Phosphorus compounds, protonation

Protonation and solvation in strong aqueous acids, 13, 83 Protonation sites in ambident conjugated systems, 11, 267 Pseudorotation in isomerization of pentavalent phosphorus compounds, 9, 25 Pyrolysis, gas-phase, of small-ring hydrocarbons, 4, 147... 

Intermediates such as 224 resulting from the nudeophilic addition of C,H-acidic compounds to allenyl ketones such as 222 do not only yield simple addition products such as 225 by proton transfer (Scheme 7.34) [259]. If the C,H-acidic compound contains at least one carbonyl group, a ring dosure is also possible to give pyran derivatives such as 226. The reaction of a similar allenyl ketone with dimethyl mal-onate, methyl acetoacetate or methyl cyanoacetate leads to a-pyrones by an analogous route however, the yields are low (20-32%) [260], The formation of oxaphos-pholenes 229 from ketones 227 and trivalent phosphorus compounds 228 can similarly be explained by nucleophilic attack at the central carbon atom of the allene followed by a second attack of the oxygen atom of the ketone at the phosphorus atom [261, 262], Treatment of the allenic ester 230 with copper(I) chloride and tributyltin hydride in N-methylpyrrolidone (NMP) affords the cephalosporin derivative 232 [263], The authors postulated a Michael addition of copper(I) hydride to the electron-... 

The e.s.r. spectra of phosphorus compounds have been reviewed.101 The phosphorus hyperfine splitting (ap 33.5 G) of the radical anion (77) is within the 25—36 G range of phosphorin radical anions.102 The cis- and fra/w-isomers of 1,2-bisdiphenylphos-phinoethylene gave the same radical anion (78). The unpaired electron is coupled to all the protons in the molecule as well as to the two phosphorus atoms, and shows that the electron is completely delocalized. Only when caesium was used as the gegenion in THF could a metal interaction be detected. The spectrum in this case corresponded to the association of two caesium ions with the radical anion, the third... 

Y Kiso, M Kobayashi, Y Kitaoka, K Kawamoto, J Takada. A theoretical study on the zone mobility-pH curve in paper electrophoresis of low-molecular-weight compounds with a dissociable proton and its application to phosphorus compounds. J. Chromatogr. 36 215-228 (1968). 

Adduct formation results in well-defined species. Generally speaking, phosphorus compounds act as Lewis bases [exceptions being penta-valent phosphorus halides as reviewed by Webster <1966 106)] for other examples in which the relevant Lewis acids are metalloid derivatives see references 1966, 107 and 1969, 186. Adducts involving boron have recently been reviewed elsewhere(1969 94 andl02) and are by far the most numerous and use has been made of phosphorus, boron, proton and fluorine resonances, in some cases at varying temperature. 

T0 prepare models of TA, the corresponding cyclic alkylene phosphoric acids cannot be directly polymerized because the presence of acidic protons of the phosphate group makes the ionic polymerization impossible. Thus, cyclic phosphorus compounds with blocked third functions have to be used. These are phosphates., phosphoramidates and phosphites. After polymerization the obtained polymer is converted by deblocking into the polyalkylene phosphate, e.g. polysalt or polyacid form. 

The chemistry of the JV-oxides of oxazole has not been explored as thoroughly as that of the pyridine analogues. Both types of compounds are reversibly protonated to give iV-hydroxy cations, form complexes with iodine and with tetracyanoethylene, and both are deoxygenated by triphenylphosphine and other tervalent phosphorus compounds. 

The interactions of LSR with various organophosphorus substrates have been reported (460-463). Yb(fod)3 and Pr(fod), are considered to be the best LSR for organophosphorus compounds. Proton shifts are, as usual, dominated by pseudocontact interactions. shifts are predominantly pseudocontact in nature but have sizeable contact contributions for phosphine and phosphoryl compounds. In contrast P shifts have large contact components where direct phos-phoryl-oxygen or phosphorus-lanthanide interactions occur. Large pseudocontact P shifts for triethyl phosphite indicate little or no direct phosphorus-lanthanide interaction. 

Although ethylmethylphenylphosphine oxide was the first tetrahedral phosphorus compound to be resolved , only negative results were obtained when attempts were made to resolve methyl(a-naphthyl)phenylarsine oxide (142) by protonation and separation of (-i-)-a-bromocamphor-jc-sulphonate salts, or (c>-carboxyphenyl)methylphenyl-arsine oxide (143) or its anhydride 144 after protonation and use of (—)-brucine or (-l-)-morphine . The reversible combination of a tertiary arsine oxide with water was recognized at the outset and it is this property that is responsible for the racemization - ... 

FIGURE 24. Correlation between core ionization energy and proton affinity for arsenic and phosphorus compounds. Reprinted with permission from Reference 90. Copyright (1979) American Chemical Society... 

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