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Research Article | DOI: https://doi.org/10.31579/2690-1919/257
* Department of Chemistry, Faculty of Science, Misurata University, Libya.
*Corresponding Author: Ramadan Ali Bawa, Department of Chemistry, Faculty of Science, Misurata University, Libya.
Citation: Ramadan A. Bawa and Amany H. Elgroshi. (2022). Synthesis of Some Organic Ammonium Formate Salts and Study of their Antifungal Properties. J Clinical Research and Reports, 11(4); DOI:10.31579/2690-1919/257
Copyright: © 2022, Ramadan Ali Bawa. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Received: 10 June 2022 | Accepted: 30 June 2022 | Published: 11 July 2022
Keywords: organic ammonium formate salts; ionic liquids; spectroscopic; antifungal properties
This work is concerned with the preparation of a number of organic ammonium formate salts (or ionic liquids; ILs) throughout a reaction between the formic acid and some aliphatic and aromatic amines including the ammonia. Five organic ammonium formate salts were formed, some of them were in the form of solid salts and others were as the ionic liquids (ILs) at room temperature. The yields of the prepared organic salts ranged from (21%) to (79%). However, some attempts towards the preparation of other fifteen organic salts were not successful. The resulting five organic ammonium formate salts/ionic liquids were characterized using a number of spectroscopic techniques such as the infrared (IR), the nuclear magnetic resonance spectroscopy (1HNMR) and the mass spectrometry (ms). The collected spectroscopic data confirmed the formation of theses organic ammonium formate salts. The antifungal properties of the prepared organic ammonium formate salts were investigated against the aspergillus niger (A. niger), and the antifungal results were compared with the antifungal effect of the commercially available antifungal agent Daktarin, which was used as a reference in this study.
Ionic liquids (ILS) at room temperature (liquid organic salts) have received great attention from scientists, due to their various useful properties. Although they are composed of cation and anion, they exist as liquids at room temperature, therefore, they have been used broadly as moderators for interactions. They appeared as non-aqueous media in the enzymatic reactions. Furthermore, their chemical and physical properties (density, viscosity, melting point, etc.) could be adjusted through the cation or the anion.These properties are important for enzymatic reactions [1]. Ionic liquids were dated back to 1914, which the first ethyl ammonium nitrate 1 was identified (Fig. 1) [2].
Figure 1: The first reported ionic liquid
They generally consist of an organic cation (ammonium derivative) and inorganic anion or organic anion. Therefore, they belong to the salts, usually in the form of viscous liquids with melting points below 100 °C and some of them are liquids at temperatures below 400 °C [2]. Ionic liquids are important compounds, since they have a number of applications in various fields of science and research. Their biological activities attracted the interest of scientists in the field of biochemistry and medicine. The first report on liquid salts "Air and humidity at room temperature" was made by Wilkes and Zaworotko in 1921. Studies have shown that ionic liquids possess great effectiveness in the chemical synthesis and catalysis. Ionic liquids are molten salts that are liquids at temperatures below 100°C, the antimicrobial activity of ionic liquids greatly attracted researchers' interest. Many ILS inhibit the growth of different types of bacteria and fungi, thus, ionic liquids have been used as anti-bacterial and anti-fungal agents [3,4]. The ionic liquids have several applications in the food, environmental and biological fields [5]. Since ionic liquids consist of ions, they have various physical characteristics of low volatility, viscosity and electrical conductivity, making them very important type of slats possessing numerous applications in chemical analysis and other fields [6]. Ionic liquids are organic salts that have melting points of 100°C or less [7]. They are environmentally friendly chemical compounds and their physical properties could be adjusted for specific applications [8].
1. Materials
Formic acid, ammonia, methyl amine, triethyl amine, ethylene diamine and chloroform were purchased from EMSURE and CDH.
2. Instrumentation
Melting point was measured on a Barnstead electrothermal IA 9100. The pH was measured using Jenway pH meter 3505. 1HNMR spectrum was recorded on a JEOL 500 spectrometer. Residual proton signal from the deuteriated solvents were used as references [DMSO (1H, 2.50 ppm)]. Coupling constants were measured in Hz. Infrared spectrum was recorded on Jasco FT/IR-4100 Fourier transform infrared spectrometer. Mass spectrum was recorded on a Shimadzu Qp–2010 Plus spectrometer.
3. Methods
3.1 Procedure for the preparation of the organic salts
A literature procedure for the preparation of the organic salts was adapted to obtain the targeted organic salts [9].
