Synthesis, surface, thermodynamic properties and Biological activity of dimethylaminopropylamine surfactants

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JIEC-1861; No. of Pages 8 Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx

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Synthesis, surface, thermodynamic properties and Biological activity of dimethylaminopropylamine surfactants Samy M. Shaban a,*, Ismail Aiad a, Mohamed M. El-Sukkary a, E.A. Soliman b, Moshira Y. El-Awady a a b

Petrochemical Department, Egyptian Petroleum Research Institute, Cairo, Egypt Faculty of Science, Ain Shams University, Cairo, Egypt

A R T I C L E I N F O

Article history: Received 10 December 2013 Accepted 6 January 2014 Available online xxx Keywords: Cationic surfactants Quaternary ammonium salts Surface parameters Themodynamic parameters Biological activity

A B S T R A C T

The chemical structure of the prepared cationic surfactants which formed through condensation reaction between dimethylaminopropylamine (DMAPA) and butyraldehyde then quaternized by three fatty alkyl bromide was confirmed by FTIR, 1HNMR and mass spectroscopy. The chemical structure of prepared compounds has an effect on surface properties. By increasing the hydrophobic chain length, the values of CMC and ’max decrease while Amin value was increased. The Thermodynamic parameters showed that adsorption and micellization processes are spontaneous. It is clear that the prepared cationic surfactants tend to adsorb at surface, then it aggregate to form micelle. The prepared surfactants showed good biological activity against Gram-positive and negative bacteria and fungi. The prepared cationic surfactant showed aggressive effect on the sulfate reducing bacteria growth. ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

1. Introduction Surfactants are amphiphilic compounds that contain polar or ionic head group and non-polar residues. In the water or similarly strongly hydrogen-bonded solvents, they self-associate at concentrations above the critical micellar concentration (CMC) to form association colloids called micelles. Micelles have interfacial regions containing ionic or polar head groups [1]. Have widespread importance and application such as detergent, paints, coatings formulation, demulsification [2], drilling mud and petrochemical recovery in petroleum industry and due to similarity in chemical structure of quaternary ammonium compounds and cellular constituents eases their destructive action towards microorganisms biocides [3,4]. DMAPA contains one primary and one tertiary amine group, so it has numerous uses in the production of other chemicals. Final products include agricultural chemicals, anti-static agents, binding agents, carburetor detergents, fabric softeners, flocculants, fungicides, ion exchange resins, phthalocyanine dyes, and water-resistant textile fibers [5]. Derivatives based on DMAPA can be used in fuels as cloud point reducers, dispersants, and stabilizers for prevention of deposits or icing and reduction of octane number requirements. Derivatives are also used as dispersants, anti-oxidants, and corrosion

inhibitors for lubricants [6]. The biocidal activity of the cationic surfactants was greatly developed in the last 20 years due to increase of self-immunity for microorganisms toward the conventional biocides [7–10]. This study aimed to prepare some of cationic surfactants using commercial materials like DMAPA and butyraldehyde then studing their surface and thermodynamic properties including, CMC, Amin, PC20, Gmax, pCMC DGomic and DGoads then evaluate these cationic surfactants as biocide against fungi and bacteria.

2. Experimental 2.1. Materials All the reagents were analytical grade and used as received dimethylaminopropylamie (DMAPA), decyl bromide, dodecyl bromide and hexadecyl bromide were purchased from Aldrich Chemicals Co. and the butyraldeyde was purchased from AL-Nasr Chemical Co. Solvents (ethyl alcohol absolute, diethyl ether and acetone) are high grade and purchased from Algomhoria Chemical Co. 2.2. Instruments

* Corresponding author. Tel.: +20 1276792188; fax: +20 222747433. E-mail address: [email protected] (S.M. Shaban).

The chemical structure of the synthesized compounds was characterized by:

1226-086X/$ – see front matter ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jiec.2014.01.020

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 FTIR spectra using ATI Mattsonm Infinity seriesTM, Bench top 961 controlled by Win FirstTM V2.01 software. (Egyptian Petroleum Research Institute).  1HNMR was measured in DMSO-d6 by Spect Varian, GEMINI 200 (1H 200 MHz). (Micro-analytical Center, Cairo University).  Mass spectra was measured by GC MS-OP1000EX (Micro Analytical Center, Cairo University). ¨ SS Company, Germany) using the  Tensiometer-K6 processor (krU ring method.

