Synthesis and characterization of Schiff's bases of sulfamethoxazole
© Hussain et al.; licensee Springer. 2014
Received: 5 January 2014
Accepted: 18 February 2014
Published: 28 February 2014
Schiff's bases are excellent ligands which are synthesized from the condensation of primary amines with carbonyl groups.
The classical reaction for the synthesis of Schiff's bases in an ethanolic solution and glacial acetic acid as a catalyst was followed in the synthesis of substituted sulfamethoxazole compounds.
Some Schiff's bases containing sulfamethoxazole nucleus have been synthesized and characterized. The present compounds are hoped to be applied in the photostability of PVC.
Schiff's bases are an important class of organic compounds . They were first reported by Hugo Schiff in 1864 . Schiff's bases are condensation products of primary amines with carbonyl compounds. The common structural feature of these compounds is the azomethine group with the general formula RHC = N-R1, where R and R1 are alkyl, aryl, cycloalkyl, or heterocyclic groups . Structurally, a Schiff's base (also known as imine or azomethine) is a nitrogen analogue of an aldehyde or ketone in which the carbonyl group (>C = O) is replaced by an imine or azomethine group. Schiff's bases have also been shown to exhibit a broad range of biological activities, including antifungal, antibacterial, antimalarial, antiproliferative, anti-inflammatory, antiviral, and antipyretic properties [3, 4]. Imine or azomethine groups are present in various natural, naturally derived, and nonnatural compounds. The imine group present in such compounds has been shown to be critical to their biological activities [5–7]. Schiff's bases are important compounds owing to their wide range of industrial applications . Schiff's bases are used in the photostabilization of poly(vinyl chloride) polymers against photodegradation by ultraviolet radiation [9–11] and are also used to improve poly(methyl methacrylate) from degradation  and to prevent polystyrene from photodegradation by their addition to polymer films [13, 14].
Fourier transform infrared (FTIR) spectra were registered on a SHIMADZU (8300, Kyoto, Japan) infrared spectrophotometer, using KBr discs. Proton nuclear magnetic resonance (1H-NMR; 600 MHz) spectra were obtained at room temperature with Bruker equipment (Madison, WI, USA) using TMS as an internal standard in dimethyl sulfoxide (DMSO). Melting points were recorded using hot-stage Gallenkamp melting point apparatus (Loughborough, UK) and were uncorrected. Analytical grade chemicals (BDH, G.C.C., Hopkin & William Corporation, Poole, UK) were used throughout the project.
Results and discussion
Physical properties of the prepared Schiff's bases
Physical data of the prepared compounds
Elemental analysis, theoretical (actual)
190 to 192
148 to 150
122 to 124
142 to 143
110 to 112
FTIR spectroscopy for sulfamethoxazole and its derivatives
υ(C = N) imine (cm−1)
υ(C = N) ring (cm−1)
UV spectroscopy for sulfamethoxazole and its derivatives
Absorption bands (nm)
π → π*
π → π*, n → π*
π → π*, n → π*
π → π*
π → π*
π → π*
The 1H-NMR spectrum of compound (1) showed the following characteristic chemical shifts (DMSO as a solvent): the singlet signal at δ = 2.212 ppm suggested the attribution of the protons of the CH3 group, the singlet signal at δ = 6.029 ppm suggested the attribution of the proton of CH of the isoxazole ring, the multiplet signal at δ = 6.743 to 7.768 ppm suggested the attribution of the protons of two aromatic benzene rings, the singlet signal at δ = 8.764 ppm suggested the attribution of the proton of the CH = N group, the singlet signal at δ = 9.352 ppm suggested the attribution of the proton of the NH group, and the singlet signal at δ = 10.525 ppm suggested the attribution of the proton of the OH group.
1 H-NMR data of sulfamethoxazole and its derivatives
C-H isoxazole ring
Aromatic benzene rings
6.743 to 7.768
6.789 to 7.749
A solution of sulfamethoxazole (0.001 mol) in absolute ethanol (30 ml) was slowly added to a solution of aldehyde (0.001 mol) in absolute ethanol (20 ml). The stirred reaction mixture was refluxed for 12 h. After cooling, a precipitate was formed which was collected by filtration, then washed with cold ethanol, and recrystallized from ethanol.
Five Schiff's bases: (1), (2), (3), (4), and (5), were synthesized as derivatives of sulfamethoxazole and characterized by UV, FTIR, and 1H-NMR spectroscopies and elemental analysis (CHNS).
The authors acknowledge the Department of Chemistry, College of Science, Al-Nahrain University for their encouragement.
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