Schradan (OMPA, octamethylpyrophosphoramide) [bis-[dimethylamino]- 
phosphonous anhydride] 
Using the rate constant for the hydrolysis of schradan (at 25°C., 
as 4.8 x 107-3 x [HT] min-1l), calculations indicated that 312 and 1040 
days would be required for 50% and 904 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 1073 mg /hr/cm? at 15°C (996). 
Metabolic degradation of schradan in plants, animals, and insects 
gave rise to the same highly active and anticholinesterase compound (34, 
NOD. a2 2 we Seog GOO Ls Solis Vols sous bee ey SOO Sp Oho or Ovales. O22 162 3% 
637, 638, 1090, 1091, 1097, 1098, 1346, 1402, 1403). Using countercurrent 
distribution data, solvent partitioning characteristics enzymatic inhibi- 
tor assays, and chemical reactions, the data indicated that this metabolite 
is the monophosphoramide oxide of schradan (239, 240, 241, 243). This 
underwent isomerization with subsequent loss of formaldehyde and formation 
of heptamethylpyrophosphoramide. These studies indicated that, while 
formation of the N-oxide is the primary pathway, some hydrolysis of the 
phosphate also occurred (639). 
In the locust (Schistocerca gregaria Forsk.) fat body, the pro- 
duction of an esterase inhibitor was dependent upon the presence of 
particulate and soluble fractions of the cell contents, required 
oxygen, and was activated by Cattor Met ions (445). 
286 
