Organic Fluorine as a Hydrogen-Bond Acceptor: Recent Examples and Applications
For more than three decades, the ability of a fluorine atom involved in a C–F bond to act as a hydrogen-bond acceptor has been a controversial issue. Throughout the years, more and more evidence has been published to support this hypothesis and it is now difficult to doubt the existence of the hydrogen bond with organic fluorine. However, since this interaction has low binding energies, it is sometimes difficult to clearly demonstrate its presence or effect in a system. In the present review, only the most recent examples from the literature are presented and the different techniques used to prove the presence of these C–F···H–X hydrogen bonds are compared and discussed according to the accepted criteria for hydrogen bonding detailed by a recent IUPAC committee. Even with its weak interaction energy, hydrogen bonds to organic fluorine have the potential to affect properties of practical systems in different spheres of chemistry. All the recent examples of such effects are highlighted. 1 	Introduction 2 	Properties 3 	C(sp2)–F 3.1 	O–H as Donor 3.2 	N–H as Donor 3.3 	C(sp2)–H as Donor 3.4 	C(sp3)–H as Donor 4 	C(sp3)–F 4.1 	O–H as Donor 4.2 	N–H as Donor 4.3 	C(sp2)–H as Donor 4.4 	C(sp3)–H as Donor 5 	Conclusion