Acid-promoted reactions of ethyl linoleate with nitrite ions: Formation and structural characterization of isomeric nitroalkene, nitrohydroxy, and novel 3-nitro-1,5-hexadiene and 1,5-dinitro-1,3-pentadiene products

The reaction of ethyl linoleate (1) with NO2- in different air-equilibrated acidic media resulted in the formation of complex patterns of products, so me of which could be isolated by repeated TLC fractionation and were formul ated as the nitroalkenes 2-5, the novel (1E, 5Z)-3-nitro-1,5-hexadienes 6/7 , the novel (E,E)-1,5-dinitro-1,3-pentadiene derivatives 8 and 9, and the n itro alcohols 10/11 and 12/13 by extensive GC-MS and 2D NMR analysis, as ai ded by 1D Hartmann-Hahn proton mapping experiments. Similar reaction of met hyl oleate gave mainly nitroalkene (14/15) and allylic nitro derivatives (1 6/17). Formation of 2-13 may be envisaged in terms of HNO2-mediated nitrati on pathways in which regioisomeric beta-nitroalkyl radical intermediates de rived from attack of NO2 to the 1,4-pentadiene moiety of 1 evolve through c ompetitive H-atom abstraction and free radical combination routes.