P-H group

Tbe presence of P-H groups amongst the products of these reactions was one of the earlier sources of confusion in the structures of hypophosphorie and isohypophosphoric acids. 

The structure of isohypophosphoric acid and its salts can be deduced from nmr which shows the presence of 2 different 4-coordinate P atoms, the absence of a P-P bond and the presence of a P-H group (also confirmed by Raman spectroscopy). It is made by the careful hydrolysis of PCI3 with the stoichiometric amounts of phosphoric acid and water at 50° ... 

The chemical shifts of the P—H group have been tabulated for 150 compounds. Like many other heteroatom-bound protons, the chemical shift range is large (r 0 —12 p.p.m.). In this case shielding of the proton increases with decrease in co-ordination number at phosphorus. The... 

D-Ribofuranose-type phospha sugars 50 (R=OH, Et, and Ph) and 2-deoxy-D-ribofuranose analogues 51 (R=OH and Me) in Fig. 3 have been prepared via longer reaction pathways by a similar ring closing intramolecular addition reaction of a P - H group to an aldehyde of sugars shown in Scheme 14 [17-20]. 

Like known metal phosphates with extra-large microporous channel structures, the structure of ZnHPO-CJ 1 is unstable upon heating due to the existence of P H groups and strong H-bonding guest-host interactions. When heated at 280 °C for 3h, its structure collapses after the removel of the occluded organic molecules. 

Hypophosphorous acid can also be aminoalkylated in the absence of mineral acid, (aminomethyl)phosphorous acids (12) are formed but in the presence of acid the second P-H group can also be substituted with formation of bis(aminomethyl)-phosphonic acids 323... 

Abstract This chapter describes recent advances in metal-catalyzed C-P bond formation, which may be classified into two types of reactions. In hydrophosphina-tion and related processes, P-H groups add across unsaturated C-X (X = C, N, O) bonds. Phosphination of electrophiles typically results in substitution at sp or sp carbon the P-H group is removed, often by a base. The scope of both nucleophilic and electrophilic partners in these processes is surveyed, and the proposed mechanisms and intermediates in the metal-catalyzed reactions are described. 

These reactions involve the same organophosphorus substrates, but, in contrast to hydrophosphination and related reactions, the P-H group is not transferred to the electrophile. 

This chapter has examined recent advances in metal-catalyzed C-P bond formation. Both reactions in which P-H bonds are added to an unsaturated substrate (hydro-phosphination and related processes) and those in which the P-H group is removed... 

When a polymer chain stops its growth after chain transfer, an active center is vacated to allow the formation of a new polymer chain. The chain transfer by the elimina tion of the p-H group is not important for most Ziegler-Natta catalysts, but it is the major chain termination reaction for most metallocene catalysts. The elimination of the p-methyl group does not occur in multiphase catalysis, but is the most important chain termination mechanism for the metallocene catalysts containing CpzMClz-MAO, where M is zirconium (Zr) or hafnium... 

The P-H group of diesters of H-phosphonic acid is highly reactive and participates in a variety of chemical reactions such as oxidation, addition to C=C double bond, C=N (Schiff bases), ketones, isocyanates, and condensation reactions. 

Owing to the presence of the P-H group, diesters of H-phosphonic acid can be oxidized by molecular oxygen to the corresponding phosphates [69]. 

The evaluation of amine or alcohol or thiol occurs by a mechanism involving deprotonation of the P-H group from the corresponding nucleophile— NRj, SR, or OR, and formation of an active nucleophile—dialkyl phosphonate anion. 

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