Petroleum crude, alkane characterization

Several methodologies can be used to identify not only crude or refined product type, but also the brand, grade, and, in some instances, the source crude. The petroleum industry has yielded conventional methods for the characterization of refined products. The simplest is the routine determination of API gravity and development of distillation curves where NAPL is present. More sophisticated methods include gas chromatography and statistical comparisons of the distribution of paraffinic or n-alkane compounds between certain C-ranges. With increased degradation and decomposition, the straight-chain hydrocarbons ( -alkanes) become less... 

Advances in petroleum characterization at the molecular structure level by GC-MS methods renewed interest in OSC. Within the past few years, at least one-thousand new and novel OSC that previously were not known to be present in petroleum and bitumens have been reported. Tentative molecular structures inferred from GC-MS and other techniques have been confirmed in many cases by synthesis of authentic reference-compounds. The difficult and time-consuming synthetic work has been crucial in validating many of the novel structures. Another key finding has been that immature bitumens and crude oils (samples that have not received significant thermal stress) differ markedly from the previously known OSC in that they have carbon-skeletons resembling ubiquitous biomarker hydrocarbons (e.g., n-alkanes, isoprenoid alkanes, steranes, and hopanes). This similarity, of course, suggests that the hydrocarbons and OSC have common biogenic precursors. 

To a solution of alkene (1 2.0 mmol) and the nucleophilic additive (10 nunol) in acetonitrile (12 mL) were added (diacetoxyiodo)benzene (DAIB 3.0 nunol), and iodine (1.5 mmol) in one portion, and the mixture was stirred at room temperature for 2 h for completion. The reaction mixture was then poured in water (40 mL) and extracted with dichloromethane (2 x 30 mL), followed by decolorizing the reaction mixture with the addition of required amount of solid NaHSOa. The combined organic extract was then dried over anhydrous magnesium sulfate and evaporated to yield the crude product, which was purified by colunm chromatography (petroleum ether/dichloromethane) on silica to afford iodo-alkane 2. Each of the products was characterized by spectral studies. 

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