Allenes ethylene -

Investigation of Ethane, Propane, Isobutane, Neopentane, Cyclopropane, Cyclopentane, Cyclohexane, Allene, Ethylene, Isobutene, Tetramethylethylene, Mesitylene, and Hexamethylbenzene. Revised Values of Covalent Radii (by Linus Pauling and L. O. Brockway)... 

Fig. 6.—Theoretical intensity curves for allene, ethylene, isobutene and Takles X and XI tetramethylethylene. The s-scale for ethylene has been decreased by 3%, to show the quantitative agreement between the measured s values and the curve with C=C = 1.34 A.

Allene Ethylene Butadiene Cyclobutadiene Furan Pyrrole Thiophene Stilbene Benzoquinone Vinyl bromide sym-Dibromoethylene (cis-trans mix.) Tribromoethylene Trichloroethylene Tetrachl or oethylene... 

In Table 23 a summary of linear correlations between molecular properties of allenes, ethylenes, benzenes, and carbonyl compounds is given. Generally, these correlations are only valid for mono- and 1,1 -disubstituted allenes with a mirror plane symmetry, so that one can strictly distinguish tt and electronic states of the molecules. Furthermore, it may be expected that such kinds of correlations are only valid for molecules with comparable rotamer populations, i.e. comparable spatial ligand arrangements (Section II.B). 

Pyrolysis of 1,2,7-octatriene at dlO C gives l-bicyclo[4.2.0]octane and 6-methylenebicyclo[3.2.0]heptane (Scheme 9.91) This is an example of an intramolecular allene-ethylene [2 -h 2] cycloaddition which may or may not be concerted (see Chapter 6, Section 2.6). 

Carhon-carbon bond distances. The electron diffraction investigation of ethane, propane, isobutane, neopentane, cyclopropane, cyclopentane, cyclohexane, allene, ethylene, isobutene, tetramethylethylene, mesitylene, and hexamethylbenzene. Revised values of covalent radii. J. Am. Chem. Soc. 59 (1937) 1223—1236. (Linus Pauling and L. O. Brockway). SP 60 The electron diffraction study of digermane and trigermane. J. Am. Chem. Soc. 60 (1938) 1605—1607. (Linus Pauling, A. W. Laubengayer, and J. L. Hoard). 

The dienoplules for reaction with butadiene can be alkenes, allenes, and alkynes. Simple alkenes like ethylene are poor dienoplules resulting in sluggish reactions. Substituted olefins, X—C=C—X, are more reactive when X and/or X are C=C, Ar, COOR, COOH, COH, COR, COCl, CN,... 

Photoaddition of acetylene, 349 Photoaddition of allene, 349 Photoaddition of dichloroethylene, 349 Photoaddition of ethylene, 348 Photoaddition of hexafluoroacetone, 345 Photoaddition of maleic anhydride, 348 Photochemical addition of ethylenes and acetylenes to steroidal enones and dienones, 343... 

The irradiation of the thiophene in gas phase yields ethylene, allene, methyl-acetylene, carbon disulfide, and vinylacetylene. No Dewar thiophene or cyclo-propene derivatives were isolated (69CJC2965). The irradiation in liquid phase gave the Dewar thiophene which can be trapped as a Diels-Alder adduct with furan (85JA723). The Dewar thiophene and cyclopropene-3-thiocarbaldehyde can be obtained by irradiation in argon matrices at 10 K (86JA1691). 

Analogy between the Delocalized Orbitals of a Hydrocarbon Skeleton (Ethylene, Ethane, Allene, Propane, etc.) and the T Delocalized Orbitals of Conjugated Chains... 

The polymerization filling was effected by the ion-coordination mechanism [17-19]. The monomers were ethylene, propylene, allene, os-butylene, butadiene. The fillers were mineral materials such as ash, graphite, silica gel, glass fibers. The ultimate aim of filler conditioning prior to polymerization is to secure, on its surface, metal complex or organometallic catalysts by either physical or chemical methods [17-19],... 

Snider and coworkers125 have reported the Lewis acid catalyzed [2 + 2]cycloaddition of (phenylsulfonyl)allene 112. The reaction with methylenecyclohexane in dichloro-methane gives a 25% yield of an 8 1 mixture of 210 and 211 (equation 132). An addition reaction of l-(p-tolylsulfonyl)ethylene with enamines gives aminocyanobutanes via the zwitterionic intermediate (212) as shown in equation 133126. 

Fig. 5.—Radial distribution curves for (A) allene, (B) ethylene, (C) isobutane, (D) tetramethylethylene, (E) mesitylene and (F) hexamethylben-zene.

