AT-alkanes

Atlantic ocean waters collected from the surface to 4500 m show a similar composition in dissolved hydrocarbons. The hydrocarbons represent ca. 20% of the total lipid extract n-alkanes occur to an extent of ca. 12% of the total hydrocarbons, ranging from C,4 to C37, with a maximum at n-Cz7 to n-C3o (Barbier et al., 1973). Iliffe and Calder (1974) reported that the dissolved non-polar hydrocarbon fraction was characterised by relatively large amounts of n-alkanes having between fifteen and twenty carbon atoms and small amounts of n-alkanes with more than twenty carbon atoms. 

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Acetonitrile can be produced by catalytic ammoxidation of ethane and propane over Nb-Sb mixed oxides supported on alumina, with selechvities to acetonitrile of about 50-55% at alkane conversions of around 30% [133]. In both cases, CO forms in approximately a 1 1 molar ratio with acetonitrile, owing to a parallel reaction from a common intermediate. When feeding n-butane, the selectivity to acetonitrile halves. Bondareva and coworkers [134] also studied ethane ammoxidation over similar types of catalyst (V/Mo/Nb/O). 

Catalyst activities were measured at alkane conversions 6 - 80% for the gas mixture of reactants [90.6 vol.% of He + 8.4 vol.% of O2 + 0.96 vol.% of C2Hg] (-2.5-fold over-stoi-chiometric excess of oxygen the space velocity 2 10 h ). Samples of the reactor effluent were injected periodically into a chromatograph with a catarometer. Carbon dioxide and water were obtained as major products in all catalytic runs. Traces of ethene were also detected in some runs. 

It is therefore easy to predict that the research and pre-development work aimed at alkane functionalization using oxygen should incorporate in comparable amount various ingredients. Recent developments announce these changes. These ingredients are ... 

We report here the results of an investigation of the geometry of the CH5 ion by the CNDO/2 method 100>. Considerable interest was aroused by the geometry of this ion, thought to play an important role for the interpretation of the structure of the transition state in electrophilic substitution at alkanes. Three configurations have been explored, which have D3, C4 , and Cs symmetry (Fig. 21). The following parameters have been... 

AT-alkanes are dominant constituents of natural hydrocarbons in the marine environment and their ease of analysis by gas—liquid chromatography explains that this class is relative well documented. 

H. Hogeveen, A. F. J. Bickel, Chemistry and spectroscopy in strongly acidic solutions electrophilic substitution at alkane-carbon by protons, J. Chem. Soc., Chem. Commun., 1967, 635-636. 

Hie free radical chlorination of three alkanes (cyclohexane, 2,3-dimethylbutane, and neopentane) was examined both in SC-CO2, and, for comparison purposes, in conventional organic solv ts. All of these experiments were carried out at 40 °C, and at alkane concentrations < 0.03 M 20). At such low alkane concentrations, little monochloride arises from reaction of Cl with alkane comprising die cage walls, ku (Scheme 1). 

Adamson AW (1990) Physical chemistry of surfaces, 5th ed. Wiley, New York, p 101 ff Alejandro 1, Tddesley DJ, Chapela GA (1995) Molecular dynamics simulation of the orthobaric densities and surface tension of water. J Chem Phys 102 4574—4583 Allen HC, Gregson DE, Richmond DL (1999) Molecular structure and adsorption of dimethyl sulfoxide at the surface of aqueous solutions. J Phys Chem B 103 660-666 Aveyard R, Saleem SM (1976) Interfacial tensions at alkane-aqueous electrolyte interfaces. J Chem Soc, Faraday Trans 1(72) 1609-1617... 

Broadbelt, LJ, Stark SM, Klein MT (1995) Termination of computer-generated Reaction mechanisms species rank-based convergence. Ind Eng Chem Res 34 2566- 2573 Brooks BT (1952) Evidence of catalytic action in petroleum formation. Ind Eng Chem 44 2570-2577 Brouwer DM, Hogeveen H (1972) Electrophilic substimtions at alkanes and in alkylcaibonium Ions. Prog Phy Org Chem Vol 9 Wiley-Intersdence. 

Electrophilic substitutions at alkanes and in alkylcarbonium ions and the properties of n-alkanes have been reviewed. Barriers to rotation and rota-mer preferences in various acyclic alkanes have been determined. The... 

