untitled ISSN 215 Quatern as chem Bartosz Łę 1 Department of 2 Institute of Pla * Corresponding Tel.: +48.61.665 ARTICLE IN DOI: 10.5155/e Received: 18 M Accepted: 17 Ap Published onlin Printed: 30 June KEYWORDS Ionic liquids Antifeedants Antimicrobials Surface activity Carboxylic acid Crop protection 1. Introduct Quaterna ammonium tertiary ami method, also described a Heidelberger [3]. In 193 characterize century scie (chlorides an wide range surfactants, catalysts dur and anticorr used as sk antistatic a Benzalkoniu chloride (D (CET) are ac products. T makes them end of the 53‐2249 (Print) nary amm micals for ęgosz 1,*, Ag f Chemical Technol ant Protection, Nati g author at: Depart 53541. Fax: +48.61. FORMATION eurjchem.7.2.217‐2 arch 2016 pril 2016 ne: 30 June 2016 e 2016 S y ds n agents tion ary ammonium salts (quats) ines with alkyl o known as th at the end of r first discover 35 Domagk sy d their antiba entists have f nd bromides) of interestin which destro ring phase‐tran rosive propertie kin antiseptics agents, clean um chloride ( DA) or hexad ctive ingredien heir low toxi safe, effective 20th century, E / ISSN 2153‐225 htt Euro monium no crop prot gnieszka Bie ogy, Poznan Univer ional Research Inst tment of Chemical T 6652852. E‐mail ad 224.1428 m compounds (Q are the prod l halides. This he Menschutkin f 19th century red the antibac ynthesized lon acterial activiti focused on w due to the fact ng properties. oy bacteria an nsfer catalysis a es. At present, Q s, disinfectants ing agents a (BA), didecyld decyltrimethyla nts in the comp city to warm‐ and low‐cost an due to the w uropean Journal Europ 57 (Online)  20 tp://dx.doi.org/ pean Jo Journal we onanoate tection dziak 1, Tom rsity of Technology titute, Poznan, 60‐3 Technology, Pozna ddress: blegosz@w ABSTRACT The use of ren chemical synth traditional ole properties. Su metabolites fr protecting the biological prop this study, th presented. Th pressure. The characterized reduced the su obtained non deterrence act the synthesize allowed to link Cite this: Eur. QACs) or quate ucts of reacti universal syn n reaction, was y [1,2]. Jacobs cterial effect of ng‐chain QACs ies [4]. In the water soluble t that they exh They are ca nd fungi, serv and exhibit ant QACs are still w s, fabric soft and preserva dimethylammo ammonium bro positions of cle ‐blooded orga ntimicrobials. B orks of Roger l of Chemistry 7 pean Journal of C 016 Atlanta Pub 10.5155/eurjche ournal ebpage: www ‐based io masz Klejdys y, Poznan, 60‐965, P 318, Poland n University of Tec wp.pl (B. Łęgosz). newable chemic hesis. Numerous eochemicals du ubstances such a rom plants or m em from diseas perties, the natu he synthesis an he reactions wer e products we by good surfa urface tension o nanoates was a tivity, comparab ed ILs were als k surface proper J. Chem. 2016, 7 ernary on of nthesis s first s and QACs s and e 20th QACs hibit a ationic ve as istatic widely eners, atives. onium omide eaning anisms By the s and Sed qua wid chlo of IL with pro con App for solv ILs exh III [12 stat bas ioni stra pro ILs (2) (2016) 217‐ Chemistry lishing House LL em.7.2.217‐224. of Che w.eurjchem.co nic liquid sz 2 and Juliu Poland hnology, Poznan, 6 cals has become s naturally occur ue to the fact t as pelargonic (no microorganisms, ses, herbivores ural chemicals ar nd properties o re conducted in ere obtained w ace active prop of water to 21.86 also examined ble to natural occ so active toward rties with biolog 7(2), 217‐224 ddon, QACs w alified as ionic dely spread in orides and brom Ls. Synthesis of IL h desired ph operties of ILs, s nductivity, are propriate comb use in electroc vents and cataly for technologic hibit high biolog generation of ,13]. Biological acti ted for certain ed on the proc ic form and pr ategy leads to operties [19,20] is not only limi ‐224 LC ‐ All rights re .1428 emistry om ds usz Pernak 1 60‐965, Poland. e one of the mo rring compound that they exhib onanoic) acid, w play a major ro or predators. T re potential com of ammonium I a short time u with high yield perties. Didecyld 6 mN/m. The fe and the studie curring antifeed ds rods, cocci a ical activity of sy ith a melting liquids (ILs) [ the 20th cent mides are comm Ls gives an op hysicochemical such as density e determined bination of catio chemistry [8,9] ysts [10,11]. Af cal purposes, it gical activity. Th ILs, is develop ivity