2.3. Synthesis The cationic surfactants were prepared in two main steps: 2.3.1. Synthesis of Schiff base compounds Equimolar of 3-dimethylamino-1-propylamine (DMAPA) was subject to condensation reaction with butyraldehyde in absolute ethanol for 6 h. The reaction mixture was left to cool then filtered. The products were recrystallized twice from ethanol to obtain on the Schiff base [11]. 2.3.2. Quaternization of prepared Schiff bases Equimolar of prepared Schiff bases were refluxed with different fatty alkyl bromide like decyl bromide, dodecyl bromide and hexadecyl bromide separately in ethyl alcohol absolute as solvent for 45 to 60 h to give the desired cationic surfactants C10BT, C12BT and C16BT, respectively, as showed in Scheme 1. The reaction mixture was evaporated under reduced pressure; the solid residue was washed with diethyl ether three times to remove the unreacted materials.

2.4.2. Antimicrobial activities 2.4.2.1. Biological activity against a wide range of bacteria and fungi. The antimicrobial activities of synthesized compounds were measured against a wide range of organisms comprising: (bacteria and fungi). The tested bacteria were Gram-positive (Bacillus pumilus and Micrococcus luteus) and Gram-negative (Pseudomonas aeuroginosa and Sarcina lutea), the used fungi were Candida albicans and Penicillium chrysogenum. The different species of tested organisms were obtained from the operation developement Center, Egyptian petroleum research institute, Egypt. An assay is made to determine the ability of an antibiotic to kill or inhibit the growth of living microorganisms, the technique which used is filter-paper disc-agar diffusion [13] where: (1) Inoculate flask of melted agar medium with the organism to be tested. (2) Pour this inoculated medium into a Petri dish. (3) After the agar has solidified, a multilobed disc that impregnated with different antibiotics laid on top of agar. (4) The antibiotic in each lobe of disc diffuses into medium and if the organism is sensitive to a particular antibiotic, no growth occur in a large zone surrounding that lobe (clear zone). (5) The diameters of inhibition zones were measured after 24–48 h at 35–37 8C (for bacteria) and 3–4 days at 25–27 8C (for yeast and fungi) of incubation at 28 8C (6) Measure each clear zone and compare between them to determine the antibiotic which is more inhibitor.

2.4. Measurements 2.4.1. Surface tension (g) At three different temperatures 25, 40 and 60 8C, the surface tension of aqueous solutions of cationic surfactants was measured using Tensiometer-K6 processor at concentration range from 1  102 to 1  108 M. The surface tension of pure water was initially obtained for each experiment for instrument calibration. Between the measurement runs, the ring was initially cleaned with pure water, then acetone. The apparent surface tension values were measured 3 times for each sample within 2 min interval between each reading and the recorded values were taken as the average of these values [12].

2.4.2.2. Biocidal activity against sulfate reducing bacteria. The inhibition activity of the prepared compounds against the Sulfate Reducing Bacteria (SRB) growth was measured using the serial dilution method according to ASTM D4412-84 [14]. SRB-contaminated water was supplied from Qarun Petroleum Co. (West Desert, Egypt). This water was used for microbial inhibition test. The test has been subject to growth of about 1015 bacteria cell/ml. The prepared compounds were tested as biocide for the SRB by dose of (5  104, 1  104, 7  105 and 5  105 M/l). The system was incubated to contact time of 3.0 h; each system was cultured in SRB specific media for 21dayes at 37–40 8C.

Scheme 1. Scheme preparation of cationic surfactants.

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Fig. 1. IR spectrum of N-(3-(butylideneamino)propyl)-N,N-dimethyldodecan-1-ammonium (C12BT).

3. Result and discussion 3.1. Chemical structure The chemical structure of the prepared cationic surfactants was confirmed by the FTIR, 1HNMR spectra and mass spectra. 3.1.1. FTIR spectra The prepared cationic surfactants showed the disappearance of both bands around 3300 cm1 (corresponding to amino group) and

around 1730 cm1 (corresponding to carbonyl group) and appearance new band around 1640 cm1 region in all prepared compounds due to mainly the imine group (C=N) formation .The prepared cationic surfactants nearly have the same main characteristic bands, for example (C12BT) showed stretching vibration band of–C–H aliphatic symmetric and asymmetric at 2855 and 2926 cm1, respectively,–N=CH– stretching at 1660 cm1, –CH2 bending at 1378 cm1, –CH3 bending at 1455 cm1 and absorption band at 1086 cm1 corresponding to C–N bond as shown in Fig. 1.

