Phosphoric acid esters cyclic

Parthaserathi et al. [238] have used the group philicity index to estimate the pK s of several phosphoric acid esters and related compounds They included the calculations in a group with anilines and alcohols, but the numerical results for the phosphoric acids appear generally good Moser, Range, and York [301] have calculated gas-phase proton affinities and basicities for a large collection of acyclic and cyclic phosphates. 

Phosphoms modified phenolics are synthesized by condensation of phosphoric acid esters and phosphorus oxychloride with phenolic resins or phenol in the presence of 1,4-dioxane [175-178], The formation of eight-membered cyclic ring structures by intramolecular esterification (Scheme 28) occurs if ortho-linked novolacs are used in the reaction with difimctional phosphorus oxychlorides [177],... 

The second area of research is flame-resistant or nonflammable electrolyte solutions. The main approach is to employ phosphate compounds in some way, either by using cyclic phosphoric acid ester as solvent or by adding a phosphazene compound as flame retardant. The next most common approach is to use halogen compounds, especially fluorine compounds such as fluorocarbon ester and fluorinated ether, as solvent. There is also the concept of a new safety mechanism whereby a flame retardant is encased in microcapsules to be released in case of battery malfunction. 

Cyclic phosphoric acid esters from phosphorodichloridates O... 

Carbohydrate phosphoramidates Cyclic phosphoric acid esters... 

Compounds which dissolve in concentrated sulphuric acid may be further subdivided into those which are soluble in syrupy phosphoric acid (A) and those which are insoluble in this solvent (B) in general, dissolution takes place without the production of appreciable heat or colour. Those in class A include alcohols, esters, aldehydes, methyl ketones and cyclic ketones provided that they contain less than nine carbon atoms. The solubility limit is somewhat lower than this for ethers thus re-propyl ether dissolves in 85 per cent, phosphoric acid but re-butyl ether and anisole do not. Ethyl benzoate and ethyl malonate are insoluble. 

Alcohols, esters (but not ethyl benzoate, ethyl malonate or ethyl oxalate), aldehydes, methyl ketones and cyclic ketones containing less than nine carbon atoms as well as ethers containing less than seven carbon atoms are soluble in 85 p>er cent, phosphoric acid. 

D. Cyclic Esters of Phosphorous Acid.—There has been some controversy about the stable stereochemistry at phosphorus in cyclic phosphites and phosphonites this now appears to be resolved by agreement in a series of papers. The stereochemistry of 2-alkoxy-4-methyl-l,3,2-dioxaphosphorins... 

B. Solvolysis of Phosphoric Acid Derivatives.—Interest continues in neighbouring-group participation in the solvolysis of phosphate esters. As a potential model compound for investigating the mechanism of ribo-nuclease action, the phenyl hydrogen phosphate ester of c/j-3,4-tetrahydro-furandiol (24) has been the subject of a detailed study. Above (and probably also below) pH 4 hydrolysis gives solely the cyclic phosphate (25)... 

For a number of reactions of cyclic di- and triesters of phosphoric acid, there are exchange data which can be rationalized on the assumption of trigonal bipyrami-dal intermediates which readily interconvert by pseudorotation. This constitutes a strong argument that at least these cyclic esters react by an associative mechanism and is suggestive evidence that simple trialkyl phosphates also react by this mechanism. The pH dependence of exocyclic versus endocyclic cleavage of methyl ethylene phosphate is readily interpreted in terms of the effect of ionization of the intermediate on the pseudorotation of these pentacoordinate intermediates. ... 

Cyclic Esters of Phosphorous Acid.—A large number of 2-substituted-4-methyl-l,3,2-dioxaphospholans (88) have been prepared and their stereochemistry and conformations investigated by 1H and 31P n.m.r.69 Unlike the corresponding 1,3-dioxans, the tra/w-isomer (88a) is favoured in all cases, and each isomer is best described in terms of two rapidly equilibrating half-chair conformers with the 4-alkyl group pseudo-axial or pseudo-equatorial. 

Reactions of Phosphoric Acid and its Derivatives.—Theoretical studies on the conformational properties of cyclic and acyclic phosphate esters, including calculations of angle and torsional strain,66 and on the reactivity of monomeric metaphosphates,67 have appeared. 

The hydrolysis in acid or base of five-membered cyclic esters of phosphoric acid proceed some 10 times faster than their acyclic analogs or the six- and seven-membered cyclic phosphates 55 56. Unlike that of dimethyl phosphate, the hydrolysis of hydrogen ethylene phosphate is accompanied by rapid oxygen exchange into the unreacted substrate57, viz-... 

---