towards ILs [14‐16]. U cess of transfor roper selection ILs with antitu ]. The transform ited to pharmac served ‐ Printed y 1 st rapidly devel ds become green bit a wide rang which are obtaine ole in their defe Therefore, due ponents of ionic ILs with nonan nder ambient te s. The synthes dimethylammon eding deterrenc ed ILs exhibite dants, azadiracht and fungi. The o ynthesized ILs. point below [5,6]. Intensive tury, quaterna monly described pportunity to o characteristic y, viscosity or e d by their s on‐anion coupl or organic syn fter many years t has been note his group of ILs ping rapidly in bacteria and f se of ILs as ph rming active su of counter ion umor, antibiotic mation of active cy. d in the USA loping trends in n alternatives for ge of attractive ed as secondary ense systems by to their unique c liquids (ILs). In noate anion are emperature and sized ILs were nium nonanoate ce activity of the d high feeding tin. Additionally, obtained results 100 °C were ly studied and ary ammonium d as precursors btain products cs. The basic electrochemical structure [7]. ling creates ILs nthesis, both as s of developing ed that ILs may s, considered as n recent years fungi has been harmaceutics is ubstances to an ns [17,18]. This c or anesthetic e substances to n r e y y e n e d e e e g , s e d m s s c l . s s g y s s n s n s c o 218 Łęgosz et al. / European Journal of Chemistry 7 (2) (2016) 217‐224 Table 1. Synthesis and thermal properties of quaternary ammonium nonanoates *. Nonanoate R1 R2 Yield [%] Tg [oC] Tc [oC] Tm [oC] Tonset5% [oC] Tonset50% [oC] 1 C10H21 C10H21 92 ‐ 18 33 180 260 2 Benzyl Alkyl 91 ‐ ‐12 ‐6 175 243 3 C16H33 CH3 95 20 93 96 193 231 * Tg‐glass transition, Tc‐crystallization temperature, Tm‐melting temperature, T5%‐decomposition temperature to 5% weight loss, T50%‐decomposition temperature to 50% weight loss. Conversion of compounds widely used in agriculture ‐ herbicides, fungicides, growth regulators is also possible. Known herbicides, such as phenoxyacetic acids (2,4‐D, MCPA, MCPP and MCPB), dicamba, clopyralid, fomesafen, glyphosate, metsulfuron methyl, or bentazone, have been successfully transformed into ILs, which resulted in increased efficiency, lower environmental impact and reduced required dose per hectare [21‐32]. Combination of herbicidal activity of the anion with different properties of the cation leads to dual‐ function ILs [33]. ILs can also be used for protection of crops against pathogenic fungi‐transforming fungicides, such as tebuconazole and propiconazole, results in efficient fungicidal ILs with improved physicochemical properties [34]. ILs also have the potential to be used also in protection of harvested grains from insects by acting as feeding deterrents. Deterrent activity is described as the ability to temporary or constantly disrupt the feeding and reproduction processes of an organism without killing it. Substances which exhibit deterrent activity are common in nature and occur in many plants [35]. Azadirachtin, obtained from Azadirachta indica, is one of the most efficient deterrent, however attempts to synthesize it under laboratory conditions require complicated reactions which involve many steps [36]. In search for cheap and efficient deterrents, ILs have been proposed as alternatives [37,38]. Based on the knowledge regarding the unique properties of naturally occurring substances, ILs with natural anions‐theophyllinates and carboxylates have been synthesized and examined as feeding deterrents [39,40]. The main concern associated with the use of large amounts of ILs, i.e. in agriculture, is their effect on environment [41]. Efficient use of ILs should compromise high biological activity directed to specific pests with negligible impact on other organisms present in soil or water. General procedures for the synthesis of non‐toxic and environmental friendly ILs have been established on the basis of several studies dedicated to this topic [42]. The use of ionic forms of substances commonly present in nature may be an alternative way to lower the toxicity and improve the biodegradability of ILs, since such substances are often characterized by promising properties [40,43]. Their potential use in various applications became one of the most popular trends in science [44]. The use of such substances in chemical synthesis is considered as a key factor in order to obtain