Hydrocarbons expulsion

The rate of hydrocarbon expulsion from mature rich oil-prone source rocks is about 8 x l(>-i to 8 x 10- m m- s-, according to a rough estimate made by England et al. (1987). England et al. s calculations are based on the subsurface conditions given in Table 3.4. 

Under hydrostatic conditions the basin-wide secondary hydrocarbon migration patterns and consequently also the final distribution of the oil and gas accumulations in a sedimentary basin are closely linked to the stable basin geometry present during hydrocarbon expulsion from the source rocks. 

The hydrocarbons expelled from the mature source rocks in separate phase, may initially occur in a very finely dispersed state. At depths corresponding to the peak phase of hydrocarbon expulsion in actively filling and subsiding basins, the hydrodynamic condition is characterized by the intermediate or the deep subsystem of burial-induced groundwater flow. Initially, the very finely dispersed hydrocarbons will move along with the burial-induced groundwater... 

Hinch, H.H. 1980. The nature of shales and the dynamics of hydrocarbon expulsion in the Gulf Coast Tertiary section. Am. Assoc. Pet. Geol. Studies Geol., 10 1-18. 

The central core is predominantly hydrocarbon. The expulsion of the hydrophobic tails of the surfactant molecules from the polar medium is an important driving force behind micellization. The amphipathic molecules aggregate with their hydrocarbon tails pointing together toward the center of the sphere and their polar heads in the water at its surface. 

Mechanism. The mechanism for the formation of the low molecular weight aromatic hydrocarbons, namely ionene and the dimethylnaphthalene compounds can be explained by the scheme of Edmunds and Johnstone (22), advanced by Vetter et al. (35). The mechanism involves cyclizatlon with twelve electron systems followed by rearrangement to a four-ring intermediate, which leads to the formation of di-methycyclodecapentaene. This leads to the expulsion of ionene and dimethylnaphthalene from the carotene molecule as volatiles and the resulting nonvolatile component has been reported (13). 

This mechanism of formation explains the sensitivity of these ions for the positional isomers. Indeed, expulsion of the ketone containing the hydrocarbon chains of the central... 

Bridged polycyclic chlorinated hydrocarbon insecticides include the dimethanonaphthalenes and methanoindenes. Their spectra are dominated by retro Diels-Alder fragmentation reactions which are accompanied, or preceded, by expulsion of Cl and/ or HC 1. A typical dimethanonaphthalene is aldrin, the mass spectrum of which is shown in Fig. 4. The corresponding epoxide of this compound, dieldrin, shows similar features. 

In flg. 3. lb the preference of the hydrophobic tails of the (anionic) surfactant molecules for the oil phase gives rise to the double layer. Such double layers are for instance encountered in some emulsions. They may also occur at the air-water interface then the driving force for their formation is the expulsion of the hydrocarbon tails from the aqueous phase. We speeik of ionized monolayers and return to them in Volume III. 

As mentioned, LiAlH4 in refluxing THF was the initial system introduced to reduce preformed tosyl-hydrazones to hydrocarbons and a number of successful conversions have been reported, representative examples of which are presented in Table 5. Alkene side products often accompany the hydrocarbon products,a result attributed to proton abstraction from the a-carbon of intermediate (59), leading to a vinyldiimide anion (64), followed by N2 expulsion and protonation during work-up (Scheme 3). With certain ketones, including 17-keto steroids, alkenes are the major s or sole product (entries 7-9, Table 5). This side reaction mimics the elimination obtained upon treatment of to-sylhydrazones with other strong bases (i.e. alkyllithiums, the Shapiro reaction 29). Note that use of LiAlD4 introduces one deuterium (with H2O work-up) or two deuteriums (with D2O work-up entries 5 and 6, Table 5, respectively). 

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