An X-ray single crystal study of C-(4-methoxy-1-vinyl)-N-phenyl nitron (1) and C-(4-methoxy-1-vinyl)-N-bromphenyl nitron (2) was undertaken. The main crystal data : (1) : C16H15NO2, a = 8.402(5) Angstrom, b = 5.408(3) Angstrom, c = 14.554(7) Angstrom, beta = 93.1(2)degrees, d(cal.) = 1.273 g/cm(3), V-cal. = 660.3 (2) Angstrom(3), Z = 2, SP. gr. Pc. M = 253.32 : (2) : C16H14NO2Br, a = 17.586(6) Angstrom, b = 14.543(5) Angstrom, c = 5.632(4) Angstrom, alpha = 89.8(2)degrees, beta = 90.8(2)degrees, gamma = 98.9(2)degrees, d(cal.) = 1.554 g/cm(3), V-cal. = 1423.0(2) Angstrom, Z = 4, Sp. gr. , M = 332.21 Compound 2, as distinct from 1, crystallizes in the form of two independent molecules. Molecules of 1 and 2 are nonplanar and have similar conformations. The photoconversion connected with the closing of the oxaziridine heterocycle was computer simulated and its possibility proved for crystals of 1 and 2 using the calculation of the unit cell free volume portion and the difference in the volumes of the initial and final molecules.