Synthesis of Anionic Surface Active Agents Containing Heterocyclic Moiety From Long Chain Fatty Alcohols

A series of novel groups of anionic surface active agent were synthesized. Synthesis of these surfactants via the reaction of long chain fatty alcohols (octyl, decyl and dodecyl) with maleic anhydride to give monoester. The monoester chloride reacted with amino derivatives of heterocyclic rings followed by addition of NaHSO3 .The surface tension, interfacial tension; Kraft point, emulsifying and wetting power were evaluated. Stability to hydrolysis, biodegradability and biological activities were measured. A comparison studies between the chemical structures and the results were done.


INTRODUCTION
Anionic surfactants are very widely distributed throughout science, technology and everyday life. Examples which at once come to mind are the washing, wetting out of textile materials, the preparation of dispersion and emulsion, the application of agricultural and a wide variety of special uses, the number of which is continually increasing 1 .
Among anionic surfactants containing an aromatic structure element are alkyl benzene sulphonate accompanied by alky-naphthalene sulfonates 2-5. In these compounds, hydrophilic sulfonic group is separated from long chain alkyl hydrophobe by single six member benzene or naphthalene rings. The structure analogues to the above ones may be surfactants containing five member heteroaromatic groups. It has been well established that various thiazole, imidazol, pyrazole, pyridine, pyrimidine and quinoline are of biological interest [6][7][8][9] . This encourage us to synthesis a novel groups of anionic surfactants containing those nucleus from long chain fatty alcohols (octyl, decyl, dodecyl alcohols ) hopping to possess good surface properties and expected to have biological activities.

3.2.I-synthesis of maleic acid monoester:
It was prepared by refluxing a mixture of maleic anhydride (1.0 mole) with fatty alcohols (1.0 mole) octyl alcohol (a), decyl alcohol (b),dodecyl alcohol (c)in benzene for six hours, in the presence of sulphuric acid as catalyst. After cooling the reaction mixture was distilled with water to ensure removal of unreacted alcohols. Further purification was effected by fractional distillation under vacuum 10 .

3.2.II-Synthesis of acyl chloride compounds:
The acyl chloride was formed by refluxing of thionyl chloride with maleic acid monester in water bath at 65 ºC for three hours. After cooling, petroleum ether was added and heated to remove excess of thionyl chloride. 20

3.2.III-Preparation of anionic compounds:
acyl chloride which was prepared in previous step was reacted with 2-amino thiazole, 2-amino imidazol,3-amino pyrazole, 2-amino pyridine,2-amino pyrimidine and 8-amino quinoline in presence of benzene as solvent for three hours to give the compounds that react with sodium bisulfate to give anionic surfactants (9-14a-c). The structures of the synthesized compounds were confirmed by infrared (IR) and nuclear magnetic resonance ( 1 H NMR). The qualitative infrared absorption spectra of the synthesized compounds were recorded on a Beckmon 4220 spectrophotometer. The 1 HNMR spectra of the compounds under investigation have been recorded in deuterated chloroform (CDCl 3 ) and /or in (DMSO) as a solvent and tetramethyl silane (TMS) as an internal reference with 90 MHz signal and 4.000 gauss magnetic field.

3.4.a Surface and interfacial tension
Surface tension and interfacial tension measurements were carried out according to Findlay 11 with a Krüss tensiometer for different concentration of the synthesized surfactants using platinum iridium ring at constant temperature 25˚C.Paraffin oil was used for the interfacial tension measurements.

3.4.b Emulsifying power
A 20-ml amount of a different surfactant solution (0.1%) was individually placed in a 100-ml cylinder and then 20 ml of the paraffin oil was added. The cylinder was shaken vigorously for 10 min and then allowed to settle. The time required to separate 18 ml of pure surfactant solution was recorded and the experiment was repeated three times for each surfactant. The average separation time of the three experiments was taken as an indication of the emulsification power of each surfactant 12 .

