Halogen antimony—hydrogen bonds

Of the solvents, aromatic and olefinic hydrocarbons are r-donors ( r-EPD) alcohols, ethers, amines, carboxamides, nitriles, ketones, sulfoxides and N- and P-oxides are n-donors (n-EPD), and haloalkanes are cr-donors (cr-EPD). Boron and antimony triha-lides are acceptor solvents (r-EPA), as are halogens and mixed halogens (c-EPA), and liquid sulfur dioxide (ti-EPA). In principle, all solvents are amphoteric in this respect, i.e. they may act as a donor (nucleophile) and an acceptor (electrophile) simultaneously. For example, water can act as a donor (by means of the oxygen atom) as well as as an acceptor (by forming hydrogen bonds). This is one of the reasons for the exceptional importance of water as a solvent. 

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