Fig. 2. 1H-NMR spectrum of N-(3-(butylideneamino)propyl)-N,N-dimethyldecan-1-ammonium bromide (C10BT).

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Fig. 3. Mass spectrum of N-(3-(butylideneamino)propyl)-N,N-dimethylhexadecan-1-ammonium bromide (C16BT).

3.1.2. 1HNMR spectra The 1H-NMR spectra data (d ppm) of compound (C10BT) showed signals at: d = 0.817 (t, 3H, –(CH2)7CH3); d = 0.868 (t, 3H, – N=CHCH2CH2CH3); d = 1.19 (m,14H, –(CH2)7CH3); d = 1.57 (m, 2H, –N=CHCH2CH2CH3); d = 1.72 (m, 2H, –CH2CH2(CH2)7CH3); d = 2.011(m, 2H, –N+CH2CH2CH2N=CH CH2CH2CH3); d = 2.2 (m, 2H, –N=CHCH2CH2CH3); d = 2.9(t, 2H, –N+CH2CH2CH2N=CH–); d = 3.2 (t,4H, –CH2N+(CH3)2CH2–); d = 3.73(s,6H, –CH2N+(CH3)2 CH2–); d = 7.79 (s, 1H, –N=CHCH2CH2CH3) Fig. 2. The 1H-NMR spectra data (d ppm) of compound (C12BT) showed signals at: d = 0.807 (t,3H, –(CH2)9CH3); d = 0.861 (t,3H, – N=CHCH2CH2CH3); d = 1.2 (m,18H, –(CH2)9CH3); d = 1.57 (m, 2H, – N=CHCH2CH2CH3); d = 1.71 (m,2H, –CH2CH2(CH2)9CH3); d = 2.03(m, 2H, –N+CH2CH2CH2N=CH CH2CH2CH3); d = 2.373 (m, 2H, –N=CHCH2CH2CH3); d = 2.905(t,2H, –N+CH2CH2CH2N=CH–); d = 3.2 (t, 4H, –CH2N+(CH3)2CH2–); d = 3.726(s,6H, –CH2N+(CH3)2 CH2–); d = 7.81 (s,1H, –N=CHCH2CH2CH3). The 1H-NMR spectra data (d ppm) of compound (C16BT) showed signals at: d = 0.86 (t, 3H, –(CH2)13CH3); d = 0.94 (t, 3H, – N=CHCH2CH2CH3); d = 1.24 (m, 26H, –(CH2)13CH3); d = 1.6 (m, 2H, –N=CHCH2CH2CH3); d = 1.77 (m, 2H, –CH2CH2(CH2)13CH3); d = 2.04(m, 2H, –N+CH2CH2CH2N=CH CH2CH2CH3); d = 2.28 (m, 2H, –N=CHCH2CH2CH3); d = 2.97(t, 2H, –N+CH2CH2CH2N=CH–); d = 3.28 (t, 4H, –CH2N+(CH3)2CH2–); d = 3.9 (s, 6H, –CH2N+(CH3)2 CH2–); d = 7.9 (s,1H, –N=CHCH2CH2CH3).

decreasing solubility thus free energy of system increase. So surfactant molecules aggregate into clusters (micelles), where the hydrophilic group are directed toward the solvent while the hydrophobic chain are directed toward the interior of micelle in a way to avoid energically unfavorable contact with the aqueous media, thereby reducing the free energy of system. Therefore, by increasing hydrophobic chain length, the tendency of surfactant molecule to form micelle increase thus CMC decreased. The decrease in CMC with rising temperatures is a result to increasing the temperatures causes a decrease in the hydration of hydrophilic group, which favor micellization (decrease CMC), also causes disruption of structured water surrounding the hydrFophobic group, an effect that disfavors micellization (increase CMC). Therefore, the relative magnitude of these two opposing effects determine whether the CMC increase or decrease over a particular temperature range [15]. From the data in Table 1, it is clear that CMC decrease by increasing temperatures, which implies that the magnitude of two factors is favoring micellization as indicated in Fig. 7.

