Chemistry:Acyl fluorides
Acyl fluorides are organofluorine compounds with the formula RC(O)F (R = alkyl, aryl). In terms of structure, they resemble the more common acyl chlorides, i.e., an acyl group bonded to a halide. The synthesis and properties of acyl fluorides are somewhat distinctive however.
Preparation
The several routes to acyl fluorides can be roughly subdivided into three approaches.[1]
Halide exchange
Acyl chlorides react with hydrogen fluoride to give acyl fluorides.[2] This reaction is relevant to the use of electrofluorination route to perfluorinated carboxylic acids, such as PFOA.
S- and P-based reagents
The OH group of carboxylic acids can be converted to fluoride using various oxophilic reagents. Aromatic (as well as aliphatic) acyl fluorides can be prepared from carboxylic acids with PPh
3 and fluoride sources.[3] Cyanuric fluoride as well as sulfur tetrafluoride also convert carboxylic acids to acyl fluorides.[4][5]
- SF
4 + RCO
2H → SOF
2 + RC(O)F + HF
Fluorophosgene
Salts of trifluoromethoxide react with carboxylic acids to give acyl fluorides. The process entails formation of difluorophosgene. Solutions of trifluoromethoxide are prepared by displacement from aryl trifluoromethyl ethers.[1]
Reactions
A common reaction of acyl fluorides is hydrolysis to the carboxylic acid.
Perfluoroacyl fluorides react with fluoride salts to perfluoroalkoxides:[6]
- C
3F
7COF + F−
→ C
4F
9O−
Utility
Acyl fluorides are intermediates in the electrochemical fluorination (ECF) route to perfluorocarboxylic acids, such as perfluorooctanoic acid).[7]
References
- ↑ 1.0 1.1 Bonnefoy, Clémence; Gallego, Adrien; Delobel, Clément; Raynal, Betty; Decourt, Maxime; Chefdeville, Emmanuel; Hanquet, Gilles; Panossian, Armen et al. (2024). "Unlocking the Power of Acyl Fluorides: A Comprehensive Guide to Synthesis and Properties". European Journal of Organic Chemistry 27 (18). doi:10.1002/ejoc.202400142. https://hal.science/hal-04591439.
- ↑ "Preparation of Acyl Fluorides with Anhydrous Hydrogen Fluoride. The General Use of the Method of Colson and Fredenhagen". J. Org. Chem. 26: 237–238. 1961. doi:10.1021/jo01060a600.
- ↑ Munoz, Socrates B.; Dang, Huong; Ispizua-Rodriguez, Xanath; Mathew, Thomas; Prakash, G. K. Surya (2019-03-15). "Direct Access to Acyl Fluorides from Carboxylic Acids Using a Phosphine/Fluoride Deoxyfluorination Reagent System". Organic Letters 21 (6): 1659–1663. doi:10.1021/acs.orglett.9b00197. ISSN 1523-7060. PMID 30840474. https://figshare.com/articles/Direct_Access_to_Acyl_Fluorides_from_Carboxylic_Acids_Using_a_Phosphine_Fluoride_Deoxyfluorination_Reagent_System/7811516.
- ↑ George A. Olah; Masatomo Nojima; Istvan Kerekes (1973). "Synthetic Methods and Reactions; IV. Fluorination of Carboxylic Acids with Cyanuric Fluoride". Synthesis 1973 (8): 487–488. doi:10.1055/s-1973-22238.
- ↑ Boswell, G. A.; Ripka, W. C.; Scribner, R. M.; Tullock, C. W. (2011). "Fluorination by Sulfur Tetrafluoride". Organic Reactions. pp. 1–124. doi:10.1002/0471264180.or021.01. ISBN 978-0-471-26418-7.
- ↑ Oppenheimer, Jossian; Hsung, Richard P.; Li, Hongyan; Lu, Ting; Wei, Yonggang (2007). "Hexafluoropropene Oxide". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289x.rn00768. ISBN 978-0-471-93623-7.
- ↑ Savu, Patricia M. (2000). "Fluorinated Higher Carboxylic Acids". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.0612211519012221.a01. ISBN 978-0-471-23896-6.
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