low‐cost and environmentally friendly compounds. Examples of this strategy, i.e. synthesis of terpenoid lactones from perillyl alcohols [45] or dialkoxy‐ benzenes from benzenediols [46], show the benefits of using natural active substrates. Nonanoic acid (pelargonic acid) is one of such substances. In nature, it occurs in many plants and is readily bio‐ degradable and non‐toxic at small doses, however it is irritant for the skin. In the industry, this acid is used in organic synthesis, pharmaceuticals, lubricants and plasticizers. Moreover, it has a number of promising properties, such as its high non‐selective herbicidal activity. Nonanoic acid is usually used as in the form of an ammonium salt or in combinations with glyphosate, another non‐selective herbicide. It is also effective as a fungicide [47]. In this study, ammonium ILs with nonanoate anion are presented as efficient antimicrobials and food deterrents. Nonanoic acid, which is commonly present in nature and exhibits a wide range of properties, was introduced into the structure of ILs as an anion. As shown in previous study, the introduction of an anion of natural origin into ILs resulted in changed physicochemical characteristics and biological properties of the prepared products [40]. Therefore, there is strong need to seek novel sources of anions, which would influence these parameters in the most optimal manner and allow to obtain ILs with a wide range of biological activity and low environmental impact at the same time. 2. Experimental 2.1. Materials Didecyldimethylammonium chloride (50% in water), benzalkonium chloride (60% C12H25, 40% C14H29, purity 97%), hexadecyltrimethylammonium chloride (97%), potassium hydroxide (95%), nonanoic acid (95%) and solvents were purchased from Sigma‐Aldrich and Avantor and used as obtained. 2.2. Instrumentation 1H NMR spectra were recorded using a Mercury Gemini 300 spectrometer operating at 300 MHz with TMS as the internal standard. 13C NMR spectra were obtained with the same instrument at 75 MHz. The purity of the synthesized nonanoates was determined by CHN elemental analysis and analysis of NMR spectra. 2.3. Synthesis Quaternary ammonium salts were synthesized in two steps reaction. The process parameters were monitored using Mettler‐Toledo EasyMax 102. Reactions were conducted under ambient temperature and pressure. The first stage of the reaction was the synthesis of quaternary ammonium hydroxide by ion exchange reaction between the corres‐ ponding quaternary ammonium chloride (didecyldimethyl ammonium ‐ DDA, benzalkonium ‐ BA or hexadecyltrimethyl ammonium ‐ CET) and a stoichiometric amount of potassium hydroxide in 2‐propanol as solvent. Reagents were mixed for 15 min at room temperature. KCl was filtered off and the obtained quaternary ammonium hydroxide was then used in a reaction with a stoichiometric amount of nonanoic acid. Neutral pH of the mixture indicated the end of the reaction. The solvent was evaporated under reduced pressure and the obtained product was dried under vacuum (0.1 bar) at 40 °C for 8 h (Table 1). Łęgosz et al. / European Journal of Chemistry 7 (2) (2016) 217‐224 219 Didecyldimethylammonium nonanoate (1): Color: White. Yield: 92%. 1H NMR (300 MHz, CDCl3, δ, ppm): 0.88 (m, 9H, CH3‐CH2), 1.26 (m, 38H, CH3‐CH2), 1.59 (m, 4H, CH2‐CH2‐N), 1.66 (m, 2H, CH2‐CH2‐COO‐), 2.15 (m, 2H, CH2‐COO‐), 3.32 (s, 6H, CH3‐N), 3.40 (m, 4H, CH2‐N). 13C NMR (75 MHz, CDCl3, δ, ppm): 179.9 (1C, COOH), 63.6 (2C, (CH2)2N), 51.5 (2C, (CH3)2N), 39.4 (1C, CH2COO), 32.1 (3C, (CH3CH2CH2(CH2)7)2N, CH2(CH2)5COO), 29.7 (4C, (CH3(CH2)2(CH2)2(CH2)5)2N), 29.5 (7C, (CH3(CH2)4(CH2)2(CH2)3)2N, (CH2)3(CH2)2COO), 26.6 (2C, (CH3(CH2)7CH2CH2)2N), 25.6 (1C, CH2CH2COO), 22.9 (5C, (CH3CH2(CH2)5CH2(CH2)2)2N, CH2(CH2)6COO), 14.3 (3C, (CH3 (CH2)9)2N, CH3(CH2)7COO). Anal. calc. for C31H65NO2: C, 76.95; H, 13.54; N, 2.89. Found: C, 77.28; H, 13.21; N, 3.15%. Benzalkonium nonanoate (2): Color: White. Yield: 91%. 1H NMR (300 MHz, CDCl3, δ, ppm): 0.86 (m, 6H, CH3‐CH2), 1.25 (m, 26H, CH3‐CH2), 1.62 (m, 2H, CH2‐CH2‐N), 1.76 (m, 2H, CH2‐CH2‐ COO), 2.18 (t, J 15.6, 2H, CH2‐CH2‐COO); 3.25 (s, 6H, CH3‐N); 3,38 (m, 2H, CH2‐CH2‐N); 4.90 (s, 2H, ArCH2N); 7.43 (m, 3H, Ar‐ H); 7.60 (m, 2H, Ar‐H). 