hymexazol (435)
Fungicide
NOMENCLATURE
Common name hymexazol (BSI, E-ISO, (m) F-ISO); hydroxyisoxazole (JMAF)
IUPAC name 5-methylisoxazol-3-ol
Chemical Abstracts name 5-methyl-3(2H)-isoxazolone (C.A. preferred tautomer)
CAS RN [10004-44-1] EEC no. 233-000-6 Development codes F-319; SF-6505 (both Sankyo)
PHYSICAL CHEMISTRY
Composition Tech. is 99% pure. Mol. wt. 99.1 M.f. C4H5NO2 Form Tech. forms colourless crystals. M.p. 86-87 篊 B.p. 202? 篊 V.p. 182 mPa (25 篊) KOW logP = 0.480 (unstated pH) Henry 2.77 ?10-4 Pa m3 mol-1 (20 癈, calc.) S.g./density 0.551 Solubility In water 65.1 (pure), 58.2 (pH 3), 67.8 (pH 9) (all in g/l, 20 癈). In acetone 730, dichloromethane 602, ethyl acetate 437, hexane 12.2, methanol 968, toluene 176 (all in g/l, 20 癈). Stability Stable under alkaline conditions, and relatively stable under acidic conditions. Stable to light and heat. pKa 5.92, weak acid F.p. 205? 篊
COMMERCIALISATION
History Fungicidal properties reported by I. Iwai & N. Nakamura (Chem. Pharm. Bull., 1966, 14, 1277); chemistry, biological properties and toxicology reviewed by K. Tomita et al. (Sankyo Kenkyusho Nempo, 1973, 25, 1). Introduced by Sankyo Co., Ltd. Patents JP 518249; JP 532202 Manufacturers Sankyo
APPLICATIONS
Mode of action Systemic soil and seed fungicide. Uses Control of soil-borne diseases caused by Fusarium, Aphanomyces, Pythium, Corticium and Typhula spp., etc. in rice, sugar beet, fodder beet, vegetables, cucurbits, ornamentals, carnations, and forest tree seedlings. Applied as a soil drench, at 30-60 g a.i./hl, or by soil incorporation, and also used as a seed dressing for sugar beet and fodder beet, at 5-90 g/kg seed. Also exhibits some plant growth stimulation activity. Formulation types DP; SL; WP; WS. Selected tradenames: 'Tachigaren' (Sankyo)
OTHER TRADENAMES
'Tachigazole' (Vapco) mixtures: 'Tachigare-Ace' (+ metalaxyl) (Sankyo)
ANALYSIS
Product analysis by glc (T. Nakamura et al., Anal. Methods Pestic. Plant Growth Regul., 1978, 10, 215) or by hplc. Residues determined by glc of a derivative (idem, ibid.). Details available from Sankyo Co., Ltd.
MAMMALIAN TOXICOLOGY
Oral Acute oral LD50 for male rats 4678, female rats 3909, male mice 2148, female mice 1968 mg/kg. Skin and eye Acute percutaneous LD50 for male and female rats >10 000, male and female rabbits >2000 mg/kg. Irritant to eyes and mucous membranes; not irritant to skin. Inhalation LC50 (4 h ?14 d) for rats >2.47 mg/l. NOEL (2 y) for male rats 19, female rats 20, dogs 15 mg/kg b.w. daily. Other Non-mutagenic, non-carcinogenic and non-teratogenic. Toxicity class WHO (a.i.) III (Table 5); EPA (formulation) III EC hazard Xn; R22| Xi; R41| R52, R53
ECOTOXICOLOGY
Birds Acute oral LD50 for Japanese quail 1085, mallard ducks >2000 mg/kg. Fish LC50 (96 h) for rainbow trout 460; LC50 (48 h) for carp 165 mg/l. Daphnia EC50 (48 h) 28 mg/l. Algae NOEL 29 mg/l. Bees Not hazardous to bees. LD50 (48 h, oral and contact) >100 mg/bee. Worms LC50 (14 d) for earthworms (Eisenia foetida) >15.7 ppm.
ENVIRONMENTAL FATE
Animals In mammals, following oral administration, hymexazol is metabolised to glucuronides. Plants In plants, hymexazol undergoes degradation to O- and N- glucosides. Soil/Environment In soil, hymexazol is degraded to 5-methyl-2-(3H)-oxazolone, DT50 2-25 d. |
