Phosphono group

In these a-phosphorylated dithioesters, the electron-withdrawing effect of the phosphono group, which strongly increases the electrophilic character of the thiocarbonyl group, makes the latter more prone to the thiophilic attack of nucleophiles and stabilizes the resulting carbanion. The main reactions of 1 with nucleophiles are summarized in Scheme 2. 

Egawa, H., Nonaka, T., Ikari, M., preparation of macroreticular chelating resins containing dihydroxyphosphino and/or phosphono groups and their adsorption ability for uranium. J. Appl. Polym. Sci. 29, 1984,2045-2055. 

Replacement of the endocyclic oxygen with a phosphono group... 

The endocyclic oxygen of carbohydrates has been replaced also with a phosphono group (Fig. 48).80 However these compounds have not found applications. 

When Schwarzenbach et al. used chloromethylphosphonic acid to phosphonomethylate amines, they noted (128, p. 1185) how slowly it reacts. The slowness is presumably due to the staggered conformation of the chloromethyl and phosphono groups, so that one of the oxygen atoms must be in the Cl—C—C plane and must hinder the approach of any nucleophile that could displace the chloride. They overcame this with long reaction times and high temperatures. In view of the lability of C—As bonds, this approach is not available with 1-haloalkylarsonic acids. Indeed, arsonochloroacetic, chloromethylarsonic, and dibromo-methylarsonic acids (129) proved inert to substitution. 

A further rearrangement recently reported is that of the triaryl epoxyethylphos-phonates (92) under the influence of BFg etherate, when one or both of the compounds (93) and (94) may be obtained, representing migration of the phosphono-group and of the aryl group, respectively. ... 

The formation of aryl ethers of (hydroxyalkyl)-phosphonic or -phosphinic derivatives from the corresponding haloalkyl phosphorus(V) acid derivative and a metal phenate may present unfortunate difficulties depending on the particular halogen, but these have been overcome by the use of sulphonate substrates, in particular the 0-4-chlorobenzenesulphonyl esters of the phosphonic or phosphinic derivative, in reactions with sodium phenates. A study of the alcoholysis reactions of the O-p-tosylates of the cis and trans isomers of diethyl (2-hydroxycyclo-hexyl)phosphonate, has shown that with a 60° dihedral angle between the two functions, the rate of reaction is sensitive to solvent nucleophilicity, and the evidence supports a bimolecular displacement. When the dihedral angle is 180°, the lack of dependence of rate on solvent and other features, support the involvement of carbocationic intermediates, with their stabilization by the phosphono group . ... 

Several theoretical studies have been directed at phosphonic acids among the earliest being that of Jaffe, Freedman, and Doak [296], who measured the pK s of 25 meta- and / ara-substituted benzenephosphonic acids and utilized Hammett s equation to rationalize the values observed, They subsequently measured the pK s of 16 orfljo-substituted compounds and concluded that hydrogen bonds were formed between the phosphono group (-PO3H2) and many of the ortho substituents. The phosphono group could act as either a donor or acceptor. 

On mild steel, the inhibiting activity and passivation characteristics exerted by carboxy and phosphono groups were determined by gravimetric measurements and electrochemical impedance spectroscopy. The organic chemicals under investigation included nitrilo(triacetic acid) (NTA), phos-phonomethyl-iminodi(acetic acid) (MPIDA), di(phosphonomethyl)glycine (DMPG), and nitrilotri(methyl-phosphonic acid) (ATMP). 

Results were obtained for chemicals with phosphono and/or carboxyl groups various types were used in order to replace very effective but toxic inhibitors, and to decrease the phosphorus content in the inhibitor. Positive correlation was found between the number of substituents with negative charge, especially with phosphono groups. As these compounds are derivatives of natural amino acids, their catabolism results in nontoxic chemicals, and the ratio of the phosphorus is lower than in the chemicals used as industrial corrosion inhibitors. Electrode impedance measurements pointed to the importance of time in the formation of a protective layer on the metal surface. 

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