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The Effect of Hydrophile and Hydrophobe Part on Surface Activity of Ester Quaternary Ammonium Compounds

Moshera Z. Mohameda1*, Samar A. Abubshait2, Eqbal J. Bushlaibi2

1 Department of Chemistry, Egyptian Petroleum Research Institute, Cairo, Egypt

2 Department of Chemistry, Imam Abdul Rahman Bin Faisal University, Dammam, Saudi Arabia

*Corresponding Author:
Moshera Z. Mohameda
Department of Chemistry,
Egyptian Petroleum Research Institute,

Received: 19-Apr-2021, Manuscript No. JCHEM-21-003-PreQc-22; Editor assigned: 22-Apr-2021, PreQC No. JCHEM-21-003-PreQc-22 (PQ); Reviewed: 06-May-2021, QC No. JCHEM-21-003-PreQc-22; Revised: 20-Jun-2022, Manuscript No. JCHEM-21-003-PreQc-22 (R); Published: 19-Aug-2022, DOI: 10.4172/2319-9849.11.6.003.

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This study deals with the synthesis of six cationic surfactants forming two groups. Using alkyl diols, bromoacetic acid, triethyl amine and triethanol amine, these surfactants were synthesized. From the analysis, it was found that the surfactants prepared are ester quaternaries. Du nouy tensiometer has been used for obtaining the surface activity of surfactants. In terms of their hydrophilic and hydrophobic part, different surface parameters were discussed. All showed the biological features such as antimicrobial activity. 


Amphiphilic quaternary ammonium ester; Du nouy tensiometer; Biodegradability; Biological activities


Ester of quaternary ammonium amphiphiles are environmentally friendly surfactants of elevated biodegradability, low toxicity and outstanding active surface characteristics. These compounds also demonstrate antitumor therapy potential, regulating plant growth and antibiotic activity [1]. Surfactants reduce surface tension is that water attracts the hydrophilic part while repelling the hydrophobic part, reducing the surface tension by interrupt attractive forces at the interface. Critical micelle concentration is one of the most phenomena for surfactant in wide applications.

Positive ions are produced when cationic surfactants are dissolved in water, so they form powerful adsorption layers on material surfaces which are negatively charged [2]. They are widely used as biocides which serve in the oil field. In this article, The ester quaternary ammonium salt surfactants have been synthesized and surface characteristics have been studied by measurement of surface tension values in water solutions using a du nouy ring tensiometer, also the biocidal activities were studied.

Materials and Methods


Perkin Elmer Infrared spectrophotometer FTIR-16FPC were used to measure Infrared spectrum for selected surfactants. Perkin Elmer Elemental Analyzer (series π 2400) was used to obtain the elemental analysis data for the synthesized surfactants [3]. Proton nuclear magnetic resonance measurements H1 NMR and 13C NMR Spectroscopy was carried out using a Bruker 400 MHZ advance and samples were taken in DMSO-d6.

Synthesis of ester quaternary ammonium salts

According to Scheme, these surfactants were obtained through two-step processes. In the first step, the alkyldiols monobromoacetate (Halo-Compounds) (2a-c) was obtained by direct reaction of 1,8-Octanediol (1a) or 1,10-decanediol (1b) or 1,12-dodecanediol (1c) (0.1 mol) with bromoacetic acid (0.1 mol) in benzene as a solvent. The calculated amount of water (1.8 ml, 0.1 mol) was removed using concentrated hydrochloric acid as a catalyst [4]. Alkaline solution of NaHCO3 was used to neutralize the catalyst. The product was separated with petroleum ether, then complete drying with dry oven under vacuum at 30°C. In the second step, quaternization of the compounds (2a-c) with triethylamine give first group (3a-c) and with triethanol amine give second group (4a-c).The final products were obtained after filtration and recrystallization several times from ethanol (Figure 1).


Figure 1: Synthesized of ester quaternary ammonium salts (3a-c),(4a-c).

Measurment of surface parameters

Surface tension, efficiency (PC20), surface pressure (effectiveness π cmc) and Critical Micelle Concentration (CMC) were determined for two prepared groups from 1 × 10−2 to 5 × 10−8 mol/L at 25°C with du nouy tensiometer with a platinum ring.

Results and Discussion

Characterization data of ester quaternary ammonium surfactants

Compounds 2a-c were confirmed before as in previous paper. The structure of the synthesized surfactants and purity were confirmed by different methods (IR, 1 H NMR, 13 C NMR and mass).

