N-(2-Chloro-4-trifluoromethyl phenyl)-4-cyano-5-amino pyrazole and derivs. of formula (I) are new (where either (1) R12 is Cl; R13 and R15 are H, F or Cl; and R14 is H or F. Provided that when R14 is F, then R15 is not H, or (2) R12, R13 and R15 are F; and R14 is H or F). Phenylhydrazine derivs. of formula (II) are also new. Cpds. (I) are pre- and post-emergence selective herbicides esp. useful against broadleaf and grass weeds in cereal, soyabean, cotton, vegetable, etc. crops. Applied at 0.01-10 kg/ha. (II) are intermediates in the prepn. of (I) and they are also herbicides.
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