3.4.c Stability to hydrolysis
A mixture of 10 ml. of surfactant and 10ml of 2N sulphuric acid or 0.05 N NaOH were placed in a thermostat at 40°C. The time it takes for a sample solution to be clouded as the result of hydrolysis shows the stability of the surfactant to hydrolysis 13 .

3.4.d Wetting properties
It was examind by standard Draves method

3.4.e Kraft point
The temperature at which 1% solution becomes clear on gradual heating gives a convenient measure of aqueous solubility 12 .

3.4.f Biodegradability%
Die-awy method using river water samples taken daily, or even more frequently, were filtered through No. 1 Whatman filter paper before measuring the surface tension 15 Measurements were periodically (each day) on each sample during the degradation test. Biodegradation percent (D) was calculated from 'the following law.

Result and discussion
The synthetic route of these surfactants was listed in scheme1.The structure of prepared surfactants were confirmed by IR and 1 HNMR as shown in table (1).

Surface active properties and related properties:
The surface active properties and related properties, including surface and interfacial tension, kraft point, foam height, emulsion stability, wetting time and stability to hydrolysis were investigated to evaluate the possible application of these products in different industrial fields. The surface activity and related properties of the synthesized compounds are given in Table (2). The surface and interfacial tension of the prepared surfactants are given in Table (2). It showed that, the prepared anionic surfactants have good surface properties while they have a strong effect on the value of surface and interfacial tension. This result indicates that these

Scheme (1) synthesis of heterocyclic anionic surfactants
Compounds have a good surface activity. The results show that the surface tension decreases with increasing the alkyl chain length 16 .

Kraft point:
The kraft point for the anionic synthesized surfactants which are freely soluble in water at 1 wt % concentration is ranged between 16 and 13 C. While the compounds showed the lowest kraft points that may be attributed to the have the shorter fatty chain length 17 .

Emulsion stability:
The process of emulsification is the dispersion or suspension of fine particles of one liquid in another immiscible liquid. The emulsifying efficiency of a surfactant was related to the polarity of the molecule or the relation between the contribution of the polar hydrophilic head and the non polar lipophilic tail. From the data recorded in Table (2) the emulsifying properties increased with increasing the alkyl chain length of the fatty acid 12 .In fact the results of emulsification have good values which make them used in different industrial applications.

Wetting time:
The wetting properties of 1.0 % solutions in distilled water were measured. The case with which the surface can be wetted by water as other liquids is an important properity suitable for many applications. Wetting powers obtained for the prepared sulfonamide surfactants are listed in Table (2).These compounds showed a good performance in wetting power. The wetting time slightly increases with increasing the chain length 18 .

Stability to hydrolysis:
All the prepared surfactants showed resistance to hydrolysis, probably because the adjacent sulpho group protects the amide linkage through steric hindrance 13 .these results make them stable in acidic and basic medium.From the measuring of the surface properties of the prepared compounds, we can notice that the change in the heterocyclic moiety have a little or no effect on this properties.

Biodegradability
A biodegradation test in ordinary river water 15 gave good or excellent results table (3). The results of biodegradation reflect the fact that the biodegradability decreases with increasing the length of saturated aliphatic chain, which make the prepared anionic surfactants environmentally favorable. 21

Biological activity
Biological activity of the synthesized compounds was reported that amino derivatives have a potential at the pharmacological level, so the antimicrobial activity of some new synthesized compounds was determined in vitro in the Botany Department, Faculty of Science, Benha University, Egypt. With the aim of obtaining specific derivatives that could be potent in medicine, chemistry or agriculture. A variety of species of G-positive bacteria (Bacillus megathorium) and Gnegative bacteria (Escherichia coli) in addition to some fungal plant pathogens (Mucor Species and Aspergillus flavus) were used, using a modified Kirby-Bauer disc diffusion method 19 .
In every case the minimum inhibitory concentration (MIC, µg/ml) was determined as the lower concentration of the compounds under study, which inhibits bacterial and fungal growth and the results are given in table (4).
It is apparent from the data, that most of the tested compounds have moderate to high activity against micro-ganisms. However, concerning the activity against G-positive bacteria (Bacillus megathorium).