Surface properties of cationic surfactants and thermodynamic parameters

The Critical Micelle Concentration (CMC) is a fundamental characteristic of each dissolved surfactant in the solvent [5]. CMC can be determined by drawing a relationship between one of the properties of the surface activity material (the surface tension of the compounds under study) and the concentration of these compounds. With rising concentration of surfactant, the surface tension reduces and then reaches a definite break point that is taken as the CMC. One of the most important factors affecting CMC values in aqueous solutions is the structure of surface active substances, which include hydrophobic groups and hydrophilic groups (Figure 2).


Figure 2: Variation in surface tension of surfactants 3a–c versus concentration at 25ºC.

Effect of the hydrophobic groups

For the all prepared compounds, the CMC values decrease by raising the length of the hydrocarbon part is due to the increased hydrophobic properties of the molecules which are the driving force of the molecules to escape from the solution to the surface (Tables 1 and 2).

Comp. PC20 mol/L) cmcγ(mN/m) cmcπ (mN/m) CMC (mol/L) maxΓ (mol/cm2) Amin (nm2) ΔG°mic (kJ/mol ) adsΔ (kJ/mol)
3a 3.16 ´ 10-5 43 29 3.16 ´ 10-3 4.38 ´ 10-11 3.75 -28.492 -28.557
3b 3.16 ´ 10-6 38 34 1.25 ´ 10-3 4.78 ´ 10-11 3.44 -33.050 -33.121
3c 5.01 ´ 10-5 43 29 6.30 ´ 10-4 6.82 ´ 10-11 2.41 -36.469 -36.511

Table 1. Surface parameters of the prepared compounds 3a-c at 25°C.

Comp. PC20 mol/L) cmcγ(mN/m) cmcπ (mN/m) CMC (mol/L) maxΓ (mol/cm2) Amin (nm2) ΔG°mic (kJ/mol ) adsΔ (kJ/mol)
4a 6.30 ´ 10-5 41 31 2.51 ´ 10-3 5.48 ´ 10-11 3.01 -29.630 -29.687
4b 1.25 ´ 10-4 47 25 1.58 ´ 10-3 5.58 ´10-11 2.95 -31.911 -31.955
4c 1.58 ´ 10-4 44 28 1 ´ 10-3 7.90 ´10-11 2.08 -34.190 -34.225

Table 2. Surface parameters of the prepared compounds 4a-c at 25°C.

Effect of the hydrophilic groups

Comparing cationic compounds 3a-c with 4a-c compounds, CMC values for 4a-c are high compared with 3a-c as the number of hydrophilic groups increase [6]. This is due to the difficulty of entering these groups into the spherical or cylindrical micelle, as well as increasing the number of polar groups, this may lead to increased charge on the hydrophilic head groups and increase the forces of repulsion between ionic groups leading to increased CMC values for the difficulty of transferring the ionic groups of water inside the solution to the non-polar core of micelle during the micellization process.

The biological effect

Biological survey of prepared ester quaternary ammonium compounds was detected at 25°C using well diffusion test method against gram-positive bacteria, some fungi and yeasts. Cetyl Trimethyl Ammonium Bromide (CTAB) has been used as a reference compound to compare its effect on pathogenic microorganisms with the effect of prepared compounds [7]. The compounds in question were dissolved in distilled water. The high biological activity of these cationic compounds can be explained by the electrostatic attraction forces between the positive charges (N+) of quaternary ammonium compounds and the negative charges of phospholipids forming the cell wall [8]. The resemblance between the hydrocarbon chains of the prepared compounds, the lipid layers and the cell membrane building blocks make adsorption easier and thus disrupts the selective permeability of the outer wall of the cell hence the biological activity of microorganisms leading to their death [9]. We can also say that the large inhibitory diameter is due to the large volume of micelle at low concentrations, which makes it suitable for interaction with the cell membrane. Recent studies have tended to use quaternary ammonium compounds in the field of biocides to prevent the reproduction of bacteria that cause significant damage to the petroleum sector as these quats have proven effective as inhibitors of the activity of Sulfate Reducing Bacteria (SRB), whose growth causes corrosion in petroleum pipelines [10]. Sulfide is corrosive and toxic and causes reservoir blocking. Hence, we can say that increasing concentration in the biocide increases the activity of the compound towards SRB, all prepared compounds show good activity compared with reference compound.


Syntheses of the ester quaternary ammonium surfactants were studied. From the effect of the both hydrophilic groups and hydrophobic part on micellar properties and thermodynamics parameters of surfactants, the following can be concluded:

• The CMC values decrease by raising the length of the hydrocarbon part, CMC values increase as the number of hydrophilic groups increase.

• Compounds under test have a high surface activity, high negative values of standard free energy for adsorption, negative values of micellization standard free energy change and high biological activity.


The authors gratefully acknowledge the Egyptian Petroleum Research Institution and Imam Abdulrahman Bin Faisal University for providing moral and financial support. The authors are also grateful to the referees for their valuable mechanistic suggestions.