The pre‐ and early post‐emergence herbicidal activity of diflufenican, a novel herbicide, is reported and attention is drawn to its ability to control important weeds in winter cereals, including Galium aparine, Veronica hederifolia, Veronica persica and Viola arvensis, which are resistant to substituted‐urea herbicides. The synthesis of a series of related compounds is described and the relationship between structure and activities against a range of plant species is examined in respect of changes in the phenyl, phenoxy and pyridine rings. The design and synthesis of a small number of compounds combining the best patterns of substitution in each of the rings is described. The resulting optimisation of herbicidal activity in the series is reported, together with field trial results comparing the herbicidal efficacy, crop selectivity and soil persistence of the most active structures.

No abstract

Radiochemically labelled (3‐14C)‐decoquinate (ethyl 6‐n‐decyloxy‐7‐ethoxy‐4‐hydroxyquinoline‐3‐carboxylate) has been synthesised and used to measure residues remaining in liver, kidney, teg muscle, breast muscle, blood, heart, fat and skin after administration to broiler chickens at a dose equivalent to 0.008% decoquinate in the feed. Residues reached their maximum levels three days after dosing began and they remained substantially constant thereafter. These levels were less than 1.0 ppm in all the tissues examined. After withdrawal of medication, residue levels fell rapidly in most tissues (<0.1 ppm after 89 h) with the exception of fat and skin.

Decoquinate has been determined in edible chicken tissues by a spectrophotofluorimetric method during and after medication with 0.004% of the conlpound in the feed for five weeks. Mean concentrations (ppm fresh weight) of decoquinate observed during treatment were 1.1 (liver), 0.8 (kidney), 0 . 2 (muscle), 0.1 (blood), 1.6 (fat) and 1.0 (skin). Similar results were obtained with nine weeks' medication at 0.003 % and eight weeks at 0.008 %. Decoquinate was eliminated rapidly when medication ceased and all tissues contained < 0.1 ppm three-four days later.

Some iodinated pyrazoles, carrying a carboxylic or sulphonic acid group either in the nucleus or in a side chain attached to a ring nitrogen, were prepared, but were of no use as X-ray contrast media.