Structure of 2-methoxy-3,5-dinitropyridine

2-Methoxy-3,5-dinitropyridine, C6N3O5H5, crystallizes in the monoclinic system, space group P21/n, with cell parameters a = 7.496(5), b = 18.38(1), c = 6.068(2) A, β = 77.18(4)°, V = 815(1) A3, and four molecules per unit cell. Its structure was solved by direct methods and refined by least-squares procedures to a final R = 4.99%, Rw = 5.42%, for 753 observed independent reflections. The molecule is not planar, a rotation of the methoxy and 3-nitro groups out of the pyridine ring (7° and 16°, respectively) is observed. The methoxy group is located syn to the ring nitrogen atom to avoid repulsion with the 3-NO2 group and adopts a geometry different from the mean reported in the literature for methoxyaromatic groups. Geometrical parameters suggested by Domenicano and Murray-Rust and Norrestam and Schepper are used to analyze substituent effects on the pyridine shape and the possible causes of non-additivity of substituent effects are discussed. The relation of molecular conformation with reactivity of the t...