Methyl difluoroacetate

Potassium fluoride [7789-23-3], KF, is the most frequently used of the alkaU metal fluorides, although reactivity of the alkaU fluorides is in the order CsF > RbF > KF > NaF > LiF (6). The preference for KF is based on cost and availabiUty traded off against relative reactivity. In its anhydrous form it can be used to convert alkyl haUdes and sulfonyl haUdes to the fluorides. The versatility makes it suitable for halogen exchange in various functional organic compounds like alcohols, acids and esters (7). For example, 2,2-difluoroethanol [359-13-7] can be made as shown in equation 9 and methyl difluoroacetate [433-53 ] as in equation 10. 

Difluoroacetic acid undergoes reactions typical of a carboxylic acid such as forming an ester when heated with an alcohol and sulfuric acid. Typical esters are methyl difluoroacetate [433-53-4], bp, 85.2°C, and ethyl difluoroacetate [454-31-9], bp, 99.2°C. It can also be photochemicaHy chlorinated to chlorodifluoroacetic acid [76-04-0] or brominated in the presence of iron to bromodifluoroacetic acid [667-27-6] (37,38). 

Methyl formate Methyl acetate Methyl propionate Methyl isobutyrate Methyl difluoroacetate Methyl trifluoroacetate Methyl monochloroacetate Methyl dichloroacetate Ethyl trichloroacetate Methyl trichloroacetate Methyl cyanoacetate Methyl methoxyacetate Methyl benzoate... 

A /cF coupling has been found by Abraham and co-workers to be a valuable tool in their studies on the rotational isomerism in methyl fluoroace-tate and methyl difluoroacetate. 

Yamaki, J. Tanaka, T Ihena, M. Sato, K. Egashira, M. Watanabe, I. Okada, S., Thermal stahUity of methyl difluoroacetate as a novel electrolyte solvent for lithium batteries electrolytes, Electrochemistry 2003, 71,1154. 

Sato, K. Zhao, L. Okada, S. Yamaki, J., LiPF(/methyl difluoroacetate electrolyte with vin-ylene carbonate additive for Li-ion batteries, J. Power Sources 2011,196, 5617-5622. 

In 2003, Yamaki et al. from Kyushu University presented in a paper that methyl difluoroacetate (MFA) (151) can be used as an additive in small quantities and reported that MFA electrolyte is a good candidate to improve the thermal stability of the lithium ion and lithium metal anode battery [146],... 

Yamaki et al. [14-16] investigated the thermal stability of fluorinated esters, which are the same fluorinated esters used as additives to improve the cycling performance reported by Nakajima et al. [12,13] prior to our study. In this study, partially fluorinated carboxylic acid esters (Table 20.1) were used as the electrolyte solvent and LiPFe as the salt. LiPFe was dissolved in methyl difluoroacetate (MEA) and ethyl difluoroacetate (EFA) to a salt concentration of 1 M. In the other fluorinated esters, however, LiPFe salt could be dissolved to a salt concentration of less than 0.2 M. Therefore, the solutions of fluorinated esters (P and 2 ) with 0.2 M of LiPFe were used, and the other fluorinated esters were saturated with LiPFe. For comparison, the solutions of corresponding esters with 0.2 M LiPFe were prepared. Similar measurements were performed employing the conventional electrolyte solution used in lithium batteries 1 M LiPFe/EC + DMC (1 1 by vol). 

Thermal stability of graphite and silicon/Li alloy ne tives, LiPFe/Alkyl carbonate mixed-solvent electrolytes, LiPFe/methyl difluoroacetate electrolyte, IiCo02 and FeFs positives with 1 M LiPFe/EC -I- DMC were investigated using DSC. Chained graphite and silicon/Li alloy showed almost the same heat output based on the amoimt of Li in each anode. LiPFe/methyl difluoroacetate electrolyte and FeFs showed a very small heat output. 

From a safety aspect of utilizing lithium-metal anodes, various fluorinated solvents have been studied as the components of electrolyte solutions for Uthium-metal cells. A typical example of these solvents is methyl difluoroacetate (MFA). MFA exhibited better thermal stability and lithium cycling efficiencies among various fluorinated carboxylic acid esters [53]. 

Another method for suppression of corrosion is the use of solvents with smaller dipole moments, such as THF, DME [260], GBL [299], or the nonflammable methyl nonafluorobutyl ether (MFE) [297]. Thus, decomposition products are less stabilized and the reaction rate of dissolution of A1 decreases. Instead, solvents with a large dipole moment such as EC can promote corrosion [300, 301]. Another promising solvent is methyl difluoroacetate (MEA), which forms a passivating layer consisting of organic compounds [302]. In an electrolyte with LiTFSI and MFA as solvent, corrosion of aluminum only starts at 5 V vs Li/Li. Moreover, the maximum observed corrosion current is about one-fifth lower than in an analogous electrolyte containing an EC/DEC blend as solvent. 

VII-I-7. Methyl 2,2-Di-fluoroacetate [Methyl Difluoroacetate, CHF2C(0)0CH3]... 

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