nitrogen-dioxide and methyl-linoleate

The reaction of methyl linoleate with low levels of nitrogen dioxide in a carrier gas, such as helium or air, at nitrogen dioxide concentrations ranging from 2 to 228 ppm was studied and the products formed were monitored. In both aerobic and anaerobic conditions, low concentrations of nitrogen dioxide reacted with methyl linoleate predominantly to form allylic products. When a 1:1 mixture of methyl palmitate/methyl linoleate was layered over an aqueous buffer and a nitrogen dioxide stream was passed from underneath, so that the stream passed through the aqueous layer before contacting the organic layer, allylic products again predominated. In the absence of air, the allylic products consisted of allylic nitro and nitrite, derivatives of linoleate, whereas in the presence of air, allylic hydroperoxides were the principal products. The findings suggest that fatty acids with doubly allylic hydrogen atoms react preferentially by a hydrogen atom abstraction reaction rather than by the addition of nitrogen dioxide to a double bond.

Topics: Fatty Acids; Linoleic Acids; Nitrogen Dioxide; Oxygen

The autoxidation of polyunsaturated fatty acids is initiated both in vivo and in vitro by nitrogen dioxide. The mechanism of the initiation process is believed to involve both addition reactions and hydrogen atom abstraction reactions, with hydrogen abstraction predominating at low levels of nitrogen dioxide. Therefore low levels of nitrogen dioxide should react with polyunsaturated fatty acids to give allylic derivatives; in an anaerobic system these derivations should be allylic nitro and nitrite compounds. Using negative methane chemical ionization mass spectrometry and other analytical techniques, we have identified these allylic nitrite and nitro compounds from the reactions of low levels of nitrogen dioxide with methyl linoleate and methyl linolenate in the absence of oxygen.

Topics: Chromatography, High Pressure Liquid; Linoleic Acids; Linolenic Acids; Magnetic Resonance Spectroscopy; Mass Spectrometry; Molecular Structure; Nitrites; Nitro Compounds; Nitrogen Dioxide; Oxidation-Reduction; Spectrophotometry, Infrared; Spectrophotometry, Ultraviolet

We showed previously that exposure of mice to atmospheric nitrogen dioxide (NO2) leads to the formation of an ether-extractable nitrosating agent (NSA) in the skin, which produced N-nitrosomorpholine (NMOR) from morpholine in vitro but not in vivo (under our conditions). We now report that NO2 bubbled into hexane solutions of methyl linoleate (MLIN) produced a similar NSA that reacted with morpholine in dichloromethane solution to produce NMOR. The NSA yield increased sharply as MLIN concentration was raised, with a maximum 0.1% yield of NSA from MLIN. The NSA yield from MLIN was four times that from methyl oleate and seven times that from methyl stearate. The NSA derived from MLIN travelled on thin-layer chromatography more slowly than the main weight fraction; whereas TLC of NSA in the skin lipids of NO2-exposed mice and in untreated mouse skin lipids exposed in vitro to NO2 produced NSA that travelled more rapidly than the main weight fraction.

Topics: Air; Animals; Chemical Phenomena; Chemistry; Chromatography, Thin Layer; Linoleic Acids; Lipids; Mice; Nitrogen Dioxide; Nitrosamines; Skin