Allen, H. C., and E. K. Plyler The structure of ethylene from Infrared... 

In the original paper, Eddowes and Hill (1977) had reported that, in addition to 4,4 bipyridine, 1,2 bis(4-pyridyl) ethylene (2) was a more effective promoter of cytochrome c electrochemistry than the 4,4 bipyridine and SSBipy was better than both. This lead Allen and colleagues (1984) to postulate that the prerequirement for successful promoter activity was bifunctionality of the form ... 

This reaction has an accompanying endothermicity of ca 4 kJmol-1. Said differently, methylation of ethylene is some 4 kJmol-1 more exothermic than of allene. How general is this greater exothermicity of alkylation of monoolefins over that of related allenes Proceeding to the three cumulated 5-carbon dienes, we may consider the reactions... 

Acetylene is sufficiently acidic to allow application of the gas-phase proton transfer equilibrium method described in equation l7. For ethylene, the equilibrium constant was determined from the kinetics of reaction in both directions with NH2-8. Since the acidity of ammonia is known accurately, that of ethylene can be determined. This method actually gives A f/ acid at the temperature of the measurement. Use of known entropies allows the calculation of A//ac d from AG = AH — TAS. The value of A//acij found for ethylene is 409.4 0.6 kcal mol 1. But hydrocarbons in general, and ethylene in particular, are so weakly acidic that such equilibria are generally not observable. From net proton transfers that are observed it is possible sometimes to put limits on the acidity range. Thus, ethylene is not deprotonated by hydroxide ion whereas allene and propene are9 consequently, ethylene is less acidic than water and allene and propene (undoubtedly the allylic proton) are more acidic. Unfortunately, the acidity of no other alkene is known as precisely as that of ethylene. 

To illustrate the importance of vicinal connectivity of conjugating units, we consider two dienes in non-vicinal relationships 1,5-hexadiene, 9, and allene, 10. As shown in Table 3.19, the direct diene conjugations are negligible in both species, on account of spatial separation in 9 and symmetry-imposed orthogonality of the two pi planes in 10. Consistently with the essential absence of conjugation, the unsaturated C—C bonds of 9 and 10 have calculated bond orders characteristic of ethylene or other unconjugated systems and the ficc NLMOs have essentially localized character ... 

We have previously seen examples of the carbon-like formulas of mononuclear and dinuclear osmium compounds, namely the methane-like tetrahydride (4.50c), ethylene-like H20s=CH2 (4.51c) and H2Os = OsH2 (Table 4.15), acetylenelike HOs = CH (4.54c) and HOs = OsH (Table 4.15), allene-like H2C = Os = CH2 (4.55a), and so forth. While the coordination numbers and Lewis-like formulas are formally analogous, the actual structures of Os and C species may be quite similar (e.g., the Td structures of OsfL and CH4) or dissimilar (e.g the strongly bent Cs structure of H20s = CH2 [Fig. 4.13(c)] versus the planar D2h structure of H2C = CH2). 

Fig. 8 shows a plot of the calculated 48) reaction path for the reaction of 1S carbon atoms with ethylene. It will be seen that the intermediate carbene (28) is formed exothermically, but that its rearrangement to allene (29) requires much activation (50 kcal/mole). At first sight this seems inconsistent with the evidence that the reaction takes place readily at -190 °C. 

Evidently a large part of the energy liberated in the approach of the carbon atom to ethylene will go into this normal mode — which is the one required for conversion of 30 to 31. Unless the interconversion of vibrational energy is incredibly efficient, one would then expect the initially formed 30 to be converted to 31 even at the lowest temperatures. The fact that allene is formed at -190° is not therefore surprising. On the other hand the existence of a large barrier between 30 and 31 would prohibit rearrangement of 30 if formed under milder conditions free cyclopropyl carbenes do not rearrange to allenes if formed by conventional methods in solution 49). 

Scheme 2.38 Functionalized allenes formed by 1,4-addition of organolithium reagents to enynes and electrophilic trapping with aldehydes (111, 112) ketones (113,114), ethylene oxide (115) and carbon dioxide (116).

Ethylene and styrene derivatives react with various propargylic silyl ethers in the presence of zirconocene(II) to afford allenic products in high yield (Scheme 5.7). For example, substrate 67 was transformed into the trisubstituted allene hydrocarbon 68 in 93% yield under the reaction conditions [20]. In the synthesis of various tetraalkylated allenes, in which several of the alkyl substituents also contained triple bonds, allowing these substrates to be cydized intramolecularly into aromatic com-... 

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