13C NMR (75 MHz, CDCl3, δ, ppm): 179.5 (1C, COO), 133.0 (2C, Ar‐C), 130.2 (1C, Ar‐C), 128.9 (2C, Ar‐C), 127.6 (1C, Ar‐C), 67.2 (1C, Ar‐CH2N), 63.0 (1C, CH2N), 49.5 (2C, (CH3)2N), 39.3 (1C, CH2COO), 31.8 (2C, CH2(CH2)10N, CH2(CH2)5 COO), 29.4 (1C, CH2(CH2)2COO), 29.2 (1C, CH2(CH2)7N), 29.1 (2C, (CH2)2(CH2)3COO), 27.1 (1C, CH2(CH2)2N), 26.2 (CH2CH2 COO), 25.2 (1C, CH2CH2N), 22.5 (2C, CH2(CH2)11N, CH2(CH2)6 COO, 13.9 (2C, CH3(CH2)12N, CH3(CH2)7COO). Hexadecyltrimethylammonium nonanoate (3): Color: White. Yield: 95%. M.p.: 94‐96 °C. 1H NMR (300 MHz, CDCl3, δ, ppm): 0.96 (m, 6H, CH3‐CH2), 1.29 (m, 32H, CH3‐CH2), 1.33 (m, 4H, CH2‐CH2‐CH2‐N, CH2‐CH2‐CH2‐COO), 1.62 (m, 2H, CH2‐CH2‐ N), 1.73 (m, 2H, CH2‐CH2‐COO), 2.40 (m, 2H, CH2CH2COO), 3.24 (m, 2H, CH2‐CH2‐N), 3.30 (s, 9H, CH3‐N). 13C NMR (75 MHz, CDCl3, δ, ppm): 178.9 (1C, COO), 66.6 (1C, CH2N), 53.0 (3C, (CH3)3N), 38.1 (1C, CH2COO), 31.7 (2C, CH2(CH2)13N, CH2(CH2)5 COO), 29.4 (7C, (CH2)6(CH2)3N, CH2(CH2)2COO), 29.1 (2C, (CH2)2(CH2)9N), 29.0 (4C, (CH2)2(CH2)11N, (CH2)2(CH2)3COO), 26.6 (1C, CH2CH2N), 26.0 (1C, CH2CH2COO), 23.0 (1C, CH2 (CH2)2N), 22.5 (2C, CH2(CH2)14N, CH2(CH2)6COO), 13.9 (2C, CH3(CH2)15N, CH3(CH2)7COO). Anal. calc. for C28H59NO2: C, 76.12; H, 13.46; N, 3.17. Found: C, 75.94; H, 13.58; N, 3.00%. 2.4. Solubility The solubility of the prepared ILs was determined according to Vogel`s Textbook of Practical Organic Chemistry [48]. Popular representative solvents were chosen and ranked in descending order of Snyder polarity index value (water ‐ 9.0, methanol ‐ 6.6, DMSO ‐ 6.5, acetonitrile ‐ 6.2, acetone ‐ 5.1, ethyl acetate ‐ 4.4, chloroform ‐ 4.1, toluene ‐ 2.3, hexane ‐ 0.0). The term “complete solubility” refers to ILs, which were dissolved (0.1 g of IL) in 1 mL of solvent, while the term “limited solubility” means that the IL was dissolved in 3 mL of solvent. The term “insoluble” was used to describe no solubility of 0.1 g of IL in 3 mL of solvent. Tests were conducted at 20 °C under ambient pressure. 2.5. Thermal stability Thermal transition temperatures were determined by DSC, with a Mettler Toledo Stare DSC1 (Leicester, UK) unit, under nitrogen. ILs (between 5 and 15 mg) were placed in aluminum pans and heated from 25 to 120 °C at a heating rate of 10 °C/min, cooled with an intracooler at a cooling rate of 10 °C/min to ‐100 °C, then heated again to 120 °C. Thermo‐ gravimetric analysis was performed using a Mettler Toledo Stare TGA/DSC1 unit (Leicester, UK), under nitrogen. ILs (between 2 and 10 mg) were placed in aluminum pans and heated from 30 to 450 °C at a heating rate of 10 °C/min. 2.6. Surface tension The surface tension was determined using the pendant drop method. The measurements were carried out by the use of a DSA 100 analyzer (Krüss, Germany, accuracy ± 0.01 mN/m) at 25 °C (temperature controlled using a Fisherbrand FBH604 thermostatic bath ‐ Fisher, with the accuracy of 0.1 °C). The principle of this method is to form an axisymmetric drop at the tip of a syringe needle. The image of the drop (3 mL) from a CCD camera was taken and digitized. The surface tension (in mN/m) is calculated by analyzing the profile of the drop according to the Laplace equation. The values of the critical micelle concentration (CMC) and the surface tension at the CMC (γCMC) were determined from the intersection of the two straight lines drawn in low and high concentration regions in surface tension curves (γCMC vs log C curves) using a linear regression analysis method. The basis for the determination of the contact angle is the image of the drop on the examined surface (paraffin). After determination of the actual drop shape and the contact line, the drop shape is adapted to fit a mathematical model used to calculate the contact angle. The most exact method to calculate this value is Young‐Laplace fitting (sessile drop fitting). Complete drop contour is evaluated. After successful fitting of the Young‐ Laplace equation, the contact angle is determined as the slope of the contour line at the 3‐phase contact point (solid‐liquid and liquid‐air). The measurements were carried out by the use of DSA 100 analyzer, Krüss. 