The liquid amine (1 mmol) was placed in a round-bottomed flask being immersed in a water bath. The carboxylic acid (1 mmol) was then added drop wise to the amine at a temperature of 70° C over 1 hour while stirring. The temperature was raised to 80° C after the addition of the carboxylic acid was complete. The reaction mixture was stirred at this temperature for further 2 hours, cooled to room temperature and dried.
4. The analytical data for the formic acid ammonium salts
Ammonium formate:
Yellow oil (3.28 g, 52.00 mmol, 21% yield); FT-IR vmax 2527 cm-1 (N+-H), 1704 cm-1 (C=O); δH (500 MHz; DMSO) 8.23 (H, s, H-COO̶), 7.38 (4H, br s, +NH4); m/z (CH5O2N, Mwt. 63.06) [M]+ 63.05 (6%), 62.05 (2.02%).
Methylammonium formate:
Yellow oil (3.30 g, 42.90 mmol, 69% yield); FT-IR vmax 2527 cm-1 (N+-H), 1704 cm-1 (C=O); δH (500 MHz; DMSO) 8.23 (3H, s, +NH3), 7.96 (H, s, H-COO̶), 2.33 (3H, s, CH3); m/z (C2H7O2N, Mwt. 77.08) [M]+ 77.05 (1.8%), 62.90 (0.21%), 59.05 (100%).
Triethylammonium formate:
Yellow oil (6.23 g, 42.39 mmol, 68% yield); FT-IR vmax 2679 cm-1 (N+-H), 1797 cm-1 (C=O); δH (500 MHz; DMSO) 8.28 (H, s, H-COO̶), 6.05 (1H, br s, +NH), 2.92 (6H, q, J = 7.60 Hz, 3 × CH2CH3), 1.10 (9H, t, J = 6.70, 3 × CH2CH3); m/z (C7H17O2N, Mwt. 147.22) [M]+ 147.15 (0.01%), 101.15 (21.87%), 87.86.15 (100%).
Ethylenediammonium monoformate:
Yellow oil (5.25 g, 49.55 mmol, 80% yield); FT-IR vmax 3346 cm-1, 3286 cm-1 (free NH2), 2695 cm-1 (+NH3), 1565 cm-1 (C=O); δH (500 MHz; DMSO) 8.43 (H, s, H-COO̶), 7.97 (3H, s, +NH3), 3.08 (2H, t, J = 5.70 Hz, -CH2), 2.56 (2H, t, J = 10.45 Hz, -CH2), 2.47 (2H, s, NH2); m/z (C3H10O2N2, Mwt. 106.12) [M]+ 106.10 (0.08%), 61.05 (10.11%), 60.05 (19.65%), 59.00 (100%).
Ethylenediammonium diformate:
Yellow oil (6.88 g, 45.24 mmol, 72% yield); FT-IR vmax 2104 cm-1 (2 × +NH3), 1565 cm-1 (2 × C=O); δH (500 MHz; DMSO) 8.25 (2H, s, 2 × H-COO̶), 3.11 (6H, s, 2 × +NH3), 2.77 (4H, s, 2 × -CH2); m/z (C4H12O4N2, Mwt. 152.12) [M]+1 153.10 (0.08%), 71.00 (83.72%), 58.95 (100%).
5. Determining the antifungal properties of the resulting organic salts: [10]
The agar dilution technique was used to measure the in vitro of the antifungal effect of the synthesized organic salts against the test fungi (aspergillus niger). In this method, graded concentrations of organic salts were incorporated in agar plates and inoculated in spots with the As niger. If the microorganism under study was affected notably by the incorporated antifungal agent (the organic salts), no fungal growth would be expected in agar plates with higher amounts of this antifungal drug. Fungal growth was observed as the antibiotic concentration in the agar plate diminishes. Inhibition of growth at the minimum concentration of the antibiotic (the organic salt) was considered as the end point.
1. The resulting ammonium formate salts (or Ionic liquids)
1.1 Ammonium formate:
The ammonium formate was obtained from the reaction of the formic acid and an excess of ammonia. The reaction gave only 21 % of the ammonium formate as a yellow oil (Scheme 1).
Scheme 1: The preparation of ammonium formate
The spectroscopic data revealed that the (+NH4) ammonium group appeared at 2527 cm-1 in the IR spectrum as a slightly weak broad band. The carbonyl group (C=O) was clearly seen at 1704 cm-1. The 1HNMR of the product showed the expected two signals. Additionally, the mass spectrometer also gave the exact mass for the molecular ion of (Mwt 63).
1.2 Methylammonium formate:
The methylammonium formate resulted from the reaction between the formic acid and methylamine. The methylammonium formate was obtained in a good yield 69 % as a yellow oil (Scheme 2).