3.1.3. Mass spectroscopy Mass spectrometry is an analytical technique that identifies the chemical composition of a compound or sample based on the mass-to-charge ratio of charged particles. It is also used for elucidating the chemical structures of compounds. Mass spectrum of N-(3-(butylideneamino)propyl)-N,N-dimethylhexadecan-1ammonium bromide (C16BT) was shown in Fig. 3 showed ion peaks at m/z: 460 (5%) (Corresponding to molecular weight) and at m/z: 462 (1%) (Corresponding to isotope peak). 3.2. Surface properties 3.2.1. Critical micelle concentration (CMC) Critical micelle concentration values of the prepared cationic surfactants have been obtained graphically by plotting the surface tension (g) of aqueous solutions of the prepared surfactants versus their bulk concentrations in mol/l at 25, 40 and 60 8C as showed in Figs. 4–6. By inspection data in Table 1, the CMC values of prepared cationic surfactants decrease by increasing the hydrophobic chain length this can be attributed to increasing the hydrophobicity and

Fig. 4. The surface tension against log concentration of compound (C10BT) at different temperatures.

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Fig. 5. The surface tension against log concentration of compound (C12BT) at different temperatures.

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Fig. 6. The surface tension against log concentration of compound (C16BT) at different temperatures.

3.2.2. Efficiency (PC20) The concentration required to reduce the surface tension of pure water by 20 mN/m (C20) was used to determine the efficiency of surfactant (PC20) which is the negative logarithm of C20. Efficiency values of prepared cationic surfactants are calculated and listed in Table 1. From these data, it was observed that increasing the alkyl chain length and temperature, the efficiency increase i.e., shift to lower concentration. Increasing the number of methylene groups (–CH2–) along the hydrophobic chains, increases the hydrophobicity of the molecules, hence water hydrophobic interactions increase which decreases the surface tension, followed by an increase in the effectiveness, as well as the efficiency (lower concentration) [16]. 3.2.3. Effectiveness (pCMC) Fig. 7. Effect of temperatures and hydrophobic chain length on critical micelle concentration values of prepared cationic surfactants.

pCMC ¼ g o  g The effectiveness is the difference between the surface tension of pure water (go) and the surface tension of surfactant solution (g) at the critical micelle concentration. Which give us good idea about the properties of prepared surfactants and their efficiency as a good surfactant. The most effective prepared surfactant is one which gives the largest reduction of the surface tension at the CMC. By inspection data in Table 1, it was found that the compound C12BT at 25 8C more effective surfactant, which

achieves the maximum reduction of the surface, tension at CMC reach to 41.79 [17]. 3.2.4. Maximum surface excess (Gmax) The maximum surface excess is expressed as the concentration of surfactant molecules at the interface per unit area (Gmax), which

Table 1 The Surface properties of synthesized cationic surfactant at different temperatures. Comp.

Temp. (8C)

CMC (mM/l)

pCMC (mN/m)

PC20 (mol/l)

’max  1010 (mol/cm2)

Amin (A2)

C10BT

25 40 60 25 40 60 25 40 60

1.598 1.0436 0.303 0.771 0.3845 0.184 0.0841 0.0551 0.0255

40.1 39.86 37.82 41.79 40.21 38.73 34.29 33.44 33.27

4.82 4.94 5.57 5.23 5.49 6.02 6 6.2 6.44

1.594 1.435 1.283 1.492 1.333 1.213 1.357 1.155 1.067

104.15 115.67 129.39 111.27 124.59 136.91 122.32 143.82 155.58

C12BT

C16BT

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depend mainly on the hydrophobic chain length and the temperature. The values of maximum surface excess Gmax have been calculated from surface tension using Gibb’s equation [18]. 

