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Cyclopentane, bond energy

This energy difference should be a measure of the C-C bond energy in cyclopentane. These calculations used NBO localization (the result of Boys localization was messy when visualized) and CASSCF(2,2)/6-31G. ... [Pg.544]

The difference of these represents the room temperature enthalpy of dissociation of the C-C bond in cyclopentane, i.e. the standard bond energy [68] [—195.54118] — [—195.66801] = 0.12683 = 333.1 kJ mol-1. Of the energy-difference values calculated here, this is the closest to the likely C-C bond energy [69] of cyclopentane, which should be about the same as that of butane, for which an experimental value of 363.2 2.5 kJ mol-1 and calculated values of ca. 367, 378 and 379 kJ mol-1 have been reported [70]. [Pg.546]

The heat of hydrogenation is a measure of the difference between the chemical bonding energy in the unsaturated and saturated cyclic compounds, so that to make a useful comparison between c3 clopentene and cyclohexene allowance must be made, in the heat of hydrogenation of cyclopentene, for the strain which appears in cyclopentane, but not in cyclohexane. This strain energy of 6 0 kcal/mole has been evaluated from a comparison of the heats of combustion of the cycloalkanes with the higher, normal straight-chain alkanes. [Pg.13]

Relative values, however, should ideally reflect conformational energies. If all atom and bond types are the same, as in cyclohexane and methyl-cyclopentane, the energy functions have the same zero point, and relative stabilities can be directly compared. This is a rather special situation, however, and stabilities of different molecules can normally not be calculated by force fleld techniques. For comparing relative stabilities of chemically different molecules such as dimethyl ether and ethyl alcohol, or for comparing with experimental heat of formations, the zero point of the energy scale must be the same. [Pg.50]

A recently reported investigation of the gas-phase iodination of cyclobutane between 589 and 662 K provides a value of Afff (298) = 51.14( 1.0)kcal mol for cyclobutyl radical. The C—bond energy of cyclobutane was found to be 1.8 kcal mol" higher than that of a normal secondary C—H bond and this was related to the increase in strain upon the development of an sp hybridized carbon in a four-membered ring. In gas-phase chlorinations, cyclobutane is also known to be less reactive than cyclopentane and cyclohexane. However, an interesting result has been obtained in the gas-phase chlorinations of chlorocyclobutane between 35 and 195 °C, and of methyl-cyclobutane between 74 and 150°C at ca. 58Torr. " Both substituted compounds are more reactive than the cyclopentyl and cyclohexyl homologues and this has been ascribed to release of some steric strain with formation of the substituted cyclobutyl radical. This is particularly the case for reaction at the tertiary position. [Pg.171]

Biradical I would yield cyclopentene plus ethylene, biradical II the hepta-1,6-diene. Process I may have a lower energy of activation because of the stabilization of the free electron by the secondary carbon atom and also because less energy is required to compress the appropriate carbon-carbon bond, in the cyclopentane ring to yield the cyclopentene, than to rupture the ring to give the diene. [Pg.182]

Interestingly, two of the other species in Table 3 are nitrolates, i.e. ethers of a-nitrooximes, an otherwise thermochemically unprecedented class of compounds. We already have briefly discussed one, 3-nitroisoxazoline, and the second is 1-nitroacetaldehyde 0-(l,l-dinitroethyl)oxime (ONo-ld-dinitroethyl acetonitronate), MeC (NOala—O—N=C(N02)Me. The latter acyclic species is a derivative of 1,1-dinitroethanol—we know of the enthalpy of formation of no other a-nitroalcohol or derivative. Nonetheless, we may ask if the two calorimetric data are internally consistent. Consider the condensed phase reaction 47, which involves formal cleavage of the O — bond in the nitroisoxazoline by the C—H bond of the dinitromethane. It is assumed that the isoxazoline has the same strain energy as the archetypal 5-atom ring species cyclopentane and cyclopentene, ca 30 kJ mol . ... [Pg.76]

The photodecomposition of -alkanes at excitation energies slightly above the absorption onset involves both C-H and C-C bond decompositions [18]. The dominant process is the C-H scission, (H2) 0.8-0.9, and the contribution of C-C decomposition is small. In the photolysis of cyclohexane, cycloheptane, cyclooctane, and cyclodecane, however, only hydrogen evolution was observed [[Pg.375]


See other pages where Cyclopentane, bond energy is mentioned: [Pg.545]    [Pg.545]    [Pg.190]    [Pg.43]    [Pg.190]    [Pg.467]    [Pg.199]    [Pg.253]    [Pg.91]    [Pg.92]    [Pg.92]    [Pg.92]    [Pg.70]    [Pg.44]    [Pg.45]    [Pg.45]    [Pg.46]    [Pg.145]    [Pg.560]    [Pg.259]    [Pg.290]    [Pg.268]    [Pg.199]    [Pg.1130]    [Pg.115]    [Pg.162]    [Pg.115]    [Pg.83]    [Pg.51]    [Pg.32]    [Pg.23]    [Pg.352]    [Pg.56]    [Pg.172]    [Pg.303]    [Pg.178]    [Pg.4]    [Pg.62]    [Pg.115]    [Pg.94]    [Pg.724]    [Pg.482]    [Pg.105]   
See also in sourсe #XX -- [ Pg.543 , Pg.544 , Pg.545 ]




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