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Trans-butadiene

The pole strength profiles obtained in the outer valence region of the 1,3-trans butadiene, 1,3,5-trans hexatriene and 1,3,5,7-trans octatetraene compounds relate also typically to that found (10) with low-gap hydrogen chains. They nicely reflect the competition for intensity between the main and the correlation i.e. satellite) bands in that region. In both cases, the less energetic (HOMO LUMO (10,12)... [Pg.84]

Table 13-3. Basis set dependence of activation (AEa) and reaction energies (AEr) computed using the B3LYP functional for the concerted gas-phase cycloaddition of ethylene to trans-butadiene [kcal/mol]. All calculations include zero-point vibrational contributions evaluated at the B3LYP/6-311+G(d,p) level. Table 13-3. Basis set dependence of activation (AEa) and reaction energies (AEr) computed using the B3LYP functional for the concerted gas-phase cycloaddition of ethylene to trans-butadiene [kcal/mol]. All calculations include zero-point vibrational contributions evaluated at the B3LYP/6-311+G(d,p) level.
Show that T, = 2Bg 2A. for the n-electron system in trans butadiene. [Pg.168]

As indicated above, the conventional structure of trans butadiene does not include the delocalization of the -electron system. This effect can be analyzed, at least approximately, by application of the Hfickel method. As in the example of ethylene, each carbon atom has an available p orbital-the... [Pg.375]

Fig. 8 The energy levels and wavefunotions for the r-orbitals of trans butadiene. The arrows define the electron configuration of the ground state. Fig. 8 The energy levels and wavefunotions for the r-orbitals of trans butadiene. The arrows define the electron configuration of the ground state.
The synthesis of transtactic structures is based on catalysts in which the transition metal belongs to the 3d block (Ti, Cr, V, Ni). Particular emphasis is devoted to the synthesis of trans butadiene/piperylene copolymers and to their blends with synthetic cis-l,4-polyisoprene, with the aim of increasing the "green strength" of the latter. [Pg.33]

Figure 16. Processibility and green strength of trans-butadiene-piperylene copolymers as a function of melting point and Mooney viscosity. Figure 16. Processibility and green strength of trans-butadiene-piperylene copolymers as a function of melting point and Mooney viscosity.
Fig. 6. Selected geometric parameters (A) of the optimized structures of the key species for the feasible r 2-tra7is-butadiene insertion into the r -syw-allyl-Ni11 bond along 2b—> 7b. Free energies (AG, Ain kcalmol-1) are given relative to the favorable r 3-syn,r l(Cl),A-cis/r[2-trans-butadiene stereoisomer of the precursor 2b. Fig. 6. Selected geometric parameters (A) of the optimized structures of the key species for the feasible r 2-tra7is-butadiene insertion into the r -syw-allyl-Ni11 bond along 2b—> 7b. Free energies (AG, Ain kcalmol-1) are given relative to the favorable r 3-syn,r l(Cl),A-cis/r[2-trans-butadiene stereoisomer of the precursor 2b.
Alternative pathways for coupling of two cA-butadiene or two trans-butadiene moieties, however, are unfeasible on considerations similar to those discussed for the Cg-channel (cf. Section 6.1). [Pg.210]

The cyclotrimer products are liberated in subsequent, consecutive substitution steps with new butadiene, which is an exothermic reaction (AH) for expulsion of all-t-CDT by three /ran.v-butadienes along 8b —> l b. This process, however, is endergonic by 7 kcal mol-1 (AG) after entropic costs are taken into account. Therefore, 7b and 8b (stabilized by donors) are indicated to be likely candidates for isolable intermediates of the catalytic process, while the active catalyst l b, the intermediate species 2b, in particular, and other species will not be present in a sufficient concentration, since they are either too reactive or thermodynamically too unfavorable, for experimental characterization. Overall, the cyclotrimerization process is driven by a strong thermodynamic force with an exothermicity of —44.6 kcal mol-1 (AH for the process without a catalyst) for the fusion of three trans-butadiene to afford the favorable all-t-CDT. [Pg.211]

Harmonic vibrational frequencies for s-trans butadiene have also been calculated at several levels of calculation19,21,23 24 31 35. Table 2 presents the computed values of some of the vibrational frequencies. [Pg.6]

TABLE 3. Selected force constants (mdynA 1) computed for s-trans butadiene at several levels of calculation ... [Pg.7]

State trans- Butadiene Inmy-Hexatriene11 trans- Octatetraene ... [Pg.13]

Photochemical investigations When a solution of the complex Cp2Ti (o-C=QBu) 2 is irradiated, NMR spectroscopic monitoring shows that a titanacyclocumulene is first generated, and that this species then reacts with a further equivalent of titanocene to yield the dinuclear complex with p-q(l-3),q(2-4)-trans,trans-butadiene units between the two... [Pg.366]

The polymerization of the butadiene monomers (3,4) can also be followed spectroscopically by the disappearance of the strong absorption of the monomers at 260 nm, whereas the absorption of the resulting poly-1,4-trans(butadiene)s is too small to be observed in a single monolayer. The polymers from the butadiene and methacryloyl lipids are probably better model membrane systems, because the polymer chains are still mobile and not excessively rigid as the polydiacetylenes. [Pg.220]

