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Document Type : Original Article


Department of Chemistry, College of Science, University of Baghdad, Baghdad, Iraq


The present report describes the synthesis of new the synthetic route that started by the reaction of acid hydrazide derivatives with ammonium thiocyanate to give compounds 1a-d. 1,3,4-thiadiazole derivatives 2a-d were synthesized by the reaction compounds 1a-d with concentration sulfuric acid. Finally, the reaction 1,3,4-thiadiazole derivatives 2a-d with sodium nitrate and hydrochloric acid in 0-5 °C to form diazonium salt, then diazonium salt reacted with 4-dimethylaminobenzaldehyde to synthesize azo compounds 3a-d. These new synthesized products were characterized by FT-IR, 1H-NMR for some of them and were studied regarding the effect of preparing derivatives on antioxidant activity.

Graphical Abstract

Synthesis and Characterization of New 1,3,4-Thiadiazole Derivatives Containing Azo Group from Acid Hydrazide and Studying Their Antioxidant Activity


Main Subjects


The knowledge of chemistry of heterocyclic compounds represents a basic point for the development of new heterocyclic compounds that have an important role in agrochemical, pharmaceuticals and materials science [1]. Structurally, diazoles are composed of five-membered rings containing two nitrogen atom and other non-carbon atom of either oxygen or Sulphur as heteroatoms like oxadiazoles and thiadiazol and play an important role in biological processes, especially heterocycles that contain nitrogen, because of their wide use in medicinal scaffolds for active agents [2]. The 1,3,4-thiadiazole nucleus, which makes up the azole group, is a versatile pharmacophore and exhibits a wide variety of biological activities. In addition to the 1,3,4-thiadiazole, there are three other isomers: 1,2,3-thiadiazole, 1,2,4-thiadiazole and 1,2,5-thiadiazole. 1,3,4-thiadiazole its derivatives have become interesting over the past few years and found wide applications in pharmaceuticals, dyes, photographic materials, agrochemicals and corrosion inhibition. They showed anticancer activity against different types of cancer, such as liver, cervical, colon, gastric, breast, melanoma, lung, colorectal, bone [3-6], antifungal [7, 8], anti-inflammatory [9], antibacterial activity [10] and antiparasitic [11, 12]. Currently microbial resistance to drugs is a concern in medicinal chemistry, which can be due to gene transfer or excessive drug usage. Over the last few decades, there has been an increase in drug resistance and in the detection of hospital-acquired infections caused by multidrug resistant strains and this situation is considered a public health problem. This drug resistance has compromised the treatment of infectious diseases and at the same time has stimulated the search for new bioactive substances. The antibacterial and antifungal properties associated with the thiadiazol nucleus have been widely researched as anti-microbial [13-15], antitumor [16, 17], anti-convulsant [18, 19], antioxidant [20] and antidepressant [21].

Materials and Methods

All ingredients and solvents were obtained from Fluka and Sigma-Aldrich. Gallen Kamp capillary melting point apparatus was used to measure melting points. Shimadzu model FT-IR-8400S was used to take FT-IR measurements. 1H-NMR spectra were collected in D2O solution using a Bruker spectrophotometer ultra-shield at 400 MHz using TMS as an internal standard.

Synthesis of compounds 1a-d [22]

Zainab A. et al. [23] prepared acid hydrazide, a mixture of acid hydrazide (0.02 mol), ammonium thiocyanate (0.02 mol) and concentrated hydrochloric acid (8 mL) in absolute ethanol (50 mL) was refluxed for 20 h. The solvent was evaporated and residue poured on crushed ice with stirring. Table 1 lists the physical properties of the synthesized derivatives 1a-d.

Synthesis of 1,3,4-thiadiazole 2a-d [22]

Concentrated sulfuric acid (10 mL) was added to substituted thiosemicarbazone 1a-d (0.05 mol). The mixture was heated on water bath 90 °C with stirring for 2 h, the mixture was then poured onto ice-water and neutralized with concentrated ammonia solution with cooling; the formed precipitate was filtered and washed with ether and recrystallized from ethanol. Table 1 lists the physical properties of the synthesized 1,3,4-thiadiazole 2a-d.

Synthesis of azo compounds 3a-d [24]

In beaker 1, (0.02 mol) of 1,3,4-thiadiazole 2a-d was dissolved in 8 mL of concentrated hydrochloric acid and cooled to 0 °C. 0.02 mol of sodium nitrate was prepared in 10 mL water and this solution was poured to beaker 1 drop by drop in ice bath. The resulting mixture, i.e. diazonium salt, remained in ice bath. The third solution containing 0.02 mol of 4-dimethylaminobenzaldehyde was dissolved in sodium acetate (10 mL) in beaker 2. Beaker 1 was added to beaker 2 and the addition should be gradual with keeping low temperature. The resulting product was recrystallized. Table 2 lists the physical properties of the synthesized azo compounds 3a-d.

