Homologous Series Of N-alkanes Research Articles

Enthalpies of immersion of bare and precovered graphon in a homologous series of n-alkanes

A rapid rise in the enthalpy of immersion (298 K) of Graphon in liquid n-alkanes is interpreted as arising from increasing cooperative structuring of the adjacent liquid, induced by the solid surface, in a manner reminiscent of solidification. For longer chain lengths the process may be aided by a good lattice fit of the alkane chain on the hexagonal graphitic basal planes. For both n-hexane and n-octane good agreement was found between measured enthalpies of immersion at various precoverages and those predicted from the isosteric enthalpies of adsorption.

Saturated hydrocarbons in bovine liver.

A homologous series of n-alkanes (C(14)-C(33)) and two isoprenoid hydrocarbons, 2,6,10,14-tetramethylhexadecane (phytane) and 2,6,10,14-tetramethylpentadecane (pristane) have been identified in bovine liver. Another branched but non-isoprenoid alkane and three isomers of molecular formula C(20)H(40) were partially identified. Phytane and the C(18)-C(22) and C(29)-C(33)n-alkanes were found to be the major components in liver, suggesting that at least the main hydrocarbon components were derived from various plants in the diet. The hydrocarbons were separated and identified by a series of steps involving solvent extraction, saponification, elution chromatography on alumina and silica gel columns, molecular sieving and by infrared and ultraviolet spectroscopy, followed by combined capillary gas chromatography-mass spectrometry.

Heats of Immersion of ‘Graphon’ in Homologous Series of n-Alkanes and n-Alkanols

At a given temperature, the heats of immersion of ‘Graphon’ in individual members of a series of n-alkanes (hexane to hexadecane) show a remarkable increase with increasing chain length. This effect, first noted by Robert1, has since been independently confirmed by Everett2 and also in our own laboratories. We have also found that the heat of immersion of ‘Graphon’ in n-alkanes of longer chain length is very dependent on temperature.

Hydrocarbons from human meninges and meningiomas

A lipid fraction more non-polar than sterol ester was isolated in the analysis of lipid extracts from a comparative study of normal brain meninges (dura mater) and neoplastic tissue (meningiomas) from human brain. This fraction was analyzed by thin-layer chromatography and gas-liquid chromatography and found to consist of hydrocarbons. The principal component was an homologous series of n-alkanes (C 15-C 34). Also indicated were squalene and in minor proportions two additional homologous series of alkanes. The hydrocarbon fractions of meninges and meningiomas contained the same components, but in different proportions.

Surface properties of perfluoro acids as affected by terminal branching and chlorine substitution

Abstract : When an otherwise fully fluorinated carboxylic acid molecule was altered by terminal branching and terminal chlorine atom substitution, significant increases resulted in the wettability of its adsorbed monolayer. Two new homologous series of acids (CF3)2CF(CF2)nCOOH and CF2C1(CF3)CF(CF2)nCOOH, where n ranged from 11 to 1 and 9 to 1, respectively, were adsorbed as condensed monolayers on highly polished clean disks of chromium and platinum. The critical surface tension of wetting (gamma sub c) of each resulting surface was determined by contact angle measurements on homologous series of n-alkanes, open-chain polydimethylsiloxanes, and miscellaneous other liquids. In every case the wettability, expressed as gamma sub c, was increased by branching or by terminal chlorine substitution. Thus, in the series (CF3)2CF(CF2)nCOOH, gamma sub c on chromium ranged from 13.3 dynes/cm (when n = 11) to a maximum of 15.2 (when n = 1), whereas in the series CF2 C1(CF3)CF(CF2)nCOOH, gamma sub c ranged from 17.2 (when n = 9) to around 20 (when n = 1).9 These results are excellent examples of the effect on gamma sub c on substituting one terminal chlorine atom in the surface for a fluorine atom. For a given acid monolayer, almost the same gamma sub c values were obtained on each of the two metals except that gamma sub c became larger on platinum than on chromium when the acid was a lower homolog in each series. The causes of this divergence relate to a smaller adsorption site spacing and the consequent tighter molecular packing and better chain adlineation of the adsorbed compound on chromium. (Author)