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AAPG Bulletin

Abstract


Volume: 30 (1946)

Issue: 1. (January)

First Page: 32

Last Page: 51

Title: Formation of Hydrocarbons from Fatty Acids by Alpha-Particle Bombardment

Author(s): C. W. Sheppard (2), W. L. Whitehead (3)

Abstract:

In the experiments described, four members of the saturated fatty acid series are bombarded by the alpha particles from radon and its active deposit. The energy from the radiation causes principally chemical reaction resulting in formation of carbon dioxide and the paraffine hydrocarbon corresponding with the long chain of the fatty acid bombarded. Minor reactions produce hydrogen, methane, and unidentified material of complex nature. Quantitative studies of the reaction of palmitic acid (C15H31COOH) producing n-pentadecane (C15H32) indicate maximum yield to be one molecule of the hydrocarbon to 56 electron volts expended by the alpha particles in the material.

This efficiency is theoretically low. The explanatory mechanism is simple. All of the molecules of the fatty acid are activated during bombardment to a state of high excitation. Some decompose by rupture of the carboxyl bond and a hydrocarbon is produced. Some lose hydrogen by breaking of a C-H bond in the long chain. A few decompose to give methane or minor products. Decarboxylation is the preferred reaction, but dehydrogenation always takes place.

The source of free saturated fatty acids in marine organisms and sediments is discussed. Few analyses are available, but fatty acids appear to range from 0.2 to 5 per cent of the organic content of marine bottom muds.

On the basis of these figures, the yield of the hydrocarbon during bombardment, and the radioactivity of the Antrim shale in Michigan, calculation is made of the possible contribution to petroleum from hydrocarbons formed from fatty acids by alpha particles in 10 million years. The result, 6.8×10-4 gram of hydrocarbon per gram of sediment or about 208 barrels of crude oil per acre foot of shale, is to be accepted with some caution on account of the assumptions made.

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