Neopentane Benzene

The pore size of Cs2.2 and Cs2.1 cannot be determined by the N2 adsorption, so that their pore sizes were estimated from the adsorption of molecules having different molecular size. Table 3 compares the adsorption capacities of Csx for various molecules measured by a microbalance connected directly to an ultrahigh vacuum system [18]. As for the adsorption of benzene (kinetic diameter = 5.9 A [25]) and neopentane (kinetic diameter = 6.2 A [25]), the ratios of the adsorption capacity between Cs2.2 and Cs2.5 were similar to the ratio for N2 adsorption. Of interest are the results of 1,3,5-trimethylbenzene (kinetic diameter = 7.5 A [25]) and triisopropylbenzene (kinetic diameter = 8.5 A [25]). Both adsorbed significantly on Cs2.5, but httle on Cs2.2, indicating that the pore size of Cs2.2 is in the range of 6.2 -7.5 A and that of Cs2.5 is larger than 8.5 A in diameter. In the case of Cs2.1, both benzene and neopentane adsorbed only a little. Hence the pore size of Cs2.1 is less than 5.9 A. These results demonstrate that the pore structure can be controlled by the substitution for H+ by Cs+. 

The ability of the rhenium-benzene co-condensate to activate linear- and cyclic- alkanes is quite general. We have co-condensed rhenium atoms with alkane benzene mixtures using the alkanes ethane, propane, butane, 2-methylpropane, neopentane,... 

The tris-neopentyl Mo(VI) nitride, Mo(-CH2- Bu)3(=N) [134], reacts with surface silanols of silica to yield the tris-neopentyl derivative intermediate [(=SiO)Mo (-CH2- Bu)3(=NH)] followed by reductive elimination of neopentane, as indicated by labeling studies from labeled starting organometallic complex, to yield the final imido neopentylideneneopentyl monosiloxy complex [(=SiO)Mo(=CH- Bu)(-CH2 - Bu)(=NH)] [135]. The surface-bound neopentylidene Mo(VI) complex is an active olefin metathesis catalyst [135]. Improved synthesis of the same surface complex with higher catalytic activity by benzene impregnation rather than dichlorometh-ane on silica dehydroxylated at 700 °C has been reported [136],... 

This rule works best for apolar, quasi-spherical molecules. Large deviations occur when chemical association is involved (e.g., carboxylic acids), from molecular dipolarity (e.g., dimethyl sulfoxide), and from molecular asphericity (e.g., neopentane/ -pentane). Strongly associating solvents (e.g., HF, H2, NH3, alcohols, carboxylic acids) have Trouton constants which are higher than the average value of 88 J mol K" found for nonassociating solvents such as diethyl ether and benzene. 

In particular cases bond strengths may be controlling—for example, the extreme resistance of benzene to oxidative attack may be explained by the very high C—H bond strength (12, 208). The anomalous low knock rating of neopentane may be correlated with the low strength of the neopentyl C—H bond. C—H bond strengths for methane, ethane, and neopentane are, respectively, 102, 98, and 96 kcal. per mole (82, 204). 

Terra neopentyl titanium [36945-13-8], Np4Ti, forms from the reaction of TiQ4 and neopentyllithium in hexane at —80° C in modest yield only because of extensive reduction of Ti(TV). Tetranorbomyltitanium [36333-76-3] can be prepared similady. When exposed to oxygen, (NpO)4Ti forms. If it is boiled in benzene, it decomposes to neopentane. When dissolved in monomers, eg, OC-olefins or dienes, styrene, or methyl methacrylate, it initiates a slow polymerization (211,212). Results from copolymerization studies indicate a radical mechanism (212). Ultraviolet light increases the rate of dissociation to... 

The early work of Kiselev (1957) revealed that the adsorption isotherms of n-pentane and n-hexane on non-porous quartz were intermediate in character between Types II and m. Values of C(BET) <10 were obtained and the differential enthalpies of adsorption decreased steeply at low surface coverage. More recently, the isotherms of isobutane (at 261 K) and neopentane (at 273 K) on TK800 have been found to be of a similar shape (Carrott et al., 1988 Carrott and Sing, 1989). Unlike those of benzene, these alkane isotherms do not undergo a pronounced change of shape as a result of surface dehydroxylation. This is consistent with the non-specific nature of their molecular interactions (see Chapter 1). 