Fig. 3. The pi MO s of both cis and trans butadiene as constructed from two ethylenic fragments... Fig. 3. The pi MO s of both cis and trans butadiene as constructed from two ethylenic fragments...
Fig. 5. The pi group MO s for the cis and tram geometries of the fragment (B + C) as constructed from the MO s of B and C. The resulting group MO s resemble the pi MO s of cis and trans butadiene, respectively. The symmetry labels are assigned with respect to a mirror plane (cis isomer) or a rotational axis (trans isomer)... Fig. 5. The pi group MO s for the cis and tram geometries of the fragment (B + C) as constructed from the MO s of B and C. The resulting group MO s resemble the pi MO s of cis and trans butadiene, respectively. The symmetry labels are assigned with respect to a mirror plane (cis isomer) or a rotational axis (trans isomer)...
Figure 12.11 Estimates of the pure component spectra for styrene, i,2-butadiene, ds-butadiene and trans-butadiene units in styrene-butadiene polymers, obtained using the CLS method. The vertical dashed lines indicate the four wavelengths chosen by the stepwise MLR method. Figure 12.11 Estimates of the pure component spectra for styrene, i,2-butadiene, ds-butadiene and trans-butadiene units in styrene-butadiene polymers, obtained using the CLS method. The vertical dashed lines indicate the four wavelengths chosen by the stepwise MLR method.
For dienes, the analogous correlation scheme can be established. This viewpoint leads for s-cis-and s-trans-butadiene to the following, preparatively utilizable consequences ... [Pg.76]

The diene exists primarily in a trans conformation, the cis conformer being approximately 2 kcal/mol less stable and separated from the trans conformer by a low energy barrier. At room temperature, only about 5% of butadiene molecules will be in a cis conformation. Clearly, tran -butadiene cannot undergo cycloaddition (as a diene), at least via the concerted pathway which is known to occur, and rotation into a cis conformation is required before reaction can proceed. [Pg.394]

Parr, R. G., and R. S. Mulliken LCAO self-consistant field calculation of the n-clectron energy levels of cis- and trans-butadiene. J. chem. Phys. IS, 1338 (1950). [Pg.45]

In the area of reaction energetics. Baker, Muir, and Andzehn have compared six levels of theory for the enthalpies of forward activation and reaction for 12 organic reactions the unimolecular rearrangements vinyl alcohol -> acetaldehyde, cyclobutene -> s-trans butadiene, s-cis butadiene s-trans butadiene, and cyclopropyl radical allyl radical the unimolecular decompositions tetrazine -> 2HCN -F N2 and trifluoromethanol -> carbonyl difluoride -F HF the bimolecular condensation reactions butadiene -F ethylene -> cyclohexene (the Diels-Alder reaction), methyl radical -F ethylene -> propyl radical, and methyl radical -F formaldehyde -> ethoxyl radical and the bimolecular exchange reactions FO -F H2 FOH -F H, HO -F H2 H2O -F H, and H -F acetylene H2 -F HC2. Their results are summarized in Table 8.3 (Reaction Set 1). One feature noted by these authors is... [Pg.285]

Synonyms Biethylene bivinyl butadiene buta-l,3-dicne a,y-butadiene trans-butadiene divinyl erythrene pyrrolylene vinylethylenc... [Pg.109]

Figure 2.13 (a) symmetry of p, orbital on oxygen atom in H 0 symmetry group C, . (b Symmetry of 2/m bonding MO of s-trans-butadiene symmetry Cjj. [Pg.36]

For centrosymmetric systems with a centre of inversion /, subscripts g (symmetric) and u (antisymmetric) are also used to designate the behaviour with respect to the operation of inversion. The molecule trans-butadiene belongs to the point group Cik (Figure 2.13b). Under this point group the symmetry operations are /, C2Z, and i, and the following symmetry species can be generated ... [Pg.37]


See other pages where Trans-butadiene is mentioned: [Pg.337]    [Pg.84]    [Pg.86]    [Pg.34]    [Pg.88]    [Pg.199]    [Pg.92]    [Pg.180]    [Pg.181]    [Pg.185]    [Pg.187]    [Pg.194]    [Pg.12]    [Pg.13]    [Pg.228]    [Pg.308]    [Pg.289]    [Pg.257]    [Pg.161]    [Pg.390]    [Pg.390]   
See also in sourсe #XX -- [ Pg.358 , Pg.723 , Pg.733 ]




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1,3-Butadiene, 1- 1-phenyl-, trans

1.3- BUTADIENE-1,4-DIOL, TRANS

1.3- Butadienes cis/trans interconversion

Butadiene polymers trans-1,4-polybutadiene

Cis-trans isomerization butadiene

Crystallinity trans-styrene-butadiene

Trans-Butadiene-piperylene

Trans-Butadiene-piperylene copolymers

Trans-Poly(butadiene

Trans-Poly(butadiene point

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