2.7. Feeding deterrent activity The bioassay experiments were conducted with Tribolium confusum Duv. (Larvae and adults), Sitophilus granarius L. (Adults), and Trogoderma granarium Ev. (Larvae). The insects were grown on a wheat grain or whole‐wheat meal diet in laboratory colonies, which were maintained at 26 ± 1 °C and 60 ± 5% relative humidity. Choice and no‐choice tests for insect‐feeding were conducted following a previously described procedure [49]. Wheat wafers discs (1 cm in diameter, 1 mm thick) were saturated by dipping either in ethanol only (control) or in a solution of the studied ILs (1%) in ethanol to be tested. After evaporation of the solvent (30 min of air‐drying) the wafers were weighted and offered to the insects in plastic boxes as the sole food source for 5 days. The feeding of insects was recorded under three sets of conditions: (1) on two control discs (CC), (2) on a choice between one treated disc (T) and one control disc (C; choice test), and (3) on two treated discs (TT; no‐choice test). Each of the three experiments was repeated five times with 3 adults of S. granarius, 20 adults and 10 larvae of T. confusum and 10 larvae of T. granarium. The number of individual insects depended on the intensity of their food consumption. The adults used for experiments were unsexed, 7‐10 days old, and the larvae were 5‐30 days old. After 5 days the discs were weighted and the average weight of eaten food was calculated. 2.8. Antimicrobial activity Antimicrobial activity was determined by the tube dilution method. A series of ammonium salts dilutions was prepared on Müller‐Hinton broth medium (bacteria) or Sabouraud broth medium (fungi). Suspensions of the microorganisms, prepared from 24 h cultures of bacteria in the Müller‐Hinton broth medium and from 48 h cultures in the Sabouraud agar medium for fungi, at a concentration of 106 cfu/mL, were added to each dilution in a 1+1 ratio. Growth (or lack of growth) of the microorganisms was determined visually after incubation for 24 h at 37 °C (bacteria) or 48 h at 28‐30 °C (fungi). 220 Łęgosz et al. / European Journal of Chemistry 7 (2) (2016) 217‐224 Table 2. Solubility of prepared nonanoates *. IL Solvent Water Methanol DMSO Acetonitrile Acetone Ethyl acetate Chloroform Toluene Hexane 1 ± + ‐ ‐ ‐ ‐ ± ± ‐ 2 ± + + ± ± ± + ± ‐ 3 + + + ± ± ± + ± ‐ * “+” ‐ complete solubility, “±” ‐ limited solubility, “‐” – insoluble. Table 3. Surface activity of synthesized ILs. IL CMC γCMC πCMC pC20 Γmax Amin (mmol/L) (mN/m) (mN/m) ‐ (μmol/m2) (10‐19 m2) 1 0.245 21.86 50.82 4.96 1.99 8.31 2 0.513 26.63 45.99 4.18 2.55 6.51 3 0.246 28.01 44.51 4.08 4.57 3.63 The lowest concentration at which there was no visible growth (turbidity) was taken as the MIC. Then, one loopful from each tube was cultured on an agar medium with inactivates (0.3% lecithin, 3% polysorbate 80 and 0.1% cysteine L) and incubated for 48 h at 37 °C (bacteria) or for 5 days at 28‐30 °C (fungi). The lowest concentration of the salt supporting no colony formation was defined as the MBC and MFC. The following microorganisms were used during the tests: standard strains representative of cocci ‐ Micrococcus luteus ATCC 9341, Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 12228, Enterococcus faecium ATCC 49474; rods: Moraxella catarrhalis ATCC 25238, Escherichia coli NCTC 8196, Bacillus subtilis ATCC 6633, Proteus vulgaris NCTC 4635, and fungi ‐ Candida albicans ATCC 10231, Rhodotorula rubra (Demml 1889, Lodder 1934). Standard strains were supplied by the National Collection of Type Cultures (NCTC) London and American Type Culture Collection (ATCC). Rhodotorula rubra was obtained from the Department of Pharmaceutical Bacteriology, K. Marcinkowski University of Medical Sciences, Poznan. 3. Results and discussion Quaternary ammonium nonanoates were obtained with high yields, exceeding 90% (Table 1). Water content of the dried nonanoates was measured by Karl‐Fischer method and found to be less than 300 ppm. The structures of synthesized quaternary ammonium nonanoates were confirmed with nuclear magnetic resonance (1H and 13C NMR) and elemental analysis (CHN). Table 1 presents results of thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Differential scanning calorimetry revealed that all the synthesized compounds were ILs (Tm < 100 °C). ILs 1 and 2 were high viscosity liquids at room temperature, while IL 3 was a colorless solid. Determination of phase transition tempera‐ tures also allowed to distinguish ILs which occur in liquid state at room temperature. Strong determination of phase transition characteristics by ILs structure is visible. No glass transitions were observed for ILs 1 and 2. IL 3 exhibited glass transition at the temperature of 20 °C. Crystallization and melting occurred in a wide range of temperatures. Lowest temperature values (‐19 °C for crystallization and ‐6 °C for melting) were observed for IL 2 as this IL included a non‐linear aromatic substituent in the structure of the cation. The presence of two saturated long‐alkyl chains, able to bend and mutually interact in IL 1 resulted in a crystallization temperature at 18 °C and melting point at 33 °C. Highest values were determined for IL 3, crystallization occurred at 93 °C, melting was observed at 96 °C. Thermal stability curves revealed that the obtained ILs were thermally stable up to approx. 