Phosphorous, bond number

Column, 5 pm ODS-bonded silica gel, 15 cm x 4.6 mm i.d. eluent, 60% aqueous acetonitrile containing 0.05 M phosphoric acid. Number beside symbols see Table 6.4. 

The (TMS)3SiH mediated addition of phosphorus-centered radicals to a number of alkenes has been investigated in some detail. Reaction (73) is an example of phosphorous-carbon bond formation using four structurally different phenylseleno derivatives with 3 equiv of (TMSlsSiH and AIBN in refluxing benzene for 2h. Comparative studies on the reaction of the four phosphorus-centered radicals have been obtained. Although the reaction with 1-methylene cyclohexane is efficient with all four derivatives, different selectivity is observed with electron-rich or electron-poor alkenes. 

Phosphoric acid, sulfuric acid, and the hydrogen sulfate ion are members of a group of acids known as oxoacids. An oxoacid has a central atom bonded to a variable number of oxygen atoms and OH groups. Except for the three oxoacids shown in Table (sulfuric acid, nitric acid, and perchloric acid), all of the oxoacids described in this textbook are weak acids. Chapter 17 describes in detail the chemistry of strong and weak acids, including carboxylic acids and oxoacids. 

The phosphate group is derived from phosphoric acid (H3 PO4) by replacing an O—H bond by an O—C or O— P bond. Phosphate is an important functional group in biochemistry, being involved in cellular energy production as well as acting as an important monomer in biopolymers, particularly in DNA. Bonds to phosphate groups form or break in the course of a number of important biochemical reactions. 

Abstract This chapter focuses on carbon monoxide as a reagent in M-NHC catalysed reactions. The most important and popular of these reactions is hydro-formylation. Unfortunately, uncertainty exists as to the identity of the active catalyst and whether the NHC is bound to the catalyst in a number of the reported reactions. Mixed bidentate NHC complexes and cobalt-based complexes provide for better stability of the catalyst. Catalysts used for hydroaminomethylation and carbonyla-tion reactions show promise to rival traditional phosphine-based catalysts. Reports of decarbonylation are scarce, but the potential strength of the M-NHC bond is conducive to the harsh conditions required. This report will highlight, where appropriate, the potential benefits of exchanging traditional phosphorous ligands with iV-heterocyclic carbenes as well as cases where the role of the NHC might need re-evaluation. A review by the author on this topic has recently appeared [1]. 

There are a large number of types of compounds that contain phosphorous fluorine bonds, including some of the most toxic compounds known to humankind (nerve gases such as sarin). 

A novel demonstration of the latent reactivity of the phosphoryl bond and the apparent ease with which the number of ligands around the phosphorus atom can change under very mild conditions is provided by the hydrogen phosphonate (100), prepared from catechol and phosphorous acid or PC13. When treated with DCC,... 

As a true testament to the potential long-term impact of H-bonding activation, a number of ureas, thioureas, and acid catalysts are now finding broad application in a large number of classical and modem carbon-carbon bond-forming processes. On one hand, Johnston s chiral amidinium ion 28 was elegantly applied to the asymmetric aza-Henry reactions (Scheme 11.12d). On the other hand, chiral phosphoric acids (e.g., 29 and 30), initially developed by Akiyama and Terada, have been successfully employed in Mannich reactions, hydrophosphonylation reac-tions, aza-Friedel-Crafts alkylations (Scheme 11.12e), and in the first example... 

The largest number of hydrogen bonds in crystal structures of alkyl hydroperoxides refer to intermolecular bonds between the hydroperoxide proton and functionalities of the type 0=X, where X denotes a sulfur (e.g. 27), carbon (e.g. 30) or a phosphorous atom (e.g. 32, Figure 14, Table 7)93,108,115 geometry of [l,2-bis(diphenylphosphinoyl)ethane] bis(2,2-dihydroperoxypropane) (32) in the solid state is a rare example of a bifurcated hydrogen bond between an OOH donor and an 0=X proton acceptor. 

A number of compounds containing phosphorus-metal bonds exhibit an interesting reactivity. In platinum (II) complexes, coordinated PC13 undergoes solvolysis reactions with water and alcohols to form stable orthophosphite esters or phosphorous acid (Equation 32) (66, 67). 

Also, phosphoric acid forms an extensive series of anhydrides (with P—O—P bonds), which further diversify the number and kind of phosphate esters. The most important phosphate esters are derivatives of mono-, di-, and triphosphoric acid (sometimes classified as ortho-, pyro-, and meta-phos-... 

In both DNA and RNA, the cyclic amine base is bonded to Cl of the sugar, and the phosphoric acid is bonded to the C5 sugar position. Thus, nucleosides and nucleotides have the general structures shown in Figure 24.15. (In discussions of RNA and DNA, numbers with a prime superscript refer to positions on the sugar component of a nucleotide numbers without a prime refer to positions on the cyclic amine base.)... 

This very common coordination number usually leads to a tetrahedral configuration for phosphoric acid, phosphates, and many phosphorus(V) compounds. In these compounds, the P(V) atom forms one double bond and three single bonds with other atoms. Figure 15.4.2(e) shows the structure of P4O10, whose symmetry is Td. The length of the terminal P=0 bond is 143 pm, and the bridging P-O bond is 160 pm. The bond angle O-P-O is 102°, and P-O-P is 123°. 

Table 2 illustrates that the majority of Schedule numbers allow deriving only one or a few different possible chemicals. One Schedule number however, Schedule 2.B.4, describes millions of possibilities ( Chemicals, except for those listed in Schedule 1, containing a phosphorous atom to which is bonded one methyl, ethyl or propyl (normal or iso) group but no further carbon atoms ) and more importantly, the theoretical possibilities for the nerve agents... 

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