Phosphoric acid esters monoesters

When a mixture of phosphoric acid and phosphoric acid esters is titrated with a sodium hydroxide solution two potential jumps can be observed. The first jump results from the acid group of the diester, the first neutralization step of the monoester, and the first neutralization step of free phosphoric acid. The second potential jump is caused by the second neutralization steps of the monoester and of the free phosphoric acid. The third step of neutralization of the free phosphoric acid cannot be covered by this method. Titration of acid esters can only be used for the determination of mono- and diesters of phosphoric acid when the amount of free phosphoric acid is separately ascertained. 

The main purpose of this section is to introduce derivatives of phosphoric acid. The acid chloride derivative is C1P0(0H)2, chlorophosphoric acid, and the amide derivative is phosphoramic acid, HgN-POCOHlg. These acid derivatives will not be discussed because they will not be used in this book. There are three ester derivatives of phosphoric acid a monoester 203, a diester 204, and a triester 205. There are also derivatives of pyrophosphoric acid (diphosphoric acid, 206), which include various esters. 

HO A phosphoric acid monoester HO A phosphoric acid diester 0 1 R" A phosphoric acid triester A carboxylic acid ester... 

There are some means for synthesis of defined primary or secondary esters. Monoester salts of phosphoric acid, for instance, are prepared by addition of alcohol or ethoxylated alcohol, alkali fluoride, and pyrophosphoryl chloride (C12P0)20 in a molar ratio of 0.9-1.5 0.05-1 1.0 at -50 to +10°C and hydrolysis of the Cl-containing intermediates with base. Thus, 32.3 g (C12P0)20 was treated at -50°C with 23.9 g lauryl alcohol in the presence of 0.7 g KF and the mixture was slowly warmed to room temperature and hydrolyzed with H20 and 40% NaOH to give 83% sodium monolauryl phosphate. The monoester salts showed comparable or better washing and foaming efficiency than a commercial product [12]. 

The preparation of phosphate esters has been reviewed and full details have appeared of the use of 2-chloromethyl-4-nitrophenyl esters (reported last year) in the synthesis of monoesters and mixed dialkyl esters of phosphoric acid. 

The monomeric phosphate ion 102 was first postulated in 1955 as an intermediate of the hydrolysis of monoesters of phosphoric acid in an aqueous medium 57,58). Another 24 years were to elapse before compound 102 was observed directly, and then not in solution but in the mass spectra of some pesticides. The negative ion Cl spectra of enol phosphates 94 and of the thiophosphorie ester 95 display an intense peak at m/e == 78.9590, which is unequivocally assigned to the POf ion 59). 

Monoalkyl phosphate and phosphate esters are special types of phosphoms-contain-ing anionic surfactants that are of great industrial importance. They are used for flameproofing, as antistatic for textiles, for foam inhibition, as an extreme pressure (EP) lubricant additive, as a surfactant component for alkaline, and as acid cleaners and for special cosmetic preparations (5). The commercially available phosphate ester products are complex mixtures of monoester and diester, free phosphoric acid, and free nonionic. 

Phosphorylation of alcohols and amines forming mixed esters of phosphoric acid and phosphorami-dates, respectively, is effected by triphenylphosphine and 2,2 -dipyridyl disulfide. The reaction passes through a triphenylphosphonium phosphate of type (68 equation 44) as an active intermediate. Formation of an intemucleotide linkage can be achieved by this method. °° Dimerization of monoesters of phosphoric acid producing dialkyl pyrophosphates is achieved using tributylphosphine and dibenzoyl-ethylene or p-quinonedibenzimide (equation 45). A phosphonium phosphate is the active intermediate of this reaction. ... 

Both, alkyl phosphates and alkyl ether phosphates are made by treating the fatty alcohol or alcohol ethoxylates with a phosphorylating agent, usually phosphorous pentoxide, P4OJQ. The reaction yields a mixture of monoesters and diesters of phosphoric acid, with the ratio of the two esters being determined by the ratio of the reactants and the amount of water present in the reaction mixture. The physico-chemical properties of the alkyl phosphate surfactants depend on the ratio of the esters. Phosphate surfactants are used in the metal-working industry, due to their anticorrosive properties. 

