Phosphorus compounds, hydrolyzable

The toxic organic phosphorus compounds act as powerful inhibitors of cholinesterase, an enzyme found predominantly in the nervous tissue of animals, including insects. This enzyme hydrolyzes acetylcholine, which plays an essential role in the transmission of nerve impulses. The toxicity of compounds in this series can be largely accounted for on the basis of their anticholinesterase activity (7,8,12,14, SI). 

If the action of the enzyme is to produce R—CH2—As(0)(0H)—OR (Section IV,B,2,a), the product will spontaneously hydrolyze, because water can approach the arsenic atom as a fifth ligand in a way it cannot do with the corresponding phosphorus compound. If R OH is a carboxylic or phosphoric acid rather than an alcohol, the hydrolysis is rapid, with a half-life of seconds or less, rather than of about half an... 

Figure 13.19 Examples of other phosphorus-containing hydrolyzable functionalities. In these compounds, carbons are directly bonded to phosphorus. Note that if-0-R3 is replaced by -S-Rj one obtains the corresponding thioesters.

Phosphorus(V) sulfochloride is a colorless, fuming liquid with boiling point 125° and specific gravity 1.635. The alpha form solidifies at —40.8°, while the beta form solidifies at —36.2°.7 The compound hydrolyzes slowly in water and rapidly in alkaline solution. In water, the hydrolysis products are orthophosphoric acid, hydrochloric acid, and hydrogen sulfide. Phosphorus (Y) sulfochloride is soluble in benzene, carbon tetrachloride, carbon disulfide, and chloroform. It reacts with ethanol, yielding O-ethyl dichlorothiophosphate8 (synthesis 25). 

Caution. Although the toxicity of the phosphoryl fluorohalides has not been investigated in detail, precautions similar to those suggested for the handling of volatile phosphorus-fluorine compounds should be taken. These preparations should be performed only in a well-ventilated hood, and contact with the skin should be avoided. Because the compounds hydrolyze easily, they are vesicants like hydrogen fluoride. 

Hydrolyzable phosphates and organic phosphorus compounds are not detected in the course of the determination of hydrogen phosphate ions under the conditions described here (no acid hydrolysis). In order to ensure complete differentiation of the individual phosphate and phosphorus compounds in the water sample, determination of the orthophosphate must be conducted at the latest 3 hours after taking the sample. Longer storage times may lead to shifts in the ratios between the individual forms of bonds as a result of precipitation or gradual hydrolysis. 

Sum of orthophosphate and hydrolyzable phosphorus compounds General remarks... 

Separate quantitative determination of orthophosphate, hydrolyzable phosphates and organic phosphorus compounds is not possible with the means offered by conventional water analysis if these substances are present together in dissolved form, since in the course of hydrolysis not only orthophosphates but also organic phosphate compounds are partially codetected. 

The determination of all groups of phosphates and phosphorus compounds is useful for the nutrient balance of a water since not only orthophosphate (hydrogen phosphate) but also hydrolyzable phosphates and organic phosphorus compounds can be utilized by organisms. 

Organic phosphorus compounds are converted to hydrogen phosphate ions by wet-ashing with sulphuric acid and hydrogen peroxide. The hydrolyzable... 

A low-cost and robust FIA method for total phosphorus in wastewater is based on a two-stage photooxidation/thermal digestion procedure together with a mixed oxidizing/hydrolyzing reagent for converting phosphorus compounds to orthophosphate. The formed orthophosphate is then determined by the phosphomolybdenum blue reaction. 

Acid casein and rennet casein differ principally in their inorganic content. This non-protein material consists mainly of calcium and phosphorus compounds. Acid casein has an ash content of 1—2% whilst the value for rennet casein is 7—9%. The presence of these inorganic materials markedly affects the technological properties of casein, as is discussed later. The aminoacids found in the hydrolyzate of casein are given in Table 9.3. 

The relative resistance of sphingomyelin to alkaline hydrolysis has been used to some extent as a method for estimating the sphingomyelin content of tissues (75) and of lecithins and cephalin (37,45,103). Lecithin and cephalin are quantitatively hydrolyzed into acid-soluble phosphorus compounds by normal KOH at 37 C. within 24 hours. Thus, the difference between the total phospholipid phosphorus and the saponifiable phosphorus represents the amount of sphingomyelin phosphorus. 

Early attempts to produce cephalosporin analogs by varying the 7-acylamino substituent were frustrated because, in contrast to previous experience with penicillins, a good method for producing the necessary 7-amino compound (33a) could not be found. This problem was finally solved when it was discovered that diazotization of the a-aminoadipyl residue produces an iminolactone (33b) which can be hydrolyzed to the free amine in good yield. Subsequently an improved procedure was developed which involves silylation of the carboxyl groups followed by reaction with phosphorus pentachloride to yield iminochloride (33c)... 

Phosphides are binary compounds containing anionic phosphorus (P ). Heavy metal, alkali, and alkaline earth metal phosphides exist but few of them are commercially important. Phosphides hydrolyze to the flammable and toxic gas phosphine (PH3). The hydrolysis reaction of aluminum phosphide is given below ... 

Triazanaphthalenes (446) substituted with a single leaving group have been little studied. 4-Aminopyrido[3,2-d]pyrimidine and its 6-methyl derivative have been hydrolyzed with 5N acid (100°, 30 min) and lOA alkali (95°, 3 hr, 10% yield).Attempted replacement of the 4-oxo group (via acyloxy intermediates) with phosphorus oxychloride or pentasulfide failed,in contrast to the successful replacement in the more activated 4-oxo-l,3,8-triaza analog discussed below. Similarly, the 2,4-dioxo derivative could not be thionated with the pentasulfide, and its reaction with the oxychloride was less facile than that of the 2,4-dioxo-l,3,8-triaza compound. 

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