High Molecular Weight N-alkanes Research Articles

Adsorption of crude oil on arctic terrain

Arctic terrain was divided into three layers, moss, detritus and clay, and each layer was contacted with Norman Wells crude oil. Chromatographic analysis of the crude oil extracts of the terrain layers showed that the adsorption capacity of the terrain increased with increasing organic content. The higher molecular weight n-alkanes were adsorbed to a greater extent than lower n-alkanes on the moss and detritus layers. Of the aromatics, p-xylene was adsorbed to a greater extent than benzene on all three layers of the terrain. Retention of crude oil components on Arctic terrain in the event of an oil spill would be in accord with these findings.

Reaction of ethoxycarbonylcarbene with n-hexadecane and n-docosane

The reaction of both thermally and photolytically generated ethoxycarbonylcarbene with high molecular weight n-alkanes (> C10) gives the expected C–H bond insertion products, e.g., ethyl esters of isomeric C18 acids in the case of n-hexadecane. The thermally generated species gave much higher yields, up to 75% based on the carbene precursor, ethyl diazoacetate; possible explanations are discussed. A novel variation in reactivity of the carbene towards the secondary positions of an n-alkane has been observed. In the photolyses, the relative rate of insertion of ethoxycarbonylcarbene for secondary C–H:primary C–H was found to be 2·1 at position 2, steadily falling to ca. 1·4 at the secondary positions in the middle of the chain. Similar trends were noted in thermal reactions. Other products of the reactions are described.

Kinetics of Crystal Nucleation in Some Normal Alkane Liquids

The crystal nucleation behavior of some normal alkane liquids—C16H34, C17H36, C18H38, C24H50, and C32H66—was investigated by the droplet technique. The relative undercoolings, 1—λ, (i.e., the actual undercooling in units of the absolute melting temperature) at which the crystal nucleation frequency in these liquids becomes 107 cm—3 sec—1 are 0.037 to 0.043, and almost an order of magnitude smaller than those for simple molecular substances. Crystal nucleation frequencies in droplets of C17H36 and C18H38 samples of very high purity were determined quantitatively. The frequencies were proportional to droplet volume and increased by a factor of 5000 to 8000 per 1° decrease in temperature. The results are satisfactorily described by the classical nucleation theory with values of the crystal nucleus - liquid interfacial tension σ, 7.2 erg-cm—2 for C17H36 and 9.6 erg-cm—2 for C18H38. The experimental pre-exponential factors in the nucleation expression agree with the theoretical values to well within the experimental uncertainty. The small relative undercooling and the weak glass-forming tendency in the high-molecular weight n-alkane liquids is satisfactorily explained by the hypothesis of nucleation of small segments of molecules.