175 °C, when decom‐ position of IL 2 occurs. For IL 1 5% weight loss was observed at 180 °C and decomposition of 50% of the sample occurred at 260 °C. IL 2 started to decompose at 175 °C and weight loss by 50% was noted at 243 °C. IL 3 was the most stable IL among the synthesized nonanoates. Degradation of 5% by weight occurred at 193 °C and 50% weight loss was observed at 231 °C. Generally, nonanoates with saturated alkyl chains in the structure of the cation were more stable than the IL with a benzyl substituent. The presence of a single alkyl chain promoted higher thermal stability. The obtained products were also stable in contact with air and soluble in polar solvents (Table 2). Influence of the structure of ILs on their solubility is significant. ILs with more than one alkyl chain in the cation (1 and 2) were moderately soluble in water as the most polar solvent. Due to the ionic nature of the synthesized nonanoates, the ILs were insoluble in hexane. Solubility of IL 1 in solvents with a moderate polarity index (C‐F) decreased and then returned to its previous level in solvents with lower polarity (G,H). Such behavior is most likely caused by presence of two long‐chain alkyl substituents in cation and their interactions with particles of solvents. Surface activity parameters: critical micelle concentration (CMC), surface tension at CMC (γCMC), effectiveness of surface tension reduction (πCMC), efficiency of surface adsorption on an air‐water interface (pC20), maximum surface excess concentration (Γmax) and surface area occupied by IL molecules (Amin) were characterized (Table 3). As shown in Table 3, best results were achieved for IL 1 as well as 3. This is most likely associated with the linear structure of alkyl substituents in the particle. IL 2 presented higher CMC value due to possible interactions between solvent and free electrons of the aromatic ring. The effectiveness of surface tension reduction, also called surface pressure at the saturated air/solution interphase, and the adsorption efficiency pC20 are also important surface parameters. Adsorption efficiency is defined by using the Equation (1). log (1) where C20 is the molality of the compound which leads to a reduction of the surface tension of the solvent by 20 mN/m. IL 1 reduced the surface tension of water to 21.86 mN/m which is a very good result. On the other hand, the remaining two nonanoates reduced the surface tension value to 26‐28 mN/m which is characteristic for cationic surface active compounds [50]. The higher the value of pC20 is associated with, the higher adsorption efficiency of the compound. The values of πCMC and pC20 obtained for the investigated ILs are also listed in Table 3. The relations between the surface tension values for aqueous solutions of the synthesized ILs and the log of concentration were determined (Figure 1). It can be observed that the surface tension of the aqueous solutions of the synthesized ILs showed a progressive decrease with increasing concentration and remained constant above the CMC. Contact angle values of the prepared nonanoates were determined based on drop shape analysis on the examined surface ‐ paraffin (Figure 2). Presence decrease of ammonium 42.5 ° for c exhibited the chloride and was observe 72.3 ° for chl The syn granarius, T larvae) and T activity was Values of co and R (relat follows: 1 where CC wa control, TT w the no‐choic of the food c coefficients deterrence ( good, 150‐10 IL 1 was parameters r was effective consumption activity of th than eat tr completely deterrent ac Figure 2. D e of the pelarg f contact ang salts, the conta chloride to 10 e highest differ d 34.5 ° for pe ed in case of he loride and 44.8 nthesized ILs Tribolium conf Trogoderma gra estimated base oefficients A (a tive coefficient 100 00 as the average w was the