Scheme 2: The preparation of methylammonium formate
The IR data showed the (+NH3) ammonium group at 2527 cm-1 as a broad band. The carbonyl group (C=O) was seen at 1704 cm-1. The 1HNMR of this ammonium salt showed the expected three signals for the ammonium group, the hydrogen of the formate (H-COO-) and the methyl group (CH3NH3) at 8.23, 7.96 and 2.33 ppm respectively. The mass spectrometry gave a further prove for the formation of the methylammonium formate by showing the exact mass for the molecular ion of (Mwt 77).
1.3 Triethylammonium formate:
The triethylammonium formate was obtained throughout the reaction between the formic acid and triethylamine. This triethylammonium formate was produced in a good yield 68 % as a yellow oil (Scheme 3).
Scheme 3: The preparation of triethylammonium formate
The IR spectrum showed the (+NH) ammonium group at 2679 cm-1 a broad band. The carbonyl group (C=O) was observed at 1797 cm-1. The 1HNMR of this ammonium salt showed the expected three signals for the ammonium group, the hydrogen of the formate (H-COO-) and the ethyl groups (Et3NH) at 8.28 ppm for (s, H-COO̶), 6.05 ppm (br s, +NH), 2.92 ppm for the methylene of the ethyl group (q, 3 × CH2CH3) and at 1.10 ppm for methyl of the ethyl group (t, 3 × CH2CH3) respectively. The mass spectrometry showed the formation of the triethylammonium formate as the exact mass for the molecular ion of (Mwt 147) was observed.
1.4 Ethylenediammonium monoformate:
The ethylenediammonium monoformate was prepared from the reaction between the formic acid and the ethylene diamine in a ratio of (1:1 mole/mole) respectively. This formate salt was produced in a very good yield 80 % as a yellow oil (Scheme 4).
The IR spectrum showed the free amine group (NH2) at 3346 cm-1, 3286 cm-1 as a W-shaped absorption band, which is a characteristic band for the free amino groups. The +NH bond of the ammonium group appeared at 2695 cm-1 as a broad band. The carbonyl group (C=O) was observed at 1565 cm-1. The 1HNMR data, showed the expected signlet signal for the hydrogen of the formate unit (H-COO-) at 8.43 ppm. The ammonium group +NH3 appeared as a singlet at 7.79 ppm, whereas the two methylene groups (CH2)2 showed up at 3.08 ppm and 2.56 ppm as two triplets. However, the free amino group was observed at 2.47 as a singlet. The mass spectrometric data confirmed the formation of the ethylenediammonium monoformate as the exact mass for the molecular ion of (Mwt 106) was seen.
1.5 Ethylenediammonium diformate:
The ethylenediammonium diformate was obtained throughout the reaction between the formic acid and the ethylene diamine in a ratio of (2:1 mole/mole) respectively. This diformate salt was obtained in a good yield 72 % as a yellow oil (Scheme 5).
Scheme 5: The preparation of ethylenediammonium diformate
The disappearance of the W-shaped absorption band for the primary amino groups was a good sign for the completion of the reaction and the formation of the ethylenediammonium diformate salt. The +N-H bond of the two ammonium groups (2 × +NH3) appeared at 2104 cm-1 as a broad band. The two carbonyl groups (2 × C=O) were seen at 1565 cm-1. The 1HNMR data, revealed that the appearance of the singlet signal for the hydrogens of the two formate groups (H-COO-) at 8.25 ppm. The two ammonium groups (+NH3)2 appeared as a singlet at 3.11 ppm, however the two methylene groups (CH2)2 showed up at 2.77 ppm as one singlet. The mass spectrometric data confirmed the formation of the ethylenediammonium monoformate as the molecular ion mass plus 1 (Mwt 153) was observed.
2. The effect of the ammonium salts of the formic acid (ionic liquids) on the growth of aspergillus niger:
Five ammonium salts of the formic acid were tested for their antifungal potentials against the A. niger. Their levels of inhibition ranged from 12.63% to 21.05
Five organic ammonium formate salts (or ionic liquids; ILs) have been synthesized and characterized using a number of spectroscopic techniques. These ammonium formate salts were formed as solids, whereas, others were formed as liquids (ILs) at room temperature, with yields ranging from (19.83%) to (99.00%). The antifungal properties of the resulting organic ammonium formate salts were investigated against the aspergillus niger (A. niger), and the antifungal results were compared with the antifungal effect of the commercially available antifungal agent the daktarin, which was used as a reference in this study. The highest level of inhibition was recorded for the ammonium formate reaching 39.9
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