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Alkane dispersion forces

The technique of IGC may be employed to obtain acid-base information, as suggested by Schultz and Lavielle [99], by using acid and base probe gases on a solid for which the alkane line has already been obtained. If acid-base interaction is involved in the adsorption, the retention volume should be greater than that corresponding to the dispersion force interaction alone, which should be the same as that of the equivalent alkane , i.e. the hypothetical alkane for which the value... [Pg.42]

Boiling Point. When describing the effect of alkane structure on boiling point in Section 2.17, we pointed out that van der Waals attractive forces between neutral molecules are of three types. The first two involve induced dipoles and are often refened to as dispersion forces, or London forces. [Pg.147]

Another interesting effect seen in alkanes is that increased branching lowers an alkane s boiling point. Thus, pentane has no branches and boils at 36.1 3C, isopentane (2-methylbutane) has one branch and boils at 27.85 °C, and neopentane (2,2-dimethylpropane) has two branches and boils at 9.5 °C. Similarly, octane boils at 125.7 °C, whereas isooctane (2,2,4-trimethylpentane) boils at 99.3 °C. Branched-chain alkanes are lower-boiling because they are more nearly spherical than straight-chain alkanes, have smaller surface areas, and consequently have smaller dispersion forces. [Pg.92]

Disaccharide, 997-999 1—>4 link in, 997-998 synthesis of, 1002 Dispersion forces, 62 alkanes and, 92 Disrotatory motion. 1183 Distortionless enhancement by... [Pg.1294]

Dispersion forces, dipole Interactions, and hydrogen bonds all are significantly weaker than covalent Intramolecular bonds. For example, the average C—C bond energy Is 345 kJ/mol, whereas dispersion forces are just 0.1 to 5 kJ/mol for small alkanes such as propane. Dipolar Interactions between polar molecules such as ace-tone range between 5 and 20 kJ/mol, and hydrogen bonds range between 5 and 50 kJ/mol. [Pg.769]

Note that although it may be possible for metal atoms to form a cr-complex with an alkane prior to insertion into a C-H bond, such complexes would be bound by only a few kcal/mol (comparable to dispersion forces), while metal-alkene 7r-complexes are typically bound by 20-60 kcal/mol. [Pg.277]

Fowkes, F.M. Surface effects of anisotropic London dispersion forces in n-alkanes, J. Phys. Chem., 84(5) 510-512, 1980. [Pg.1657]

The extent to which surface tension can be controlled by fluoroalkyl-containing coupling agent type treatments is summarized in Table 1. Its purpose is to simply illustrate the range of control possible detailed comparisons are unwarranted because of differences in sample preparation and choice of substrate, data acquisition and treatment. Some of the critical surface tensions (crc) are obtained with -alkanes, some with other liquids. Some of the dispersion force components (of) and polar components (of) of solid surface tension are derived by use of different equations. The reader is referred to the key references in Table 1 for full details. [Pg.68]

A. Alkanes are composed entirely of non-polar C-C and C-H bonds, resulting in no dipole interactions or hydrogen bonding. London dispersion forces increase with the size of the molecule, resulting in a higher temperature requirement to break these bonds and a higher boiling point. [Pg.273]

In the case of alkane cracking, dispersion forces between the alkane molecules and the siliceous walls of the zeolites and perhaps other nanoporous crystalline and ordered materials are possibly the most important interactions for stabilizing adsorption in the cavities, since the proton affinity of alkanes is low [104] and the electrostatic interactions between the alkane and the adsorbent are negligible [97],... [Pg.436]

Dispersion forces cannot be explained by the magnetic analogy nor by conventional electrostatics. They are weak forces that exist even in mon-oatomic gases that are symmetrical and nonpolar. It is believed that at any particular instant this symmetry is somewhat distorted due to the motion (and position) of the electrons of a given atom, which produces a momentary polarity. This momentary polarity can attract and be attracted by a similar polarity in a neighboring atom or molecule in such a way as to produce a net attraction. As we have already seen, such inductions depend on the polarizability of the molecule or atom. Dispersion forces will always be possible between molecules, but they are the only forces between nonpolar hydrocarbons such as the alkanes. For this reason alkanes are often chosen as the ideal molecules for study or for use as standards. An example of a chromatographic separation in which the only forces are dispersion forces would be the GC separation of alkanes on squalane, a branched paraffin. [Pg.30]

In the case where Li is formamide (subscript F) and liquid L2 is n-alkanes (H), the term yFp may be neglected since the surface free energy of n-alkanes consists of only the London dispersive force, as seen in Table 3. Therefore, we may rewrite Eq. (38) as... [Pg.399]

Experimental values indicate that hydration is enthalpically favored, even for hydrocarbons (see Table 4-1). For these compounds, the hydration enthalpy must be ascribed to the dispersion forces between alkanes and water molecules, which do... [Pg.108]

Since the alkanes considered are practically non-polar molecules, the interaction between any of them and the zeolite structure wiU be dominated by dispersions forces, which are known to decrease rapidly with distance. For the linear alkanes the first molecule does prefer to stay at the straight channels. However, as one increases the loading they tend to equally, occupy the sinusoidal channels where they will more strongly interact with the zeolite framework thus increasing the adsorption energy. Of course, for the... [Pg.54]

Schreiner, P. R. Chemish, L. V. Gunchenko, P. A. Tikhonchuk, E. Y Hausmann, H. Serafin, M. Schlecht, S. Dahl, J. E. R Carlson, R. M. K. Fokin, A. A. Overcoming lability of extremely long alkane carbon-carbon bonds through dispersion forces, Nature 2011,477, 308-311. [Pg.185]

Equation [2.5.43] is of course oversimplified, both in method (by using continuum theory for a layer that is only a few molecules thick) and in interpretation (the entropy is neglected, only dispersion forces are counted, so the model is restricted to liquid noble gases, simple alkanes, etc.). The equation can be compau ed with [2.5.35] with the interesting physical difference that in [2.5.35] the Helmholtz energy is seen as the driving force whereas [2.5.43] is purely energetie. These two are of course coupled. [Pg.158]

The organic molecules or "probes used to investigate the dispersive surface energies of the fiber surfaces were a series of n-alkanes. The probes used to study the non dispersive forces were chosen based on their acidic or basic character as determined by Gutmann (8). Gutmann has practically defined basicity as the donor number, DN, or electron-donor capability in the Lewis sense. The donor scale is based on the value of the molar enthalpy for the reaction of the electron donor with a reference acceptor, SbCl. ... [Pg.219]

For adsorption of nonpolar (alkane) probes involving purely dispersive forces, the work of adhesion is given by ... [Pg.332]


See other pages where Alkane dispersion forces is mentioned: [Pg.1103]    [Pg.35]    [Pg.92]    [Pg.582]    [Pg.760]    [Pg.913]    [Pg.1372]    [Pg.21]    [Pg.243]    [Pg.27]    [Pg.147]    [Pg.21]    [Pg.371]    [Pg.48]    [Pg.69]    [Pg.887]    [Pg.18]    [Pg.406]    [Pg.170]    [Pg.52]    [Pg.71]    [Pg.92]    [Pg.53]    [Pg.278]    [Pg.92]    [Pg.175]    [Pg.181]    [Pg.243]   
See also in sourсe #XX -- [ Pg.60 , Pg.90 ]

See also in sourсe #XX -- [ Pg.61 , Pg.93 ]




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Dispersion force

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