G max ¼ 

1 2:303 RT



dlog c

T

3.2.5. Minimum surface area (Amin) Minimum surface area is the average area (in square angstrom) occupied by each molecule adsorbed at the interface. Amin values increase by decreasing the angle between surfactant molecule (tail) and the interface, which describes the angular position of surfactant molecules at the interface [18]. The minimum Surface area (Amin) of prepared cationic surfactants have been calculated and listed in Table 1 based on Gibb’s adsorption equation:

1016

G max

DGoads ¼ DGomic  6:023  102  pCMC  Amin   DGomic DSmic ¼ d DT   DGomic DSads ¼ d DT DHmic ¼ DGomic þ T DSmic DHads ¼ DGoads þ T DSads



dg

where (dg/d log c) is the surface pressure, R is the universal gas constant and T is the absolute temperature. Data in Table 1, revel that by increasing the temperature and length of hydrophobic moiety of prepared cationic surfactants, shift Gmax to lower concentrations. Meaning that the surfactant molecules are directed towards the interface, decreasing the surface energy of their solutions. An increase in temperature results in an increase in the area per molecule, presumably due to increased thermal motion, which causes poorer packing of adsorbed molecules with a consequent decrease in the maximum surface excess (Gmax).

Amin ¼

DGomic ¼ RT lnðCMCÞ

N

where Amin increase by increasing the hydrophobic moiety (chain length) and temperature due to decreasing Gmax values, where by decreasing Gmax the distances between molecules will increase so Amin increase. This result is not expected as it is well known that the minimum area occupied by classical ionic surfactants at the surface of water is decreased as hydrophobic chain length increase, in part, by a competition between Van der Waals forces among hydrocarbon chains and repulsive interactions (e.g., electrostatic or hydration) between polar head groups [19]. In Table 1, Amin increases with hydrocarbon chain length for all prepared surfactants; this would be due to the fact that the balance of forces leading to the organization of the surfactants at the surface of aqueous solutions is, therefore, [17]. An increase in Amin is due to increasing temperature lead to thermal motion, which causes poorer packing.

The thermodynamic parameters of micellization and adsorption are summarized in Table 2, where theses parameters are calculated at 25, 40 and 60 8C. From thermodynamic parameters of micellization Table 2, change in free energy of micellization (DGomic) values are negative indicating that micellization process is spontaneous. In addition, DGomic increase in the negative direction by increasing both temperature and hydrophobic moiety, which imply that, the compound favor micellization [20]. DSmic are positive and increases by increasing hydrophobic chain length, which be indication on increasing in the randomness of the system upon transformation of surfactants molecules into micelle in another means the compounds favor micellization by increasing hydrophobic character thus CMC be, decreased [21]. From thermodynamic parameters of adsorption it observed that standard free energys of adsorption (DGoads) are negative which indicate that process of adsorption is spontaneous. In addition, DGoads increase in the negative direction by increasing both temperature and hydrophobic moiety length, which implies that the compounds favor adsorption at interface thus lowering surface and interfacial tension that by expanding force acting against the contracting force resulting from surface and interfacial tension [22]. Also it can be observed that DSads are positive and increase by increasing hydrophobic chain length. In comparison the thermodynamic parameter of micellization and adsorption we observed that DGoads are more negative than DGomic indicating the tendency of the molecules to adsorb at the air–water interface until complete surface coverage. Beyond this, the molecules diffuse to the bulk of their solution to form micelles. Hence, the thermodynamic aspects govern the micellization and adsorption processes. The chemical structure of these molecules is the main factor influencing their thermodynamic aspects. The DSads values are positive and slightly greater than the DSmic values for the same compounds. This may reflect the greater freedom of motion of the hydrocarbon chain at the air-aqueous solution interface. 3.3. Antimicrobial activity

3.2.6. Thermodynamics parameters of micellization and adsorption The thermodynamic parameters of adsorption and micellization of the synthesized cationic surfactants were calculated according to Gibb’s adsorption equations [20]:

In this work we aimed to evaluate the prepared cationic surfactants as biocide against some pathogenic Gram-positive (B. pumilus and M. luteus) and Gram-negative (P. aeuroginosa and

Table 2 Micellization and adsorption thermodynamic parameters of the prepared cationic surfactants. Comp

Temp. (8C)

DGomic (kJ/mol)

DHmic (kJ/mol)

DSmic (kJ/mol/K)

DGoads (kJ/mol)

DHads (kJ/mol)

DSads (kJ/mol/K)

