Synthesis and Characterization of New Heterocyclic Compounds from 2 , 5-dimercapto-1 , 3 , 4-Thiadiazole and Their Resins

In this research, a new 1, 3, 4-Thiadiazole derivatives have been synthesized by many heterocyclic reactions. Starting from (2, 5 – dimercapto -1, 3, 4-Thiadiazole) a variety of derivatives have been synthesis. Compound (1) was synthesized by the reaction of hydrazine hydrate with carbon disulphide in absolute ethanol. The compound (1) was reacted with 1, 2-dibromoethane in presence of alkali ethanol to give the compound (2). The compound (3) was formed from the reaction of compound (2) with hydrazine hydrate. Schiff base (4) was obtained by reacting of compound (3) with the compound (p-hydroxybenzaldehyde) in absolute ethanol. A variety of phenolic Schiff base (Methylolic, Etheric, and Epoxy) derivatives have been synthesized. Methylolic derivative was synthesized by the reaction of Schiff base (4) with formaldehyde in tetrahydrofuran (THF). Etheric derivative was formed from the reaction of a methylolic Schiff base (5) with saturated alcohol (Methanol).Epoxy derivative was synthesized by the reaction of epichlorohydrine with etheric derivative (6) .The last step of this research was the preparation of a composite material from mixing the Epoxy resin derivative(7), TiO2and morpholine via ring opening. All these derivatives were verified by using (FT-IR, UV) spectra photometer and 1 H-NMR spectra. Also, these derivatives were characterized using elemental analysis (C.H.N.S) .


Introduction:
1, 3, 4-Thiadiazole is one of the most important biochemical materials and it is one of the most popular isomers in the pharmaceutical and the industrial fields.The studies have shown that heterogeneous quintet rings (thiadiazole) have different activities.The first one who described 1, 3, 4-Thiadiazole was Fisher in 1882 , but the real nature of the ring system described for the first time in 1890 by Freund and Kuh [1].They found when a substitution occur in locations (2,5) of the Thiadiazole compound with two groups of thiol (SH) this will give a more power to the compound with a wide range of uses.2,5-disubstituted-1, 3, 4thiadiazole derivative has biological activities including anticancer [2] antifungal [3] anti-tubercular [4] and anti-inflammatory [5].Schiff bases are used in a wide range of applications, in biological field [6], industrial applications such as anticorrosion material for steel and alloys, photo stabilizers for poly ethylene, and the methylolic derivatives of phenolic.Schiff bases are used in the production of industrial polymers, such as PVC [7].Epoxy derivatives are poly ethers contain an epoxy groups at the end of the chain, known as oxiranes [8].These resins undergo polymerization reactions through their ring opening and their participation in a process known industrially as"curing", using hardeners such as the amine compounds.Epoxy resins are used in adhesives, coatings and composite materials [9,10].The main problem of the epoxy resin is with the passage of time suffered from break covalent bonds for epoxy resins, by sun light, therefore the addition of additives inorganic like TiO 2 and Zinc oxide to the epoxy derivative will absorb ultraviolet light in the range (300-400) nm strongly [11], leading to non-absorption of these rays by the epoxy molecules and active functional groups [12].

Materials and Methods
Melting points were determined on electro thermal capillary apparatus and were uncorrected; FT-IR spectra were recorded using solid KBr disc by testing Shimadzu (FT-IR 8300).Ultraviolet spectra were recorded using Shimadzu (UV-Visible) within range (200 -900) nm, the elements analysis of compounds (C.H.N.S) by using a Perkin-Elmer, RE 2400, measurement was made at College of Education for Pure Science (Ibn Al-Haitham), Baghdad University. 1 H-NMR spectra were carried out in Al-al Bayt University (Jordan) operating at 300 MHz in DMSO-d6 as solvent with the TMS as internal standard.All the chemical materials and solvents were purchased from (Isotecinc, BDH and Merck) companies.

Preparation of Saturated Etheric Derivative (6)[18]:
The saturated alcohol (Methanol) (0.8mol) with (1ml) of sulphuric acid were mixed at (5) 0 C, then (0.2 mol) of a Methylolic Schiff Base (5)was added gradually with stirring at room temperature for (1hr) with the rise of the temperature to the boiling point of the alcohol used.The reaction mixture was refluxed for (24hrs) then cooled, the mixture was neutralized with sodium hydroxide.The derivative was extracted using chloroform, recrystallized from chloroform, and then dried.

Preparation of Epoxy Derivative (7) [19]:
The epichlorohydrine (24.5 ml, 0.31 mol) was mixed with (7.2 ml, 0.12mol) of butanol and (0.01mole) of an etheric derivative, for 15 mints at (50) 0 C, then gently added (4g, 0.1mol) of sodium hydroxide in two stages with a maintained temperature below (65) 0 C .The mixing continues for (2hrs).After the first addition the aqueous layer was separated from the organic layer, then a second batch of sodium hydroxide added and mixed for (1hr) the aqueous layer were separated while the organic layer dried and recrystallized from (THF).

Preparation of Composite Material (9) from Epoxy Resin Derivative with Opening of the Ring [21]:
The Epoxy resin (0.01mole) was mixed with Methanol (20 ml), a weight ratios of 40%, 30%, 10% and 5% (of the resin weight used) of titanium dioxide (TiO 2 ) pigment will be added, with a continuous stirring, then (1.74ml, 0.02 mole) of morpholine was added, refluxed for (72hrs) the product was painted on a glass slide of quartz and left to dry for (7-10) days.

Results and Discussion
Compound (1) was prepared as shown in scheme (1).Some physical properties for this compound were listed in Table (1).

Scheme (1): Chemical equation for the preparation of derivative (1)
Compound (1) was characterized by its melting point and by (FT-IR, UV/Vis) spectrum.Melting point was recorded (159-161) 0 C.The FT-IR spectrum of compound (1), showed a medium intensity band at 1620 cm -1 was due to υ (C=N).1273 cm -1 due to υ (C=S) and showed the stretching vibration (2580) The 2 nd National Conference of Chemistry 572 cm -1 due to υ (S-H thiol) and showed the absorption band at (3251) cm -1 , due to υ (NH, thion form).This means that compound (1) can exist in the thiol and thion form.The (UV/Vis) spectrum of compound (1), Figure (6), showed the absorption band at 331nm for (n-π*) resulting from a nonbonding electronic transitions of atoms heterogeneous (S, N) to thiadiazole ring and at 236nm for (π-π*) belonging to the (C=N, azomethine group).Compound (2) was prepared as shown in scheme (2).Some physical properties for this compound were listed in the

Conclusion:
During the preparation of the new derivatives from the basic component, (2, 5-dimercapto-1, 3, 4-thiadiazole), the epoxy and methylol derivatives have been prepared,and these have great importance because they are used, widely, as industrial applications especially paints and glue industry.