Schradan (OMPA, octamethylpyrophosphoramide) (bis-[dimethylamino] - 
phosphonous anhydride) 
Using the rate constant for the hydrolysis of schradan (at 25°c., 
as 4.8 x 1073 x [HT] min’ +); calculations indicated that 312 and 1040 days 
would be required for 50% and 90% hydrolysis, respectively, in Valencia 
oranges, and 16 and 35 days, respectively, in lemons. Values obtained 
after actual treatments indicated a gradual breakdown of schradan but not 
as rapid as theory suggests. Evaporation loss has been calculated to be 
1.5 x 10> mg/hr/em> at 15°C (Metcalf and March, 1952). 
Metabolic degradation of schradan in plants, animals, and insects 
gave rise to the same highly active and anticholinesterase compound (DuBois 
et al., 1950, 1953; Gardiner and Kilby, 1950, 1952; Cheng, 1951; Hartley, 
1951; Hartley and Heath, 195la,b, 1952; Heath et al., 1952a,b; O'Brien and 
Spencer, 1953, 1955, 1956, 1957a; Glynne-Jones and Thomas, 1953a,b; Stahman 
et al., 1953; Bennett and Thomas, 1954; Davison, 1954, 1955; Thomas and 
Bennett, 1954, 1956; David and Gardiner, 1955; Arthur and Casida, 1958). 
Using countercurrent distribution data, solvent partitioning characteristics, 
enzymatic inhibitor assays, and chemical reactions, the data indicated that 
this metabolite is the monophosphoramide oxide of schradan (Casida et al., 
1953, 1954a,b). This underwent isomerization with subsequent loss of 
formaldehyde and formation of heptamethylpyrophosphoramide (Hartley, 
1954). These studies indicated that, while formation of the N-oxide is 
the primary pathway, some hydrolysis of the phosphate also occurred 
(Heath et al., 1955). 
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