvent, and the intrinsic viscosity were related to the mass average molecular mass ... 

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