The Photolytic Degradation of Picloram

Summary. The effects of sunlight and ultraviolet light (253.7 nm) on 4‐amino‐3,5,6‐trichloropicolinic acid (picloram) in a basic aqueous solution were investigated. Electron‐capture gas chromatography determinations showed that approximately 20% of a 2 × 10 −2 M concentration of picloram was degraded for each 48‐hr exposure to ultraviolet light of an intensity of 200 μW/cm 2 . Decomposition by sunlight was slower and more variable. Precipitation of the degradation products with AgNO 3 indicated that two chloride ions were liberated for each molecule of picloram that was degraded. Titrations indicated that acids were formed in the degradation process, and ultraviolet spectra showed that the pyridine nucleus was destroyed. Chromatograms of the methylated decomposition products showed that at least five products were formed. The effect of the addition of a free radical scavenger, hydroquinone, on the rate of decomposition was investigated but no definite conclusions could be drawn. La dégradation photolytique du piclorame