Quinquevalent phosphorus acids
This chapter shows, as in previous years, the most important achievements of the 2019 year in the area organophosphorus compounds containing three P–O bonds (phosphates), two P–O and one P–C bonds (phosphonates) as well as one P–O and two P–C bonds (phosphinates) in addition to the phosphoryl group PO. Each of the main sections covers synthesis, reactions, biological and miscellaneous aspects. As in the previous year for the first time, in order to improve transparency of the reviewed material, a new subsection division has been continued in this year, as well. Thus, all main sections devoted to chemistry of phosphoric, phosphonic and phosphinic acids, and their derivatives have been subdivided onto “synthesis and reactions” including pure synthesis without applications, “synthesis and biological applications” and “synthesis and miscellaneous applications” including synthesis which is aimed at further applications research. Moreover, as in the previous year, due to the emergence of the new catalysts based on phosphonic and phosphinic acids, this material has been reviewed in the separate section, placed in the end of the whole chapter, after review of all three main groups of compounds. In this year, the area devoted to phosphoric and phosphonic acids and their derivatives showed a further, continuing progress and dominated traditionally over a small subsection of phosphinic acids and derivatives.