 Antioxidant activity [25]

The solution was protected from light by covering the test tubes with aluminum foil. DPPH (4 mg) was dissolved in 100 mL of ethanol. Some of the produced compounds were used to make various concentrations of 25, 50, 100 ppm. It was made by dissolving 1 mg of the chemical in 10 mL of ethanol to make 100 ppm, then diluting it to 50 and 25 ppm. The concentrations were made in the same way. 1 mL of the diluted or normal solution 25, 50, 100 ppm was added to 1 mL of DPPH solution in a test tube. After 1 h of incubation at 37 °C, the absorbance of each solution was measured using a spectrophotometer at 517 nm. The following equation was used to determine the potential to scavenge DPPH radicals.

I% = (Absorption blank–Absorption sample)/Absorption blank × 100

Results and Discussion

Acid hydrazide derivatives were used to make new 1,3,4-thiadiazole 3a-d with an azo group Scheme 1 and the mechanism of synthesis 1,3,4-thiadiazole Scheme 2.

Scheme 1: All synthesis compounds 1a-d, 2a-d and 3a-d

Scheme 2: The mechanism of synthesis 1,3,4-thiadiazole

Stretching vibrations band to the NH2 group at 3421-3301 cm-1 and absorption bands to the C=S group at 1118-1174 cm-1 were observed in the FT-IR spectra of derivatives 1a-d [26]. These compounds' other stretching vibration bands were shown in Table 1. The stretching vibration bands to the C=S group disappeared in the FT-IR spectra of 1,3,4-thiadiazole derivatives 2a-d, but stretching vibration bands to the C=N thiadiazol ring at 1639-1649 cm-1 appeared and the other stretching vibration bands for these compounds were displayed in Table 1. Finally, in the FT-IR spectra of azo compounds containing 1,3,4-thiadiazole 3a-d stretching vibrations bands to the NH2 group disappeared and stretching vibrations bands to the N=N azo group appeared at 1541-1546 cm-1 and stretching vibrations band to the C=O aldehyde group appeared at 1731-1747 cm-1.

The other stretching vibration bands for these compounds are shown in Table 2. 1H-NMR spectrum [27] of compounds 1a, 2b, 2c and 3b are listed in Table 3. The procedure was used to measure antioxidant activity based on the DPPH stable free radical sweep effect, the antioxidant function of some selective synthesized of some produced compounds, and ascorbic acid.

Table 4 shows some of the newly synthesized compounds and antioxidant activity against DPPH free radicals, with a high scavenging percentage and compression with ascorbic acid. The decrease in absorbance at 517 nm was used to measure the DPPH radical's ability to reduce.

Furthermore, organic compounds with an electron donating group (NH2, OCH3, and OH) that can operate as free radical agents and resist oxidation have been extensively established. Figure 1 depicts that the molecule 1,3,4-thidiazole (1b, 1d, and 2d) has the highest antioxidant activity [28].

Table 3: 1H-NMR spectral data (δ ppm) for some compounds


1H-NMR data of δH in ppm


2.09 (S, 3H, CH3), 2.45-2.76 (t, 4H, CH2-CH2), 2.95 (S, 3H, N-CH3), 4.10 (S, 2H, CH2-CO), 3.92 (S, 1H, NH2), 7.89 (S, 1H, NH-C=S), 8.16 (S, 1H, NH-C=O).


2.39-2.59 (t, 4H, CH2-CH2), 3.0 (S, 3H, N-CH3), 4.16 (S, 2H, CH2-CO), 6.87-7.13 (m, 5H, Ar-H), 3.56 (S, 1H, NH2).


2.52-2.78 (t, 4H, CH2-CH2), 2.95 (S, 3H, N-CH3), 4.27 (S, 2H, CH2-CO), 7.18-7.31 (m, 4H, Ar-H), 4.0 (S, 1H, NH2).


1.3 (s, 6H, N(CH3)2), 2.32-2.67 (t, 4H, CH2-CH2), 3.12 (S, 3H, N-CH3), 4.23 (S, 2H, CH2-CO), 6.92-8.22 (m, 8H, Ar-H), 10.12 (S, 1H, CHO).


Table 4: Scavenging % for some of prepare compounds

Compound No.

Scavenging %


25 mg/mL

50 mg/mL

100 mg/mL


































Ascorbic acid




Figure 1: Scavenging comparison between the prepared compounds and ascorbic acid


The prepared new 1,3,4-thiadiazole containing azo group from acid hydrazide derivatives were confirmed by using spectroscopic techniques (FT-IR and 1H-NMR). The antioxidant activity of the most compounds were strongly compressed with ascorbic acid.


The authors would like to extend their sincere appreciation to the Deanship at Baghdad University College of Science, and thank everyone who helped them to complete this research.



This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.


Authors' contributions

All authors contributed toward data analysis, drafting and revising the paper and agreed to responsible for all the aspects of this work.


Conflict of Interest

We have no conflicts of interest to disclose.



Zainab Amer


Zainab Amer, Entesar O. Al-Tamimi. Synthesis and Characterization of New 1,3,4-Thiadiazole Derivatives Containing Azo Group from Acid Hydrazide And Studying Their Antioxidant Activity. Chem. Methodol., 2022, 6(8) 604-611


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