A chlorine-based solvent such as 1,1,2-trichloroethylene (TCE), 1,2-dichloropropane, and methylene chloride has been widely used for its excellent cleaning ability. However, since chlorinebased solvent has high volatility, it is harmful to both human body and environment[1-3]. The hydrocarbon-based cleaning agent has been used as the substitute, but the problems that related to flammability and drying are being blamed. Flammability is important because many industrial facilities are not equipped with safely handle flammable hydrocarbons. In addition, hydrocarbon containing an aromatic hydrocarbon, such as benzene, toluene, and xylene are being regulated due to its high toxicity on human body and environmental pollution[4,5]. Therefore, development of new environmentally acceptable cleaning agent would be highly desirable.

Fluorinated organic compound in which hydrogen atoms has been replaced by fluorine atoms has a higher flash point[5] than that of the fluorine free compound. It is also known that ester compounds have an important role in cleaning dirty metal surfaces[7,8].

Herein, we describe a synthesis and evaluation of fluorinated ester compounds which exhibit low toxicity to human body due to their low flammability.

The core structure of the new fluorinated target compounds (1-7) is ester group which connected to polyol chain. The synthesis of target compounds is outlined in Scheme 1. The ester compounds (1-7) were synthesized by esterification reaction of trifluoroacetic acid (TFA) with polyols in the presence of acid catalysis in moderate yield.

All synthesized ester compounds (1-7) were estimated for their possibility of cleaning agent by examining physical properties which were conducted by Korea Institute of Petroleum Management by using standard methods. All compounds have various

good physical properties which are almost similar to other cleaners[9,10]. When flash point of all compounds (1-7) was compared with that of non-fluorinated (hydrogen substituted) compounds, the data indicated all compounds show high flash point that related to flammability (Table 1). This finding suggests that all synthesized compounds (1-7) can be a new candidate as nonflammable cleaning agent.

All new compounds (1-7) were evaluated for their cleaning efficiency by simple immersion cleaning method. A specimen was prepared by cutting in 60 mm × 40 mm size of stainless steel plate and weighted. The surface of the above specimens was applied with four kinds of contaminants, paraffin-based drawing oil, flux abietic acid, water-insoluble cutting oil, and lubricating oil which were used for various industrial processing.

The weight that was added with the specimen was recorded down to four places of decimals. The above specimens were immersed in 100 mL of compounds (1-7) for 1 to 5 minutes to dissolve oil in the cleaning agent. After that, the specimens were dried and weights were measured.

Three tests were performed on each compound. Using the above

values, the amount of oil that was initially adhered on the specimen and the amount oil that was removed by the cleaning agents were calculated and putted on a percentage basis in Figure 1, 2, 3, and 4.

Figure 1, 2, 3 and 4 indicate that all compounds (1-7) show some low cleaning efficiency for four contaminants in 1-2 minutes dipping. However, gradual increment of dipping time can raise cleaning efficiency. Although the data in Figure 3 indicate that all compounds exhibit lower cleaning ability toward cutting oil, it is observed that in the case of the present study more than 80% of pollutants on the surface were almost removed within 5 minutes. Accordingly, one might suggest that these compounds (1-7) are suitable for new nonflammable cleaning agents.

Generally, all proton nuclear magnetic resonance (NMR) spectra were recorded on a Varian Unity Inova spectrometer at

300 MHz and are reported in parts per mllion (ppm) on the δ scale relative to chloroform-d₁. (* δ (chemical shift) = difference between a resonance frequency and that of a reference substance/ operating frequency of the spectrometer)

Ethane-1,2-diyl bis(2,2,2-trifluoroacetate)(1)

To a stirred solution of ethylene glycol (2.0 kg, 28.95 mol) and p-TsOH (396 g, 2.89 mol) in toluene (3.0 L) was added slowly TFA (6.65 L, 86.85 mol) at room temperature. The resulting mixture was heated to remove water for 3 hours. After cooling, methylene chloride (4.0 L) was added to the reaction mixture. The organic layer was washed with water (2 × 4.0 L) and dried with MgSO₄, filtered, and solvent evaporated under reduced pressure. The crude product was purified by vacuum distillation (20 mmHg, 100-105 ℃) to afford 1 (4.98 kg, 81%); ¹H NMR (300 MHz, CDCl₃) δ 4.68 (s, 4H).

Propane-1,3-diyl bis(2,2,2-trifluoroacetate) (2)

(20 mmHg, 110-115 ℃, 80%), ¹H NMR (300 MHz, CDCl₃) δ 2.2 (m, 2H), 4.5 (t, J = 7.0 Hz, 4H).

Butane-1,4-diyl bis(2,2,2-trifluoroacetate) (3)

(20 mmHg, 115-120 ℃, 77%), ¹H NMR (300 MHz, CDCl₃) δ 1.90 (t, J = 6.8 Hz, 4H), 4.4 (t, J = 6.8 Hz, 4H).

Pentane-1,5-diyl bis(2,2,2-trifluoroacetate) (4)

(20 mmHg, 125-128 ℃, 73%), ¹H NMR (300 MHz, CDCl₃) δ 1.50 (m, 2H), 1.9 (m, 4H), 4.4 (t, J = 6.5 Hz, 4H).

Hexane-1,6-diyl bis(2,2,2-trifluoroacetate) (5)

(20 mmHg, 127-130 ℃, 69%), ¹H NMR (300 MHz, CDCl₃) δ 1.45 (m, 4H), 1.8 (m, 4H), 1.85 (m, 4H), 4.4 (t, J = 6.8 Hz, 4H).

Propane-1,2,3-triyl tris(2,2,2-trifluoroacetate) (6)

(10 mmHg, 139-142 ℃, 70%), ¹H NMR (300 MHz, CDCl₃) δ 4.20-5.05 (m, 5H).

2,2-Bis((2,2,2-trifluoroacetoxy)methyl)propane-1,3-d iyl bis(2,2,2-trifluoroacetate) (7)

(10 mmHg, 150-154 ℃, 60%), ¹H NMR (300 MHz, CDCl₃) δ 4.40 (s, 8H).

In summary, we have prepared seven new unprecedented fluorinated ester compounds (1-7) in moderate yield from TFA and corresponding polyols. These compounds can be applicable to various industrial cleaning fields as nonflammable cleaning agent because of their good physical properties and cleaning abilities for contaminants. The future work including formulation of (1-7) with other solvents to find out nonflammable cleaning systems is under investigation in our laboratory.