Organophosphorus compounds,

Organophosphorus compounds used as insecticides contain the pentavalent phosphorus atom. In the fundamental state the phosphorus atom has a 3s 3p external configuration however, 3d orbitals also contribute to the formation of its compounds. Transition to the 3s 3p 3d state, corresponding to the trigonal bipyramide, requires a high activation energy of about 800 KJ/mole (Hudson, 

The major part of the phosphorus-containing insecticides cannot be considered as organophosphorus compounds in the strict sense because they do not contain a P—C bond. These compounds are esters, amides, anhydrides and fluorides of phosphoric, phosphorothioic and phosphorodithioic acids. Most of them can be classified in one of the types shown in Table 1.2. 

The number of insecticides containing a P—C bond and thus considered as organophosphorus compounds in the strict sense is considerably lower. They are predominantly esters of alkane- and benzenephosphonic acids and their sulfur analogues ,  

Phosphorus trichloride is the starting material used most frequently for the preparation of the esters, amides and anhydrides of phosphoric and phos-phorothioic acids. It can be oxidised to phosphoryl chloride (4) and, heated with sulfur in the presence of a catalyst, to thiophosphoryl chloride (5) (Perot, 1962). 

Thiophosphoryl chloride (5) can also be prepared by the introduction of chlorine into a mixture of disulfur dichloride and yellow phosphorus (Kovacs et ai. 1972). 

8 Organophosphorus compounds. Phosphorus-carbon bond fonnation takes place by the reaction of various phosphorus compounds containing a P—H bond with halides or tritlates. Alkylaryl- or alkenylalkylphosphinates are prepared from alkylphosphinate[638]. The optically active isopropyl alkenyl-methylphosphinate 778 is prepared from isopropyl methylphosphinate with retention[639]. The monoaryl and symmetrical and asymmetric diarylphosphi-nates 780, 781, and 782 are prepared by the reaction of the unstable methyl phosphinate 779 with different amounts of aryl iodides. Tnmethyl orthoformate is added to stabilize the methyl phosphinate[640]. 

Dialkyl arylphosphonates and alkenylphosphonates are prepared by the coupling of halides or triflates with the dialkyl phosphonate 783[64l-643]. 

Phosphine oxides are prepared similarly[644]. Selective monophosphiny-lation of 2,2 -bis[(lrifluoromethanesulfonyl)oxy]-l,1 -binaphthyl (784) with diphenylphosphine oxide using dppb or dppp as a ligand takes place to give optically active 2-(diarylphosphino)-1,1 -binaphthyl (785). No bis-substitution is observed[645,646]. 

The mixed triarylphosphine 787 can be prepared by the reaction of (trimethylsily )dipheny phosphine (786) with aryl halides[647]. Ph3P is converted into the alkenylphosphonium salt 788 by the reaction of alkenyl tri-flates[648]. 

5 Displacement Reactions with Carbon, O.xygen. and Sulfur Nucleophiles 

Edmondson (ed.) Dictionary of Organophosphorus Compounds, Chapman and Hall, New York, 1988, 1347 pp. 

The translucent, cream-coloured benzene solvate was characterized by single-crystal X-ray analysis and by Pnmr spectroscopy. The first free phospha-alkyne stable to polymerization 

ScHMiDPETER and K. Karaghiosoff, in H. W. Roesky (ed.), Rings, Clusters and Polymers of Main Group and Transition Metals, Elsevier, Amsterdam, 1989, pp. 307-43. 

The aromatic heterocycle phosphabenzene C5H5P (analogous to pyridine) was reported in 1971, some years after its triphenyl derivative 

6-Ph3C5H2P. See also HP=CH2 29 and [P(CN)2] ° (p. 484). The burgeoning field of heterocyclic phosphorus compounds featuring 

C-chiral hydroxy phosphorus derivatives, which have been described so far in the literature, are secondary alcohols. Thus, the syntheses of non-racemic compounds of this type comprise two main approaches (cf. C-chiral hydroxyalkyl sulfones. Section 2.2) asymmetric reduction of the corresponding keto derivatives and resolution of racemic hydroxyalkanephosphorus substrates. 

