Hexene hexadienes

If various feeds give the same TPR spectrum for their end product, a common rate determining step can be assumed. This was the situation when TPR spectra of benzene formed over Pt-AljOj from adsorbed n-hexane, 1-hexene, and 1,5-hexadiene were studied. This re-confirms the hexane-hexene-hexadiene stepwise mechanism since cyclohexane, cyclohexene, and cyclohexadiene gave another type of TPR spectrum (62b). 

There are different methods to cleave benzyl ether bonds. The most common one is hydrogenolysis with palladium on carbon or platinum as catalysts under H2 atmosphere. The standard solvents are ethanol or ethyl acetate. Pd is the preferred and milder one, because the use of Pt at any rate results in aromatic ring hydrogenation. Also a number of methods have been developed in which hydrogen is generated in situ, e. g. from cyclo-hexene, -hexadiene or formic acid (see Chapter 7). 

This type of coiled conformation, in which a certain number of monomer units are present in a certain number of turns, would cause the terminal carbon atom of a free radical, formed by the scission of a carbon-carbon bond in the polymer chain backbone, to be in close proximity to, and to interact with, a specific carbon atom, or a hydrogen atom linked to a specific carbon atom, in the turn. Thus, in an isotactic polyethylene molecule, which contains three monomer units per turn and is represented by the structure in Fig. 2, the scission of the Qg - Cm bond would bring C 6 in close proximity to or C 2 or the hydrogen atoms linked to any one of them. If Qe containing the unpaired electron attacks the C i, a six-membered ring may be formed feq. (15)]. It has been observed that in an intramolecular cyclization, the fastest reactions are those which proceed via six-membered rings However, cyclohexane (I) may lose one or more hydrogen atoms to a free radical and form hexene, hexadiene, hexane, and other compounds as shown below. 

CO2. propene. butenes, pentenes. pentadienes. hexene, hexadienes. hexatrienes. benzene, toluene, heptene. heplatriene. methacrylic acid, xylene, octatriene. octadiene. nonalriene. hexenedienoic add, decatriene. decatetraene. decapentaene. undecatriene. methylbenzoic acids, trimelhylbenzoic acid... 

SO2. hexenes, hexadienes, methyl methacrylate, toluene, naphthalene, dodecadienes... 

Frequently, the Af//298 of an alkane is accurately known but Af//298 values of one or more of the several alkenes or alkynes that can be hydrogenated to it are not known. The hydrogenation experiment then yields Af//298 (alkene or alkyne)by Eq. (1.3). A simple example is that of the isomeric linear hexenes, hexadienes, and 1,3,5-hexatriene, all of which can be hydrogenated to give w-hexane. Conditions are usually such that A H calculated from hydrogenation data is very close to the enthalpy of formation of the alkene in the standard state Af//29g. A less usual situation is determination of the Af//298 of the product alkane by combining Ahyd//29g with the known A f//29g of an alkene. 

Hexene, hexadiene, hexatriene, and cyclohexadiene were found to be intermediates for the dehydrocyclization of hexane to benzene. Only dehydrogenation occurred on the Cr203 catalyst. It was claimed that cyclization of hexatriene was a gas phase reaction. 

The reaction hexenes —> hexadienes was demonstrated without using radiotracers both on oxide and metal catalysts, Nil 1 and Ptj l Mixtures containing [ " CJ-hexene contributed to the clarification of the further reaction pathway. These studies showed that neither the hexene cyclohexane nor the hexene —> cyclohexene ring closure pathway took place.Table 2 indicates that radioactivity appeared in both the hexatriene and 1,3-cyclohexadiene fractions when their inactive form was admixed to radioactive hexene. The aromatisation of both inactive components was much more rapid than that of hexene, therefore their specific radioactivities showed very low absolute values, however, these were still higher than that of benzene produced mainly from these non-radioactive precursors. The true precursor of ring closure should have been cis-cis-1,3,5-hexatriene. Its ring closure takes place without any catalyst from 513 The stepwise dehydrogenation of open-chain hydrocarbons produces cis- and trans-isomers of alkenes and alkadienes. Any c s-c s-triene... 

The reaction sequence hexane--------- hexenes----hexadienes-------> benzene has been... 

Poly(sulfur dioxide-co-methyl methacrylale-co-l-hexene) (24.2/1) 700-800 SO2, hexenes, hexadienes, metlyl methacrylate, toluene, naphthalene, dodeadienes 204... 

Sodium amalgam converts perfluoro(3,4-dimethyI-3-hexene) to perfluoro-(3,4-dimetliyl-2,4-hexadiene at room temperature in 70% yield [62] (equation 31). 

Der Bis-[2-phenyl-2-cyan-vinyl]-ather (1) wird iiberwiegend zum 2,5-Diphenyl-hexen-(2)-disdure-nitril (III) reduziert. Je nach Kathodenpotential wird zusatzlich 2,5-Diphe-nyl-hexadien-(2,4)-disaure-dinitril (II) bzw. bei 2 V das 2,5-Diphenyl-hexandisaure-dinitril (IV) erhalten. Da es sich hier primar um die Rekombination zweier radikalischer Spaltprodukte des Athers I handelt, ist cine hohe Depolarisator-Konzentration vorteil-haft2 ... 

