An open chain compound was obtained by reaction of benzil with thiocarbohy-drazide in acidic condition. Its derivative, namely, benzil bis-(5-isopropylidene-3-thiocarbohydrazone) has been structurally characterized by X-ray single crystal diffraction method. Crystallographic data: C22H26N8S2, Mr=466.62, monoclinic, space group C2/c, a=12.215(3), b=11.473(2), c=17.032 (3)A, B=98.96(2)0, V=2357.7(9)A3, Z=4, Dc=1.32 g/cm3, F(000)=1040, u(Mo Ka)=2.43 cm-1. Final R=0.050, Rw=0.061 for 1103 unique and observed reflections with I> 3o(I). The effect of the structures on the formation of the open-chain intermediates during the cyclization of (2:2) Schiff base macrocyclic compound has been discussed and a possible mechanism for the ring closure has been suggested. An open chain compound was obtained by reaction of benzil with thiocarbohy-drazide in acidic condition. Its derivative, namely, 5-isopropylidene-3-thiocarbohydrazone has been structurally characterized by X-ray single crystal diffraction method. Crystallographic data : C22H26N8S2, Mr = 466.62, monoclinic, space group C2 / c, a = 12.215 (3), b = 11.473 (2), c = 17.032 (3) A, B = 98.96 (2) 0, V = 2357.7 ) A3 Z = 4, Dc = 1.32 g / cm3, F (000) = 1040, u (Mo Ka) = 2.43 cm -1 Final R = 0.050, Rw = 0.061 for 1103 unique and observed reflections with I> 3o (I). The effect of the structures on the formation of the open-chain intermediates during the cyclization of (2: 2) Schiff base macrocyclic compound has been discussed and a possible mechanism for the ring closure has been suggested.