2-oxopropanephosphonate 40 (R = Me) proved to undergo the desired reaction to give (+)-(R)-diethyl 2-hydroxypropanephosphonate 41 (R = Me) in 78% yield and with ee = 98%/  

However, the most common and important method of synthesis of chiral non-racemic hydroxy phosphoryl compounds has been the resolution of racemic substrates via a hydrolytic enzyme-promoted acylation of the hydroxy group or hydrolysis of the 0-acyl derivatives, both carried out under kinetic resolution conditions. The first attempts date from the early 1990s and have since been followed by a number of papers describing the use of a variety of enzymes and various types of organophosphorus substrates, differing both by the substituents at phosphorus and by the kind of hydroxy (acetoxy)-containing side chain. 

these methodologies were used to resolve 1-hydroxyalkanephospho-nates 41 by either their enzyme-mediated acylation (Method A) or hydrolysis of the corresponding acyloxy derivatives 42 (Method B) (Equation 23). Selected examples are collected in Table 3. 

In a similar way, non-racemic 2-hydroxyalkanephosphonates (phosphine oxides) 43 and their 0-acyl derivatives were obtained (Equation 24, Table 4). 

PH3 is used as a starting material in the production of a variety of organophosphorus compounds. The most important reaction types consist of the addition of a P-H bond of PH3 to the C=C bond of alkenes or to the C=0 bond of aldehydes and ketones. These reactions and other reactions with organic compounds are described in Section 1.3.1.5.10, pp. 267/87, including a large number of related patents. 

Certain metalloids, like phosphorus and arsenic, when compounded with organic groups, are classed as organometallics. Organophosphorus compounds include four organic groups  

Organic compounds of arsenic syn. organoarsenic compounds are all toxic. They include phenyldichloroarsine, a tear gas and solvent. 

Metal alkyl and aryl oxyhydrides are similar to alkoxides in that they involve a metal hydride attached to the oxygen from an alkyl or aryl alcohol. Examples include the aluminium metal hydride sodium bis(2-methoxyethoxy) aluminohydride and lithium aluminium-tri-tert-butoxyhydride. They are dangerous fire risks in contact with water and can decompose to evolve hydrogen gas. 

Water-reactive, see Dangerous When Wet Materials and Division 4.3, p.58 

Common oxidizers include the peroxides and superoxides (those compounds containing the peroxy group, -0-0-, such as peroxysulphuric acid), bisulphates, bromates, chlorates, nitrates, permanganates, and persulphates. Organic peroxides are common. 

Regitz, Chem. Rev. 90, 191-213 (1990). See also M. Regitz and O. J. Scherer, Multiple Bonds and Low Coordination in Phosphorus Chemistry, Georg Thieme Verlag, Stuttgart, (1990). 

2-coordinate and 3-coordinate P has been fully reviewed/ as has the equally active field of phospha-alkenes -P=C j and diphosphenes 

The ylide Ph3P=CH2 can readily be made by deprotonating a quaternary phosphonium halide with n-butyllithium and many such ylides are now known  

Critical position/ factor Effect on carcinogenic potential Rationale 

Alkyl chain length T ifCHjor C2H5 Better alkylators 

Alkyl substitution J, if bulky or polar substituents Steric/electronic hindrance of metabolic activation 

Electron withdrawal arising from the inductive effect in the a and from the resonance (mesomeric) effect in the fi position of nitroalkenes (Table 4.48) induces deshieldings of similiar magnitudes and large two-bond carbon-proton coupling constants (up to 8 Hz). 

Carbon-13 NMR spectra of all nitro compounds are characterized by quadrupolar broadening of the a carbon signal. 

The nerve gases dyflos and sarin (Fig. 11.55) were discovered and perfected long before their mode of action was known. Dyflos, which has an ID50 of 0.01 mg kg-1, 

The mechanism is the same as before, but the phosphorylated adduct which is formed after the first three stages is extremely resistant to hydrolysis. Consequently, the enzyme is permanendy inactivated. Acetylcholine cannot be hydrolysed and as a result the cholinergic system is continually stimulated. This results in permanent contraction of skeletal muscle, leading to death. 

