Spectrochimica Acta Part A 79 (2011) 1493–1498 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy j ourna l ho me page: www.elsevier.com/locate/saa Experimental and theoretical assessment of the mechanism involved in the reaction of steroidal ketone semicarbazone with hydrogen peroxide Kamlesh Sharma a , Shivani B. Mishra b , Ajay K. Mishra b,∗ a Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, PO Wits, 2050, South Africa b Department of Chemical Technology, University of Johannesburg, P.O. Box 17011, Doornfontein 2028, South Africa a r t i c l e i n f o Article history: Received 18 February 2011 Received in revised form 30 April 2011 Accepted 5 May 2011 Keywords: Steroidal triazolidinone Stereoselective synthesis Density functional theory Frontier molecular orbital Free radical reaction mechanism a b s t r a c t 3-Acetoxy-5-cholestan-6-one semicarbazone 1 on reaction with hydrogen peroxide affords selectively 3-acetoxy-5-cholestan-6-spiro-1 ′ ,2 ′ ,4 ′ -triazolidine-3 ′ -one 2. The structural assignment of the product was confirmed by spectral data and elemental analysis. A free radical mechanism of the present reaction was described successfully by calculating theoretical models of 1, A, B and 2, using DFT with B3LYP/6-31G* basis set. It was found that the reaction undergoes through the formation of two radical intermediates and the only one isomer of the product in which –NH–CO– group is cis with respect C5-H, was selectively obtained. Frontier molecular orbital, spin electronic density, electrostatic potential and atomic charges were discussed. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The establishment of an efficient method for synthesizing tria- zolidinones, the nitrogen-containing heterocyclic compounds has received great attention for drug design in the development of pharmaceutical and agricultural field. It has been reported that triazolidinone has the ability to increase the yield of the plant food, which is contained in the plant storage organs like potatoes [1]. It is also reported that triazolidinone does activate the human adrenergic receptor [2]. Krenzer has emphasized on synthesis and herbicidal activities of different type of triazolidinone [3,4]. Var- ious research workers have adopted different approach towards the synthesis and structural determination of triazolidinones [5–9]. However, Schantl and Gstach have reported the synthesis of tria- zolidinone from arylazoalkylisocynate using Grignard reagent via nucleophilic addition [10]. In recent years, density functional theory (DFT) has become a shooting star in molecular quantum mechanics for explaining the reaction mechanisms. The main idea of DFT is to describe an interacting system of fermions via its density and not via its many- body wave function. Thus the development of better and better exchange-correlation functional made it possible to calculate many molecular properties with comparable accuracies to traditional correlated DFT methods, with more favorable computational costs [11]. According to the literature, it has been proved that DFT has ∗ Corresponding author. Tel.: +27 11 5596180; fax: +27 11 5596425. E-mail address: amishra@uj.ac.za (A.K. Mishra). a great accuracy in reproducing experimental data of molecular structural properties, IR frequencies, intensities, etc. [12–14]. In continuation of our previous work on synthesis and theo- retical investigation [15–19] of biologically interesting steroidal compounds, herein we present a novel and convenient method of formation of steroidal spiro-triazolidinone. Its structure is estab- lished by physical, elemental, spectral and computational data. A free radical reaction mechanism of the present reaction is also described implying the density functional theory. 2. Materials and methods 2.1. General The IR (KBr) spectrum recorded on a Perkin-Elmer 782 infrared spectrophotometer. 1 H NMR spectra was recorded on a Bruker BZH- 200 instrument. Chemical shifts are reported in parts per million downfield from tetramethylsilane. Multiplicities of proton reso- nance were designated as singlet (s) and multiplet (m). Melting point reported is uncorrected. Chloroform and hydrogen perox- ide were purchased from the Aldrich Chemical Company. Light petroleum ether and ethyl acetate were supplied by Merck. 3. 3-Acetoxy-5-cholestan-6-spiro-1 ′ ,2 ′ ,4 ′ -triazolidine- 3 ′ -one 2 The solution of 3-acetoxy-5-cholestan-6-one semicarbazone 1 [20] (1.05 g, 2.10 mmol) in chloroform (25 mL) was treated with 1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2011.05.005