ASIAN JOURNAL OF CHEMISTRY ASIAN JOURNAL OF CHEMISTRY http://dx.doi.org/10.14233/ajchem.2015.19075 INTRODUCTION Azomethines are generally known as Schiff bases to honour Hugo Schiff, who synthesized such compounds. These are the compounds containing characteristic -C=N- group. Several methods have been reported for the preparation of azomethines. Selvam et al. 1 have prepared sulfonamide and its derivatives as anti-HIV agents. More et al. 2 have marked the biological activity of Schiff bases synthesized from aminothiazoles. The field of Schiff bases has been fast developing on account of the wide variety of possible structures for the compounds depending upon the aldehydes and amines. Schiff bases are considered as a very important class of organic compounds, which have wide appli- cations in many biological aspects 3 . Schiff bases have been widely used as compounds because of high stability of the coordination compounds of them 4 . The π-system in a Schiff-base often imposes a geometrical cons- triction and affects the electronic structure as well 5 . Electronic structure methods provide useful information on the molecular structure and charge distribution, so they are useful to under- stand and describe systems where electronic effects and mole- cular orbital interactions are dominant. Depending on the theoretical assumptions used for calculations, electronic struc- tural was carried out using density functional theory/B3LYP 6-31G base method. Our aim in this work is to give a deeper insight into the best structure effect on the stability of salicylidene-2,4- diaminophenol and to compare predictions made from theore- tical observations using DFT calculations. Synthesis and Theoretical Studies of Salicylidene-2,4-diaminophenol RASHED TALEB RASHEED Applied Chemistry Division, Applied Sciences Department, University of Technology, Baghdad, Iraq Corresponding author: E-mail: r_awsy@yahoo.com Received: 3 February 2015; Accepted: 23 March 2015; Published online: 16 July 2015; AJC-17397 Schiff-base isomers derived from salicylaldehyde and 2,4-diaminophenol has been synthesized and characterized by FTIR and UV- visible spectroscopy. Theoretical calculations of Schiff-base were studied by quantum chemical calculations. The optimized structure of Schiff-base was obtained by density functional theory at B3LYP/6-31G level. Also total energy, heats of formation, dipole moment, point group, molecular orbital’s energy of HOMO and LUMO, energy gaps (Eg) and ΔG reaction were calculated and here we suggested the better Schiff base structure may be form. According to theoretical study and based on the results of density function theory (DFT), L3 possesses higher stability state compared with other isomers studied. Keywords: Synthesis, Salicylaldehyde-2,4-diaminophenol. Asian Journal of Chemistry; Vol. 27, No. 11 (2015), 4037-4039 EXPERIMENTAL Absolute ethanol, salicylaldehyde (B.D.H Company), 2,4- diaminophenol dihydrochloride from (Fluka Company). Physical measurements, FTIR-8400S Shimadzu in the range of 4000-200 cm -1 . Absorption Spectra in absolute ethanol with the concentration of (1 × 10 -5 ) M were determined on a UV- VIS-1650 PC Shimadzu spectrophotometer, at wavelength (200-1100) nm at 25 °C. Synthesis of Schiff base compound: Salicylaldehyde (1.22 g, 10 mmol) and 2,4-diaminophenol dihydrochloride (1.97 g, 10 mmol) were separately dissolved in 25 mL ethanol absolute. The two solutions were mixed and refluxed for 2 h on a hot plate magnetic stirred (Scheme-I). The condensation product was filtered, washed with cold ethanol and recrysta- llized with ethanol, dried in oven to 2 h at 110 °C. Schiff base was characterized by FTIR and UV/visible spectra. Computational methods: Theoretical calculations were done using the density functional theory (DFT) method imple- mented in the Gaussian 03 suite of programs 6 with the B3LYP functional using the 6-31G base set 7,8 . DFT/B3LYP combina- tion is known to produce good estimate of molecular properties related to molecular reactivity 9 . RESULTS AND DISCUSSION In this paper, we describe the synthesis of Schiff base in good yield. The compound is stable at room temperature and is non-hygroscopic. UV/visible spectra of Schiff base