NOMENCLATURE

Common name pencycuron (BSI, draft E-ISO, (m) draft F-ISO)

IUPAC name 1-(4-chlorobenzyl)-1-cyclopentyl-3-phenylurea 

Chemical Abstracts name N-[(4-chlorophenyl)methyl]-N-cyclopentyl-N'-phenylurea 

CAS RN [66063-05-6]  Development codes NTN 19 701 (Bayer) 

PHYSICAL CHEMISTRY

Mol. wt. 328.8  M.f. C₁₉H₂₁ClN₂O  Form Colourless, odourless crystals.  M.p. 128 °C (modification A); 132 °C (modification B)  V.p. 5 ´ 10^-7 mPa (20 ºC, extrapolated)  K_OW logP = 4.68 (20 °C)  Henry 5 ´ 10^-7 Pa m³ mol^-1 (20 °C)  S.g./density 1.22 (20 °C)  Solubility In water 0.3 mg/l (20 ºC). In dichloromethane 270, toluene 20, n-hexane 0.12 (all in g/l, 20 ºC).  Stability On hydrolysis (25 ºC), DT₅₀ 280 d (pH 4), 22 y (pH 7), 17 y (pH 9). Photodegrades in water and on soil surfaces. 

APPLICATIONS

Mode of action Non-systemic fungicide with protective action.  Uses Can be used as a foliar spray and dust application, a seed treatment, or by soil incorporation. Control of diseases caused by Rhizoctonia solani and Pellicularia spp. in potatoes (15-25 g/100 kg seed, 3-5 kg/ha in seed furrow), rice (150-250 g/ha foliar), cotton (45-75 g/100 kg seed), sugar beet (500 g/ha foliar), vegetables (1250-1500 g/ha drench and incorporation in field at transplanting), ornamentals and turf. In particular, control of black scurf of potatoes, sheath blight of rice, and damping-off of ornamentals.  Formulation types DP; DS; FS; SC; WP.  Compatibility Compatible with a number of other fungicides and insecticides, e.g. edifenphos, captan, thiram, fenthion. 

ANALYSIS

Product analysis by lc (CIPAC Handbook, 1992, E, 173-8). Residues determined by glc; details available from Bayer AG.

MAMMALIAN TOXICOLOGY

Oral Acute oral LD₅₀ for rats >5000 mg/kg.  Skin and eye Acute percutaneous LD₅₀ (24 h) for rats and mice >2000 mg/kg. Non-irritating to skin and eyes (rabbits). Not a skin sensitiser.  Inhalation LC₅₀ (4 h) for rats >268 mg/m³ air (aerosol); >5130 mg/m³ air (dust).  NOEL (2 y) for male rats 50, female rats 500, dogs 100, male and female mice 500 mg/kg diet.  ADI 0.02 mg/kg b.w.  Other Non-teratogenic, non-carcinogenic, non-mutagenic.  Toxicity class WHO (a.i.) III (Table 5); EPA (formulation) IV 

ECOTOXICOLOGY

Birds LD₅₀ for bobwhite quail >2000 mg/kg.  Fish LC₅₀ (96 h) for rainbow trout >690 mg/l (11 °C), bluegill sunfish 127 mg/l (19 °C).  Daphnia EC₅₀ (48 h) 0.27 mg/l.  Algae EC₅₀ (96 h) for Scenedesmus 0.56 mg/l.  Bees Not hazardous to bees; LD₅₀ (oral and contact) >100 mg/bee.  Worms LC₅₀ (14 d) >1000 mg/kg dry soil.  Other beneficial spp. Not toxic for carabid beetles (Calathus fuscipes, Pterostichus melanarius) up to 25 kg/ha. Under practical conditions, no negative effects on soil micro-organisms. 

ENVIRONMENTAL FATE

Animals In rats, following oral administration, up to 74% is eliminated within 3 days in the urine and faeces, either as the unchanged material or as metabolites. Eleven metabolites have been identified (I. Ueyama et al., J. Agric. Food Chem., 1982, 30(6), 1061-1067). The main metabolic pathway comprises hydroxylation of the phenyl group to various diol and triol compounds which are frequently eliminated as sulfate and glucuronic acid conjugates.  Plants Degradation only to a low degree. The hydroxylated metabolites (partly as conjugates) can be considered to be the main metabolites.  Soil/Environment Leaching and adsorption behaviour in soil characterises the compound as slightly mobile. Degraded in soil very effectively in laboratory studies. Based on determined DT₅₀ values, the compound can be classified as moderately stable to stable. The main metabolites are derivatives of p-chlorobenzylamine and p-chlorobenzylformamide.