Loxynil (3,5-Diiodo-4-hydroxybenzonitrile) 
Photolysis of 3,5-diiodo-4-hydroxybenzonitrile (ioxynil) was a 
factor in its herbicidal action. The herbicidal and molluscicidal 
actions of ioxynil and bromoxynil, the bromine analog, are more toxic 

in light than in dark. When irradiated with ultraviolet light for 20 
hours, in benzene, ioxynil was converted into 3,5-dipheny1-4-hydroxy- 
benzonitrile. The corresponding monoiodo derivative gave 3-phenyl-5- 
hydroxybenzgonitrile. Within tissues of plants, ioxynil probably lib- 
erates free radicals which interfere with plant functions (Ugochukwa 
and Wain, 1965). 
After ioxynil was fed to a cow, a compound was isolated from the 
urine that appeared to be a conjugate of 3-iodo-4-hydroxybenzonitrile 
(Fisher et al., 1965). 
Isolan (1-Isopropy1-3-methy1-5-pyrazolyl dimethylcarbamate) 
Pyrolan (1-Phenyl-3-methyl-5-pyrazolyl dimethylcarbamate) 
It has been shown that microsomal enzymes, requiring TPNH and oxygen, 
act on N,N-dialkylcarbamates. Dealkylation occurs with formation of 
formaldehyde from N,N-dimethylcarbamates. In such a system isolan was 
degraded and formaldehyde was released at acid, but not neutral, pH. 
Pyrolan reacted similarly (Hodgson and Casida, 1961). 
Exposure of isolan to ultraviolet radiation showed formation of 1- 
isopropyl-3-methyl-pyrazolone and an unidentified compound. Similar treat- 
ment of pyrolan gave rise to l-phenyl-3-methylpyrazolone. Three uniden- 
tified compounds were also observed after prolonged irradiation (Eberle 
and Gunther, 1965). 
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