Compounds with phosphorus as the key element that have been investigated for extreme-pressure additive activity add up to an impressively long list. But only a few of them have turned out to be of practical utility and these are predominantly esters of phosphoric acid or derivatives of thiophosphoric acid. In this section we shall be concerned only with those compounds in which phosphorus in combination with oxygen constitutes the key structure dithiophosphates and related derivatives are discussed in Section 11.2.6. The four main types of phosphorus oxyacid esters treated in the present section are shown in Table 11-12. Phosphoric and phosphorous acids are trifunctional hence there are three or-ganophosphorus structures to be considered the neutral triester, the monoacidic diester and the diacidic monoester. 

Phosphoric and sulfuric acid derivatives possess crucial properties that allow them to uniquely fill their many roles in biochemistry. Phosphoric acid may be esterified to form a monoester, diester, or triester (Figure 1). Sulfuric acid may be esterified at one or two positions, to form a monoester or a diester. Sulfate diesters are highly reactive, and have not been found in nature nor do phosphate triesters occur naturally. The hydrolysis of both phosphate and sulfate esters are thermodynamically favorable, but nucleophiles are repelled by the negative charge of the ionized forms. The resulting kinetic stability of phosphate monoesters and diesters, and of sulfate monoesters, is a major factor in their suitability for biological roles. For example, the half-life for hydrolysis of alkyl phosphate dianions by water is approximately 1.1 X 10 years k=2 x 10 s ) at 25°C. Such species... 

Fig. 1. A conceivable pathway for converting a monoester of phosphoric acid into a diester. It is shown with (1) the original ester, (2) its phosphonomethyl analogue, and (3) its arsonomethyl analogue.

Phosphoric acid can form esters with alcohols. It can form monoesters, diesters, and triesters. A general representation of the formation of phosphoesters is given below. R represents the alkyl group. 

We have seen the formation of sulfonate esters from sulfinic acids. Sulfuric acid (A) can form esters as well—either the monoesters (B) or the diester (C), which is known as a dialkyl sulfate. Esters of phosphoric acid (D) play a prominent role in biology. The phosphate linkages in nucleotides (see Chapter 28, Section 28.5) are important. Using D as a template, draw the mono- and diesters of phosphoric acid using cyclopentanol as the alcohol component. Take each of the phosphate esters you have drawn and draw the product you will obtain when they are treated with a base such as sodium hydride (NaH). 

There are at least three possible biochemical mechanisms for the activation of carboxyl groups a phosphoric acid anhydride, an adenylate, or a thiolester may be formed. Since radioactivity was not incorporated from either ATP or [2- H adenin]-ATP, into the activated intermediate, a coenz3nne A ester was likely to be present.. Indeed, the activated intermediate was shown to contain coenzyme A and OSB (II) in the ratio 1 1. Thus, hydrolysis of the activated intermediate and quantitative determination of OSB (II) and coenz3 e A by HPLC showed that the activated OSB (II) was a monoester of coenzyme A. In addition, quantitative determination of OSB (II) by its known specific radioactivity and of coenzyme A by means of a coupled enzyme assay gave an identical result. Finally, when the -succinylbenzoate coenzyme A ligase preparation was incubated with C-OSB and H-coenzyme A, the ratio of... 

A nucleotide is a nucleoside in which a molecule of phosphoric acid is esterified with a free hydroxyl of the monosaccharide, most commonly either the 3 -hydroxyl or the 5 -hydroxyl. A nucleotide is named by giving the name of the parent nucleoside followed by the word monophosphate. The position of the phosphoric ester is specified by the number of the carbon to which it is bonded. Figure 28.3 shows a structural formula of adenosine 5 -monophosphate, AMP. Monophosphoric esters are diprotic acids with values of approximately 1 and 6. Therefore, at pH 7, the two hydrogens of a phosphoric monoester are fully ionized, giving a nucleotide a charge of -2. 

Phosphoric acid A phosphoric acid monoester A phosphoric acid diester A phosphoric acid tri ester... 

---