When a dipolar molecule is dissolved in a magnetically anisotropic solvent consisting of disc-shaped molecules, e.g. benzene, the NMR signals of the solute H-atoms are usually shifted upheld with respect to their positions in an isotropic solvent such as 2,2-dimethylpropane (neopentane) or tetraehloromethane cf. the preceding discussion of (Ta in Eq. (6-21). The specific solvent-induced H NMR chemical shift of a solute H-atom signal when the solvent is changed from a reference aliphatic solvent to an aromatic solvent is called aromatic solvent-induced shift (ASIS) and is defined according to Eq. (6-24) [278, 279],... 

Subscript designates ligancy of atom, i.e., number of atoms bonded to central atom. The entropy contribution must be corrected by the addition of any electronic entropy, R In qny where qn is the electronic partition function. The quantity R n a must also be subtracted from the total entropy to correct for symmetry. symmetry number of the final species. Values taken from S. W. Benson and J. H. Buss, J. Chem, Phys., 29 (1958). These quantities are not to be used for cyclic structures such as benzene compounds. Estimates of Cp and are good to about 2 cal/mole- K for most species but may be poorer for heavily substituted species such as neopentane. They may also be poorer for very simple H-containing species such as NH3 and CH4. 

Irradiation of tetraneopentyltitanium (II) in benzene/toluene or hex-afluorobenzene solutions gave neopentane as the major organic product along with some 2,2,5,5-tetramethylhexane [Eq. (10)] and a black precipi-... 

Schrock and co-workers (20) noted that irradiation of the title complex 13 in benzene solution gave a green complex analyzing for ZrCl3(PMe3)2, along with neopentane and 2,2,S,S-tetramethylhexane [Eq. (12)]. Tlie... 

Early adsorption studies indicated that the effective micropore openings in natural and synthetic mordenites were about 4A (2) and not ca. 7A as required by structural data. Later it was shown that this probably was caused by partial blocking of the main channels by calcium and/or sodium cations (3, 22). Sorption in the side channels is limited normally to molecules smaller than n-butane (4.9A) (3), while the main channels in hydrogen-mordenite are nearly filled by the larger cyclohexane (22), benzene, and neopentane molecules (3) of critical diam-... 

With this sample both methanol and dichloromethane give reversible isotherms and the same micropore volume. A much smaller micropore volume is given by benzene indicating that almost 40% of the pores or pore entrances are of size between that of dichloromethane and benzene. On the other hand, only a relatively small amount of low pressure hysteresis is present on the benzene isotherm indicatii that the remaining pores and pore entrances are significantly larger than the benzene molecule. A more complete characterisation of this sample would require the use of a larger probe molecule, such as neopentane. 

Sorption. Sorptive data on Q/ZSM-4 are consistent with the idea of 12 ring tunnels because molecules such as neopentane, cyclohexane, and benzene have easy access. Capacities are quite low as compared with Y zeolite as would be expected from the lower void volume available. 

In contrast measurements of carbon Is electron binding energies in several hydrocarbons yielded a rather narrow range of chemical shifts. For instance, one cannot make a distinction between the carbon atoms of neopentane and those of benzene because their Is binding energies are virtually the same (290.4 eV). Ethane... 

In addition to these exchange reactions, a number of alkane/alkane and al-kane/arene exchange reactions could be studied as equilibria (benzene, toluene, cyclopropane, methane, ethane, neopentane, cyclohexane). Determination of equilibrium constants allowed calculation of AG° values and estimation of relative metal-carbon bond energies. Wolczanski concluded that the differences between metal-carbon bond energies and the corresponding carbon-hydrogen bond energies were essentially the same [82]. 

Wolczanski also investigated the chemistry of a tantalum imido system. In this system, elimination of hydrocarbon from the bis-amido imido complex occurs with difficulty at 183°C to give an amido bis-imido complex. The elimination is reversible, with the bis-imido species not being directly observed (Scheme 10). Under methane pressure, the phenyl complex loses benzene and adds methane. Neopentane, benzene, and toluene (benzylic activation) were also found to undergo activation, but not cyclohexane. The authors conclude from their equilibrium studies that the differences in metal-carbon bond strengths are approximately equal to the differences in carbon-hydrogen bond... 

Guest species CH4, CzHfi, Xe, O2, H2S, CO2 Ar, Kr, N2, CjHs, i-C4Hio, (CH2)30 Butane, neopentane , benzene, cyclopentane , cyclohexane, cycloheptane , cyclo-octane , adamantane ... 

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