Adams catalyst, platinum oxide, Pt02 H20. Produced by fusion of H2PtCl6 with sodium nitrate at 500-550 C and leaching of the cooled melt with water. Stable in air, activated by hydrogen. Used as a hydrogenation catalyst for converting alkenes to alkanes at low pressure and temperature. Often used on Si02... 

Under standard conditions of temperature and pressure (STP), the first four members of the alkane series (methane, ethane, propane, and butane) are gases. As length of the carbon increases the density of the compound increases (pentane) to C yHgg are liquids, and from C.,gH3g, the compounds exist as wax-like solids at STP. 

Yin G Z and Nicol M 1985 Photochemistry of naphthalene in alcohol or alkane solutions at high pressures J. Phys. Chem. 89 1171... 

The expense is justified, however, when tackling polymer chains, where reconstruction of an entire chain is expressed as a succession of atomic moves of this kind [121]. The first atom is placed at random the second selected nearby (one bond length away), the third placed near the second, and so on. Each placement of an atom is given a greater chance of success by selecting from multiple locations, as just described. Biasing factors are calculated for the whole multi-atom move, forward and reverse, and used as before in the Metropolis prescription. For fiirther details see [122, 123. 124. 125]. A nice example of this teclmique is the study [126. 127] of the distribution of linear and branched chain alkanes in zeolites. 

For a multicomponent system, it is possible to simulate at constant pressure rather than constant volume, as separation into phases of different compositions is still allowed. The method allows one to study straightforwardly phase equilibria in confined systems such as pores [166]. Configuration-biased MC methods can be used in combination with the Gibbs ensemble. An impressive demonstration of this has been the detennination by Siepmaim et al [167] and Smit et al [168] of liquid-vapour coexistence curves for n-alkane chain molecules as long as 48 atoms. 

The tliird part is tire interaction between tire tenninal functionality, which in tire case of simple alkane chains is a metliyl group (-CH ), and tire ambient. These surface groups are disordered at room temperature as was experimentally shown by helium atom diffraction and infrared studies in tire case of metliyl-tenninated monolayers [122]. The energy connected witli tliis confonnational disorder is of tire order of some kT. 

Methane, CH4, is the first member of this series, all of which have the general formula C H2 + 2- Every carbon atom in any alkane molecule has a tetrahedral eonfiguration and is joined to four other atoms. Alkanes are resistant to attack, at room temperature, by... 

The species produced through ionization of an electron from a ir-orbital (such as from a C-H or a C-C bond of an alkane in mass spectrometry) cannot be represented at all by a connection table, yet the RAMSES notation can account for it as shown in Figure 2-59. 

Table 7.2. Group contributions to Cf, S°, and AHf for ideal gases at 25 °C, 1 atm, for alkanes.

This series expansion is truncated at a specified order and is probably most easily implemei ted within a predictor-corrector type of algorithm, where the higher-order terms are ahead computed. This method has been applied to relatively simple systems such as molecuh fluids [Streett et al. 1978] and alkane chain liquids [Swindoll and Haile 1984]. 

The bond matrix expresses 2 C—C bonds plus 8 C—H bonds for propane and 3 C—C bonds plus 10 C—H bonds for n-butane. Eaeh enthalpy of atomization is obtained by subtraeting the enthalpy of formation of the alkane from the sum of atomie atomization enthalpies (C 716 H 218 kJ mol ) for that moleeule. For example, the moleeular atomization enthalpy of propane is 3(716) +8(218) — (—104) = 3996 kJ mol . Enthalpies of formation are available from Pedley et al. (1986) or on-line at www.webbook.nist.gov. 

The hydrogen atom attached to an alkane molecule vibrates along the bond axis at a frequency of about 3000 cm. What wavelength of electromagnetic radiation is resonant with this vibration What is the frequency in hertz What is the force constant of the C II bond if the alkane is taken to be a stationary mass because of its size and the H atom is assumed to execute simple harmonic motion ... 

Natural gas, depending on its source, contains—besides methane as the main hydrocarbon compound (present usually at >80-90%) — some of the higher homologous alkanes (ethane, propane, butane). In wet gases the amount of C2-C5 alkanes is higher (gas liquids). 

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