averag ce test and C an consumed in th was used to (T), based on th 01 good, 100‐50 the most effici reached or wer e in both choic n in the no‐cho his substance, s reated wafers ignored the tivity was 200. Łęgosz et al. Figure 1. Surf Drop shapes of the gonate anion in gle values. F act angle value .6 ° for IL 1. ence between C elargonate. The exadecyltrimeth ° for IL 3. were tested fusum (both a anarium (larvae ed on the amoun absolute coeffic of deterrence) weight of the fo ge weight of th nd T expressed e choice test. T evaluate the he following cr 0 medium, < 50 ient feeding det re close to maxi ce and no‐choic oice test shows ince the insects . The S. gra treated wafer . The larvae of . / European Jou face tension of the e prepared ILs (upp n ILs caused a For didecyldim e was lowered Benzalkonium CA values ‐ 68.6 e smallest diffe hylammonium against Sito adult specimen e). Feeding dete nt of food consu cient of deterr ) were calculat ood consumed he food consum the average w The sum of thes total coefficie riteria: 200‐151 0 weak. terrent ‐ values mum (Figure 3 ce test. The ver very good dete s preferred to s narius beetles rs and their T. confusum (T rnal of Chemistry synthesized ILs as per) on paraffin ba rapid methyl d from m salts 6 ° for erence salts ‐ ophilus n and errent umed. rence) ted as (2) (3) in the med in eights se two ent of 1 very s of all ). IL 1 ry low errent starve s had total T‐198) and leve mos IL 1 stro S. g dete tota obt conf larv IL ( gra dete con amo y 7 (2) (2016) 21 s function of conce ase compared to ch d T. granarium el of T. The bee st resistant org 1 was very go onger deterrenc granarius beet errence of IL 2 al deterrence c ained IL a very Fi The prepared fusum (T‐181) vae of T. confusu (T‐159). The T narius beetles a errence (T‐141 nsumed food co ounts. Efficacy 17‐224 ntration at 25 °C. hlorides (lower): a (T‐198) were c tles (adults) of ganisms to the t ood to all test ce effect compa tles and larva was lower tha coefficient oscil good deterrent igure 3. Deterrent IL 2 was most ) and larvae o um exhibited a index value wa and stayed with 1). No‐choice t ontaining the te of IL 2 increas a) 1, b) 2, c) 3. characterized b T. confusum (T tested IL. Deter insects. This I ared to azadira ae of T. confu an IL 1, howeve llated above 15 t (Figure 4). t activity of IL 1. efficient towar f T. granarium higher toleranc as lower only in hin a range goo test revealed th ested compoun sed during cho 221 by a little lower T‐183) were the rrent activity of L has an even chtin in case of fusum. Feeding er the values of 50, making the ds beetles of T. m (T‐184). The ce to the tested n the case of S. od coefficient of hat the insects nd, but in small ice test, where r e f n f g f e . e d . f s l e 222 insects consu with azadira for all tested Feeding was characte tested ILs. A deterrents. T activity is s activity and (Figure 6). Figure 6. Dete [51] towards S. IL 1 wit cation was m umed the food achtin IL 2 exh d insects. Figure 4. Feeding deterrence of I erized by the lo All ILs can be The influence o strong. Correla the structure o Figure 5. De errent activity of granarius. th two long al most effective to Łę from the treate hibited a weake g deterrence activi L 3 is presente owest deterrenc described as of long alkyl ch ation between of synthesized eterrent activity of synthesized nona kyl chains in t owards S. grana ęgosz et al. / Eur ed wafers. Com er deterrent ac ty of IL 2. d in Figure 5. T ce activity amon very good or ain on the dete feeding deter ILs was determ IL 3. anoates and azadi the structure o arius, while IL 3 ropean Journal of mpared ctivity This IL ng the good errent rrence mined rachtin of the 3, with only acti org the Wh pro (T) out dete dete betw betw loga req and gra Figu Figu prop pro The resu obs corr as f and tim chlo form for inve MIC ILs (Ta case non the sign effe 4. C amm thei obt con f Chemistry 7 (2) y a single long‐ ivity. A similar anisms. Anti‐fe tested organi hen compared operties were o for this IL exc of four tested o Since the chem ermine both errence activit ween these tw ween the valu arithm of the uired to reduce d feeding dete narius, T. conf ure 7. ure 7. Correlation perties of the synth The curves re operties and sur e highest surfac ults obtained d served that the respond to a de feeding deterre d antifeedants e. The antimicr orides ([QAC][C mulations