C10BT

25 40 60 25 40 60 25 40 60

S15.96 S17.87 S22.44 S17.77 S20.47 S23.82 S23.26 S25.53 S29.29

– 22.06 53.63 – 35.97 32.03 – 21.90 33.29

– 0.1275 0.2283 – 0.1802 0.1676 – 0.1514 0.1878

S18.47 S20.65 S25.38 S20.57 S23.49 S27.01 S25.78 S28.43 S32.4

– 24.75 53.52 – 37.49 31.77 – 26.74 33.86

– 0.1449 0.2368 – 0.1947 0.1764 – 0.1761 0.1989

C12BT

C16BT

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Table 3 Antimicrobial activity of synthesized surfactants against pathogenic bacteria and fungi. Compound

Erythromycin Metronidazole C10BT C12BT C16BT

Inhibition zone diameter (mm/mg sample) Pseudomonas aeuroginosa

Sarcina lutea

Bacillus pumilus

Micrococcus luteus

Candida albica

Penicillium chrysogenum

30 – 17 16 14

44 – 28 31 20

32 – 21 14 18

32 – 25 25 19

– 27 32 24 22

– 25 23 19 20

S. lutea) bacteria and some pathogenic fungi (C. albicans and P. chrysogenum). The results of antimicrobial activity are recorded in Table 3, indicating that the synthesized compounds have antimicrobial activity rang from a moderate to slight high effect on Gramnegative bacteria and high on Gram-positive bacteria and very high effect on fungi compared to the drug reference used. The inhibition zone for P. aeuroginosa ranges from 14 to 17 mm/mg compared to 30 mm/mg for Erythromycin drug, for S. lutea range from 20 to 31 mm/mg compared to 44 mm/mg for Erythromycin drug, for B. pumilus range from 14 to 21 mm/mg compared to 32 mm/mg for Erythromycin drug, for M. luteus range from 19 to 25 mm/mg compared to 32 mm/mg for Erythromycin drug, for C. albicans range from 22 to 32 mm/mg compared to 27 mm/mg for Metronidazole drug, for P. chrysogenum range from 20 to 23 mm/ mg compared to 25 mm/mg for Metronidazole drug. The difference in their activities depends on the hydrophobic chains of surfactants. The cut-off effect has been noted when the alkyl chain is 10 carbon atoms (C10BT), which have the maximum inhibition zone in which the activity increases progressively in a homologous series of compounds, with increasing chain length up to a critical point, beyond which the activity decreases [23]. Several theories have been postulated as to why this cut-off effect occurs, first have associated this cutoff with a limit in solubility, they proposed that as the alkyl chain increases, lipid solubility increases at a rate faster than the change in partition coefficient (lipid/aqueous) theory [24]. At this higher chain length, partitioning is limited, making the concentration at the site of action insufficient to have a significant effect on the membrane of the cell wall. Hence, according to this theory the activity of compounds should be ordered as follow C10 > C12 > C16 chain due to increase lipid solubility from from C10BT to C16BT. Other accounts attribute this cut-off to a decrease in perturbation of the membrane at higher chain lengths, proposing that the longer alkyl chain molecules better mimic molecules in the lipid bilayer, causing less of a disruption in the membrane [25]. Other theory based on critical micelle concentration (CMC), as surfactants chain length increase, their tendency toward micelle formation is greater, noted by the lower CMCs at higher chain lengths as discussed previously so the tendency to form micelles becomes greater than the tendency to move toward the interface (the membrane), and thus the concentration at the action site becomes decreased, also, as the size of the diffusing species increases from the size of a monomer to that of micelles, their diffusibility and permeation abilities will decrease, affecting their action on the microbial cell wall and hence according to this theory the activity of compounds should be ordered as follow C10 > C12 > C16. Other theory based on surface and thermodynamic properties surfactants which showed tendency of prepared compound towards adsorption at the interfaces which facilitate their role of adsorption at the bacterial cell membrane, where increasing DGoads enhances the higher adsorptivity of prepared compound, from previous thermodynamic results DGoads increase by increasing chain length, and hence according to this theory the activity of compounds should be ordered as follow C16 > C12 > C10 chain.