Reactivity ratios for 1-hexene (M ) with 5-methyl-1,4-hexadiene CM2) copolymerization at 30 c in hexane solvent using a Et2AlCl/6-TiCl3 AA catalyst system (Al/Ti atomic ratio s 1.5) were determined. The compositions of copolymers were measured by 300 MHz 1H-NMR spectroscopy. The reactivity ratios, calculated by the Tidwell-Mortimer method, were 1.1 + 0.2 for each of the two monomers. 

Materials. 5-Methyl-1,4-hexadiene was obtained by the codimerization of isoprene and ethylene with a catalyst (18) consisting of iron octanoate, triethylaluminum and 2,2 -bi-pyridyl. The product mixture which contained principally 5-methyl-1,4-hexadiene and 4-methy1-1,4-hexadiene was fractionated through a Podbielniack column to yield high purity (>99%) 5-methylxhexadiene, b.p. 92.80C,njj 1.4250 (Lit. (19) b.p. 88-89°C, np 1.4249). 1-Hexene (99.9% purity), 1-decene (99.6% purity), 4-methyl-1-hexene (99.5% purity) and 5-methyl-l-hexene (99.7% purity) were obtained from Chemical Samples Co. 6-TiCl3 AA (Stauffer Chemical Co.j contains 0.33 mole AICI3 per mole of TiClj). Diethylaluminum Chloride was obtained from Texas Alkyls (1.5 M in hexane). 

Further confirmation of the structure and tacticity of poly/5-methyl-l,4-hexadiene)was obtained from X-ray diffraction and u-NMR data of its hydrogenated polymer (Scheme 2). The hydrogenated polymer sample showed a highly crystalline pattern (Figure 7), with diffraction spots that were well defined. This pattern was identical to that of isotactic poly(5-methyl-l-hexene) as reported in the literature (26) (measured identity period, 6.2 A lit., 6.33 A). 

We showed (7) earlier that copolymers of higher a-olefins, particularly 1-hexene, with 5-methyl-1,4-hexadiene can be sulfur-cured readily and that they contain unsaturation approximating the level of the methylhexadiene charged. In view of this and the excellent durability (8) during flexing exhibited by vulcanizates of such copolymers, we were interested in determining the copolymer structure and the reactivity ratios of 1-hexene and 5-methyl-l,4-hexadiene during copolymerization. 

The NMR spectrum of the copolymer prepared from an equimolar mixture of the monomers is shown in Figure 10. In this spectrum, five well separated regions of NMR peaks were observed. The assignments of the peaks (Table III) were made by using the existing spectral information on homopolymers of 1-hexene and 5-methyl-1,4-hexadiene as well as the intensity variations among the copolymers with different monomer charge ratios. 

Figure 8. 13C-NMR spectra of (A) hydrogenated poly(5-methyl-l,4-hexadiene) and (B) poly(5-methyl-l-hexene).

Figure 10. 300 MHz IH-NMR spectrum of a deuterobenzene solution of an equimolar copolymer of 5-methyl-l,4-hexadiene and 1-hexene prepared with a EttAlCl/ S-TiCl, catalyst at 0°C in pentane solvent.

MHz - H-tWR SPECTRAL DATA OF AN EQUIMOLAR COPOLYMER OF 1-HEXENE AND 5-METHYL-1,4-HEXADIENE... 

COPOLYMER COMPOSITION vs MONOMER FEED COMPOSITION FOR 1-HEXENE/5-CH3-l,4-HEXADIENE COPOLYMERIZATIONS... 

The reduced reactivity of 5-methy1-1-hexene is consistent with the expected steric effect due to methyl substitution at the 5-carbon position. Apparently, the internal double bond in 5-methyl-l,4-hexadiene assists in its complexation at the active site(s) of the catalyst prior to its polymerization and thereby the "local concentration" of this monomer is higher than the feed concentration during copolymerization with 1-hexene. This view is consistent with the observation that the overall rates of polymerization, under the same conditions, are much lower for the system containing 5-methyl-1,4-hexadiene. 

To do so, one can take the enthalpy of formation of n -hexane from Pedley, and with the phase independence assumptions in Reference 7, employ the enthalpies of hydrogenation of 1-hexene and 1,5-hexadiene from References 11 and 12 respectively. Alternatively13, one can forget about the first quantity altogether and simply take the difference of the enthalpies of hydrogenation of the diene and twice that of the monoene. This reaction is endothermic by 1.1 1.8 kJ mol-1, a value statistically indistinguishable from the absence of any interolefin interaction in the diene. Relatedly, for the isomeric 1,4-hexadienes 14 and 15, equation 8 may be used. 

Independent double bonds (i.e., without conjugation) have molar absorptivities that are approximately multiples of the molar absorptivity for one double bond. For instance, 1,4-hexadiene has twice the molar absorptivity of 1-hexene but absorbs at the same wavelength. 

The hydrogenation of simple alkenes, such as hexene, cyclohexene, cyclo-hexadiene and benzene, has been extensively studied using biphasic, alternative solvent protocols. These hydrocarbon substrates are more difficult to hydrogenate compared to substrates with electron withdrawing groups. Benzene and alkyl substituted aromatic compounds are considerably more difficult to hydrogenate... 

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