were the synthesized estigated again C/MBC and MIC were effective able 4). The calculated e of P. vulgari nanoates remai MIC/MBC a nificantly. Addi ective antimicro Conclusions This study f monium nonan ir properties. T ain compound nfirmed by NMR ) (2016) 217‐224 ‐chain alkyl sub r trend was als eedant propert sms have bee to azadirach btained for IL ceeded the resu organisms. mical structure their surfac ty, an attempt wo parameters w e of pC20 para surfactant con e the surface te errence of th fusum and T. n between surfac hesized nonanoate eflect the depen rface activity o ce activity of IL during the feed e lower pC20 v ecreased effecti ents The correla properties has obial activity Cl]) and their w e the basis for d nonanoates. A nst bacteria an C/MFC values. towards most d values differed is and C. albica ined at the sam and MIC/MFC itionally, IL 1 c obial agent amo focused on th noate‐based ILs The employed ds with high R and elemental 4 bstituent, exhib so observed fo ties of azadira n described p htin, the bes 1. The total coe ults of azadira s of the obtain e properties to describe th was conducted meter, describ centration in t ension of water e obtained IL granarium are ce activity and fe es. ndence betwee f the synthesize L 1 matches w ding deterrence values in case iveness of the s ation between s been examine of quaternar widespread use conducting ap Antimicrobial p nd fungi by de Results show of the tested m d from 8 to 46 p ans. Activity o me level as the C values did can be indicate ong studied ILs. he synthesis s and subsequ synthesis meth yields and h l analyzes. ited the lowest or other tested achtin towards reviously [51]. t anti‐feedant efficient values chtin for three ned nonanoates and feeding he dependence d. The relations ed as negative the bulk phase r by 20 mN/m, Ls towards S. e presented in eeding deterrence en antifeedants ed nonanoates. with the highest e test. It can be of IL 2 and 3 synthesized ILs surface activity ed for the first ry ammonium in disinfectant propriate tests properties were etermining the that the tested microorganisms ppm only in the f the obtained ir precursors ‐ not change ed as the most of quaternary ent analysis of hod allowed to igh purity, as t d s . t s e s g e s e e , . n e s . t e 3 s y t m t s e e d s e d ‐ e t y f o s Łęgosz et al. / European Journal of Chemistry 7 (2) (2016) 217‐224 223 Table 4. Antimicrobial activity of synthesized ILs and their precursors. Species Activity a [QAC][C8COO] [QAC][Cl] [DDA] b [BA] c [CET] d [DDA] b [BA] c [CET] d M. luteus MIC 0.1 0.2 0.2 0.1 0.1 0.5 MBC 0.1 0.5 0.5 0.1 0.1 1.0 S. aureus MIC 0.1 1.0 0.5 0.1 0.2 1.0 MBC 1.0 1.0 2.0 0.2 2.0 1.0 S. epidermidis MIC 0.1 2.0 0.2 0.1 2.0 0.5 MBC 0.2 2.0 0.5 0.2 2.0 2.0 E. faecium MIC 0.2 2.0 4.0 0.1 1.0 1.0 MBC 0.2 2.0 8.0 0.2 1.0 2.0 M. catarrhalis MIC 0.1 2.0 0.1 0.1 1.0 1.0 MBC 1.0 4.0 0.5 0.2 2.0 1.0 E. coli MIC 0.1 0.5 0.5 0.1 1.0 0.5 MBC 0.1 2.0 1.0 0.2 2.0 4.0 P. vulgaris MIC 16.0 31.0 62.0 4.0 8.0 31.0 MBC 16.0 62.0 62.0 8.0 16.0 62.0 B. subtilis MIC 0.1 0.5 0.2 1.0 1.0 1.0 MBC 0.1 0.5 0.2 2.0 1.0 2.0 C. albicans MIC 4.0 2.0 8.0 4.0 2.0 1.0 MFC 16.0 8.0 8.0 4.0 4.0 1.0 R. rubra MIC 4.0 2.0 31.0 4.0 2.0 0.5 MFC 4.0 8.0 31.0 4.0 2.0 0.5 a Unit in ppm. b Didecyldimethylammonium cation. c Benzalkonium cation. d Hexadecyltrimethylammonium cation. It was established, that the structure of the cation had a notable influence on the physicochemical characteristics (thermal stability and solubility), surface activity and biological properties (feeding deterrence and antimicrobial activity) of the studied ILs. The conducted tests confirmed that each of the obtained ILs was characterized by good surface and biological activity. Among the studied ILs, the most promising results were exhibited by didecyldimethylammonium nonanoate. This IL was most efficient in terms of surface active properties (surface tension of water reduced to 21.86 mN/m) as well as feeding deterrence (higher activity compared to the standard, azadirachtin, for three out of four tested organisms). The obtained results indicate that the specific shifts in properties of the obtained ILs may be mainly attributed to the structure of the cation. The presence of two long alkyl chain substituents in didecyldimethylammonium nonanoate contributed to beneficial changes. 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