So magnitude of these factors determines when cut-off occurs, according to data in Table 3, the cut-off was observed with surfactants with chain length (C10). Sulfate reducing bacteria (SRB) produces H2S, which increases the corrosiveness of brine and causing metals to crack and blister. In addition, bacterially (biogenic) produced H2S reacts with iron that is solubilized at the anode, thereby removing another corrosion byproduct to accelerate the corrosion process. The antimicrobial activity of the three cationic surfactants has been tested against sulfate reducing bacteria (SRB), using serial dilution method at doses 1  104, 5  104, 7  105 and 5  105 M/l and the results were listed in Table 4. SRBcontaminated water used for microbial inhibition test has been subject to growth of about 1015 bacteria cell/ml. The tested surfactants have very high activity against sulfate reducing bacteria even at very low concentration, maximum activity was observed for compound (C12BT) at concentration 5  104 M/l, where at this concentration there are complete kill for SRB. The structures of the cytoplasmic membranes of bacteria are essentially the same in Gram-positive and Gram-negative strains. The main constituents of the cytoplasmic membrane are phospholipids and membrane proteins. The phosphatidylethanolamine (almost neutral at physiological pH) is a major component present in the bacterial cytoplasmic membrane and that phosphatidylglycerol and its dimer, cardiolipin (both of which are negatively charged at physiological pH), are major acidic components [26]. There are great differences between Gram-positive and Gramnegative bacteria in the structure of cell walls as shown in Fig. 8. Gram-positive bacteria possess a relatively simple cell wall structure which is composed mainly of peptidoglycan and teichoic acid. The overall structure of the cell wall of Gram-positive bacteria is somewhat mesh-like [27]. On the other hand, the structure of the cell wall of Gram-negative bacteria is much more complicated than that of Gram-positive species. The peptidoglycan layer is rather thin, but there is an outer membrane outside the peptidoglycan layer. The outer membrane is composed mainly of lipopolysaccharides and phospholipids, and their significant role is to protect the bacterial cell from attack by foreign compounds, such as disinfectants. Therefore, the mechanism of action of such cationic surfactants on bacteria is originally focused on their adsorption tendency on the cellular membranes [28]. In Gram-positive bacteria, the adsorption is occurring in the lipoteichoic acid layer which is characterized by the charged nature and the ability to interact with the positively charged molecules and in Gram-negative bacteria Table 4 Biocidel effect of the prepared compounds against sulfate reducing bacteria, SRB. Conc. Blank Compound C10BT C12BT C16BT

5  104 (M)

1  104 (M)

7  105 (M)

5  105 (M)

15

10 10 Nil 10

102 10 104

102 10 105

104 102 106

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Fig. 8. Structure of the bacterial cell walls.

Fig. 8, the lipid layer (highly nonpolar layer) is the target of the positively charged biocide molecules [29]. At the complete coverage, the molecules penetrate through it. Furthermore, the positive charges in the cationic molecules neutralize the negative charges on the bacterial cell membranes. The adsorption disturbs the selective permeability of these membranes, and causes a severe disturbance of the biological reactions inside the cells due to the diffusion of several compounds from the environment due to the absence of the selective permeability [30]. In addition, the presence of the halogen atoms (Br) as counter ions increases the activity when they penetrate into the cells. 4. Conclusion The chemical structure of prepared compounds has an effect on surface properties where increasing hydrophobic chain length decrease CMC, ’max while Amin increase. Thermodynamic parameters showed that processes of adsorption and micellization are spontaneous and prepared cationic surfactants tend to adsorb at surface first then it form micelle. The prepared surfactants showed good biological activity against Gram-positive and Gram-negative bacteria and fungi. References [1] M.Z.A. Rafiquee, Nidhi Saxena, Sadaf Khan, M.A. Quraishi, Mater. Chem. Phys. 107 (2008) 528. [2] S. Jarudilokkul, E. Paulsen, D.C. Stuckey, Bioseparation 9 (2) (2000) 81. [3] Juliusz Pernaka, Joanna Kalewskaa, Hanna Ksycin’kab, Jacek Cybulskib, Eur. J. Med. Chem. 36 (2001) 899. [4] E. Serres, P. Vicendo, E. Perez, T. Noel, I. Rico-Lattes, Langmuir 15 (1999) 6956. [5] Huntsman, Dimethylaminopropylamine, in: Technical Bulletin, 1995 www. huntsman.com/.performance_chemicals/media/DMAPA.pdf Searched May 3, 2004.

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