Abstract Stereochemistry of (E)-and (Z)-1-(5-nitro-2-furyl)-2-Y-ethylenes and 1-(5-nitro-2- thienyl)-2-Y-ethylenes (where Y= CH 3 O, 4-CH 3 C 6 H 4 O, N 3 and Br) and of E and Z isomers of methyl 2-methyl-3-(2-furyl) propenoate and methyl 2-methyl-3-(2-thienyl) propenoate was studied by 1 H NMR spectroscopy. With 1-(5-nitro-2-furyl)-2-Y-ethylenes, it was found that the preferred conformation of the furyl substituent relative to the side chain ...