As mentioned earlier, these agents were discovered before their mechanism of action was known. Once it was known that they acted on the cholinesterase enzyme, compounds such as ecothiopate (Fig. 11.57) were designed to fit the active site more accurately. 

The insecticides parathion and malathion (Fig. 11.58) are good examples of how a detailed knowledge of biosynthetic pathways can be put to good use. Parathion and malathion are, in fact, non-toxic. The phosphorus/sulfur double bond prevents these molecules from antagonizing the active site on the cholinesterase enzyme. The equivalent compounds containing a phosphorus/oxygen double bond are, on the other hand, lethal compounds. 

Fortunately, there are no metabolic pathways in mammals which can convert the phosphorus/sulfur double bond to a phosphorus/oxygen double bond. 

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Triethyl phosphite is a colourless mobile liquid, insoluble in water. Trialkyl phosphites are valuable intermediates in the preparation of many organophosphorus compounds they readily form dialkyl esters of alkylphosphonic acids by the Arbusov reaction (p. 311). 

Chapman and Hall Chemical Database Chapman and Hall, Ltd. Dialog Dictiona of Organic Compounds (5th ed.), Dictiona of Organometallic Compounds, Carbohydrates, Mmino Mcids, Peptides, Dictionay of Antibiotics and Eelated Compounds, and Dictionay of Organophosphorus Compounds... 

G. M. Kosolapoff, Organophosphorus Compounds,]ohxiXJ A.ey 8c Sons, Inc., New York, 1950 G. M. Kosolapoff and L. Maier, Organic Phosphorus Compounds, Wiley-Interscience, New York, 1972. 

G. M. Kosolapoff, Organophosphorus Compounds, ]ohss Wdey Sons, New York, 1950, p. 16. 

F. R. Hardey, ed.. The Chemisty of Organophosphorus Compounds, Vols. 1—4, John Wiley Sons, New York, 1990. 

When saccharin is treated with diethyl phosphorothiolothionate, the 3-ethylmercapto compound is obtained, rather than the expected organophosphorus compound (77 ACS(B)460). Treatment of saccharin with phosphorus pentoxide and amines gives 3-(substituted-amino)-1,2-benzisothiazole 1,1-dioxides, via an intermediate phosphate (81ZN(B)1640). Reduction of saccharin with zinc and hydrochloric acid gives 2,3-dihydro-l,2-benzisothiazole 1,1-dioxide, the method being used to estimate saccharin in foodstuffs (75MI41701). 

Benzisothiazole, 3-hydroxy-acylation, 6, 159 alkylation, 6, 159 chlorination, 6, 160 organophosphorus compounds, 6, 159... 

Diphenylphosphinic acid [1707-03-5] M 218.2, m 194-195 , pK 1.72. Recrystd from 95% EtOH and dried under vacuum at room temperature, [see Kosolapoff Organophosphorus Compounds J Wiley, NY, 1950 Kosolapoff and Maier Organic Phosphorus Compounds Wiley-Interscience, NY, 1972-1976.]... 

Polyurethane foam Halogenated compounds including PCBs, dioxins, furans and organophosphorus compounds... 

Organohalogenated compounds and substances which may form such compounds in the aquatic environment Organophosphorus compounds Organotin compounds... 

Organophosphorus compounds (malathion, dimethoate, phorate, and parathion methyl)... 

The addition of isocyanides and azide to aldehyde-derived enamines has led to tetrazoles (533,536). On the other hand the vinylogous amide of acetoacetic ester and related compounds reacted with aldehydes, isocyanides and acids to give a-acylaminoamides (534). Iminopyrrolidones and imino-thiopyrrolidones were obtained from the addition of cyclohexylisocyanide and isocyanates or isothiocyanates to enamines (535). An interesting method for the formation of organophosphorus compounds is found in the reactions of imonium salts with dialkylphosphites (536). 

Class 6 Poisons such as acetone cyanohydrin, acetonitrile, acrylonitrile, allyl alcohol, allyl chloride, airiline, epiclilorohydrin, lead alkyls, organophosphorus compounds. 

Many organophosphorus compounds are highly toxic and frequently lethal. They have been actively developed for herbicides, pesticides and more sinister purposes such as nerve gases which disorient, harass, paralyse or kill. ... 

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