RESEARCH In the gas phase, a parallel reaction complicates the picture. This other reaction gives an equilibrium mixture of both cis- una fmitx-I-bromo-l-propenes. The cis- and trans-1 -hromu-1 -propenes are distinguished via their infrared spectra and by their retention times in vapor phase chromatography. Liquid phase reactions, Skell says, are d o n e in a vacuum line using cquimolar amounts of propine and HBr. Reaetants are irradiated with ultraviolet light at —78° to —60° C. In gas phase reactions, conditions that avoid condensation of product are used. Results in the liquid phase can b e explained by one of these mechanisms, Skell explains. First is that a bromine atom makes a stable cf.s-radical. Or, the reaction occurs when a bromine radical adds to a pro^ine-HBr complex, closely followed by transfer of the iydrogen atom. Still another possibility is that the reaction is termolecular—between propine, HBr, and a bromine radical. The scientists hoped that gas phase experiments would pinpoint the right mechanism. But the gas phase product isomerizes too rapidly and no definite conclusion could b e reached. Further work in the propine and other acetylenic systems is under way. Simple olefins also add HBr in a stereospeciRc trans process, as shown by experiments with deuterium bromide and 2-butenes. Skell says that cis-2butene is converted to pure threo-3deutero-2-bromobutane, while trans2-butene gives the pure cry thro isomer.
New Light on Oil Convincing evidence suggests that oil started from physical rather than chemic a l process
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NATIONAL cussed origin of MEETING petroleum again Petroleum came to the fore Chemistry in a Symposium on the Chemical Aspects of the Origin, Migration, u:id Accumulation of Oil, sponsored by the Division of Petroleum Chemistry. 54
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But some of t h e work descriticd by symposium speakers points up the probably physical origin rather than chemical—and independently conducted work supplements and supports the physical concept. Improved analytical instruments and techniques are playing a key role in unravelling the secret of petroleum*" origin. Warren G. Meinschein, Vlagnolia Petroleum, has employed high molecular weight mass spectrometry and recording infrared, visual, and ultraviolet spectrometers to obtain more knowledge of the composition of the naturally occurring hydrocarbons. He concludes that the hydrocarbons found in recent sediment soils, marine sediments, and crude oils are similar to each other and are closely related to compounds farmed in plants and animals. However, the principal differences between the sediment and petroleum hydrocarbons are distributional or physical rather than chemical, and it is this fact that strongly suggests that the conversion of sediment hydrocarbons to petroleum is accomplished primarily by physical processes. Meinschein finds that crudes and sediments contain hydrocarbon arrangements resembling those found in bile acids, sex hormones and cholesterol. Too, h e notes that normal paraffins arc distributed about like they are in plants and insect waxes. On the other band, he finds that t h e more abundant plant and animal material, such as cellulose, lignin, carbohydrates, and proteins, are not similar to the hydrocarbons found in sediments and do not appear t o be important sources of petroleum. He concludes that sediment hydrocarbons represent an intermediate stage in petroleum formation. However, since the sediment hydrocarbons are so closely related to those in oil, he believes that petroleum is probably formed by physical rather than chemical means. • Missing Link. The question is: How are these ^ hydrocarbons flushed from the sediment clays? Their solubility in water is not sufficient to explain the migration. An insight into what the physical process might be comes from the research of Edward G. Baker, Esso Research and Engineering. This work suggests that crude oil originates when the sedimentary basin compacts and
sedinient hydrocarbons dissolve in waters containing natural solubilizers and then come ont of solution as oil droplets. Research at the Esso labs shows the relationship between crude oil composition and individual hydrocarbon solubilities in dilute colloidal electrolyte solutions, supporting the migration-in-aqiieous-solution mechanism. Aqueous solutions of colloidal electrolytes o r soaps solubilize hydrocarbons, but t h e details are not understood. However, with high enough concentration and temperature, the molecules of a colloidal electrolyte will spontaneously associate in water to form micelles. Whatever the detailed structure of the micelles may be, they possess an interior that bears some resemblance to a liquid hydrocarbon. It is for this reason that, when an aqueous soap solution is placed in contact with hydrocarbons, the hydrocarbons can dissolve in the interior of the soap micelle, as well as in the water itself. This leads to greater solubilities than would otherwise be obtained. Baker investigated the effects of several organic soaps, including sodium laurate, stéarate and naphthenate, all of which occur naturally in the earth. With these solubilizers, various hydrocarbons were soluble in water about in t h e proportions in which they are found in crude oil. T h e work also may explain the variation in crude oils. If all crude deposits collected from ordinary water, they should all have the same composition—but they don't. Although the distribution of individual homologs is similar from one oil to the next, crude oils differ in the extent to which the different classes of hydrocarbons occur. T h e studies of hydrocarbon solubilities in dilute colloidal electrolyte solutions suggest that the predominant hydrocarbon in a crude varies simply because t h e types of electrolytes that were available to solubilize the sediment hydrocarbon varied. Taken together, Meinschein's a n d Baker's work suggests that sediments composed of decayed organic matter are compacted into hard rock or clay under great pressure and temperature. As the sediment compacts more, t h e water-soap-hydrocarbon emulsion is squeezed from the clay to more permeable soil. T h e mixture then migrates through t h e soil and the oil drops b e hind to form oil beds or reservoirs.
